Combi Boiler. System Drainage.


Occasionally it may be necessary to drain down a combi boiler and central heating system. This may be to facilitate maintenance procedures, cleaning the system or the addition of extra radiators.

The process is relatively simple, but prior to attempting to drain a system, it is advisable to ensure that the person carrying out the draining also knows how to re-fill, add inhibitor and pressurise the system once the work has been carried out.

The method of pressurising of a combi boiler system varies between model and manufacturer. Instructions for pressurising may be found in the boiler user’s manual.

It is important to note that if the actual boiler requires draining, this must only be carried out by a competent person. Draining a combi boiler system does not involve draining the internal part of the boiler.

Before draining the combi boiler system it is important to ensure that the mains electricity supply to the boiler and any system programmers are turned off. This is to prevent the boiler operating with an empty system, which could seriously damage the boiler.

It is not necessary to turn off the mains water supply when draining a combi boiler system.

To drain the central heating system, first, locate the drain tap. This will be on the ground floor or the lowest point of the system. Occasionally it will be conveniently located at the end of a leg of pipe leading from a radiator to the outside of the property. If not, a length of hose will need to be attached to the spigot and run to the outside of the property or to a ground level drain entrance.

With the drain tap opened, water should start to flow out of the system. This flow will need to be supported by opening up the bleed valves on all the radiators attached to the system, starting at the top of the property or the radiator furthest from the drainage tap. Air entering the system will replace the vacating central heating fluid.

With the system drained, now is a good time to flush through the central heating system to remove debris. This is best accomplished by engaging the services of a specialist company, however, some sludge and debris can be removed by operating the refilling device to allow water to flow through and out of the system. It will be necessary to close off the radiator bleed valves to facilitate the flushing through of upstairs radiators.

Once any maintenance work has been accomplished, the system can be refilled and pressurised.

Firstly, the drain tap should be closed off. It is then essential to go round all the radiators and close off the bleed valves using the radiator bleed key.

At this point, it is essential to add an inhibitor solution into the system. A good way to do this is to locate the plug at the top of one radiator. This plug will be at the opposite end to the bleed valve. Removing this screw threaded plug will reveal an opening into which the required amount of inhibitor can be added using a funnel or open-ended tube.

The correct amount of inhibitor required by the system can be calculated by using the information supplied with the inhibitor.
Do not forget to replace and firmly tighten the radiator plug after adding the inhibitor.

Water should now be allowed back into the system using the filling loop or the refilling device appropriate to the particular boiler. This may be a key type facility, which operates an internal valve system within the boiler.

As water re-enters the system, the pressure gauge on the boiler should start to register an increase in system pressure. If it does not, immediately close off the filling loop and check the entire central heating system for any leaks. It may be found that a bleed valve on a radiator has not been closed off correctly or some new work on the system is leaking.

When the pressure indicator on the boiler reads one bar, the filling loop should be turned off and all the radiators bled to remove trapped air in the system. The bleed valves on the radiators should be bled from the nearest radiator to the boiler along and up to the radiators upstairs, or the furthest from the boiler. It will be necessary to return to the boiler filling loop and re-fill the system after bleeding the air from each radiator.

With all the air removed from the system, the filling loop should be operated to pressurise the system up to the manufacturer’s recommended cold pressure operating level. This is usually between 0.5 and 1.5 bar.

Once the correct pressure is reached, the boiler power, the programmers, and the timers can be turned back on.

The boiler and central heating should now operate correctly. Any banging or loud gurgling sounds will indicate that air is still trapped within the system, as will any radiators that are hot at the base but cold at the top.

To remedy these situations, the radiators will need further bleeding to remove the trapped air.

To clean a combi boiler system, the process is similar to that described above.

First, drain down the system. Flush through with clean water. Refill with water and a suitable cleaning fluid such as Fernox. Re-pressurise the system and run for 48 hours. Drain down the system again. Flush through with clean water and refill the system with inhibitor. Finally, re-pressurise the system.

Before undertaking any DIY work on a combi boiler central heating system, it is advisable to check that the work will not invalidate any warranty on the boiler that might be in place.

Gas-Fired Absorption Heat Pumps

Whilst high-efficiency gas condensing boilers are currently the norm for new domestic water-heating installations, an attractive alternative is currently under development.

Heat pumps, in general, have slowly gained acceptance in the UK. The practice of extracting ambient heat energy from the environment and then concentrating it into a usable heat source has been around for many years. However, in the early days, the size of the equipment required for the process limited its application to the heating of commercial or large building structures.

Gradually, technological advancements enabled the size of the installations to be dramatically reduced, making them suitable for domestic utilisation. The move towards promoting renewable energy alternatives ensured that the uptake of heat pumps and the research into more efficient systems continued.

Vapour compression heat pumps are now becoming widely used in domestic situations to provide under-floor heating and supplement domestic hot water supply systems.

Although the installation of vapour compression heat pumps marks a considerable leap forward in attitudes towards reducing CO2 emissions and reducing fossil energy consumption, there has still been a level of concern about the use of HFC refrigerants as the internal heat transfer medium. Concerns about the escape of HFC compounds into the atmosphere have acted as a deterrent when considering the installation of heat pumps.

In addition, the need to compress refrigerants in vapour compression heat pumps requires electricity to operate a compressor. This reduces the overall energy efficiency factor.

Vapour compression heat pumps are designed to provide lower temperature background heating through a large surface area heating element that heats from ground level upwards.

Conversely, a condensing boiler produces high-temperature water that circulates through the relatively small surface area of radiant and convection heat emitters.

What is needed is a heat pump that can extract sufficient heat from the external ambient environment and convert it into a high-temperature energy source. This could provide copious domestic hot water at the required temperature plus enough surplus heat to power the installed central heating system.

Gas fired heat pumps are likely to provide the solution. They have been used extensively to heat large buildings. Now they are being developed and pioneered as the appliance that could consign condensing gas boilers to history.

Unlike their vapour compression counterparts, gas fired heat pumps use natural gas as a heat source to drive an extremely efficient heat collection and transfer system.

The principle at the heart of gas-fired heat pumps is the process of using a generator-absorber heat exchange cycle.

In this cycle, ammonia is used as a refrigerant or generator, and water acts as an absorber in the process.

A gas burner heats a water and ammonia solution contained within a closed loop system. This evaporates the ammonia, which turns to a gas. The ammonia gas under pressure passes into a condenser. In condensing, it releases heat, which is recovered to supply the domestic system. In condensing, it also becomes low-pressure ammonia in a liquid form. This liquid ammonia needs to evaporate and to do so; it draws heat from the ambient external air. In doing so, it becomes absorbed back into the water and returns to being a water-ammonia solution. This continual process powers the operation acting as a pump.

Because of this mode of operation, the system has no moving mechanical parts. This means that maintenance is negligible. It also means that the system operates quietly and unobtrusively.

The heat recovered from this process is considerably higher than the gas heat input required to operate the burner. The process delivers hot water in excess of 65 degrees centigrade. This is quite adequate for all domestic requirements.

The advantage over a condensing boiler is that the hot water has been produced by using a fraction of the amount of gas that a condensing boiler would use to provide the same heat output. Where condensing boilers are described as being up to eighty percent efficient, gas-fired heat pumps offer an efficiency factor of around one hundred and forty percent. The cost savings in energy consumption are therefore quite significant and it is hoped that the installation of a gas-fired heat pump will pay for itself within five years.

Even though the performance of gas-fired heat pumps is affected by changes in the external ambient temperature, they can still operate quite effectively at sub-zero temperatures.

It is possible to reverse the process to supply a highly efficient cooling system that can be operated during the hotter months of summer.

Although they can be used to extract heat from a ground source and other environmental heat retaining mediums, gas fired heat pumps are particularly suited to collecting heat from the air. As such, they are designed to be sited externally. The new versions starting to enter the domestic market can be freestanding or attached to the building.

It is hoped that eventually they will provide a suitable replacement for condensing boilers that have come to the end of their working life.

Because of the high heat output and the method of operation, gas fired heat pumps can be plumbed into any already installed heating system. It is likely that they will eventually form part of the ongoing process of the retrofitting of technological advances in the manufacture of water heating and control systems into existing installations.

Gas fired heat pumps are still in the process of further development. It is likely that as time progresses, purchase and installation costs will reduce and heat transfer efficiency will increase. However, gas-fired heat pumps are likely to rapidly become the accepted replacement for condensing boilers.

 

 

 

Combi Boiler Pressure Checks

Gas combination condensing boilers, better known as combi boilers, are highly efficient water heaters. They are compact fuel misers, designed and installed to extract the maximum heat from their fuel source.

Unlike their open vented counterparts, combi’s are designed to run a pressurised hot water central heating system that eliminates the need for feed and expansion tanks. This attribute is most advantageous in a property where available space is limited.

Like any sophisticated appliance, combi boilers respond well to good and regular attention. Annual maintenance and servicing by suitably qualified engineers will help to keep a combi in good operating condition. This provides peace of mind for a homeowner in knowing that the boiler is performing in line with requirements and unlikely to break down in the depths of winter.

However, combi boilers require another simple check that can be carried out by the homeowner. Checking that the combi boiler operating pressure is correct and undertaking the necessary operations to maintain it is a relatively easy task.

A combi boiler pressure check should be carried out once a month on a correctly functioning boiler.

The pressure within the central heating system is registered on an analogue dial or digital display panel. In most modern combi boilers, the dial or display is located on the boiler. This can be either on the front, sometimes beneath a protective flap, or at the base, but not always immediately visible due to the boiler cover. It is not usually necessary to remove the boiler cover to observe the pressure register.

Very occasionally, the pressure registering display device is located separately from the boiler but is generally in the vicinity of it.

To locate and correctly identify the pressure gauge, the homeowner should refer to the combi boiler instruction manual.

Having located the pressure-registering device the current pressure within the system can be ascertained. A normal pressure range will be between 1 and 2 bar. On an analogue gauge, a black needle will indicate the pressure on the numbered dial face. On some models, the acceptable cold working pressure area will appear as a green coloured fraction on the dial face. Occasionally a further red needle will be present. This is adjustable and can be set to indicate the optimum operating position that conforms to the manufacturer’s recommendations.

As operating pressures may vary between manufacturers and boiler models, the manufacturer’s instruction manual should be consulted to establish the correct pressure ranges.

Where a boiler appears to be operating at a lower pressure than recommended, the system will require pressurising.

To pressurise a combi boiler central heating system, a filling loop is usually provided as part of the installation. The loop consists of a short length of flexible metal or plastic tubing. This will have screw fittings at each end. There should also be valves at either end of the loop. These may be of a lever or screwdriver operated type.

Before commencing to pressurise the system, the gas burner on the boiler should be turned off. It is probably easier to work on a cold boiler and central heating system.

With the loop valves in the closed position, one end of the loop must be screwed onto cold-water input branch feed beneath the boiler. The other end should be attached to the cold-water branch from the mains cold feed. Both these feed points will have flow control valves.

With the loop securely attached, the loop valves can be opened. The mains water branch feed valve can also be opened. To commence pressurisation, the cold mains inlet feed valve should be carefully operated. The sound of water entering the boiler should be heard.

Whilst observing the boiler pressure indicator gauge or digital display, the valve should be kept open until the correct pressure has been achieved and registers on the display.

Once the correct pressure has been reached, the valves on the loop and the two feed pipes should be turned off.

The filling loop can then be disconnected and the boiler operated. It is not good practice to leave a filling loop permanently attached to a combi boiler.

On some combi boilers, a filling loop is not required and the boiler has an internal pressurising system. This is operated by a dedicated key that has to be inserted into the base of the boiler. The key locks into an internal pipework mechanism and turning it operates the pressurising system. The pressure gauge must still be monitored. When the correct pressure is achieved, the key can be unlocked and removed.

On some boilers, instructions on pressurising are displayed on the boiler. However, the best practice is to consult the operator’s manual where detailed instructions for pressurising the specific boiler model will be found.

After pressurising, the central heating radiators may require bleeding. After bleeding the radiators, the pressure gauge should be re-checked, as it is often necessary to add a little more pressure into the system.

If, when attempting to pressurise a combi, the pressure cannot be raised, immediately check the entire system for evidence of a possible leak. Another cause of not being able to pressurise the system is an inadequate mains water pressure. This may be caused by maintenance operations or burst pipes on the mains network. Often, when the mains pressure is low, the boiler will not function by design.

Where a combi boiler loses pressure frequently, a fault may lie within the central heating system or the boiler itself. If, after checking the system for leaks and checking the boiler’s pressure release valve for faulty operation no problems are evident, it may be necessary to employ the services of a qualified engineer.

Significant problems can often occur when a combi boiler is installed to replace a conventional boiler. The pressure produced by a combi boiler may cause problems in an older central heating system. It is important to have the old system professionally pressure checked prior to installing a combi boiler.

When properly maintained and cared for, a combi boiler will continue to work efficiently and reliably for many years.

 

 

Problems with Dead Legs

I recently bought a new washing machine. Not that there is anything particularly out of the ordinary in doing so. The working life of a modern washing machine seems to be considerably shorter than that of the robust models of the past. Whether that is due to the increasing complexity of the electronics or the designed-in time-dependent failure of its components is a matter of opinion.

The main thing that did attract my attention was the fact that the new machine had just one water inlet hose. My previous washing machine had two independent water inlet hoses, one for hot and the other for cold water supply.

It seems that now one cold supply hose is the only water inlet connection required.

This naturally left a length of redundant hot water supply pipe. Although it was fitted with an inline valve to close of the hot water flow, I decided to fit a blanking cap to the hose connection end as a secondary precaution against leaks.

Unknown to me I had just created a dead leg.

That might have been the end of the story had I not read an article about the increasing awareness of the potential problems of microbial proliferation in domestic water supplies, particularly in dead legs.

A dead leg is a section of water pipe that branches from a T-junction and is blanked-off due to it no longer being required. It can also refer to a section of water pipe that services an appliance that is infrequently used.

Apparently, such lengths of pipework can become traps for silt and organic material. This provides the perfect environment for the development of microbial agents that can pose a danger to householders.

This is particularly the case in respect of dead legs on hot water systems.

Although hot water may be flowing through the domestic system at a temperature and flow rate that prevents microbial development, a dead leg remains as a sump for collecting debris.

The water temperature in the main domestic circulation is usually at a high enough temperature to inhibit microbial growth, but in a dead leg, the water stagnates at a lower temperature.

The dead leg on a hot water system may pool water at the optimum temperature to allow scale formation. The surface provided by developing scale, the presence of nutrients from collected sludge and the warmth from the water provide the ideal environment for the development of dangerous organisms.

Organisms such as Amoebae, Ciliates, Coliforms and Algae may proliferate and disperse into the main circulation. However, Legionella and Pseudomonas bacterium can also flourish.

So how do these organisms get into the hot water supply to begin with?

Mains cold water from the provider is chlorinated to destroy most potentially harmful organisms, but contamination can still occur due to leaking supply pipes or unprofessional plumbing work.

Perhaps the greatest source of contamination is a water storage tank, particularly one that is uncovered or that has an unscreened overflow pipe.

Although regular flushing of the hot water system, either intentionally as a maintenance task or by continual domestic usage, will help to prevent microbial contamination, dead legs will remain un-flushed and prone to scale formation. The scale provides a perfect material for organisms to adhere to.

Fragments of contaminated scale can break away from formations in dead legs and become suspended in the domestic water flow.

In the case of Legionella, the bacterium can survive the flowing hot water temperature and then incubate in lengths of T-pipes supplying hot water outlets when the temperature drops in-between outlet demand.

The bacterium can also thrive in showerheads in-between usage, particularly where scale buildup in the showerhead provides niches for development.

Although microbes in contaminated hot water can be harmful if ingested, bacterium like Legionella pneumophilia can be dangerous when inhaled.

The inspiration of aerosol particles can penetrate deep into the lungs.

Aerosols are minute water droplets suspended in the air. They are created by water falling onto a hard surface; such as occurs when running a tap, a bath, or having a shower. Flushing a toilet or spraying water will also produce aerosols.

Whirlpool and Jacuzzi type bath installations are now being identified as potential sources of microbial incubation and harmful aerosol formation, particularly where regular sanitation and cleaning maintenance is neglected.

Aerosol particles in the air can remain suspended and circulate on air currents for over twenty minutes.

Although Legionella infections are not passed from person to person, they do occur in clusters. The symptoms can vary from mild flu-like conditions to life-threatening pneumonia. People with compromised immune systems or pre-existent lung conditions are the most vulnerable to acquiring Legionella infection. The mortality rate can be high among confirmed cases in susceptible people.

However, it is thought that many mild cases go undiagnosed and that the incidence of Legionella infections amongst the population is much higher than the identified and confirmed cases suggest.

On the Continent, plumbing procedures encourage the installation of loop systems rather than T installations to help to prevent microbial development problems in domestic hot water supplies.

Best practice and Water Regulations now issue guidance on dead legs and associated blind ends. It is recommended that redundant T water pipes are removed and the T replaced with a standard in-line pipe connection.

It is also worth noting that landlords of rented properties must undertake a risk analysis of the potential for water-borne infectious agents to develop in services installed in properties they let. They must also take action to make safe any potential sources of microbial contamination. Failure to do so can expose the landlord to criminal action and substantial litigation issues should subsequent related harm occur to a tenant.

I have now removed my blind end and in conjunction with a regular flushing of my entire domestic hot water system, can rest assured I am doing as much as practical to reduce the chances of my household contracting a water-borne infection.

 

 

 

Identifying and Fixing a Damaged Heating Pipe

There is no doubt about. You have a boiler losing pressure and you have no idea why. You’ve checked the central heating radiators and pipes for any visual signs of leaks and found nothing.

You’ve also called out the boiler engineers and they have checked the boiler over for faults and replaced a suspect part. The expansion vessel is working normally and there is no overflow from the pressure release valve.

Yet still, over a period of a few days the boiler operating pressure starts falling and you have to keep topping the system up.

The real worry is that there is a leaking pipe under the floorboards, or worse still, buried within the new hydronic under-floor heating system you’ve just had installed under the ground floor.

This is going to take a little bit of detective work to find just where that leak is hiding.

That is of course if it is a leak.

Just because boiler engineers are Gas Safe registered it does not mean they are all seasoned and highly experienced. Unfortunately, there is a minority who are inclined to diagnose the most likely fault, replace a part and hope for the best. When they are called back, they simply move on to the next likely fault and eventually fix the boiler by the expensive process of gradual elimination.

So, back to our devil of a problem. To see whether the boiler is at fault, the following technique may help.

The boiler should be isolated from the system by turning off the flow and return valves to heating networks and the mains inlet source. The boiler must have at least one bar of internal pressure registering on the pressure gauge.

The boiler should be left unused for at least 12 hours. If the pressure drops within that time, then the fault very likely lies with the boiler. If the pressure is maintained, the fault probably lies somewhere within the heating circulatory system.

Of course, whilst the test is in operation there will be no domestic hot water available, particularly if you have a combi type boiler. If you are fortunate to have a hot water storage cylinder with an alternative electrical element heating source, you will not be affected by this temporary domestic hot water problem.

If the boiler appears to be at fault, get the boiler engineers back and insist that they rectify the fault.

If the heating circulatory system appears to be the problem, you should have a dedicated heating network that feeds the under-floor heating system separately from the radiator network. The manifold which connects the hot water to the under-floor heating pipes should have isolation valves fitted. On this manifold, it is often usually possible to turn off the under-floor heating or the radiator network separately so that each can run either together or independently depending on the household requirements.

With the boiler operating at normal pressure, isolate each network flow and return valves independently for at least 12 hours and monitor the boiler pressure. A drop in pressure on either network will indicate which has the leak. A drop in pressure on both networks means that you either have leaks in both networks or that there is a leak in the pipework from the boiler to the manifold. To identify whether the latter is the case, turn off all heating network flow and return valves with the boiler operating at normal pressure for 12 hours. If the pressure drops then the leak lies on that circuit.

If there are no pressure drops within the circulatory system, call the boiler engineers back, again.

When diagnostics suggest that the under-floor heating network has a leak, depending on the warranty you have, contact the installers. If you installed it yourself or it is out of warranty, check your household insurance for cover.

It is possible to get a general idea of where the under-floor heating leak is located by using thermal imaging equipment. If it can be located, the area can be dug up and the leak found and repaired or bypassed with a new loop of pipe.

Dealing with leaks in under-floor heating can be expensive to address. The wrong diagnosis can lead to the entire floor being dug up and no leak being found. When initially laying under-floor heating it is wise to protect any pipes from the corrosive action of concrete.

If all indications lead you to suspect that the leak lies somewhere within the central heating network, it is important to thoroughly inspect all accessible parts of the pipe-work and attached appliances for any visual signs of leakage. On hot pipes, water from minor leaks will very quickly evaporate.

Where forethought has provided isolation valves at important junctions, these can be used to isolate sections in the elimination process previously described.

Narrowing down the area of the leak will allow for close scrutiny of a small section of visible pipes and fittings. Occasionally the most unlikely source of a leak may be the culprit, such as a loose compression fitting or a faulty radiator check valve. Appliance fittings such as those attaching pumps and motorised valves must also be checked.

Once narrowed down and without any visual signs of a leak, attention must be drawn to pipe-work hidden below floorboards etc.

Lifting floorboards in a limited area may give an instant visual indication of a leaking pipe. Possible compression fitting failings or badly soldered joints will show up as a damp patch on the surface beneath the fittings. Sometimes a nail hammered into floorboards and puncturing a pipe is the culprit.

Before attempting to repair a leaking pipe, always turn off the boiler and mains water. If the heating flow section cannot be isolated, the system will have to be drained.

Repair is usually straightforward and limited to either re-tightening or replacing compression joints, or removing the affected section of copper or plastic pipework. A new piece of pipe is then inserted and secured with appropriate fittings. The use of in-system circulating leak repair fluids is not recommended. They can cause other damage to the system and often invalidate warranties.

Once the pipe-work is repaired, the system can be re-filled. Do not forget to include inhibitor. Radiators may need bleeding.

Hopefully, the problem will be solved. However in some rare cases, leaks are never found, or one is discovered and fixed, only for more to appear. The householder continues to suffer from system pressure issues that indicate leaking pipes and has to continue the unresolved chore of frequently topping up the system. In cases like these, it is likely that there are numerous minor failings, particularly in old systems. In these situations, a complete central heating replacement is probably long overdue.

 

Fitting a Magnetic Filter? DIY!

If at any time you thought that your wet central heating system was a ‘fit and forget’ feature, I am sure that now, and possibly as a result of experience, you’ll have come to a completely different opinion.

Perhaps you might have thought that you could save money by running your central heating for a a few years without regular maintenance.

Trouble is, sooner or later your system is going to start deteriorating and could eventually succumb to a rather expensive failure.

Something of a false economy.

In addition, a lack of regular attention will cost you more than inconvenience and costly breakdowns.

Running a poorly maintained system can send your heating bills sky high as the pump and boiler struggle to heat and push water through constricted, scaled pipes, sludge and sediment clogged radiators and mineral-encrusted heat exchangers.

Regardless of the type of system you’ve had installed, whether it is a sealed combi, open or a vented heating system, the most common problem you are likely to experience is that of natural corrosion of the metallic components of the system.

This can be reduced very effectively by periodically power flushing the system and by the regular use, and maintaining of, an adequate concentration of inhibitor.

However, power flushing can leave behind stubborn sediments that could eventually dislodge and become suspended in the circulating water. These particles, usually composed of metal oxides, can continue to cause damage to boiler components even in what might have been considered a cleaned system.

This, combined with a continual accumulation of debris, can increase the frequency of the need to power flush.

The answer to removing these particles lies in the introduction of a magnet into the system.

There are a number of domestic magnetic filters available, but the most popular and effective is the Magna Clean device.

The Magna Clean is a compact filter appliance of simple but ingenious construction containing a powerful internal magnet. This very effectively collects any metallic particles suspended in the water. Its small size means that it can be fitted unobtrusively in confined spaces.

Many central heating maintenance companies recommend the fitting of a Magna Clean device, particularly after power flushing or the installation of a new boiler.

And they will also quote you a considerable sum to do so, along with a repeat fee for annual cleaning and maintenance!

However, a Magna Clean is self-powered, has no moving parts and is simple to install.

A Magna Clean can be purchased from most D.I.Y. outlets and comes in a number of designs that will fit into most central heating installations.

You can expect to pay between one hundred and one hundred and fifty pounds for the appliance including VAT.

Although the best time to install a Magna Clean is following a power flush, it is not a precondition.

The main advantage of installing a Magna Clean following a system flush is that the boiler or heating device has already been turned off and the system has been drained.

When the system is drained, the Magna Clean should be installed between the last radiator on the system and the system boiler. Generally, the device is fitted on the return hot water pipe just below the boiler.

The device should always be plumbed into the pipework in accordance with the manufacturer’s instructions. This is not a complicated procedure and can be accomplished in minutes.

The Magna Clean Pro 2 is perhaps the simplest device to fit and requires a 150 mm section of pipe to be cut out of the return hot water circuit. The device can then be securely connected into this gap with a spanner. The inlet and outlet valves are self-contained and the device can be removed and replaced anytime quite easily.

The Magna Clean Pro 2 also has an addition trap at the base of the device to collect non magnetic particles.

It is recommended that the Magna Clean magnet should be cleaned once a year, but it is probably wise to clean it more frequently, particularly on an older system where previous inhibitor and flushing practices may have been neglected.

To clean the magnet, close the inlet and outlet valves on the device. Release any pressure in the unit by turning the bleed valve at the top, and then unscrew the device top with the dedicated tool which is provided when the device is purchased. Then remove the magnet in its accompanying plastic sleeve.

The surface of the plastic sleeve will very likely be coated in black ferrous sludge, even after a short period of operation. It is the monitoring of this sludge that will give an indication of the level of contamination within the system and the frequency with which the filter should be cleaned.

To clean the magnetic filter simply run it under running water to wash away the sludge particles. The filter can then be inserted back into the device, the top replaced and the valves opened. The bleed valve on top should be operated to remove any trapped air.

Job done.

Beware of heating companies who, after installing a new boiler, suggest the installation of a Magna Clean device as an alternative to power flushing. Operating a new boiler without power flushing can invalidate the boiler warranty.

The Magna Clean installation should be seen as complementary to good central heating maintenance and not as an alternative.

It is estimated that the use of a Magna Clean device can knock up to sixty pounds of annual heating bills.

That has to be a saving worth considering.

Defective Motorised Valves

If you have a conventional wet heating system and boiler, the chances are that you will have at least one motorised valve incorporated into your system.

A motorised valve is a type of flow director, which operates to direct the flow of hot water from the boiler to either the domestic hot water cylinder circuit or the central heating circuit. Some types of diverter valves can direct the hot water flow to both circuits simultaneously.

A domestic hot water storage cylinder, heated by an internal coil and carrying hot water from the boiler is referred to as an indirect system. This system will usually comprise of a programmable time switch, room and cylinder thermostats and normally one or more motorised valves to control the central heating and domestic hot water supply.

These valves are usually operated by small electric motors and are activated by thermostats or the programmable control system. They can save fuel and money by ensuring that water is only heated by the boiler when it is needed and that the heated water then only goes to the part of the system where it is required.

Motorised valves are expected to operate for long periods and are subjected to considerable stresses caused by temperature fluctuations and contaminants like sludge, grit, scale and the other pollutants often found in the heating circulatory fluids. It is not surprising that faults and defects can arise with the components of motorised diverter valves.

Because of the interaction between various regulatory devices incorporated into a boiler and heating system, a fault with one component can prevent the whole system from operating. Where a motorised diverter valve is unable to communicate with the boiler, the boiler will not operate. This situation can occur when the system has not operated for a considerable time or where the supply of hot water from the boiler to the diverter valve has been turned off or obstructed.

Other indicators of a fault with a motorised diverter valve are either hot water in the domestic hot water supply but not in the central heating system, or vice-versa, or a supply of heating to both circuits when a demand for the supply is not required.

Although motorised diverter valves are manufactured by a number of companies and design of the valves varies, two common types are found in a domestic setting. These are two-port and three-port valves.
Numerous two-port valves can be used for zoning configurations.

The installation of either a two or three-port motorised valve depends on the pipe-work layout and the system requirements. Two-port motorised valves are used for the control of either a heating or a hot water circuit. Three-port motorised valves can provide separate heating and hot water circuits. There are two types of three-port motorised valves. One will only divert the flow of water to individual circuits whilst the other provides a mid position, delivering a shared flow to both heating and hot water.

Where a fault with a motorised diverter valve is suspected, there are a number of easy checks that can be made, and where a component part of the diverter valve is found to be defective in many cases it is relatively easy to purchase the component and replace it.

A motorised diverter valve is usually positioned near to the domestic water supply hot water cylinder. A first check should be to ensure that the motor is receiving the electric power it requires to operate. It is not unusual for the supply fuse or circuit breaker to be the cause of the fault.

On most motorised diverter valve units, there is a small lever on the motor housing. This lever can be manually operated to override the motor. It can also be used to establish where a fault might originate from within the unit.

With the system and unit power turned off; gently push the manual lever across its path. A certain amount of resistance should be felt. This is caused by the motor being manually turned. The lever should slowly return to its resting position once manual pressure is removed. If the lever moves with no resistance, or will not return to its resting position and is floppy it is likely that the internal mechanics are jammed.

To check if the valve is opening correctly, the system should be powered up and electricity restored to the pump. In this state, when the manual lever is pushed over, it will operate the valve and the lever becomes floppy indicating that the valve has opened. By touching the pipe-work below the unit housing it is possible to feel the heat from whichever circuit is operating. If one pipe is hot and the other cold the valve is closed. Pushing the manual lever completely over will open the valve and both pipes should become hot.

To check the internal components of the unit, first ensure that the unit is isolated from the electrical supply.

Next, unscrew the unit housing cover and remove it. This will expose the synchron motor. The motor sits on top of, and operates, the gearing mechanism situated directly below it. The gearing mechanism operates a spindle that either raises or lowers a ball to open and close the valve or in some models, rotates a shoe to direct water from one pipe to another.

The motor should be circuit tested to establish whether a current can pass through to operate it. If the circuit is not complete, then the motor will need replacing.

The old motor is easy to remove, however, the wire connections will need to be cut and then rejoined with connectors when installing the new synchron motor.

New synchron motors are easily obtainable and relatively cheap to purchase. It is important to ensure that the correct motor for the unit model is purchased. The motor must be rewired into the system in an identical manner to the one it replaces.

Occasionally the fault may lie with the micro switches that operate sensors informing the boiler of the unit’s valve position. These can be checked for voltage continuity across the system to discover if the fault is related to the switches.

Finally, a fault may lie with the gearing and spindle. If the connecting plate that attaches the motor and gearing housing to the pump valve mechanism has two securing screws, the housing section can be removed. If the connecting plate has four screws and the valve cannot be isolated by gate valves, the system will have to be drained before the connecting plate and housing section can be removed.

Removing the head unit will expose the spindle, which operates the valve. This can be turned with a small spanner or grips. It will not turn far. Occasionally the spindle will be slightly seized. This can be remedied by giving the spindle a sharp jerk with a spanner to free it. If the spindle is completely seized, the valve will need removing and replacing. If gate valves have been installed the valve can be isolated. If not, the system will have to be drained.

If the spindle is free and the gearing or micro switches in the unit head are at fault, a new complete head unit can be purchased and easily installed.

Where the identification of a fault with a motorised gate valve cannot be established, or where the necessary skills are not available for the user to undertake the repairs, the assistance of a qualified plumbing engineer should be sought.

Micro CHP Boilers

So. You’ve just upgraded your old central heating boiler to a brand new, highly efficient condensing combi boiler and you’re feeling pretty good about it. It came with an excellent warranty and service package and you’ve been advised that the central heating, the remote access control system and the sophisticated programming features are all examples of the latest technology.

Then your neighbour gleefully informs you that he is planning to install a micro CHP system. This naturally deflates your buoyant demeanour and sends you scurrying to the internet to see what advantages your neighbour might be obtaining.

Combined heat and power (CHP) boilers have been around since the 1970s. Due to their size, weight, cost and operating noise, they have generally only been suitable for industrial and large communal facilities. They have been installed to primarily generate electricity, usually by internal combustion engines and dynamos, with the secondary heat by-product being utilised for central heating purposes.

In recent years, technological advances, spurred on by rising energy costs, have enabled the concepts of the commercial CHP boilers to be adapted for domestic operation. These new compact and vastly superior devices are referred to as micro CHP boilers.

Although much of the technology is still in the developmental field, some micro CHP boilers are available on the market.

Current models are similar in size to a large domestic condensing boiler and are wall mounted. They are also plumbed into the central heating system in much the same way. They do require installation by a Gas Safe engineer and a Micro-generation Certification Scheme (MCS) approved installer. What makes domestic micro CHP boilers special is that in producing heat for domestic hot water and central heating, they also use the heat to generate electricity for the home. Any surplus electricity is then directed back into the grid. The boiler owner receives a payment for the electricity produced for domestic use and also a payment for surplus electricity fed back into the grid.

At first sight, it can all appear very attractive, and no doubt, the neighbour has seen this as an opportunity too good to miss.

There can be no doubt that electricity produced from a remote power station is a dirty, inefficient fuel. Only about 30% of the energy from the source fuel is actually available to the consumer. The rest is lost in production and supply.

Being able to produce electricity at the point of usage has great advantages and can provide energy efficiency levels in excess of 90%.

The vast majority of micro CHP models currently available employ the actions of a Stirling engine to generate electricity. Stirling engines are classed as external combustion engines. They utilise the properties of internal chambers filled with a gas, usually helium. This gas is responsive to areas of hot and cold within the chambers. Applying heat to the gas causes alternating pressures as it moves to a colder area, and vice-versa. This movement operates a displacer and piston. The piston moves up and down inside a copper coil at around fifty times a second to produce electricity, which is fed into the domestic electrical supply.

The Stirling engine generates about 1 kW of electricity as it operates.

Because these boilers use gas in a very controlled and efficient manner, the general idea is that the Stirling engine should operate continuously using small amounts of gas to efficiently generate electricity, and supplement the domestic central heating and hot water supply, with a boost heating facility to raise the hot water system to demand levels.

Every electrical kW produced and used by domestic consumption receives a payment from the energy supplier. This acts as an inducement to produce electricity and as a payment for not using the supplier’s inefficient electricity source. On top of that, any surplus electricity is directed back into the grid and receives a FIT payment (the Feed In Tariff) from the provider for each kW produced. The micro CHP boiler must be installed correctly by an MCS installer to qualify.

So where are the pitfalls?

The major drawback is the cost. Currently, purchase and installation costs are in excess of £5000. The life expectancy of models on the market is around ten years. With gas and electricity fuel prices so volatile, it becomes difficult trying to assess whether, or when, the capital expenditure and the interest payments on any financial assistance packages would justify installation.

There have been calls for a substantial increase in the FIT to make installation of micro CHP boilers more attractive, but as yet, there has been no movement on that proposal. As such, any financial advantages are likely to be very modest over the long term.

Perhaps the main obstacle for installing current micro CHP boilers is the situation in a potential buyer’s home.

Householders have responded favourably to Government incentives and environmental concerns over recent years. They have improved insulation and many have installed a variety of heat saving devices. Some have adopted technologies that supplement heat requirements with heat recovered through accumulators.

The amount of gas that is required to heat a well-adapted home is now significantly less than in previous times.

However, demand for electricity is increasing. Households now require constant electricity, not constant heat.

The 1 kW electrical output of a micro CHP boiler with the current FIT and kW subsidy does not make the installation of the boiler a realistic proposal at the moment.

The future for micro CHP boilers is, though, looking good. Manufacturers are developing superior alternatives to Stirling engines. Ceres are developing fuel cell technologies that will revolutionise domestic heat and electrical production. Within these fuel cells, heat and electricity can be generated without combustion removing all the problems associated with it.

Hydrogen cells are being developed to utilise the energy produced by micro CHP boilers and other green energy generating technologies. Hydrogen can be produced by surplus electrical activity and then used to generate electricity again at peak demand.

These green and clean modifications incorporated into, or complimenting micro CHP systems will make installation more of an attractive proposition in the future. The electrical kW output produced is much greater. Already the major energy companies are voicing disquiet about the possibility and implications of millions of micro energy producers feeding surplus energy back into the grid. And with some justification!

Perhaps lots of micro energy producers supplying a local network might be the answer to the ailing, aging and costly grid network, in addition to the public’s growing disquiet about the energy company’s extortionate energy generating profits.

In the meantime, compliment your neighbour for considering becoming a torchbearer and protagonist of nascent technologies.

 

Unvented Hot Water Cylinders – The Future?

An unvented hot water cylinder can be the answer to a loft converter’s prayer. Especially when available space and the shortage of it is a major consideration that most homeowners are faced with when considering improvements to hot water installations.

The biggest drawback with vented hot water cylinders is the need for a water storage header feed tank, usually situated in the loft. There the water sits, waiting to be heated and often exposed to airborne contaminants. In addition, when the time comes for it to work its way into the cylinder for heating and then on its journey to a hot water outlet, it must do so usually under the gentle force of gravity and with a little assistance from atmospheric pressure. The unbalanced pressure between mains cold water and gravity fed hot water can lead to irritating problems. A good head of pressure may be achievable from a header tank in the loft of a three-story building, but flats and single story dwellings will need to install pumps to maintain an acceptable flow rate of hot water.

Added to that, and probably an overlooked factor is the low level of copper contamination leached from the copper cylinder into the heated water. It is probably wise to avoid swallowing it and adding to the other environmental copper sources slowly accumulating within our bodies.

Perhaps, in the days before central heating and cylinder jackets, there was something comforting about that great copper vessel hidden away in the airing cupboard alongside a couple of bubbling demijohns, mushroom spawn and germinating cucumber plants. However, time moves on and brings with it progress and advantages that can revolutionise our way of life.

Unvented hot water cylinders have been around for some time, particularly on the continent. Consequently, they are well tried and tested and for a variety of reasons, very efficient.

There are two types. Direct and Indirect. The direct system is heated solely by two internal electric elements.

The indirect system is heated by an external boiler, although a backup single internal electric element is usually incorporated. The external boiler heats water, which then passes through a copper coil in the cylinder. The heat is exchanged to the water in the cylinder and returns back to the boiler for re-heating. The requirement for heating is governed by a thermostat attached to the cylinder.

An unvented system is connected directly to the mains supply eliminating any need for a header feed tank. This mains supply provides the great advantage of increased water pressure compared to that of a vented system. It also eliminates any need for complimentary pumps to increase hot water pressure.

This extra pressure on the hot water system allows for greater flexibility in the choice of mixer taps and the benefits of being able to install power showers.

On a suitable and well-installed system, very little drop in water pressure is noticed when multiple hot water outlets are operated at the same time.

Because this system operates at a greater pressure than a vented installation, certain modifications are incorporated in the design to accommodate the differences and eliminate potential problems. A device called a balancer is usually installed on the mains inlet to ensure that equal pressure is present on both the hot and cold outlets.

The cylinder itself is generally made of stainless steel and constructed to withstand the extra pressure it is subjected to. The cylinder is also insulated with materials that represent the cutting edge of energy conservation, and as such dramatically reduce the loss of heat into the atmosphere and consequently increase the efficiency of the system.

Hot water expands and in the absence of the expansion route provided by a vented system, the unvented cylinder incorporates either a small external diaphragm water and air operated expansion vessel, or an internal air bubble type expansion facility. One or more tundish safety components are added for extra safety and they also give a visual indication if a heating problem occurs.

Where unvented systems have been installed without proper consideration, the most common problem for homeowners has been that the system does not perform within expected tolerances. An unvented system, operating on mains pressure requires a minimum mains pressure and minimum mains flow rate to operate correctly. This is often not checked prior to installation. An unvented system requires a minimum mains pressure of 1.5 bar and a minimum flow rate of 20 litres/minute.

Where insufficient mains water pressure and flow rates are identified it is possible to acquire an additional accumulator cylinder. This device intercepts the mains supply prior to it entering the hot water cylinder and stores the extra water, conveying additional pressure directly to it so that when water is drawn through the unvented cylinder it is replaced by cold water from the accumulator at an adequate pressure.

The compact and uncomplicated nature of unvented hot water cylinders is also enhanced by a reduced maintenance requirement and a considerable warranty period on the cylinder.

Where space is at a premium they are ideally suited, and compared to the output limitations of room sealed combination boilers, they are likely to be the system of choice. The potential for modification to enable contribution from other external heat sources i.e. solar power is possible.

Unvented Hot Water Cylinders – The Future?

An unvented hot water cylinder is much, much more than the answer to a loft converter’s prayer. However, space and the shortage of it certainly seems to be a major consideration most homeowners are confronted with when considering improvements to hot water installations.

The biggest drawback of course with vented hot water cylinders is the need for a water storage header feed tank, usually situated in the loft. There the water sits, waiting to be heated and often exposed to airborne contaminants. In addition, when the time comes for it to work its way into the cylinder for heating and then on its journey to a hot water outlet, it must do so usually under the gentle force of gravity and with a little assistance from atmospheric pressure. The unbalanced pressure between mains cold water and gravity fed hot water can lead to irritating problems. A good head of pressure may be achievable from a header tank in the loft of a three-story building, but flats and single story dwellings will need to install pumps to maintain an acceptable flow rate of hot water.

Added to that, and probably an overlooked factor is the low level of copper contamination leached from the copper cylinder into the heated water. It is probably wise to avoid swallowing it and adding to the other environmental copper sources slowly accumulating within our bodies.

Perhaps, in the days before central heating and cylinder jackets, there was something comforting about that great copper vessel hidden away in the airing cupboard alongside a couple of bubbling demijohns, mushroom spawn and germinating cucumber plants. However, time moves on and brings with it progress and advantages that can revolutionise our way of life.

Unvented hot water cylinders have been around for some time, particularly on the continent. Consequently, they are well tried and tested and for a variety of reasons, very efficient.

There are two types. Direct and Indirect. The direct system is heated solely by two internal electric elements.

The indirect system is heated by an external boiler, although a backup single internal electric element is usually incorporated. The external boiler heats water, which then passes through a copper coil in the cylinder. The heat is exchanged to the water in the cylinder and returns back to the boiler for re-heating. The requirement for heating is governed by a thermostat attached to the cylinder.

An unvented system is connected directly to the mains supply eliminating any need for a header feed tank. This mains supply provides the great advantage of increased water pressure compared to that of a vented system. It also eliminates any need for complimentary pumps to increase hot water pressure.

This extra pressure on the hot water system allows for greater flexibility in the choice of mixer taps and the benefits of being able to install power showers.

On a suitable and well-installed system, very little drop in water pressure is noticed when multiple hot water outlets are operated at the same time.

Because this system operates at a greater pressure than a vented installation, certain modifications are incorporated in the design to accommodate the differences and eliminate potential problems. A device called a balancer is usually installed on the mains inlet to ensure that equal pressure is present on both the hot and cold outlets.

The cylinder itself is generally made of stainless steel and constructed to withstand the extra pressure it is subjected to. The cylinder is also insulated with materials that represent the cutting edge of energy conservation, and as such dramatically reduce the loss of heat into the atmosphere and consequently increase the efficiency of the system.

Hot water expands and in the absence of the expansion route provided by a vented system, the unvented cylinder incorporates either a small external diaphragm water and air operated expansion vessel, or an internal air bubble type expansion facility. One or more tundish safety components are added for extra safety and they also give a visual indication if a heating problem occurs.

Where unvented systems have been installed without proper consideration, the most common problem for homeowners has been that the system does not perform within expected tolerances. An unvented system, operating on mains pressure requires a minimum mains pressure and minimum mains flow rate to operate correctly. This is often not checked prior to installation. An unvented system requires a minimum mains pressure of 1.5 bar and a minimum flow rate of 20 litres/minute.

Where insufficient mains water pressure and flow rates are identified it is possible to acquire an additional accumulator cylinder. This device intercepts the mains supply prior to it entering the hot water cylinder and stores the extra water, conveying additional pressure directly to it so that when water is drawn through the unvented cylinder it is replaced by cold water from the accumulator at an adequate pressure.

The compact and uncomplicated nature of unvented hot water cylinders is also enhanced by a reduced maintenance requirement and a considerable warranty period on the cylinder.

Where space is at a premium they are ideally suited, and compared to the output limitations of room sealed combination boilers, they are likely to be the system of choice. The potential for modification to enable contribution from other external heat sources i.e. solar power is possible.

The Building Regulations Approved Document G (section G3) regulations require that a hot water storage vessel with a capacity of more than 15 litres, which does not incorporate a vent pipe to the atmosphere, should be installed, commissioned, inspected and serviced by a competent person.

Central Heating Thermostats

Energy efficiency is the greatest objective of nearly every environmental and cost conscious household today. Achieving that objective requires the installation of appliances and complimentary devices, which conserve heat, prevent heat loss and extract the maximum amount of output from the minimum amount of input.

From the perspective of looking at achieving greater boiler efficiency, it is interesting to examine how introducing complimentary devices improves the overall operation of the boiler and system.

Modern condensing gas boilers are extremely efficient at producing hot water for heating and domestic use. They supply on demand as and when it is required. With a combi boiler, when a demand for domestic hot water creates a pressure differential in the domestic hot water supply, the boiler senses the differential and springs to life producing almost instantaneous hot water.

The boiler responds to a command.

Like a pressure differential, a thermostat provides a command. The command is either to operate the boiler or to turn the boiler off. It can also command valves to open and close.

Some boilers even incorporate a thermostatic control to command the boiler to operate when ambient temperatures fall below a certain level and act to prevent the boiler and its internal pipes from freezing.

A basic room thermostat will monitor the temperature of its surroundings. It can be set to operate at a certain temperature. If the temperature falls below the desired temperature, it will command the boiler to start. As the temperature rises and exceeds the desired level, the thermostat will instruct the boiler to stop.

This simplistic thermostatic operation forms the basis of controlling the environment that the boiler’s central heating facility is designed to satisfy.

It is also the regulating device that maintains an adequate supply of stored hot water in a domestic hot water cistern.

On very basic central heating systems, one wall mounted thermostatic control is fitted in a cool area of the house, for instance in a hallway, and this becomes a point of temperature reference which informs the central heating output throughout the entire house. To work efficiently, the thermostat must be placed where it cannot be affected by a direct heat source, for example, sunlight or a wall heater. From the remote point, the thermostat is wired to the boiler by discreet cabling. The recommended domestic environment temperature is between 18C and 21C. Unless individual radiators are turned off, all rooms occupied or not will be maintained at the reference temperature.

The introduction of a timer into the system can override the thermostat to disable the boiler at certain times during the day, for instance, overnight or when the house is empty during the day.

The incorporation of a timer into a thermostat provides even greater scope for environment control. Modern digital thermostats can be programmed to operate the boiler to maintain various pre-set temperatures throughout the day and on various days. For instance, the programmer may wish the central heating to come on and heat the house to 18C at 7.00 a.m. when they get up, then reduce the temperature to 14C when they leave the house for work at 9.00 a.m. They may also programme the heating to restore the heat level to 18C at 5.00 p.m. when they return from work and reduce it again to 14C when they go to bed at 11.00 p.m. They can also programme different instructions for the weekend and override all settings whenever they wish.

The installation of wireless digital thermostatic programmers enables central heating installers to add controls quickly without the need for extensive wiring. Some modern programmable devices are capable of ‘learning’ about user habits and the environment in which the device is operating. They can be programmed to provide a set temperature at a given time and they then calculate the time at which the boiler should be commanded to operate in order to satisfy the programmer’s request. Eventually, they can formulate a programme based on the user’s preferences and no longer require programming.

Thermostatic radiator valves (TRV) added to radiators enables householders to set individual room temperatures. The valves are easy to install and can be used in any room other than that which incorporates the main thermostatic control device. These devices require no operating power source and work very efficiently by controlling the rate of flow into, and, therefore, the heat output, from the radiator. They are good at regulating temperatures in rooms where extraneous heat sources, like direct sunlight, heat a room at the front or back of the house whilst other shaded rooms are cooler. They do not work efficiently where radiators are housed in screens or when obstructions are placed in front of the thermostats impeding airflow around the device.

Thermostats, which control motorised valves, can regulate the flow of central heating fluid to various areas and rooms in the house. Three-port valves can supply both the central heating and the domestic hot water supply at the same time.

Advances in thermostatic control have led to the development of Remote Energy Management devices that enable householders to set, programme and monitor their heating systems from almost anywhere in the world. The thermostatic device is connected to the home broadband network allowing Wi-Fi access via smartphone, tablet or P.C. by the householder when they are away from home.

As further advances in technology provide greater control over heat and energy management, the opportunity of benefits to consumers will continue to increase.