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.

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.



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.


Notification of Gas Work


Imagine the scenario. You’ve had your property on the market for a considerable period. Now you have finally found a buyer and also the house of your dreams. Then your solicitor informs you that there is a problem with the new property’s gas installations in respect of Local Authority notification and the Building Regulations.

The Building Regulations require that in England, Wales and Guernsey, certain controlled building services have a mandatory requirement of notification to the relevant Local Authority. The controlled services include the installation of gas appliances, namely, boilers, water heaters, warm air heaters, gas fires, flue dependent cookers and heating systems.

In Northern Ireland and Scotland, there is no mandatory notification requirement, however, homeowners can obtain a Declaration of Safety Certificate that can reassure possible purchasers that a competent person has installed a gas appliance.

The term ‘competent person’ is key to obtaining a Building Regulation Compliance Certificate. Although it is quite possible to seek approval for gas installations from the Local Authority directly, the process of inspection and authorisation required to comply with certification can prove costly.

An installer registered with a Competent Person Scheme is qualified to carry out specific types of work in accordance with Building Regulations, and will usually deal with all building control issues on your behalf. A registered competent person is authorised to self-certify certain completed gas installations. This has the advantage of significantly reducing the cost of obtaining your own Local Authority notification.

For gas work notification and competent persons, Gas Safe registered engineers are the only persons legally permitted to install gas appliances and consequently issue self-certification to comply with the Local Authority requirements under the Building Regulations.

Although Gas Safe registered engineers are professionally obliged to notify the Local Authority, compliance with Building Regulations requirements is ultimately the responsibility of the property owners. As non-compliance can incur considerable inconvenience and a hefty fine of up to £5000, it is in the homeowner’s interest to ensure that a Building Regulation Compliance Certificate is issued by the Local Authority. The certificate relates solely to the property and should be kept safe. A Gas Safe engineer should notify the Local Authority within thirty working days after completion of the work.

Where a Gas Safe registered engineer fails to notify the Local Authority in accordance with requirements, the homeowner should complain to Gas Safe. They will issue instructions to the registered engineer to submit the notification, but they have no powers of enforcement.

All too often property owners are unaware of statutory requirements and are easy prey for rogue gas fitters. It is an inevitable fact that a Competent Person Registration Scheme, particularly the one operated by Gas Safe, can deter unscrupulous engineers from alerting the register to completed gas installations. This is because Gas Safe, operating as a central database of completed installations requiring Local Authority Buildings Regulations Compliance Certificates attracts the attention of HMRC.  This means that  some engineers and businesses can be investigated on suspicion of  tax evasion.

Of course, any database of information similar to that used by the operators, Capita PLC in respect of Gas Safe, is bound to be of interest to the big companies, particularly those who manufacture gas appliances and the energy providers. Notifications lodged with the details of an engineer’s customers and their addresses are quite valuable. Some engineers feel that passing their customer’s information back to Gas Safe might be a little unethical.

Such issues aside, although compliance with Local Authority and Building Regulation requirements can seem bureaucratic, there can be no doubt that stringent regulations are in the customer and consumer’s best interests. Where gas safety is the priority, professional and competent installations are a necessity in avoiding the consequences of poor, unqualified and dangerous workmanship. Too often the drive to cut costs in a very competitive market results in corner cutting procedures that lead to extensive problems at a later date.

Where a problem with Building Regulations relating to gas installations becomes identified during a property sale, the issues can be resolved. The absence of a Buildings Regulation Compliance Certificate does not necessarily mean that the Local Authority has not received notification. A request can be made to the Local Authority to confirm compliance and a replacement certificate can be purchased.

Where no notification exists and the installation contravenes Local Authority and Building Regulation requirements, it is the responsibility of the property owner to remedy the situation. Depending on the nature of the installation it is possible to get a Gas Safe registered engineer to re-commission an appliance and obtain the necessary documentation. Whether the Local Authority pursues the matter further in respect of the previous non-compliance is a matter of their discretion.

Alternatively, the property purchaser may apply to have appliances checked over by a Gas Safe registered engineer to ensure that they are safe and with no at risk issues. They can also obtain a gas safety inspection certificate.

The lack of any required Buildings Regulation documents or failures of notification can cause considerable delays in exchanging contracts during property sale procedures. Costs can escalate when seeking confirmation and the property value can be reduced in favour of the purchaser to accommodate any remedial requirements.

Gas and other Energy Saving Tips

Although recent world-wide gas and oil commodity prices have seen unprecedented falls, as North Sea gas supplies start to dwindle and the United Kingdom is obliged to compete with a growing demand for gas on the global markets, it would seem that the long term outlook for household energy bills is likely to forecast sharp price increases.

More and more, householders are being forced to examine their fuel usage and look for ways to economise and live within their tight budgets.

However, economizing is not necessarily a euphemism for austerity. On the contrary, it is more about using energy sources wisely and efficiently. It is about extracting as much benefit as possible from each hard-earned pound spent on fuel and minimising expensive waste.

It can also be quite encouraging, especially when using energy usage monitors. It is very satisfying to watch domestic fuel consumption drop in response to a few minor changes to the home and to the occupant’s behaviour.

Energy saving appliances are all well and good but the way they are operated has a greater bearing on economy than might be imagined.

Likewise, loft and wall insulation coupled with triple glazing may help to prevent heat dissipation through the fabric of the home, but it will not prevent draughts from unshielded keyholes or open fire chimney vents from sucking that expensive heat into the cold outdoors.

So, if you have uncovered a previously boarded off fireplace and discovered a rustic Victorian cast iron focal point, make sure the chimney is capped off or buy a dedicated chimney balloon that inflates to fill the gap.

Fit letter box brushes, keyhole flaps, check door seals and ensure that the traditional wooden floorboards and old skirting boards that have been revealed to add character to your home are sealed to plug gaps. Warm coloured fitted carpets are good insulators. Seal the gaps where pipe-work exits through walls, however, take care not to block any air vents.

Good, heavy and thickly lined curtains, properly hung, are excellent insulators but during even the coldest day, the sun is a great source of extraneous heat so let the sunshine in.

Fitting reflective foil behind radiators can prevent heat being lost through walls behind them.

Move furniture around so that you are not sitting next to exterior walls.

A tropical living environment is great for shorts, T-shirts, iced beer and lethargy, but not so forgiving on the household fuel budget. Thermals, chunky polo neck sweaters and cups of steaming tea are far more nostalgic, as is dropping the thermostat a few degrees to bring back an equally nostalgic and retro style fuel bill.

A cool bedroom is great for a good night’s sleep. An electric under blanket ensures a cosy bed to fall into no matter how cold the weather is outside.

Upgrade central heating controls and install a multi-function programmer for a more dedicated system of home heating management.

Gas as a fuel is considerably cheaper than electricity. Solar, wind and heat accumulation sources are currently free. It is therefore advantageous to invest in technology to exploit these natural resources to compliment gas and electrical energy consuming appliances.

When cooking on a gas or electric hob, anything cooking in boiling water is immersed in that liquid at 100C. It does not matter how high you turn up the regulator setting, the water in the pan will never rise higher than boiling point.
Any extra heat surplus to that required to maintain a gentle, rolling boil is energy wasted. A flame or heat source that extends beyond the circumference of the base of the pan is also wasted energy. Make sure the gas flame is crisp and blue. Yellow colours indicate inefficient combustion.

Pilot lights can use 40% more energy than electronic ignition.

Putting lids on pans and using pressure cookers saves time and energy usage. Try turning off cooking appliances a few minutes before food is ready and allow cooking to continue on the residual heat. Oven doors rack up the running costs when opened frequently during cooking. A quick peek can drop the oven temperature by 20%. Keeping the glass viewing front clean will prevent the need to open the oven door.

Likewise, excessive opening of fridge and freezer doors when pondering or grazing, gnaws away at energy efficiency targets.

Low flow shower heads and reduced time showering can make a big difference to hot water usage. So can fixing dripping hot taps or refraining from washing and rinsing under a flowing hot tap.

Washing machines will now operate effectively at much lower temperatures due to the introduction of low temperature washing detergents. A full load is the most economical way of operating the machine.

If a hot water cylinder is installed in the property, setting the thermostat to 50C can usually satisfy the temperature requirement of the domestic hot water supply. An adequately insulated cylinder will also conserve the temperature of the heated water.

Keeping the boiler and central heating system in top condition is a must for ensuring gas is utilised efficiently. Anything that impedes the efficiency of the system is likely to reflect quite dramatically on the energy bill. Small inefficiencies combine over a short period to inflate energy costs and most of these can be rectified or eliminated quite easily.

Reducing energy costs can become a healthy compulsion and with practice, may eventually lead to the disconnection of the energy monitor itself, thus saving a few operating watts of electricity and representing the epitome of gas and energy efficiency.

Boiler Emissions

Unless you have direct access to a renewable energy source or nuclear power then the chances are you are going to have to rely on a supply of fossil fuel to heat your home. Your electricity might be ultra clean at the point of using it, but most of its generation, some distance away, will have depended upon the combustion of a fossil fuel, and by the time you get to use it a great proportion of the energy used to create and distribute it will have been lost. In the great scheme of things, electricity generation and distribution is a rather inefficient process.

If your central heating system is powered by a fossil fuel, or for that matter any combustible fuel, then you are going to have to employ the process of combustion to release the energy from the fuel to distribute around your home.

Whichever way you look at it, combustion requires a gas and a heat source. It does not matter what material the combustible fuel is, it will only burn as a gas. It also requires another gas, oxygen which is a component of air to complete the process.

If your central heating is powered by coal or oil, then you are going to have to provide a substantial amount of heat to generate and maintain the release of a gas from the fuel source to facilitate combustion. The purpose of the boiler is to burn the hydrogen in the fuel with oxygen from the air to produce heat.

For a boiler running on gas, the process of having to create a gas is eliminated, although, with bottled gas, the fuel is a liquid under pressure, which is allowed to boil at normal air pressure to revert to its gaseous state.

This is one of the reasons why a gas boiler is extremely efficient. The flammable gas being utilised as a fuel simply requires a source of ignition. A pilot light or a spark will generate a heat source of around 1500 degrees Fahrenheit, which is in excess of the 1100 degrees Fahrenheit required to ignite the fuel.

The other component in the combustion process is oxygen, which makes up about one-fifth of the composition of air.

Combustion will provide the energy you require to heat the water and the by-products of the process are vented through a flue.

It is the availability of oxygen, which is the crucial factor in the combustion process because inadequate combustion will produce emissions other than carbon dioxide (and water). These extra by-products of incomplete combustion can be particularly noxious. Incomplete combustion also significantly reduces the efficiency of the boiler.

A combustion efficiency analysis is an effective way of determining how efficiently a boiler’s combustion process is operating. By knowing the chemical composition of the fuel and measuring the flue gas temperature and either the oxygen or the carbon dioxide levels in the flue vent, the boiler efficiency can be calculated.

The flue gases and temperature are taken with an electronic analysing device pre-programmed to undertake the required calculations. The probe of the device is inserted into the flue area of the boiler in accordance with the boiler manufacturer’s instructions. The post-combustion gases and temperature are analysed and a digital readout is produced. Some analysers allow a hard copy printout to be produced directly. Most boilers are capable of a combustion adjustment operation to improve combustion where an analysis reveals an inadequacy.

It would be impractical to expect to achieve perfect combustion where oxygen levels in the flue gave a reading of zero and flue gas temperature was very low. There are too many variable factors that can influence combustion. However should the combustion process become affected by too little oxygen, the process can become fuel rich and this can cause excess production of carbon monoxide and a possibility that unburned gas could cause an explosion outside the combustion chamber.

An acceptable oxygen reading in the flue should be between three and five percent.

There are other by-products of combustion that can cause problems. Oxides of nitrogen and sulphur can be problematic, as can the particles of soot and other unburned hydrocarbons. These should be minimised by adopting a comprehensive programme of boiler maintenance and regular testing.

Adequate flue ventilation is vital and consideration has to be undertaken when deciding where to position a flue to prevent the by-products of combustion re-entering the home or adjoining properties.

Modern condensing boilers produce another emission. Condensing hot gases and water vapour produce an acidic solution which must be drained into an external drainage facility. Because of its acidic composition, ensuring that the drain connects with the waste domestic or surface water drainage system will dilute the acid and reduce the potential for corrosion.

With older gas boilers and unvented gas appliances, it is important to ensure that an adequate supply of air is available to provide good combustion and also facilitate a good flow of air through the property to remove by-products of combustion such as carbon dioxide, carbon monoxide and of course, condensation forming water vapour.

Gas boilers should burn gas to produce a crisp blue and very hot flame. This can only be achieved by monitoring and good maintenance. Fine-tuning will ensure that boiler emissions are kept within legal and acceptable tolerances, safe operation is maintained and that energy is consumed in a highly efficient manner.

Weather Compensators

The introduction of gas fired condensing boilers marked a great step forward in significantly reducing domestic gas consumption and improving energy efficiency. The corresponding savings in domestic energy costs has helped to stimulate an increasing awareness of environmental issues, and a growing industry is developing to provide practical solutions to maximise efficiency.

Gas can longer be perceived as an infinite commodity. The need to prolong the availability of fossil fuels in a world of growing demand is quite evident. Such demand and scarcity have created record global prices and forced governments to look closely at their energy supply and security issues.

Home-owners continue to look for devices that can further improve the energy usage and efficiency measures already installed within their own homes.

Where a condensing boiler has been installed, the fitting of a weather compensator can modify the central heating operation to ensure that the benefit obtained from the condensation of flue gases is maximised.

A weather compensator can also improve comfort levels within the home.

Most condensing boilers are able to utilise the weather compensating technology. Some have it fitted as a standard built in part of the boiler construction and complimented by an external sensor.

Weather compensating devices are small, sensing units that are fitted externally, ideally to a north or north-west facing wall. This position is to prevent solar gain from the sun’s east-west and southerly direction affecting the unit’s operation. The weather compensator is wired up to the boiler’s internal controls.

Weather compensators work by monitoring the external temperature. They are in constant communication with the boiler and relay information about the current weather conditions to it.

By monitoring the external temperature, the weather compensator is predicting how the external temperature will affect the internal temperature of the property.

Heat generated by the boiler and distributed through the central heating system gradually dissipates through the walls, windows and roof into the atmosphere. Good quality insulation and draft exclusion measures can reduce the rate at which this heat loss takes place. However, it is this gradual heat loss that necessitates the need for the boiler.

When a drop in room temperature is sensed by the room thermostat or radiator TRV’s, these devices instruct the boiler to operate. However, the boiler’s response is to operate at full capacity until the room temperature rises sufficiently to cause the thermostatic devices to operate again. When the boiler receives the thermostat’s signal that the room’s pre-set temperature has been reached, it turns itself off.

Although this process is very efficient, for a condensing boiler the operation is not as efficient as it could be.

This is because the boiler is responding solely to the internal room temperature. The boiler has to supply hot water until instructed by the thermostat to stop, often operating to give more frequent, short bursts of heat than necessary and overshooting in its attempt to play catch-up when trying to maintain a steady room temperature.

However, the internal room temperature is affected by external environmental conditions. When the weather outside turns cold, the heat loss through the walls is greater. When the walls and other external surfaces are cold, heat dissipates through them much faster.

Conversely, when the external temperature is mild or warm, heat within the property is retained for longer.

In order for a condensing boiler to operate effectively, hot water returning through the central heating system must be below 57 degrees centigrade to allow flue gases to condense efficiently. Efficient condensation allows the latent heat contained within the flue gases to be collected and conserved within the system, rather than being lost.

Hot bursts of energy as a response to thermostatic commands often results in central heating fluid return temperatures too high to allow an effective condensation process to take place.

Weather compensators act as a prediction device warning the boiler that either a falling or a rising temperature will affect the building’s capacity to maintain a predetermined internal temperature.

When the weather starts to turn cold, the weather compensator communicates the rate of lowering temperature through its constant communication with the boiler.

Being, as it were, forewarned, the boiler starts to operate at a lower temperature, earlier than it would by thermostatic control alone. This has the effect of compensating for the slow dissipation of heat from the building.

Conversely, in milder temperatures, the boiler will turn itself off or run at a much lower temperature in response to warmer external temperatures long before the internal thermostats register the drop in heat requirement.

This process causes the boiler to operate at lower temperatures and helps to ensure that the returning central heating fluid is at a temperature below 57 degrees centigrade more frequently than would otherwise be the case. This helps to maximise the condensation heat exchange process.

Although a weather compensator can make boiler operation very efficient, householders may take some time to adjust to the situation of having cool radiators during freezing weather. Most people associate cold weather with having radiators that are too hot to touch. However, the objective of using weather-compensating equipment is to maintain a comfortable and stable internal room temperature.

Hot spots caused by very hot radiators are eliminated, as are sudden peaks and troughs in energy demand.

The weather compensator helps to maintain a steady constant room temperature rather than allowing the boiler and thermostats to continually function by responding to variations in room temperature.

However, getting used to cooler radiators that maintain a good steady room temperature may only be of long-term concern to households who have become accustomed to drying their washing on super-heated radiators.

In the long term, people who fit weather compensators report an improvement in the maintenance of comfort levels within the building and a more than welcome reduction in energy usage and the subsequent cost.

Weather compensators are relatively cheap to fit and once installed and pre-set to user requirements require little or no maintenance. They should be left to work without any consumer interference, other than the operation of an over-ride facility should the need ever arise.

Before investing in the purchase and installation of a weather compensator, the homeowner should consult the boiler user manual for particular specifications. Not all homes will get the full benefits from the installation of a weather compensator.

What To Do If You Think You Have A Gas Leak

If you are certain, or you have good reason to suspect that, you have a gas leak you should immediately turn off the gas at the domestic mains supply. Householders might wish to make themselves aware of where the property’s mains supply meter and shut-off valve are located to allow them to do so should the need arise.

After turning off the mains gas supply, the windows and doors of the property should be opened to vent the accumulated gas. During this period, it is crucial to avoid using equipment that might produce an ignition spark. You should then contact your energy provider for further advice. They are obliged to attend free of charge.

If you do not know how to turn off the supply, and gas is leaking from a fractured pipe or a damaged appliance which cannot be isolated, you should remove yourself and others from the property and phone 0800 111 999. This is a 24 hr emergency number. Do not operate a mobile or conventional phone from inside your property. Any electrical spark or other forms of ignition may cause an explosion.

Gas, used under the correct procedures and with modern well-maintained appliances is a very safe fuel.

However, natural gas itself and other gases formed because of combustion, incomplete combustion and inadequate ventilation are dangerous and can kill or seriously injure people who are exposed to them.

Natural gas can cause injury and death on its own simply by displacing the air in the property, or by ignition and explosion of concentrations of the gas in the air. A concentration of only five percent is sufficient.

Although natural gas itself is odourless, a distinctive and instantly recognisable sulphurous odour, called mercaptan, is added to the gas to aid its detection and indicate its presence.

Should you ever need to check gas pipe joints or connections for evidence of leaking gas, a mixture of water and detergent sprayed onto the area would indicate leakage by forming bubbles and foam.

A slow and almost unnoticeable natural gas leak can cause illness over time and any unexplained symptoms that only occur whilst residing in the property should be investigated.

Natural gas leakage is not the only gas leakage to be aware of. Carbon monoxide, as a by-product of the combustion process is normally safely vented through a flue into the outside atmosphere. If the flue becomes blocked, this gas can escape back into the property.

The problem with carbon monoxide is that it is odourless. Because of this, the occupants are often not aware of its presence. Although symptoms of nausea, headaches and dizziness are classic, these symptoms can easily be ignored or passed-off as general illness. Carbon monoxide in high concentrations can be lethal in seconds when inhaled and occupants can succumb before they are able to escape from the property. Slow, prolonged exposure can cause irreversible brain damage.

If there is any suggestion of carbon monoxide poisoning, affected occupants should seek urgent medical attention. A blood test will confirm exposure.

Potential problems with gas can be eliminated by professional installation combined with regular service and maintenance procedures. These should be carried out by Gas Safe Registered Engineers. Always ask to see their I.D. card.

If you are a tenant of the property, it is the landlord’s legal responsibility to ensure that gas appliances are maintained appropriately.

Vigilance by the occupier is also a good method of avoiding potential problems. The observation of gas flames on cookers and boilers burning with yellow or orange flames, pilot lights frequently blowing out, brown scorch marks on appliances and unusual amounts of condensation on windows are a good sign that something may not be right and that further investigation is required. Appliances should also be checked for any signs of wear and tear that could impede their efficient operation.

These indicators should not be ignored or passed-off as being due to the age of the appliances. All flames on appliances should be crisp and blue. This is a sign that the required amount of oxygen is available and that combustion is complete.

The fitting of a carbon monoxide alarm is essential. This should carry a recognised Kite Mark or similar EU standard and be marked EN50291.

If the detector is battery operated, its operation should be checked regularly. Some detectors warn by a visual colour change, but it should be noted that most carbon monoxide fatalities occur during sleep. An audio warning is far superior.

It is worth remembering that carbon monoxide is not only a by-product of natural gas combustion. Any combustion of fossil and solid fuel produces poisonous gas by products, including carbon monoxide.

The proper and adequate ventilation of the by-products of combustion through dedicated and regularly serviced flues and vents can prevent most problems occurring.

The use of any energy source incorporates a risk of injury to the user. Being aware of the risks and the measures that can be taken to minimise that risk are important factors in maintaining the safe operation of appliances.


Automatic Air Vents

There is nothing more disturbing than the banging and gurgling noises that can issue from boilers and the hot water systems they supply. Often the noise is caused by air in the system. This can be air that has entered the system during repair or maintenance procedures, or air that is entering the system regularly and causing unacceptable operating noises. Regular addition of air into the system can be indicative of a general fault in the design, layout or operation of the system.

Automatic air vents (AAV’s) are handy devices that can be fitted to automatically expel air from hot water systems.

Most boilers incorporate some form of AAV, often concealed below the external casing, and therefore out of reach of any DIY or unregistered installer. However, these devices may not remove air trapped within the wider hot water system.

In these situations, the fitting of an AAV in the circulatory network may alleviate the effects of the problem. Bungalows and single storey dwellings, where insufficient head of pressure can sometimes allow air to enter into the hot water system, will benefit considerably from the fitting of an AAV.

Although a number of companies manufacture domestic AAV’s, the general principle of valve operation for inline valves is much the same. The valve is installed into the hot water system at the highest point.

This highest point must be on the positive sides of any water pump. This can be identified by locating the pump and establishing the direction of flow. This will be indicated by an arrow, usually cast into the pump housing.

Fitting an AAV on the opposite side of the pumped flow can result in air being drawn into the system by creating reverse pressure in the valve. This will naturally compound the problem rather than alleviate it.

There is often a part of the system that crosses from one point to another by virtue of an incline followed by a decline in the pipes horizontal plane. It is at the apex of points like this that air is likely to congregate and in some cases severely restrict or prevent water flow.

This is an ideal location for the installation of an AAV. To maximise operation, the AAV should be plumbed into the system by inserting a ‘T’ piece joint into the main pipe-work and providing a few inches of vertical pipe between the valve and the main pipeline. This vertical pipe will ensure that a suitable pressure of air builds up to push water back down this pipe and cause the valve to function efficiently.

The valves contain a float mechanism that allows air to be expelled. The float contains air that provides buoyancy allowing the float to sit on top of the water surface contained with it in a chamber. Because air will collect in the highest point of a system, air enters the chamber and displaces the water. This causes the water level in the chamber, and the float, to fall. As the float drops, its attached mechanism opens a valve to release the air. As the air disperses, the water level rises in the chamber again, raising the float and closing the valve.

The valve also incorporates a closure nut at the external outlet of the air release valve. This can be manually operated to close the valve in the event of it becoming faulty and starting to expel hot water. This can be caused by sticking float or valve seal. Routinely giving the valve a sharp tap with a hammer will help to prevent an infrequently operating valve from sticking.

Although many AAV’s claim to have an inbuilt sealing device to close off the circuit and allow the valve to be removed for servicing, it would most unwise to rely on it. It is better to turn-off the boiler and pumps and release any pressure prior to removing an inline AAV.

In a central heating system, trapped air in radiators is usually released through the bleed valve located on each radiator. A build up of air, and other gases, can become a frequent occurrence on some central heating systems leading to inefficient operation. Radiators are often cold at the top and air in the system can accelerate corrosion in the radiators dramatically reducing their lifespan. This is particularly so where inhibitor has not been added regularly and central heating maintenance schedules have been disregarded.

Where the frequent necessity of radiator bleeding has become onerous, small AAV’s, particularly designed for individual radiators can be fitted.

These devices can be readily purchased from most DIY and plumbing merchants, usually for around ten pounds.

Fitting these devices is generally straightforward. With the heating and pumps turned off, and the system cool enough to work on, each radiator should be turned off at the inlet valve and the lock-shield valve. The lock-shield valve is located at the opposite end of the radiator to the inlet valve and is usually operated by removing the white cap and turning the exposed spindle with a spanner or set of grips.

Before attempting to fit the device, any pressure in the radiator must be released by operating the radiator bleed valve.

The AAV can be installed by removing the bleed valve and directly replacing it. Many people prefer to leave the bleed valve installed and simply attach the AAV by removing the locking nut at the opposite end of the radiator to the bleed valve and fitting the AAV there. Because many radiator AAV’s contain check valves to prevent air being drawn into the system, leaving the bleed valve in place allows for easy operation if the system requires draining.

Once installed, the system and pumps can be turned back on and a hissing sound should issue from the AAV indicating that trapped air is being expelled. Once the air is removed, the AAV should automatically close to prevent central heating fluid escaping.

Before working on radiators, sufficient precautions must be taken to catch any spills of central heating fluids, which can irreversibly stain any materials they come into contact with.

If, after fitting an AAV on a radiator, air remains in the radiator, it may be due to too much air preventing the AAV operating at all. This can be remedied by turning off the boiler and pumps and removing the AAV. Then, by turning on the pumps, water will fill the radiator expelling any air. As soon as water dribbles from the fitting point, the AAV must be quickly replaced.

Fitting an AAV will remove air from a hot water system. Re-occurring problems with air in the system should be investigated to determine the cause.

Sometimes the water supply simply contains too much air when it is supplied to the property. This can often be caused by extensive maintenance work carried out by the utility company and may be a temporary but irritating situation.

Excessive quantities of air in the system may indicate a potentially serious problem with the boiler or the water supply and professional help should be obtained to prevent damage to the system.


Avoiding Frozen Condensate Pipes

Few people who had a condensing boiler at the time will ever forget the severe winter of 2009/2010. Temperatures dropped to minus twenty degrees centigrade in some areas. That winter revealed a flaw in the generally accepted principle of fitting condensing boiler condensate disposal pipes externally.

An external condensate pipe might have withstood the rigours of that un-typical winter had it been sufficiently insulated. As it was, few condensate pipes were insulated and they subsequently froze.

As a result, condensate could not escape from condensing boilers and backed up into the boiler causing temporary boiler shut down. This resulted in hundreds of calls to boiler manufacturers and heating engineers requesting call-outs to malfunctioning boilers. Good news for heating engineers, but bad news for boiler owners who had to stump up for the cost of the call-out to defrost their condensate pipes.

As a result, and in anticipation of the possibility of further severe winters caused by global warming in the future, installation recommendations for boiler condensate drainage systems were modified.

It is now recommended that, wherever possible, the location and routing of condensate pipes should be internal rather than external.

For home-owners considering the installation of a new condensing boiler, the connection to a suitable internal drainage point is something that can be arranged at the planning stage. The location of a new boiler has to take into account a number of factors including condensate drainage. The convenient connection to services, existing central heating networks, the exit for the flue and the direction of the plume are all major considerations that must be addressed prior to installation.

Where a heating engineer is contracted to install a new condensing boiler, the necessary and suitable connection of the condensate drainage requirements, in line with the boiler manufacture’s recommendations, should be a part of the installation package. The condensate pipe-work must also comply with The Building Regulations, (Drainage and Waste Disposal) requirements. It is important to check with the boiler installer that installation contract covers all the necessary requirements prior to commencing work.

A boiler can produce up to four litres of condensate daily, and this can be directed into a number of internal drainage points. Internal soil and vent stacks, sinks, showers and washing machine drainage pipes are all feasible outlets. However, due to the acidic nature of the condensate, pipes must be of a suitable plastic composition. Condensate typically has a pH of between three and four, making it about as acidic as orange juice. Nevertheless, over time this can corrode metal and any other susceptible material it comes into contact with. Copper pipe-work is particularly vulnerable to the corrosive properties of boiler condensate and should never be used.

All condensate connections to internal drainage points must be in-line with Building Regulations. Gravity fed condensate pipes must comply with minimum fall angles and drain into the nearest possible outlet. Pipe diameters are also a regulated aspect.  The fitting of condensate drains into pipes containing visible air breaks, or traps, or the installation of such devices that create them is an important regulatory condition that must be met. Many boilers incorporate internal traps to prevent flue gases being expelled inappropriately. These will not prevent odours from drainage systems entering the property. The incorporation of condensing pipes into drainage systems at a suitable point does require some sort of trap to be fitted.

When condensate cannot be removed via a gravity fed installation, for example, where a boiler is to be located in a basement and a drainage point is higher than the boiler, dedicated pumps must be installed to facilitate drainage. Installing a condensing boiler without a suitable drainage facility for the condensate will render the boiler unsafe and it should not be operated.

Where condensate is directed into an external drainage point, such as an external stack or a gutter down-pipe connected to the sewage disposal system, the condensate pipe must be insulated at any external points. An air gap must also be maintained.

If it is absolutely impractical to install an internal boiler condensate drainage system, the home-owner must be advised about the problems associated with external condensate drainage pipes. It is not acceptable to fit an external condensate drainage pipe simply out of convenience.

Boilers that work on a siphoning process of condensate drainage are better suited for external condensate drainage. These boilers allow condensate to be expelled in short gushes, rather than continuous drips. This reduces the potential for a gradual build up of ice in freezing conditions and the eventual blocking of the pipe.

The technical requirements for condensate pipe installations are given in BS 6798:2009 and also in the individual boiler manufacturer’s handbook.

For existing boilers with external condensate pipes already in place the situation is a little different. If the boiler is a recent installation and still under warranty, it may be possible to have an external condensate pipe re-routed internally free of charge.

For existing external condensate drainage pipes and ones that have been installed due to practicalities, adequate pipe insulation is essential. No external condensate pipe over three metres should be left unprotected. Insulation must incorporate a waterproof layer to prevent rainwater entering the insulation material and freezing in contact with the pipe. Care should also be taken to ensure that where the drainage connects to an outside drain, an air gap is maintained above the surface level of the drain to prevent the pipe blocking if the drain freezes. Similar consideration should be given to dedicated soak away systems.

It is also possible to purchase electric thermally controlled pipe heating material. This wraps around external pipes and is activated by cold weather. When a minimum external temperature is detected, the material heats up preventing the condensate pipe freezing.

Maintaining boiler operation in freezing external conditions is essential. Boilers that are located in garages or lofts may be particularly susceptible to failure in bad weather if they are not sufficiently protected from frost.

A frozen condensate pipe will prevent a boiler from operating. Although defrosting the condensate pipe will re-activate the boiler, the inconvenience of having to do so can be avoided by careful planning and taking suitable precautions.