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 Fittings and Mountings

The fittings and mountings for domestic boilers are usually dedicated to specific boiler types and individual manufacturer’s boiler models, and as such are produced by the manufacturer and provided with the boiler and the installation package.

Domestic boilers include oil, wood, coal and electric fuel sources and a wide range of different models are available to choose from when considering which type of heating boiler is to be installed.

Coal or wood-fired back boilers are often found in old properties and it is very simple to remove a damaged boiler and plumb in a new one. Fittings are generally plumbing standard.

Oil fired boilers require an external large capacity oil storage tank, and the are usually floor standing. Plumbing and fitting components are generally plumbing standard, however, the boilers are often heavy and large. There are wall mounted oil fired boilers available and these are normally installed externally.

Both these types of boilers can be installed by any person with an adequate knowledge of plumbing and heating techniques, although where electrical installations are complimentary to the system, these should be installed by competent electricians.

Electric heating boilers are usually positioned discretely out of sight, although some which provide only domestic hot water on demand can be wall mounted at the point of use. The mountings should be secure, but as these units are quite light, they do not require the same weight-bearing considerations as those of complex gas condensing boilers.

Because combustion is not a process utilised by electric boilers, neither a flue nor a ventilation requirement is necessary. These boilers can run central heating systems but are considerably more expensive to operate than their gas-burning alternatives. These boilers do require basic plumbing installation techniques.

Electric boilers do not require local authority notification and can be installed by a competent electrician.

Gas boilers are a different matter. Most new gas boilers are wall mounted condensing boilers and although they can be located discretely, they require careful consideration when choosing a location.

For the purpose of flue ventilation, they require an external access point and are usually installed on the inside of an external wall.

The location of the exhaust gas flue is subject to restrictions to prevent nuisance to neighbours and to prevent any possibility of flue gasses re-entering the building. It is possible to locate a boiler externally, subject to the manufacturer’s recommendations.

The boiler installation must comply with BS 5410 and the Building Regulations Part 2. 1997.

From 1 April 2009, it is a legal requirement that gas boilers can only be fitted by a ‘Gas Safe’ registered installer.

The wall upon which the boiler is to be mounted must be surface flat and capable of supporting the weight of the appliance when it is operating full of water. This can be in excess of 100 kg with larger boilers.

The boiler will come with a dedicated template to allow markings of mounting bracket locations to be transferred to the wall. It is essential to ensure that the template is level before proceeding to mark or drill and that the position chosen allows extra area above the boiler for the installation of the flue. The template may also provide markings for a gas and water connection plate. These should also be transferred to the wall. The bracket, when fixed, must take account of the boilers clearance requirements as stated in the installation instructions.

The bracket must be attached to the wall with anchor bolts that are suitable for the wall’s construction material and the weight of the boiler.

Once the gas and water connection plate has been attached to the wall, the water and gas can be connected to the plate. The connections are standard starting left to right: heating supply, domestic hot water, gas, cold water and heating return. The manufacturer’s instructions will clearly indicate which service is required to each connection point.

When attaching the boiler to the gas supply, the correct fittings must be installed to prevent any unwanted drop in gas pressure.

A connection plate allows other trades to complete installation procedures prior to the hanging of the boiler onto the mounting bracket and final connection of the boiler.

In the absence of a connection plate, the plumbing can be made straight to the boiler directly.

Plumbing and pipe-work will be dependent on the system the boiler is designed to supply.

It is also a wise precaution to install service valves to the pipe-work to aid future service and maintenance procedures.

A drain, or the access to one, is also a requirement to accommodate pressure release valves and condensate drainage.

The positioning and installation of flue gas and air intake pipework should be in accordance with manufacturer’s instructions. Some of the components for this may not be included in the boiler installation kit. This is because variations in the flue gas assembly are dependent upon legal requirements, location, and circumstances and are generally constructed to individual requirement.

The electronics are usually the final connections to be made to the boiler. These will include room thermostats and system programmers. Other sensors may require additional connections, including mains water supply sensors and low water cut-off sensors.

Finally, the boiler can be attached to the mains electricity supply which will power all the electrical components and the boiler can be commissioned.

The connections of the electronic components and the connection to the mains supply require the skills of a competent electrician.

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.

Replacing a Boiler Expansion Vessel

Before considering the repair, replacement or modification of any parts on a boiler, it is a wise precaution to check warranties, service and maintenance contracts and insurance policies to establish whether the work is covered by them, sometimes contrary to an engineer’s advice.

Also, consider whether any repairs carried out on parts that are not covered by warranties might invalidate the warranties if performed by engineers or companies other than those that may be specified by the contracts.

Combi boilers operate using a sealed or pressurised system. Because water expands when heated, an expansion area must be incorporated into the heating system. On a combi boiler, this is usually encased within the boiler housing. It comprises of a vessel with an internal area divided by a flexible membrane. On one side of the membrane is compressed air. On the other side is the central heating fluid. The expansion vessel has a Schrader valve on the air-side where air can be pumped into that part of the vessel to maintain a suitable resistance to the water expansion. This maintenance pressure is usually around 1 bar.

When the heated water in the central heating system expands, it cannot be compressed and consequently presses against the expansion vessel’s internal membrane. This flexible membrane, in turn, distorts to apply a corresponding force on the encased air on the opposite side of the vessel. As air can be easily compressed, the air takes up the expansion volume of the hot water preventing unwanted and dangerous expansion in the heating system.

The expansion vessel in a combi boiler is generally fitted to the central heating return section within the boiler housing. The main problem with expansion vessels is that over time, the diaphragm can deform or even split.

The usual indication of problems with an expansion bottle is a rise in operating pressure registering on the boiler pressure gauge when the heating is operating. A continual increase in pressure will cause the pressure release valve to operate. This will totally remove pressure from the system and consequently, the boiler will most likely shut down. The system will then need to be refilled.

It is a wise precaution to check that the fault with pressure does not lie with a faulty pressure release valve.

Very occasionally, a loss in operating pressure is due to a damaged heat exchanger. If there is any doubt about what might be causing a loss in operating pressure, professional advice should be obtained.

When working on a boiler, the appliance must be disconnected from the electricity supply.

To check an expansion vessel locate the Shrader valve and depress the inner spindle with a pointed object. If water drips out, then the internal diaphragm has probably either perished or ruptured and is consequently defunct.

If only a faint hiss of air or nothing at all is expelled, then it may be that the compressed air side of the diaphragm has lost its pressure charge. The vessel can be recharged using any form of an air pump and attachment. It should be recharged to 1 bar. It is important to reduce pressure in the central heating system prior to attempting to recharge a vessel via the Shrader valve. It would be wise to check the Shrader valve after recharging by putting some washing up liquid on the valve end and checking for bubbles. If all is well, the problem will very likely be solved. However, if the diaphragm has become too distorted by the vessel having an inadequate air pressure, the capacity for expansion may have been reduced significantly and the heating system will operate inefficiently.

Where a ruptured or inefficient vessel has been identified, there are two choices. Either replace the vessel in the combi boiler or fit an external expansion vessel on the heating return pipe as close to the boiler as is practical.

Fitting a new internal expansion vessel into a boiler is quite an expensive business. It can be time-consuming and should be done by a Gas Safe registered engineer. This is because complex system parts of the combi boiler may have to be removed to access the vessel and sometimes the boiler will need to be removed from the wall. This involves disconnecting the flue, which can pose difficulties when refitting the boiler.

On the other hand, fitting an external expansion vessel as an alternative is a relatively simple procedure. As a Do-It-Yourself task, it is quite inexpensive and can be done relatively quickly with the minimum of disruption.

External expansion vessels can be purchased fairly cheaply, generally for around £40 depending upon the required capacity. This capacity should be established prior to purchase. The information can be obtained from the boiler manufacturer’s handbook relating to the operating capacity of the central heating system.

External expansion vessels are usually pre-charged on the air pressure side of the appliance and simply need fitting into the system. Couplings and copper pipework will be required to enable the vessel to be plumbed into the 15 mm central heating hot water return pipe.

The external expansion vessel should be securely wall mounted and plumbed as near to the boiler as possible, but due to its large size, should also be installed in a practical and unobtrusive place away from any risk of causing obstruction or injury to householders and damage to the vessel.

The central heating system will need to be drained prior to installation.

The new external expansion vessel should be plumbed into the system in such a fashion that it cannot be isolated from the heating side. It must always be an integral part of the system.

Once fitted, the system can be re-filled and operated normally. Do not forget to add inhibitor when re-filling the system. Also, check for leaks and airlocks.

The damaged and non-operational expansion vessel is left in-situ in the combi boiler and will not impede the normal operation of the boiler and system.

If the pressure relief valve has been operating prior to the installation of a new expansion vessel, it is probably wise to replace the valve.

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.

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.