SA AC REGIONAL 1 © STROMA CERTIFICATION LTD v1.3 Energy Performance Certificates Heating PRESENTED BY

SA AC REGIONAL 1 © STROMA CERTIFICATION LTD v1.3

Energy Performance Certificates

Heating

PRESENTED BY


LEVEL 3 BUILDING SERVICES TRAINING

– HEATING SYSTEMS

There are many varied forms of introducing heat to occupied areas, this guide will detail the most common forms of heating system likely to be found in buildings suitable for a Level 3 assessment.

To have an improved understanding of the types and operation of systems, some definitions require to be addressed



Direct & Indirect Heating Systems

Direct Systems

These are where the fuel is burned directly to give heat output, for example gas fired unit heaters, electric panel heaters, gas fires etc.



Indirect Heating Systems

This is where the fuel is burned by a boiler or other heat producing device to heat another media (water / air) which is then transported to a terminal device to give a heat output (radiators, fan convectors, grilles etc.).



Radiant and Convective Heating

Convective Heating

Convective heating systems use the movement of warm air to transfer heat. This air movement can be induced by natural convection or by the use of fans, for example via:

• Fan convectors• Floor or ceiling-mounted unit heaters• Central air-handling plant.



Radiant Heating

Radiant heating systems use infrared radiation to heat the building’s occupants and its fabric directly, without the need for warm air as a transfer medium. They are particularly useful for heating large volumes with high ceilings, typical of industrial buildings. Radiant systems can also provide local ‘spot heating’, and are also particularly efficient in buildings with high air change rates.



Boilers

There are many types sizes and outputs available using various fuel types to suit every type of Low Pressure Hot Water (LPHW) application, whether these are simple singular wall mounted applications to multiple floor mounted installations, the same process is occurring, Water is being heated and circulated to provide useful heat.

The boiler provides an indirect source of heat to be distributed through pipework systems which is then discharged to the space by means of radiators, convertors radiant panels or similar. The most common forms of heating devices likely to be assessed are described later within the training course



Atmospheric vs. Condensing

A condensing boiler is a high efficiency modern boiler that incorporates an extra heat exchanger so that the hot exhaust gases lose much of their energy to pre-heat the water in the boiler system. When working at peak efficiency, the water vapour produced in the combustion process condenses back into liquid form releasing the latent heat of vaporisation. The efficiencies of this type of boiler are fully dependant on the flow and return temperatures of the media heated.



Wall Mounted Boilers

This type of boiler is not dissimilar to what is likely to be found In a domestic home, however these generally have a higher output and will have components such as expansion vessels and pumps mounted remotely from the boiler itself.





Wall Mounted Multiple Boiler Installations

This type of installation has become more common over the past few years and is generally used in larger applications where one boiler is not capable of providing the required load, or where a back-up is required.

These units can be controlled on a duty / share operation which will be covered in further detail under the controls section


Wall Mounted Boilers



Floor Mounted Boilers

Floor mounted boilers will generally be found in older developments or where larger heat outputs are required. These can also be installed in multiple arrangements to increase loads and provide back-up facilities




Multiple Boilers



Boiler Efficiencies

Care should be taken when assigning boiler efficiencies to produce the Energy Performance Certificate. Manufacturers will advise efficiencies well in excess of 90%, and although this is achievable it can only be obtained under specific flow and return (F&R) conditions, especially in the case of condensing boilers.

Follow the LATEST conventions



Distribution Systems (WET SYSTEMS)

Radiators

Although delegates on this course will have knowledge of domestic wet heating systems using radiators, the following diagrams detail more complex installations to be found in commercial premises-



Radiators and convectors are the principal means of heat emission in most buildings. Less popular alternatives include exposed pipes and radiant panels for use in warehousing, workshops and factories. where appearance is not important. Embedded panels of pipework in the floor screed can also be used to create 'invisible' heating, but these have a slow thermal response as heat energy is absorbed by the floor structure.

Despite the name radiator. no more than 40% of the heat transferred is by radiation. The remainder is convected, with a small amount conducted through the radiator brackets into the wall.


Radiant Wet System



Originally. radiators were made from cast iron in three forms: Hospital. Column and Panel. Hospital radiators were so called because of their smooth. easy to clean surface, an important specification in a hygienic environment. Column radiators vary in the number of columns. The greater the number, the greater the heat emitting surface.

Cast iron radiators are still produced to special order. But replicas in cast aluminium can be obtained. Cast iron panels have been superseded by pressed profiled steel welded panels. These are much slimmer and easier to accommodate than cast iron in the modern house. In addition to the corrugated profile. finned backing will also increase the heating surface and contribute to a higher convection output. Pressed steel radiators are made in single. Double and triple panels.





Radiant & Convector Skirting Heaters

Radiant and convector skirting heaters are unobtrusive at skirting level and provide uniform heat distribution throughout a room.

Natural convectors have a heating element at a low level within the casing. This ensures that a contained column of warm air gains velocity before discharging to displace the cooler air in the room. Fan convectors may have the heater at high level with a variable speed fan located below. In summer. the fan may also be used to create air circulation.

Overhead unit heaters are used in workshops to free the wall space for benches, machinery. etc.



A variation may be used as a warm air curtain across doorways and shop entrances.

Individual unit heaters may have a thermostatically controlled inlet valve or a bank of several units may be controlled with zoning and diverter valves to regulate output.



Radiant heating systems use infrared radiation to heat the building’s occupants and its fabric directly, without the need for warm air as a transfer medium.

They are particularly useful for heating large volumes with high ceilings, typical of industrial buildings. Radiant systems can also provide local ‘spot heating’, and are also particularly efficient in buildings with high air change rates



Radiant heating systems offer the following benefits relative to convective types and are often the first choice for industrial buildings:

Energy consumption can be lower, as a result of:

Generally lower air temperatures

Reduced stratification at high level

Directional output delivers heating directly to where it is needed

Rapid warm-up

Responsive control

No air movement.



Radiant Panels Served by Boiler



Underfloor Heating Systems

Underfloor heating is far from a new concept, it was first used by the Romans whose dwellings were constructed with voids through which air, warmed by an open fire, would pass thus heating the structure.

In the more recent past electric heating elements were buried within floor screeds. These were heated over night using 'cheap rate' electricity. However, the building would overheat during the day but in the evening, when heat is generally required, no further heat was available.



Utilising today's modern multilayer pipes, control systems and high efficiency boilers, the underfloor heating systems of today are extremely comfortable and controllable.

Radiators are no longer needed so giving more room space.

The heat is more evenly distributed and dust is not circulated. Underfloor heating from the whole floor area of the house gently warms the air above, eliminating cold spots.

The warm air convects from the floor surface losing approximately 2 degrees centigrade at 2.0 meters above the floor.



Independent tests reveal that the most acceptable indoor climate is one in which the floor temperature ranges between 19-29°C and the air temperature at head level ranges between 20 and 24°C.

With radiator or convector heating systems a vertical temperature gradient is produced; colder at foot level than at the head. Underfloor heating has made it possible to reduce energy consumption by using low water temperatures. These systems, based on the development of complex and very high quality plastic pipe, such as the multilayer pipe, now account for over 60% of some European heating markets



Underfloor heating systems are suitable for both domestic and commercial applications. It has a particular advantage in public areas where exposed hot surfaces can be dangerous.

Gas, oil or solid fuel boilers can be used as the source of heat for any underfloor heating system. Condensing boilers being particularly suited as the operation of underfloor heating systems allows them

to operate in their most efficient manner.



It is possible to combine both underfloor systems with radiator systems. For example, the ground floor could be heated by an underfloor system whilst the 1st floor is heated using a wet radiator system or radiators can be fitted in the bathroom and lavatory in homes where the main system is underfloor heating.





Ducted Warm Air System

Warm air can be used as an alternative to hot water in pipes. There are no obtrusive emitters such as radiators. Air diffusers or grilles with adjustable louvres finish flush with the ceiling or floor. The heat source may be from a gas, oil or solid fuel boiler with a pumped supply of hot water to a heat exchanger within the air distribution unit. The same boiler can also be used for the domestic hot water supply. Alternatively, the unit may burn fuel directly, with air delivered around the burner casing. Control is simple using a room thermostat to regulate heat exchanger and fan.





Positioning grilles in doors is an inexpensive means for returning air to the heater. but a return duct is preferred. Fresh air can be supplied to rooms through openable windows or trickle ventilators in the window frames. If rooms are completely sealed, fresh air should be drawn into the heatinq unit.







Distribution Systems (DIRECT RADIANT)

Gas fired radiant tube heater



Distribution Systems (DIRECT RADIANT)

Gas fired radiant tube heater



Gas fired plaque heater



Gas fired plaque heater



Electric Quartz radiant lamp: Efficiency 100% (1.0)



Electric Quartz radiant lamp: Efficiency 100% (1.0)

Follow LATEST conventions• Losses are in power station and transmission



• Distribution Systems (DIRECT CONVECTIVE)



• Distribution Systems (DIRECT CONVECTIVE)



• Floor Standing Unit Heater



Floor Standing Unit Heater



Efficiencies

Generally direct fired gas or oil appliances have good efficiencies and most of the new modern types are listed on the ECA (Enhanced Capital Allowance Scheme).

However, actual percentage efficiencies should be sought from manufacturers data, if this data cannot be collected, the default values within the SBEM interface software should be used.



De-Stratification Fans

With any conventional heating system, natural convection increases the temperature gradient.

This results in the ambient temperature at the apex of the roof being greater than the required design temperature in the occupied zone at floor level





By using a system of destratification fans, the hot air in the roof space is directed down to the required area, thus reducing the heating load



These unit are operated by a thermostat to switch the fans off or on dependent upon the temperature settings of the thermostat and the internal room temperatures. These fans are also useful in summertime to reduce cooling loads.





End of section.

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SA AC REGIONAL 1 © STROMA CERTIFICATION LTD v1.3 Energy Performance Certificates Heating PRESENTED BY