BEAMA

Under the lastest Building Regulations, Part L, effective from April 2006, installers are required to ensure as closely as possible that all domestic central heating systems on which they carry out significant upgrades (replacement boilers, etc) are brought up to the energy-efficiency standards laid down for new homes.

It may not be enough to just replace the boiler if, for instance, the existing heating controls do not comply with the lastest regulations. The job cannot be signed off as compliant unless the appropriate controls are fitted.

Because of the need to upgrade the whole system, the total cost of boiler replacement may turn out to be more than the client had bargained for and this could easily provoke some resistance.

On these occasions, installers would be very unwise to give way to requests for illegal non-compliant systems. They could find themselves in tricky situations later if system problems occured when, perhaps, other installers were involved. The correct approach would be to explain the reasons for the new components plus the fact that they will reduce system running costs and the hone's carbon footprint.

These situations also provide opportunties to sell more advanced controls and to take household energy-efficiency levels beyond minimum standards.

Obtaining Guidance

The first place to seek guidance is the 'Domestic Heating Compliance Guide', published by the Office for Communities and Local Government.

The strategic requirements of Building Regulations, Part L, can be found in ADL1A for new dwellings and ADL1B for existing dwellings.

Outline of minimum Provisions

Boiler Interlock

For both new-build and replacement systems, boiler-based systems require boiler control interlock arrangements that ensure the boilers and pumps are switched off when there is no demand for either heating or hot water. Thermostatic Radiator Valves alone do not provide interlock.

Space-Heating Zones

Dwellings with a total usable floor area up to 150m2 require at least two space-heating zones with independent temperature control, one assigned to the living area.

Dwellings with a total usable floor area greater than 150m2 require at least two space-heating zones, each having separate timing and temperature control.

Single-storey open-plan dwellings with a living area greater than 70% of the total floor area do not require zoning.

Replacement systems should be dealt with as for new-build except where the boiler only is replaced; then reasonable provision would be to control as one zone.

 Water-Heating Zones

All dwellings require separate hot water service zones in addition to space-heating zones. Separate hot water zones are not required if hot water is produced instantaneously, as with combination boilers.

Time control of space and water heating requires:

• A full programmer with separate timing to each circuit
• Two or more separate timers providing control to each circuit; or
• Programmable room thermostat(s) to the heating circuit(s), with separate timing of hot water

For Dwellings with total usable floor areas greater than 150m2, timing of the separate space-heating zones can be achieved by any of the following:

• Multiple heating zone programmers
• A single multi-channel programmer
• Programmable room thermostats
• Separate timers to each circuit
• A combination of programmable room thermostats and separae timers to each circuit

Where hot water is produced instantaneously, time control is only required for space-heating zones.

Replacement systems are dealt as with new systems, except where only the hot water cylinder is being replaced and separate time control is not present. In this case, a single timing control for both space-heating and hot water is acceptable.

Temperature control of space heating - separate temperature control of zones should be provided using any of the following:

• Room or programmable room thermostats in all zones
• Room thermostat or programmable room thermostat in the main zone and individual radiator controls on all radiators in other zones
• A mixture of the above

Temperature Control of Hot Water Service System

Domestic hot water systems should have a cylinder thermostat and a zone valve, or a three-port valve to control the temperature of stored hot water.

In dwellings with total floor areas greater than 150m2, it could be reasonable to provide more than one hot water circuit, each with separate timing and temperature controls by means of any of the following:

• Multiple heating zone programmers
• A single multi-channel programmer
• Separate timers to each circuit

Non-electric hot water controllers do not meet this requirement. In some circumstances (e.g. thermal stores) a zone valve is not appropriate; a second pump can be substituted.

Where only the cylinder is replaced, a thermo-mechanical cylinder thermostat would be minimum provision.