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| Heating appliance thermostat controls |
This section explains the range of temperature controls that are commonly available, what they do and why they are important. Controls for wet, warm air and electric storage systems are described. These controls are normally fitted away from the heating appliance, although some controls are integral with the appliance, and they are described further.
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TIME SWITCH
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Simple time control of a system that will only switch one circuit. Most suitable for combis. Should be chosen so that it is easy to understand and use, especially when there is a change to the householder’s domestic routine.
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PROGRAMMER
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A programmer can switch two circuits separately (usually heating and hot water). There are three basic types:
- a mini-programmer allows space heating and hot water to be on together, or hot water alone, but not heating alone
- a standard programmer uses the same time settings for space heating and hot water
- a full programmer allows the time settings for space heating and hot water to be fully independent.
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ROOM THERMOSTAT
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Simple room temperature control. Most room thermostats include an accelerator (or anticipator), which has the effect of smoothing out the temperature cycle, so that on and off periods are not too long. Wireless units are now available that provide increased flexibility in positioning and eliminate visible wiring.
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PROGRAMMABLE ROOM THERMOSTAT
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Allows different temperatures to be set for different periods in the day or week. Provides a better match to the householder living pattern. Important if occupancy is varied over the day or week. Provides a ‘night setback feature’ where a minimum temperature can be maintained at night. Many are battery operated and can replace a conventional thermostat without the need for additional cabling. Some also allow time control of hot water.
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FROST THERMOSTAT
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Simple override control used to avoid frost damage to the dwelling and/or boiler and system. A frost air thermostat should be fitted in a suitable place inside the dwelling so that a minimum temperature is always maintained.
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CYLINDER THERMOSTAT
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Simple control of stored hot water temperature, usually strapped to the side of the hot water cylinder. It is commonly used with a motorised valve to provide close control of water temperature.
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PIPE THERMOSTAT
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Where the boiler is fitted in an unheated area, for example a garage, a pipe thermostat should also be fitted (to the exposed pipework). This pipe thermostat is in addition to a frost air thermostat to prevent the boiler firing unnecessarily in cold weather and wasting fuel.
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