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is the most important part of any central heating system. A central
heating system is only as good as its controls, the better the controls,
the less wear and tear on the boiler and system. You will get more comfortable,
controllable temperatures and in turn the running costs will be less.
A Time Switch (clock) will switch all the system on or
off to the times you require
A Programmer will switch one, two or even three different
circuits on or off at different times or even on different days. Most
programmers have integral switches to set them up to your own personal
preferences, for example, to have the hot water and heating to come
on separately at a different time each day of the week. (Override buttons
are also fitted to programmers) A programmer should be set to cover
all the times that the property is occupied. A signal is sent out to
the cylinder and room thermostats and these will keep everything at
the desired temperatures.
If your system is warming a cylinder of water, you must have a Cylinder
thermostat, this should be set to about 55-60 deg °C and should
be positioned approximately 1/3 the height of the cylinder from the
bottom. Once this is satisfied it allows the hot water circuit to rest,
and boiler to rest if no other control is calling for heat, until some
hot water is used or the cylinder cools down naturally.
All central heating systems should have a Room Thermostat fitted, this will shut the heating circuit off, allowing the boiler
and system to rest once the air has reached the desired temperature.
As the air starts to cool slightly, the room stat brings the heating
on again to maintain the set temperature. This should be fitted about
1.5 metres high in an average temperature room with a radiator fitted,
but not in direct sunlight or above a radiator, and have no other source
of heat in that room. Usually these are best fitted in a hall or dining
room. Since April 2002 it is mandatory as part of the Building Regulations
that all new and updated systems have a room thermostat fitted.
A Programmable Room Thermostat is the same as a room thermostat,
except you can program different temperatures for different times of
the day and night, also there is no need for any other timing device
on this circuit (also acts as a frost stat). Some Models have a 7 day
option, so the temperatures and times can be set differently for each
day. This is the only control needed for combination boilers.
Radiator Valves (TRV's) fit on radiators in place of existing
valves. Inside the valve is a wax capsule which expands when heated
and stops the flow of water to the radiator. As the wax cools it contracts
and lets the water from the boiler flow into the radiator. A TRV should
not be fitted in the same room as the room thermostat as this can interfere
with its operation. When the room stat is satisfied it will shut the
pump & boiler off (providing another circuit is not calling). For best
economy just fit TRV's in rooms that are too warm (bedrooms) or in south
facing rooms and unused rooms. If you have a condensing boiler then
do not fit too many TRV's, usually no more than a third of all radiators,
as they will reduce the high efficiency of the boiler.