What Is A Programmer - Honeywell Y9420H Sundial RF2 Pack 2 User Manual

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WHAT IS A PROGRAMMER?

...an Explanation for Householders (as recommended by the Energy Savings Trust)
Programmers allow you to set 'On' and 'Off' time periods. Some models switch the central heating and
domestic hot water on and off at the same time, while others allow the domestic hot water and heating to
come on and go off at different times. Set the 'On' and 'Off' time periods to suit your own lifestyle. On some
programmers you must also set whether you want the heating and hot water to run continuously, run under
the chosen 'On' and 'Off' heating periods, or be permanently off. The time on the programmer must be
correct. Some types have to be adjusted in spring and autumn at the changes between Greenwich Mean
Time and British Summer Time. You may be able to temporarily adjust the
heating programme, for example, 'Override', 'Advance', or 'Boost'. These
are explained in the manufacturer's instructions. The heating will not work
if the room thermostat has switched the heating off. And, if you have a hot-
water cylinder, the water heating will not work if the cylinder thermostat
detects that the hot water has reached the correct temperature.
WHAT IS A ROOM THERMOSTAT?
...an explanation for Householders (as recommended by the Energy Savings Trust)
A room thermostat simply switches the heating system on and off as necessary. It works by sensing
the air temperature, switching on the heating when the air temperature falls below the thermostat
setting, and switching it off once this set temperature has been reached. Turning a room thermostat to
a higher setting will not make the room heat up any faster. How quickly the room heats up depends on
the design of the heating system, for example, the size of boiler and radiators. Neither does the setting
affect how quickly the room cools down. Turning a room thermostat to a lower setting will result in the
room being controlled at a lower temperature, and saves energy. The heating system will not work if a
time switch or programmer has switched it off. The way to set and use your room thermostat is to find
the lowest temperature setting that you are comfortable with, and then leave it alone to do its job. The
best way to do this is to set the room thermostat to a low temperature – say 18ºC – and then turn it up
by one degree each day until you are comfortable with the temperature. You won't have to adjust the
thermostat further. Any adjustment above this setting will waste energy and cost you more money.
If your heating system is a boiler with radiators, there will usually be only one room thermostat to
control the whole house. But you can have different temperatures in individual rooms by installing
thermostatic radiator valves (TRVs) on individual radiators. If you don't have TRVs, you should choose
a temperature that is reasonable for the whole house. If you do have TRVs, you can choose a slightly
higher setting to make sure that even the coldest room is comfortable, then prevent any overheating
in other rooms by adjusting the TRVs.
Room thermostats need a free flow of air to sense the temperature, so they must not be covered by
curtains or blocked by furniture. Nearby electric fires, televisions, wall or table lamps may prevent the
thermostat from working properly.
Honeywell Control Systems Ltd.
Arlington Business Park,
Bracknell
Berkshire
RG12 1EB
Technical Help Desk: 08457 678999
www.honeywelluk.com
50047645-003 A
© 2009 Honeywell International Inc.