Operation Manual

3
WHAT IS A PROGRAMMER?
General Description
Your Honeywell ST9400A provides timing control for both your central heating and
hot water systems, letting you set ON and OFF periods to suit your own lifestyle.
The ST9400A does not directly control the temperature but works together with other
temperature controls, such as room thermostats and cylinder thermostats, to control
your heating and hot water system in your home.
ST9400A has 1-day programming and 2 on/off periods per day. It is simple to use but
still allows heating and hot water to be set at different times from each other.
The following instructions explain how to programme and use the ST9400A to
provide the most home comfort at the least cost.
The way to use a Programmer
Think about the time periods when you are typically in the house and when you are
not, and also the times when you use a lot of hot water. These are the times you
should use as the basis for the programmes. It will be necessary to allow some
heat-up time for the heating system after periods when it has been off – this would
typically be 1 - 1½ hours, depending on your house and your preferences.
Other features are commonly available on the Programmer to enhance comfort and
convenience, for example, OVERRIDE, EXTRA HOUR, and MODE buttons.
A typical use of the OVERRIDE feature is when you return home unexpectedly for
the rest of the day and the heating is off. Just press the OVERRIDE button and the
heating will come on until the next programme time, at which point it will follow the
normal programme. The advantage here is that you do not have to remember to
switch off because the normal time programme does this for you.
A typical use of the EXTRA HOUR button would be if you returned to the house for
a short period when the heating and hot water were off. Pressing the appropriate
EXTRA HOUR button gives you 1, 2, or 3 hours of heating, exactly when you need
it. Another typical use is when the heating is already on and you want it to stay on a
little longer - just press EXTRA HOUR and, for that day only, an hour will be added
to the end of the time at which heating normally goes off.
The MODE buttons allow you to select how you want to operate heating and hot
water independently. The most obvious use is to switch heating OFF during the
summer months, but you may also use this feature if you take a mid-week day off
work, you can then set the MODE to ONCE to keep the system ON during the day
from the first programmed ON time till the last programmed OFF time.