heating thermostat?

A

animaal

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My house is approx. 13 years old. It has a gas boiler (unchanged since the house was built), with a mechanical timer switch. It's one of those circular timers with a "notch" representing each 15 mins of the day, and an "off-timed-on" switch. There's also a thermostat with a temperature control on the wall in the hall.

I can't seem to get the thermostat to do anything. How's it supposed to work? For the thermostat to function, should the switch at the boiler be on or off? Also, would the thermostat usually be wired into the timer or the boiler itself?

Thanks.
 
Look on the timer switch as just an on/off switch, the on/off controlled by either the off-timed-on sliding switch, or by the relevant notch when set to Timed.

Think of the thermostat switch as a basic on/off switch that is controlled by temprature. You set the temprature which turns it from on to off, or off to on.

The electrical power for the boiler goes through the timer switch, to the thermostat switch on the wall, then to the boiler to activate it.

So the following are the possible states

Timer switch Off - the boiler is off - no power is going to go to the bolier, hence boiler is off. Thermostat switch state is irrelevant
Timer switch On - Thermostat switch off - no power is going to the boiler, hence boiler is off
Timer switch On - Thermostat switch on- power is going to boiler, hence boiler on

That's it, simples.

My advice, set the thermostat switch to the temprature you desire, normally 18~20 degrees. Then set the timer switch to "timer", and set the segments to "on" for the times when you want the heating to be active. Sometimes it may be an idea to set them to "on" before you arrive home, to give the rads a chance to heat up, and to "off" a bit before you go to bed as there will be some latent heat still there.

When you are happy with that, have a look at "set back" functions of the thermostat (if it has them), which in effect allow two temprature settings, one for "normal" mode, e.g. 20 degrees, and one for "set back" mode, the purpose of which is to ensure that the temprature does not fall below a set level, e.g. 12 degrees. Of course, for "set back" to work, the dial timer has to be on, so power goes to through the thermostat to the boiler.

And finally, there is one other switch, that is the safety thermostat on the boiler itself. It is the one with the red "reset" button on it. Its purpose is to ensure that the boiler never overheats. It should not be used as part of the normal control of the house heating.

Hope this helps,
Buddyboy
 
Thanks Buddyboy, that explains it all nicely. Now I know how to test the whole setup, and see if the thermostat actually works.
 
Forgot to add...

The thermostat switch can initally be tested to see if it is mechanically sound, by turning it fully down and slowly turning it up. You should hear an audible "click" when it passes the actual room temprature, i.e. when it turns itself from "Off" (room temp is greater than switch set temprature) to "On" (room temp is less than switch set temp and heat is needed).

If you don't hear a click it is possible that the thermostat is faulty, although it is fairly rare.
 
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