Thermostat OFF = no heat at all?

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usrbin

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A thermostat on the wall with a temperature dial and an on/off switch. Put it to a given setting - say 22C - and whenever the heat falls below that level, it'll fire up the boiler (assuming the boiler itself is on).

But what about the on/off switch on the stat? I would have thought that, when this is OFF, it's as if the thermostat isn't there at all, i.e. the heat goes straight to the rads (again, assuming the boiler is on), regardless of the ambient temp/dial setting.

In fact, when this switch is OFF, there's no heat to the rads at all. Is this correct? Should the thermostat need to be powered ON to allow heat into the system?

(Follow-on question: is this what Normally Open and Normally Closed mean? Or do they relate to whether the current temp is above or below the set point on the dial?)

Thanks!
 
We have two thermostats in our house, one like what you have but there is another one in the hot press(orange in colour) The one that you have sends out the signal that the house is cold but the one in the hot press is the one that open the water to the rad's when the correct water temp is met. So if the house is cold and the switch says "yes" put the water into the rads but if the thermostat inside the hot press says the water is not hot enough(set to high) it will never release the water to the rads till it's piping.
Most houses have these in the hot press, Maybe check it should be on one of the hot pipes out of the tank.
 
Thanks Mr2 - that's good advice; I hadn't checked the hot press but as it happens all seems to be fine there; the stat/control on the cylinder itself isn't set prohibitively high.

What I'm really wondering about is the function of the On/Off power switch on the wall thermostat. By turning this off, I would have expected that the heat would be always on; conversely, in order for the thermostat to do its job of controlling rads etc., I thought it would have to be On.

In fact, when I turn Off the thermostat, it's as if I've turned it down to zero, and the rads never come on. Guess my question is, is that behaviour normal, or is this one wired wrong?

Thanks again
 
usrbin said:
In fact, when I turn Off the thermostat, it's as if I've turned it down to zero, and the rads never come on. Guess my question is, is that behaviour normal, or is this one wired wrong?
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That sounds right. When the stat is off it cant allow the control voltage go to the motorised valve (or boiler depending on your setup) to activate it. So stat off = temp off
 
She seems to be working right,As dahamster says when it's turned off the whole thing is off.
 
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