Boiler Protection Thermostat
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Boiler Protection Thermostat

by Shark » Sat Aug 19, 2023 12:53 pm

A while back we had a new boiler fitted and we use a Hive thermostat.
The original thermostate was disconnected but the boiler protection thermostat was left connected (although I believe no longer used/required).
We are not decorating and have blanking plates to replace both thermostate housings.
Questions is, can we simply connect the 2 red wires in a electrical block and then put the other cable in another block and then put the blanking plates on the wall?
Thanks for any advice.

Mr White
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Re: Boiler Protection Thermostat

by Mr White » Sat Aug 19, 2023 3:07 pm

A boiler protection thermostat is also know as a frost stat and is usually found outside (In a suitable weather proof box) The idea being regardless of what the programmer is set for, if the temperature outside drops below a set temperature, the frost stat tells the boiler to come on. It heats the property so in turn stops the pipes from freezing.

As for can you connect wires together, that is a simple sounding question, but as it is not possible to see from this end of a computer what the wires do / are connected to. If it helps it is similar with lights, people take down a light and ask how to re connect it, same answer.

That said, if you thermostat has markings, it may help if you can take an infocus picture showing the markings along with the coloured wire.

On the other hand, if you are 100% sure said thermostat is not LIVE and no longer used you could put each wire in its own choc bloc

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Re: Boiler Protection Thermostat

by ericmark » Sat Aug 19, 2023 4:34 pm

The old bi-metal strip thermostat normally had a heater to reduce the difference between on and off temperatures so had three wires, feed, return and neutral, however often for frost protection the heater was not required so it may be only two wire.

In the main they would work a motorised valve which would in turn switch boiler on off, so in the main 230 volt, however there were some 24 volt versions, so some testing is required.

Again in theroy there should be one point of low voltage isolation for the central heating, but when I moved in here not only multi points but also from different distribution units.

There are normally some clues, often one can find the motorised valves either by the hot water tank or the boiler. Hive is an odd one out as thermostats go, both in not having the option for ebus connection, and allowing the two contacts with the duel channel version to power the boiler and motorised valve independently, Plus the way the TRV's connect to it, so it needs to be in an area normally kept cool as it will stop accepting demands for heat once it hits 22 degs C.

I am not saying it is a bad thermostat, but an odd one out, likely better than Nest even when Nest has got OpenTherm, but this means one has to be careful and one needs to know how yours is wired.

If my own house, I would take pictures to show how wired, and put each wire in a block connector and then see if heating still works, if it does then simple blanking plate so you know where the wires are.

I would also use my non contact voltage tester to see if it shows live, although readings from these can be misleading.

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