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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> Extra thermostat https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1444774807 Message started by JohnD on Oct 13^th, 2015, 11:20pm

Title: Extra thermostat
Post by JohnD on Oct 13^th, 2015, 11:20pm

Dear all

We have an empty house I am working on with the thermostat (battery operated all singing all dancing) set at 11 degrees. Worked brilliantly last winter until the batteries failed at which point it cost me £100 in heating bills as we didn't go down there for a week. Place was like a sauna.

I want to wire in a back up stat but the honeywell room stats I would normally think of are 240 volts.

Any suggestions?

Thanks

John

Title: Re: Extra thermostat
Post by Headrush on Oct 14^th, 2015, 12:04am

Unless your stat is wireless, there must be a feed coming into the stat from the boiler or electrical system which switches out either just on or on/off, depending on the heating system. Just replace your current stat with any common or garden mechanical stat and use it as a 'non all singing, all dancing' switch. The voltage will probably be standard 240v.

Title: Re: Extra thermostat
Post by thescruff on Oct 14^th, 2015, 9:19am

Give us some information johnD.

Boiler and existing stat make/models

Title: Re: Extra thermostat
Post by CWatters on Oct 14^th, 2015, 2:00pm

It's not obvious how you want the backup stat to operate...

Do you want it to ..

a) Stop the main stat leaving the heating ON all the time as happened before? In which case the two stats would need to be in series - so that both stats must call for heat before the heating comes ON.

or

b) Turn the heating ON if the main stat fails in the OFF state (eg to prevent a frozen pipe). In which case they would need to be in parallel so either stat can call for heat.

Not sure it's possible to do both at same time.

Title: Re: Extra thermostat
Post by thescruff on Oct 14^th, 2015, 8:37pm

Its possible CW in series is best but you can use relays.

To be honest nest or Hive would be a far better option and the OP would have full control from his mobile where as he/she can turn it on/off from home without visiting the property Assuming he has a router

Title: Re: Extra thermostat
Post by JohnD on Oct 15^th, 2015, 4:58pm

The idea was to have the two in series - should be o.k. The clever one in the living room, and the other by the boiler as a back up.

Boiler is a Baxi 105e and the thermostat a Honeywell CM 67

My mobile isn't that clever- I don't like technology that is cleverer than me.

Now that the my son has moved out and it is just my building site again we don't need the programmable one at present.

Thanks

John

Title: Re: Extra thermostat
Post by thescruff on Oct 15^th, 2015, 11:35pm

Depends how you want to use it . but you could have a frost stat turning it on say below 8c and a pipe stat turning it off say at 50c

Title: Re: Extra thermostat
Post by CWatters on Oct 16^th, 2015, 11:22pm

Quote:

The idea was to have the two in series - should be o.k. The clever one in the living room, and the other by the boiler as a back up.

That would prevent a high bill in the event one stat fails in the ON position.

However it make it more likely you would have a burst pipe. Because you need both stats to work in order to turn the heating ON. If either stat fails in the OFF position the other cannot turn the heating ON because they are in series.

Title: Re: Extra thermostat
Post by CWatters on Oct 16^th, 2015, 11:26pm

Quote:

Depends how you want to use it . but you could have a frost stat turning it on say below 8c and a pipe stat turning it off say at 50c

I think that would work. As long as the frost stat could still turn on the heating if the pipe stat failed in the OFF position.

Title: Re: Extra thermostat
Post by Lurch on Oct 22^nd, 2015, 2:00am

If you are going to fit them in series and the manual stat will be at 11 then the programmable one will never be able to get the place above 11 so you might as well just do away with it and fit the manual one in its place while you are working there.

If you really want 2 stats then you wire them in parallel, but stick a switch in series with the programmable one so the manual one keeps the place at 11 while you are away.