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New Thermostat Help Needed with Replacing Nest with new Thermostat

Postby tomstabb » Mon Nov 16, 2015 5:30 pm

Hi there,

I'm not asking information on how to do something, rather how someone else will do something, which will hopefully inform my purchasing.

I bought my house in September 2014 and quickly had my dodgy thermostat removed (wired in) and a Nest installed (wireless). After numerous technical issues I've finally given up and I'm getting it removed.

The previous thermostat was wired and the area it was installed was plastered over.

I need to get someone to install a new thermostat, but how are they going to do it? Am I going to get the whole system rewired? I'm very confused by the whole process and don't know which thermostat to buy, so any advice would be great.

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Postby TedBundo » Wed May 03, 2017 1:45 pm

I know this is an old thread and I'm quite sure you got your ac thermostat issue figured out by now, but I figured I'd answer it for anybody that stumbles across this in the future looking for help.

When you initially installed the nest you had mentioned that you were switching from a wired thermostat... the wires should still be right behind the wall where it was plastered over. Simply cut out a small hole in the wall and you should be able to pull the wires through.
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Postby ericmark » Sun May 07, 2017 6:21 am

It would depend on who installed the Nest when my father's house had new central heating installed for some reason they completely removed the wires for the old wired thermostat, seemed to me crazy to go from hard wired to wireless in the same location.

With a wired thermostat it is cheap enough to install a programmable thermostat and they work well, but with wireless I fitted the Horsmann HRFS-1 programmable thermostat, which proved rather unreliable, but the Honeywell Y6630D non programmable works A1 in same location, the latter has a built in tester to work out if the signal strength is OK, and has a warning if the signal is not received once an hour, the former just sticks at last signal so will over or under heat when signal is lost.

One of the reasons I was considering NEST is the coms is two way, so should have error checking.

The problem I have is where the thermostat is there is also an outside door, open the door and hall gets cold, so there is a TRV on the radiator which will then open allowing a reasonable flow of hot water to radiator to quickly reheat the hall, at around 17°C the TRV starts to close and the wall thermostat is set to 18°C so the heating is delayed for last degree holding the boiler on so it can heat the rest of the house. It actually works well, however any change to the thermostat setting has to be mirrored with the TRV setting. So the stops are set on the thermostat to 18°C to stop anyone turning up the heat, as if they did the boiler would never stop.

With NEST I could fit a eTRV set to follow the NEST however an eTRV tends to be more accurate, you actually set temperature rather than some number so the window of operation is a lot narrower, which is normally good, but not so sure when working with a thermostat in the same room.
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