Honeywell Sundial Plan Wiring Centre - Permanent Live - Nest

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The cable disappears behind the plaster ... I had assumed it emerged at the fused spur - blue on Live Out - and in the adjacent box - brown to switched live.
 
This evening ( a couple of days ago) I'm being told the boiler appears to be running with the picture of a flame showing even though neither heating or hot water are being called for.

This problem is happening again as we speak ... my son who lives at the house has just rung to say the heating was on and the radiators hot at 1925 this evening when they arrived home even though it wasn't set to come on until 1930. He's observed the flame on the screen when neither heat or water are being called for ... thinking it may be due to the pipe stat I got him to take a picture of the dial ...

Could it be turning the heating on ???

The temp of the house is around 18 degree C at this moment

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If the wires at the pipe stat end are blue and brown and I disconnect them at the fused spur (Blue) and the adjacent box (Brown) tomorrow and the pipe stat is dead then there can't be anything else connected to it ... can there?

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you will have to find which live goes to the frost stat and remove it.

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But to be honest I dont think that is your problem, it will still have to be removed, but the frost stat shouldnt be kicking in at thistime of year especially during the day
 
Is it fair to say a pipe stat was never fitted without a frost stat?

If so, there is no frost stat in view in the property.

If it was in the garage and is still connected, it is behind the plaster.

If ever there was one and someone removed it while converting the garage and they connected the two wires together would that make the pipe stat into another “room stat” ?

What would happen if someone removed the frost stat and disconnected the wires?
 
My first job tomorrow is to turn the dial up on the pipe stat and see if it turns the boiler on.
 
turning the pipe stat up wont do anything unless the frost stat is calling for heat

Is it fair to say a pipe stat was never fitted without a frost stat?
No there would be absolutely no point

Isolate the power then remove both wires in the pipe stat, terminate them and insulate them, beware they are both lives no matter what colours are used, do not join them together you want to break the circuit, then the frost stat is now not connected to the boiler , so if still ghost firing then that wasnt the problem
 
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I'm not sure about the nest, but with Hive it has a setting called"ready by"
So if you set it to say 21° at 1930 it will come on early, so the temperature will be 21° at 1930. Not just start heating up at 19.30
 
John, with the Nest there is no “ready by” option, ours at home clicks on at the precise selected time.

Ian, thank you I’ll do that this afternoon.

Quite separately I don’t think the Y plan valve is working as it should. This morning HW on 6 to 7 and CH on 7 to 8 and the radiators were hot at 0645.

I need to check if the HW was set to ON at 1925 yesterday which would account for the CH heating up early.
 
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you will have to find which live goes to the frost stat and remove it.

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The thermostats are usually wired in series, not parallel. That way both thermostats have to be calling for heat at the same time for the frost protection to kick in.

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This way, the frost stat fires up the heating when the area in which it's located in drops to 5 degrees. Then when the pipe stat [located on the coolest return leg to the boiler] reaches its set point [25 to 30 degrees] it turns the heating off. This way the system just gets warm enough to stop anything freezing but prevents it getting up to the usual operating temperature and heating the property unnecessarily.
 
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Talk about making a mountain out of a mole hill, I have already told you how to completely isolate the pipe stat, if it is indeed still connected to anything, you are just looking for problems that dont exist
 
Sorry Ian, As soon as I get chance I'm going to disconnect the pipe stat wires from the fused spur and the boiler switched live as you suggest.
 

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