Central heating thermostat

littlespark · Jan 2, 2023

We can only guess at what all the wires are.

The fact that it’s in a pattress and not a proper joint box… we have no clue what diagram the installer was following.

freddo · Jan 2, 2023

littlespark said:
We can only guess at what all the wires are.

Looking at what terminals the valve is connected to greatly reduces the number of unknowns.
Terminals from left to right: Hot water on from timer to cyl stat, Hot water off from programmer and cyl stat, Boiler call for heat, Heating on from programmer to room stat, Heating call from room stat, Neutral. The last one could be permanent live or pump overrun from boiler. The block on its own earth.

timhoward · Jan 2, 2023

littlespark said:
We can only guess at what all the wires are.

But it's much more fun this way! In fact Danfoss 3 port zone valve wiring is a known entity and has stayed the same luckily even for 30+ years!
As per @freddo 's comments:
Grey is Hot Water Off
Brown/White is Heating On
Blue is Neutral
and Orange is the output signal to ask the boiler to fire up.

[ElectriciansForums.net] Central heating thermostat

So with 100% certainty we can say that with the Heating set to ON and stat all the way up then 2 and 3 should measure 230v to Neutral (marked)
I agree with Brian and Freddo that 1 is the controller asking for heat. So this should also measure 230v to Neutral.
Obviously this needs doing very carefully.
That will quickly reveal what is going on.

buzzlightyear · Jan 2, 2023

1) when you call for heat does the boiler kick in when the time clocks on.
Does the boiler kick in when you
Turn the stat on
2) does the stat on the cylinder call for hot water
3) does the hot water comes in.
Zone valve work from the time clock
Does the valve move.
Is it a two chanel time clock.

Alan Stirrup · Jan 2, 2023

timhoward said:
But it's much more fun this way! In fact Danfoss 3 port zone valve wiring is a known entity and has stayed the same luckily even for 30+ years!
As per @freddo 's comments:
Grey is Hot Water Off
Brown/White is Heating On
Blue is Neutral
and Orange is the output signal to ask the boiler to fire up.

View attachment 105004

So with 100% certainty we can say that with the Heating set to ON and stat all the way up then 2 and 3 should measure 230v to Neutral (marked)
I agree with Brian and Freddo that 1 is the controller asking for heat. So this should also measure 230v to Neutral.
Obviously this needs doing very carefully.
That will quickly reveal what is going on.

Fantastic, thanks Tim I'll check this tomorrow. Thanks Buzz I'll reply to your helpful questions tomorrow too.

Alan Stirrup · Jan 3, 2023

I'll test the wires later today when I get home from work but I have a quick question to ask. Would the wiring on my thermostat accommodate one of these digital/programmable units such as this?

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buzzlightyear · Jan 3, 2023

Before you start ordering some thing
That might not be compatible. With the system, for a replacement dryton stat.

brianmoooore · Jan 3, 2023

Alan Stirrup said:
Would the wiring on my thermostat accommodate one of these digital/programmable units such as these

It looks like you may have the neutral present at the stat, that some installations lack, but in my experience of 'stats similar, but not identical, to the one in the link, it might need a permanent live to preserve its programming, which will need the 'stat wiring to be arranged so that is is before the programmer instead of after.
The one's I have in one of my properties will default to their 'off' position if their power is interrupted.

Edit: Also worth noting that there are two types of these kinds of 'stats. Ones with the temperature sensor built in, and ones where they connect to a remote temperature sensor on a 2m or so lead.

Alan Stirrup · Jan 3, 2023

brianmoooore said:
It looks like you may have the neutral present at the stat, that some installations lack, but in my experience of 'stats similar, but not identical, to the one in the link, it might need a permanent live to preserve its programming, which will need the 'stat wiring to be arranged so that is is before the programmer instead of after.
The one's I have in one of my properties will default to their 'off' position if their power is interrupted.

Edit: Also worth noting that there are two types of these kinds of 'stats. Ones with the temperature sensor built in, and ones where they connect to a remote temperature sensor on a 2m or so lead.

Is that the blue wire for neutral, Brian, I don't think that's connected at the junction box.

Alan Stirrup · Jan 3, 2023

So 1&3 are pulling 244 & 245 volts respectively but number 2 is dead, do we have a culprit?

brianmoooore · Jan 3, 2023

Is the 'stat turned up?
The red at 1 should be the other end of the red at the 'stat, so check there as well.
The blue may not be connected at the moment, but it can be, if needed.

Alan Stirrup · Jan 3, 2023

brianmoooore said:
Is the 'stat turned up?
The red at 1 should be the other end of the red at the 'stat, so check there as well.
The blue may not be connected at the moment, but it can be, if needed.

Yes Brian, the stat was turned up thanks.

Alan Stirrup · Jan 4, 2023

So now we have power in the stat wire, I've no idea why, all I did was open the connections on that block, push them in further and tightened them up.

brianmoooore · Jan 4, 2023

Does that mean everything works now?

buzzlightyear · Jan 4, 2023

brianmoooore said:
Does that mean everything works now?

Drum roll with the elephant on top.

Central heating thermostat

littlespark

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freddo

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timhoward

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buzzlightyear

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Alan Stirrup

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Alan Stirrup

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BHT 002GC Boiler Heating Programmable Thermostat Digital Touch Screen Thermost H | eBay

buzzlightyear

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brianmoooore

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Alan Stirrup

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Alan Stirrup

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brianmoooore

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Alan Stirrup

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Alan Stirrup

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brianmoooore

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buzzlightyear

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