Discuss New thermostat doesn't turn on combi boiler in the Central Heating Forum area at PlumbersForums.net

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Hi,

The house I've bought came without a room thermostat. Just a combi boiler with a timer. So I bought a room thermostat, installed it, but it doesn't turn on the heating. Here are some photos to illustrate.

IMG_20191009_101049.jpg
IMG_20191009_101110.jpg
IMG_20191009_101130.jpg
So as you see I've piggybacked of the Live and Neutral input from the boiler to power the thermostat (the white cable). The black cable connects to the 1 and 2 on the first diagram.
When I turn the power on, the boiler powers on and the thermostat as well. When I increase the temperature on the thermostat I hear it click, but nothing happens.

I also have one of these timers:
IMG_20191009_101203.jpg
I've tried every setting on it, nothing works.

What am I doing wrong :)

Thanks for having a look at this!
 
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oz-plumber

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I would say you have to disconnect the timer in the boiler.
Is that a Baxi boiler?

You may have to piggyback the live terminal from the boiler supply to the live terminal on the thermostat port.
Then work out which wire and where it sends the signal back to.
Is the timer in the boiler connected to the circuit board or does it take its power directly from the terminal block
 
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Hi,

The way that you have connected the wireless the thermostat receiver is in series with the integral timer. So it ( the wireless thermostat) will only work if the integral timer is set to permanently on or properly disconnected. By disconnecting, I mean that the circuit for the integral timer must be left closed.

For the wireless receiver do not loop over a permanent 240v supply - the boiler terminals 1 and 2 provide the live feed / neutral return.
 
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It is a Baxi boiler. I'm already piggybacking of the live terminal from the boiler supply. The timer is connected to the circuit board, not to the terminal block. I've tried disconnecting the timer, but that didn't work. Probably because as you said Brambles, I'd need to close the timer circuit. But with the timer connected and left in the permanent ON position, the room thermostat still doesn't turn on the heating.
 

ShaunCorbs

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Don’t think it will work as you’ve wired up the live to the neutral on the stat

So stat side remove the blue wire

Boiler side remove both and only put the brown wire where the blue wire is

Should work now unless you’ve blown the receiver
 
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I cannot recognise the type of wireless transmitter that you are using. Your boiler requires the wireless transmitter to close the terminals 1 and 2 at the boiler to call for heat. The transmitter you are using appears ( from the diagram on the rear panel to deliver 240v as the call for heat. That is incorrect. Test it by using a mutlimeter. Your boiler requires continuity across the transmitter terminals one and two when calling for heat. I think you ate getting 240v across those terminals on call for heat.

As stated earlier, once that issue is corrected, you will still have the issue of the timer being wired in series with the thermostat.

You need to be a bit careful when wiring those types of thermostats into boilers without knowing what is required. You are lucky that you have wired it to a 240v and not to a no or low volts connection.
 
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Don’t think it will work as you’ve wired up the live to the neutral on the stat

So stat side remove the blue wire

Boiler side remove both and only put the brown wire where the blue wire is

Should work now unless you’ve blown the receiver
Wait wait wait :)
The Thermostat has 2 blue wires, one in the black wire (the left 2 wires) and one in the white wire (the right 2 wires). Which one should I remove?
The way it's connected now the thermostat turns on, so I'd think the live and neutral are correctly connected no?
 
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Read the boiler manufacturer’s instructions and the electrical diagram therein. The input your boiler requires is a 240v switch, with the boiler providing the 240v (just like a light switch). What you are doing is delivering a 240v supply from the thermostat transmitter to the boiler.

The thermostat transmitter needs to be reconfigured as a “switch”.

The boiler MI’s also show the connections to properly remove the integrated timer.
 
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I cannot recognise the type of wireless transmitter that you are using. Your boiler requires the wireless transmitter to close the terminals 1 and 2 at the boiler to call for heat. The transmitter you are using appears ( from the diagram on the rear panel to deliver 240v as the call for heat. That is incorrect. Test it by using a mutlimeter. Your boiler requires continuity across the transmitter terminals one and two when calling for heat. I think you ate getting 240v across those terminals on call for heat.

As stated earlier, once that issue is corrected, you will still have the issue of the timer being wired in series with the thermostat.

You need to be a bit careful when wiring those types of thermostats into boilers without knowing what is required. You are lucky that you have wired it to a 240v and not to a no or low volts connection.
This is the thermostat I'm using: Click
I'm not really sure what you're saying here, but the way I understand how it works is this:
Before I installed the thermostat terminals 1 and 2 were connected with eachother. The timer then controlled the switching on and off function of the boiler. There's 230V running between terminal 1 and 2.
I've now interrupted terminal 1 and 2 by installing a thermostat in between them, in series with the timer. When the thermostat asks for the heating to switch on, a relais in the thermostat clicks and connects terminal 1 and 2 again. If the timer is set to permanent on as well, the boiler should switch on. That doesn't happen.

The "Load" text on the Thermostat between L1 and N2 is just something they've printed on it, but the manual shows a "switch" drawing (the thermostat can be used for different kinds of heating installations).

Is what I'm saying correct?
 

quality

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Don’t think it will work as you’ve wired up the live to the neutral on the stat

So stat side remove the blue wire

Boiler side remove both and only put the brown wire where the blue wire is

Should work now unless you’ve blown the receiver
what he said . .
 

ShaunCorbs

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Wait wait wait :)
The Thermostat has 2 blue wires, one in the black wire (the left 2 wires) and one in the white wire (the right 2 wires). Which one should I remove?
The way it's connected now the thermostat turns on, so I'd think the live and neutral are correctly connected no?
Black set of wire sheathed
 
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what he said . .
The Thermostat has 2 blue wires, one in the black wire (the left 2 wires) and one in the white wire (the right 2 wires). Which one should I remove?
The way it's connected now the thermostat turns on, so I'd think the live and neutral are correctly connected no?
 

ShaunCorbs

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The Thermostat has 2 blue wires, one in the black wire (the left 2 wires) and one in the white wire (the right 2 wires). Which one should I remove?
The way it's connected now the thermostat turns on, so I'd think the live and neutral are correctly connected no?
See above black sheathed wires
 

ShaunCorbs

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Correct that’s it . .
 
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The way Shaun has described will work ( as you have marked up) , in essence using the 240v positive from the thermostat transmitter rather than the feed from the boiler as it was designed to do. Just think how a light switch operates it opens and closes the live (positive) side of the circuit ( or should do if wired correctly)
 
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Well that worked, you guys are geniuses, thanks a million !
Still not clear though why the way I originally connected it didn't work, since that thermostat basically acts like a switch between the 230v supply from the boiler no?
 
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No. The thermostat wired in the way you connected it was delivering 240v across the boiler terminals. Without being tedious, the positive feed to the thermostat transmitter should be taken from the boiler terminal 2 not the mains incommer to the boiler
 

ShaunCorbs

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Well that worked, you guys are geniuses, thanks a million !
Still not clear though why the way I originally connected it didn't work, since that thermostat basically acts like a switch between the 230v supply from the boiler no?
No. The thermostat wired in the way you connected it was delivering 240v across the boiler terminals. Without being tedious, the positive feed to the thermostat transmitter should be taken from the boiler terminal 2 not the mains incommer to the boiler
Doesn’t matter where it’s wired to aslong as it’s after the boiler spur

Op is happy
 
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