So I have a combi, my thermostat is Honeywell dt90e. Wanted to change thermostat to a programmable so bought a 2 wire programmable stat when wired In. The stat is calling for heat but boiler won't fire. I took stat off and connected a wago to both wires and the boiler fires straight away. Has anyone had this before or anyone know what's wrong. Thanks
- Thread starter Harry Thomas
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A
Aquarius
I've got x2 brand new thermostats one is danfoss and other is flowmasta so surely can't be X2 faulty stats
A
Aquarius
There is 2 terminals . A common and a on. So it's pretty basic when the thermostat is calling literally sends a live back down and boiler will fire. I have wired to the manufacturers diagram , also tried the other way around and still getting nothing.
A
Aquarius
The new models thermostat s are danfoss tp5000si and flowmasta td230w if that helps
M
Murdoch
doesn’t the Danfoss model need live and neutral too?
think the Flowmasta unit also needs live and neutral
what made you think you could use these?
A
Aquarius
Danfoss has a battery, mains and rf version of this. Can’t seem to find flowmasta version. Are you able to provide photos of wiring?
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The existing thermostat was 2 wire which is live and neutral. So that's why I went for the danfoss and flowmasta as they're the same. The only difference is, is programmable.
All I've done is put the live to port 1 and neutral to port 2. Have tried swapping them but nothing happens. The cable has two which is 1.5mm live and neutral
M
Murdoch
BUT your 2 core cable, despite it being red/black or brown/blue is NOT live and neutral.
Okay I'm assuming as followed the wiring backs and goes to a junction box and it's linked to boiler live and neutral
Okay but how comes the existing room stat works without a switch live or am I getting the terms confused so have I got a live and switch live ( no neutral)
A
Aquarius
M
Murdoch
because all it is , is a switch so live and switched live ...............
Best you get somebody with knowledge involved .
This
Okay glad we cleared that up I have basic knowledge in it, still can't figure why boiler won't fire, because It works when I connect with a wago but not when wired to stay and there's only 2 ports on the stat
M
Murdoch
A
Aquarius
One last ditch attempt to help. Can you post a photo if your wiring? Might be something obvious.
This is likely the situation. However, I can’t find the instructions online for the flomasta (Rubbish anyway, bin it).
When you look at the danfoss instructions, that particular model comes with sub models (hard wired, rf wireless, battery hard wired).
You have 2 wires for the old stat. They will be a live connection (common) and a switched live.
You’ve identified the common as per you post where you say it’s connected to the boiler live (this is for safety, so when the boiler is isolated for maintenance, power to the stat is off).
The other wire must be a switched live as there is no other way to signal the boiler to come on. You’ve also proven this by wago linking the two wires.
Now, with this in mind, the replacement stat/programmable stat you choose, need power. You can’t use a hard wired 240v stat, as you’ve not got enough wires to provide a live/neutral/switched live.
So this means we have to use a battery powered unit. It uses battery power to operate itself and switch the incoming common to switched live.
If the common is 240v, it will switch and send back 240v, if the common is 24v, it sends that back.
With the danfoss, the instructions say that the common should be connected to port 2 and the switched live to port 3.
If you’ve got a multimeter, you can check the switch is working using continuity across the ports when the stat is calling/not calling.
If you prove the stat switch is working as above and you’ve proven the wiring with the wago, I’m at a loss.
When you look at the danfoss instructions, that particular model comes with sub models (hard wired, rf wireless, battery hard wired).
You have 2 wires for the old stat. They will be a live connection (common) and a switched live.
You’ve identified the common as per you post where you say it’s connected to the boiler live (this is for safety, so when the boiler is isolated for maintenance, power to the stat is off).
The other wire must be a switched live as there is no other way to signal the boiler to come on. You’ve also proven this by wago linking the two wires.
Now, with this in mind, the replacement stat/programmable stat you choose, need power. You can’t use a hard wired 240v stat, as you’ve not got enough wires to provide a live/neutral/switched live.
So this means we have to use a battery powered unit. It uses battery power to operate itself and switch the incoming common to switched live.
If the common is 240v, it will switch and send back 240v, if the common is 24v, it sends that back.
With the danfoss, the instructions say that the common should be connected to port 2 and the switched live to port 3.
If you’ve got a multimeter, you can check the switch is working using continuity across the ports when the stat is calling/not calling.
If you prove the stat switch is working as above and you’ve proven the wiring with the wago, I’m at a loss.
Thank you Timmy D will try that in next few days
No need for that , I understand need a course on it don't do much electrics
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