Terry12
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Registered: 24th Sep 07
Location: Manchester
User status: Offline
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I've just removed an old Honeywell thermostat from my mum's central heating system. It's an old system with a tank in the loft.
There are only 3 wires for the thermstat, Live, Earth and Neutral.
I've wired it up like these instructions say to, But there is no power going to the boiler now. Any ideas how it should be wired?
This is on the inside of the case.
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Terry12
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Registered: 24th Sep 07
Location: Manchester
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On the first diagram what is on the Neutral wire before it is wired to the thermostat?
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Gary
Premium Member
Registered: 22nd Nov 06
Location: West Yorkshire
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Neutral would be live to boiler I'd say.
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mattk
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Registered: 27th Feb 06
Location: St. Helens
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try swapping the live and neutral round
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Terry12
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Registered: 24th Sep 07
Location: Manchester
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Cheers guys. I tried swapping the live and neutral to no avail.
It seems the spurred switch isn't getting power. Can I test if there's power to the switch and thermostat with a normal multimeter?
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Gary
Premium Member
Registered: 22nd Nov 06
Location: West Yorkshire
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Yep 
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Terry12
Member
Registered: 24th Sep 07
Location: Manchester
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Sorted. Just spoke to my cousin who is a plumber and his brother who's an electrician. They're going to come and save my skin and check everything out
I find it strange that changing a simple thermostat would cause it to breakdown, Unless i've blown a fuse that I don't know about.
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Terry12
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Registered: 24th Sep 07
Location: Manchester
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We've found that the switch spur is getting 230v but putting nothing out, So we bypassed the switch and got the boiler running but only the hot water light is lit. There is no hot water but I am assuming that's because the tank needs to fill up as we drained it down. The pipes around the boiler are getting hot.
The central heating light is still not coming on and the pump is not pumping, I've tried switching the neutral and live as suggested and then switched them back, Also I fitted the old thermostat and still the central heating is not working.
Any suggestions guys?
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Gary
Premium Member
Registered: 22nd Nov 06
Location: West Yorkshire
User status: Offline
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Turn it Off and back on again 
Honestly no idea withOut looking
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Terry12
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Registered: 24th Sep 07
Location: Manchester
User status: Offline
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quote:
Originally posted by Gary
Turn it Off and back on again
Honestly no idea withOut looking
Tried that. It's a strange one.
Does the hot water need to run for a while before the central heating will fire or do they generally both fire up together if both switched on?
Reason I ask is because the system was drained down and left off for the last month, Tonight it was filled with water and a cleaner then switched on. The hot water lit up straight off but the central heating did nothing.
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Tom J
Organiser: South Wales
Premium Member
Registered: 8th Sep 03
Location: Bridgend
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bled the radiators? enough pressure in the rad system?
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Terry12
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Registered: 24th Sep 07
Location: Manchester
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Just tested the neutral and live atthe thermostat and there's no voltage. I assume there should be
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ash_corsa
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Registered: 15th Apr 04
Location: Shrewsbury
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Stat should always be live.
Have you got a 3 core and earth cable at the stat or a twin and earth?
One will be perm live, the other will be a switched live out, some stats use a neutral some don't so if you've only got a twin and earth make sure the new stat you fit doesn't need a neutral.
It looks like the stat your trying to fit requires a neutral, however the instructions you've posted a pic of are for a different model.
You could temporarily join the two cables together at the stat this will call for heat and should fire the boiler if the programmer is set to CH ON, if that works your using the wrong type of room stat.
Do you have an s or y plan system? I you don't know the difference a y plan uses one three port valve and an s plan uses two two port valves.
[Edited on 18-09-2011 by ash_corsa]
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Terry12
Member
Registered: 24th Sep 07
Location: Manchester
User status: Offline
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I've only got a twin and earth running to the stat.
The instructions has 3 wiring diagrams, Seems I have the wrong stat then
When you say 2 and 3 port valves, Where are the valves?
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