Hello all.
I've a saunier duval combi in my garage. It's a bit of a pain going in to the garage in the evenings to turn the heating on/off, so I'm planning on fitting a room thermostat in the property's entrance hall. I've done all of the ground work - drilled through the gable-end masonary from the ceiling and down into the garage so I can run the cable, and mounted the themostat in the hallway, so now "all" I need to do is the wiring. The wiring diagram that came with the themostat suggest that only a permanent live feed is required from the boiler. The diagram shows a live from the boiler running to the NO in the 'stat and then from the NO to the COM. My interpretation of this is that I simply need to run the live from the boiler to the NO and then run a very small length of live wiring from the NO to the COM. It seems odd, as there's no suggestion that a neutral or earth is required. Any advise, chaps??
Many thanks for reading.

Make and model of the stat and boiler model please.

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Hello there,
the boiler is a Glow Worm Xtrafast.
The stat is a Horsmann DRT1.
The diagram on the stat manual shows live in (from where I don't know) to COM and out at NO to the boiler. No neutral or earth pictured. Am I to take a live from the boiler's FSU in the garage to the stat's COM and then run a live from the stat's NO to the live at the boiler?
Many thanks

Hi,

How it works is you tell me what you have and I'll tell you how to do it.

If you give me the wrong information you, can and will likely damage the boiler.

For example we started off with a Saunier Duval of an unknown model, and now we have a Glowworm Xtrafast.

In the meantime don't touch the boiler, unless you have a few hundred quid to chuck away.

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Dave

www.drlgas.co.uk

The Horsmann DRT1 has volt free contacts and is battery powered and class II so as you have said just two wires. The Glow Worm Xtrafast think you are looking at page 17 on this so it seems it can be done. It's just a case of replacing link with two wires going to thermostat. Personally I would have used a DRT2 which also has a clock.

There is no direct connection to mains. The 2.7 wiring diagram is miss leading. It just two wires replacing link going to com and NO.

Before you can give any advice other than a guess which I don't do.

We need the information, especially the boiler make/model.

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Thanks, guys.
Apologies, thescruff, the boiler is a "glow worm xtrafast 120". It has a saunier duvall sticker on the undercarrage from when it was last serviced so I made a mistake there. (I have boiler cover with glow worm but when they come out to service it they come from saunier duvall or vailant, so presumably GW, SD, and Vailant are all the same company.)
I have the DRT1 manual and, if possible, I will upload the wiring diagram.

How does this DIY diagram look? A friend did it and forwarded it to me.

FCU L===red core of T&E Only=======COM STAT -- NO=======black core of T&E Only===== Boiler L
FCU N---------------------------------------------------------------------------------------------------------Boiler N
FCU E---------------------------------------------------------------------------------------------------------Boiler E

I know how it is wired thanks, all I need is the correct information.

Check the manual and find E on page 17 as referred by Ericmark above.

Remove the link and connect one terminal to COM and the other too NO

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Ignore friends and thinking.

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Does this help.

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I'm giving this a try now, thescruff. Thanks for your quick posts!
So, ignore the diagram forwarded to me. OK, will do!!

Yes.

Where you see the link (E) remove it, the left connection is NO in the stat and the right connection is COM. no other wires are needed

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I don't understand. Apologies. I'm trying to figure it out. It might take me a while, as did wiring my bathroom extractor earlier today!