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installing thermostat on boiler.

Postby Ollie999 » Fri Dec 04, 2009 10:09 am

Bought a thermostat for a combi boiler and can't work out how to wire it in. The thermostat is 230v, the instrusctions say 230v input and output, and has terminal connectors for N L SL. The boiler has 2 connections for a thermostat that currently just has a bit of cable connected between them meaning the heating is permanently on unless switched off manually. the voltage between the 2 connectors in the boiler however is only 12v. does this mean that the thermostat is incompatible with the boiler? If not how should it be wired?
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Simply Build It

Postby rosebery » Fri Dec 04, 2009 7:07 pm


It would be a good plan to identify what it is that you a trying to connect to what by reference to manufacturer and model / part number rather than a generic "boiler" and "thermostat".

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Postby DEEARR2 » Fri Dec 04, 2009 8:23 pm

If you have a standard mechanical type thermostat then connect across L & SL. The N connection is there to operate an anticipator that closes the on/off differential by a couple of degrees.
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