Heating Problems

antlyn

Was at a friends house earlier, she has been renovating it and is after getting a new heating system. She has a wood pellet boiler fitted, which is not yet commisioned. Her sparks (and apprentices!) couldn't wire up part of her heating, so she called me as I'm an Elec Eng. But I've never seen this setup before. They have a contactor wired to bring in the boiler when called for. The room stats aren't required just yet, but there are two tank stats (not for the solar!) on the new hot water tank and they said that the installer who is currently away, said that the higher stat will call the boiler when the temp in the tank drops below a certain temp, e.g 50 degrees but the lower stat will ensure the boiler keeps running until it reaches roughly 70 degrees. Am I right in thinking that the stats are in series??? The idea of this system is to keep the boiler running when the first stat comes up to temp, without having to refire the boiler. Would anyone have a wiring diagram for this. Thanks

marknjb

the top one u would wire to the coil of the contactor use the contact that closes when it goes below 50 then u would put the second stat in series with one of the contacts on the contactor asa hold on for the coil useing the contact in the stat that will open when it gets to 70 that should work dont knopw how to do diagram on computer

Bruthal

Maybe something like this, it shows the 2 stats controlling the contactor which has 3 sets of contacts in the drawing here, one used as the hold on here. The 2 free sets of contacts can then bring on the boiler, depending how its brought on, maybe the Live feed through one of the contacts to the boiler or Live and Neutral through both contacts, or if the boiler has auxilary control terminals, one of the contactor spare contacts can bridge that.