advice on sensor for pumping stove water to rads and more

[ozzylowe]

Hi, i'm about to fit a wood burning stove with a back boiler. I need to pump the water to a heat store, but i want to pump it only when the water temp is say 70 on the outlet, to keep the fire temp up. I intend to fit a thermistor on or teed into the 28mm outlet pipe and feed this to a small control unit, which will control the pump.

Any ideas on a type of thermistor and control unit? Supplier?

As the system won't thermosyphon to the heatstore i intend to fit some overheat rads in the attic, isolated via honeywell V4043B or similar valves in case of power failure.(normally open unlike a zone valve) Do i need just one, or would two be better on both feed and return?. I read they're not meant for continuous use, is there anything better?

My pipe layout to the overheat would be neater if it dropped down from the stove about 8 inches before going round a corner (two elbows) then vertically up two floors, i know thermosysphons work best when the pipe travels continuously upwards, or is at least flat but can anyone confirm i won't get away the system i described, or is it a case of trial and error?

Sorry for rambling, getting into unchartered territory, i.e bitten off more than i can chew!

Hope this all makes sense, i can give more detail if required

Thanks

Chris

 

[oilman]

Use a standard pipe thermostat. You should also have one on the return to prevent pumping when the return water is too low. Otherwise you will get corrosion problems. You MUST have a thermal heat leak which is NOT obstructed. I suppose this could be via the valve you propose as long as the valve is a NORMALLY OPEN type. Remember you have to cope with electrical power failure.

www.euroheat.co.uk sell control packs which will be worth looking at. Ring their technical department for details of the best setup.