Pump CH water to outhouse automatically?

11 Jun 2013
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United Kingdom
Hi folks,

I want to put some a pair of underground heating pipes over my garden (about 25 meters) to an outbuilding to power a radiator in there.

I think it's too far for the combi boiler to pump by itself so I was going to help it by putting a seperate pump on that pair of pipes.

When I've installed underfloor heating before, the Grundfos pump they supply you with automatically turns itself on when the flow gets warm... So that's what I want to install, a pump which will come on whenever it detects the inlet pipe is getting warm.

Only trouble is I can't seem to see how the underfloor heating setup does this, and none of the pumps I can buy seem to say anything about how it works.

Any advice?

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Wouldn’t you want it set up as a separate zone? Add another diverter valve, with a thermostat and timer to trigger a pump and the boiler indipendantly for that zone.

Saves you heating an empty outbuilding every time the heating is on, or even worse over heating the house trying to warm the cold outbuilding.
I think running the primary heating circuit ( the circuit that feed the radiators ) 50 metres under ground would not be a good idea.

You could consider a secondary ciruit to the outbuilding and couple this to the primary circuit by a heat transfer unit.

Any faults / leaks / antifreeze in the secondary circuit would not affect the primary circuit and house heating.

Only run the secondary circuit pump when the out buildng needs heat ( and the boiler as well )
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Don't do it. Install an electric oil heater and a timer or smart plug to control when it turns on.
That's going to either cost a lot to install, or a lot to run. Which one it is depends on the quality of the installation. The proper pipe to run this in is Uponor Thermo Twin (or similar), which is £60 per metre. If you do it in that, you shouldn't lose too much heat to the ground and it shouldn't significantly increase your heating bills. If you're expecting to lob a couple of lengths of Speedfit in a trench with some cheap grey insulation round them, however, you can expect your heating bills to be quite high and also expect it to freeze in the Winter when you've not got it turned on, because that stuff ain't waterproof.

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