ASHP for UFH

[Big Neil]

Lets assume the DHW is dealt with by a seperate means (sunamp maybe), and UFH by a ASHP. How is it plumbed together? IS it just  flow and return directly from the ASHP to and from the UFH manifold/manifolds?

[ProDave]

In  it's simplest form yes.  Some people recommend a small buffer tank so the ASHP is not cycling on and off so much. My own ASHP drives my UFH directly.

[epsilonGreedy]

A recent thread of mine touches on this subject.

 

 

[PeterW]

Depends .....

 

If you get a decent ASHP with full inverter driven compressor and modulation down to a low level then you can go direct from ASHP to manifold. The issue becomes when you need something with a peak load higher than a small unit (ie need a 8/12kw unit due to higher heat requirement) that the modulation doesn’t go low enough and when the zones start shutting off and you reach within 2-3c of the blending point you may get short cycling. You can go for pure fixed flow temp from the ASHP and lose the blending sets etc entirely but this needs a decent controller that allows you to set up temperature curves. 

 

Second option is to use a small 60 litre or so buffer tank and let this smooth out the modulation and short cycling issues. 

[PeterW]

Just bear in mind that you also need to run antifreeze in the whole system if it’s direct connect - dosing and filling is one issue if it’s direct, but a buffer increases the volume and subsequent antifreeze need and cost. 

[Big Neil]

Thanks chaps.