PV hot water divert to Willis Heater to supplement UFH

[Johnnyt]

Would it possibly be worthwhile and could you fit a PV hot water divert to a willis heater to before the mixing valve on UFH.

Thinking of this as we have excess exported on good days in the winter and anything to reduce cost if heating would be a bonus this winter.

Even if a couple of hundred watts was available it wouldn't be wasted.

I don't have a buffer tank as my boiler can modulate down to 2kW

 

[ProDave]

Diverting to an immersion in the HW tank would be better and work all year.

 

You would have to be sure the circulation pump was running before diverting to a willis heater.

 

A far simpler idea is dump to a small convector heater.  We do that in the shoulder seasons, if there is more surplus PV than the immersion heater can absorb then I turn on a 700W convector heater.

[Johnnyt]

I'm having my DHW divert and battery fitted on Wednesday, at last!

This would be an additional divert.

I see your point re pump, or would another option would be have a moderate buffer fitted with an immersion in that and turn the stat down.