Heat Pump question

Reed_Richards

I don't have the same degree of faith that @Screwdriva does in Heat Geek certified installers; such a pity he passed by the opportunity to get a heat pump himself in favour of a super-duper gas boiler.  But I agree that there are lots or warning signs about "Bad Power" that you would be wise to heed.  My installer did the initial survey at no charge, I had to pay an initial deposit but I was not asked for the balance until the work was completed.

One point, heat pumps need to defrost, just like fridges but very much more frequently within a particular range of temperatures.  Whilst they are doing this they are not heating your house so they lose efficiency because they then need to operate at a higher temperature to catch up with the heating.  The worst case scenario is a damp climate like ours at temperatures close to 0 C.  That's another reason why a heat pump in Helsinki might work a bit better, drier air so less time spent defrosting.  

Netexporter

 The worst case scenario is a damp climate like ours at temperatures close to 0 C.  That's another reason why a heat pump in Helsinki might work a bit better, drier air so less time spent defrosting.  

Which is what makes the Cosy 6 an interesting prospect, as it was developed in Northern Ireland, with a damp climate in mind.

Reed_Richards

I'm not saying that the Cosy 6 is not interesting but I don't think you can get around the need for heat pumps to defrost themselves.

Netexporter

Reed_Richards said:

I'm not saying that the Cosy 6 is not interesting but I don't think you can get around the need for heat pumps to defrost themselves.

I didn't say there was no need for de-frosting but I have read that mitigating the losses from defrosting was part of the design brief for the Cosy 6.

Reed_Richards

I'm sure there are efficient and less efficient ways to defrost but that wasn't what I was thinking about.

Supposedly, the most efficient way you can run a heat pump is to maintain an output water temperature that just matches the needs of your house, rather than cycling between Off and On with a higher water temperature.  When your heat pump has to spend 5 minutes an hour defrosting (or whatever that time is) then it has to cycle between Defrosting and On with a higher water temperature (compared to what would be required if it could remain on continuously).  So that makes the fundamentals of heating your house less efficient.  

Patrol

Reed_Richards said:

One point, heat pumps need to defrost, just like fridges but very much more frequently within a particular range of temperatures.

For ASHP. No such need for GSHP (but aware that's outside this subject)

I do have a question though, is there any visible sign of the defrost activity. Asking as a house fairly close to me has an ASHP and there are often emissions of vapour/mist/steam from that direction. I assume it may be from the ASHP and I think the unit must be about 10 years old now

shinytop

Patrol said:

Reed_Richards said:

One point, heat pumps need to defrost, just like fridges but very much more frequently within a particular range of temperatures.

For ASHP. No such need for GSHP (but aware that's outside this subject)

I do have a question though, is there any visible sign of the defrost activity. Asking as a house fairly close to me has an ASHP and there are often emissions of vapour/mist/steam from that direction. I assume it may be from the ASHP and I think the unit must be about 10 years old now

Yes. Emissions of water vapour at the end of each defrost cycle. All do this regardless of age.