£6200+ for oil boiler change - is quote reasonable?

Netexporter

You will be best served by an ASHP that uses R290 (propane) as the refrigerant. You can maintain a higher flow temperature for a given COP, compared to a machine with the "traditional" refrigerants. However, you should still aim to to have as low a flow temperature as possible.

The Vaillant Arotherm+ seems to be doing well in the league tables, but that might just be a function of brand awareness.

HeatpumpMonitor.org

Reed_Richards

But R290 (propane) is heavier than air and flammable so there are restrictions on where you can site a heat pump that uses it which don't apply to heat pumps using R32.

Netexporter

Reed_Richards said:

But R290 (propane) is heavier than air and flammable so there are restrictions on where you can site a heat pump that uses it which don't apply to heat pumps using R32.

I'm aware of that. It isn't that onerous. And R32 is an extremely powerful greenhouse gas. Propane has no greenhouse effect.

Reed_Richards

Yes, propane is heavier than air; I wonder what becomes of it if it leaks?  Do they add a bit of foul-smelling chemical, as they do for propane used as a combustible gas source?

Netexporter

It dissipates, harmlessly, as long as you take precautions to prevent it entering drains etc. The units are factory charged and sealed, so leakage is extremely unlikely.

R32, and the like, cause hundreds of years of greenhouse heating if it leaks.

R290 offers far better performance.

Which do you think is preferable?

Reed_Richards

Well, my heat pump sits behind my kitchen just in front of a 2 metre section of wall between my kitchen window and the corner of the building.  There is an open drain that takes the rainwater from my roof to a soakaway at this corner.  So I'm not at all sure that I could site an R290 heat pump in the same location.

smallblueplanet

Netexporter said:

It dissipates, harmlessly, as long as you take precautions to prevent it entering drains etc. The units are factory charged and sealed, so leakage is extremely unlikely.

R32, and the like, cause hundreds of years of greenhouse heating if it leaks.

R290 offers far better performance.

Which do you think is preferable?

Thanks for the extra info, R290 sounds preferable I have lined up a couple of quotes in the New Year to start with. I will use these to gain extra info about what they think I should do and what I can do. The ASHP could go at the end of the utility room/garage I hope, there are no water drainage inlets nearby, it is at the start of the garden. Or maybe on the garage flat roof attached to the house side wall? Bit off the wall that one but thought it might make the pipework easier. 

Reed_Richards

smallblueplanet said:

....Or maybe on the garage flat roof attached to the house side wall? Bit off the wall that one but thought it might make the pipework easier. 

I've seen pictures of heat pumps mounted on flat roofs so it's by no means out of the question.  And anything that makes the pipework easier should be a good thing.

QrizB

smallblueplanet said:

Or maybe on the garage flat roof attached to the house side wall? Bit off the wall that one but thought it might make the pipework easier. 

My neighbours have one on brackets at upper-floor height. They've had it for years (the previous owner ran an aircon company).

Netexporter

I think you need planning permission if they're not on the ground. I'd also beware the garage roof becoming a sounding board.