R410a here, does a grand job… although it’s quite a charge at 1.6kgs for a 9kW unit….

@hughf

Posted by: @editor

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R290, or propane, is another refrigerant used in heat pumps. Its most notable feature is its exceptionally low GWP of 3, making it one of the most environmentally-friendly refrigerants available.

However, R290 is less efficient than R32. This lower efficiency means that heat pumps using R290 will consume more energy to provide the same level of heating or cooling as those using R32. Over time, this increased energy consumption could negate the environmental benefits offered by its low GWP, especially considering the CO2 emissions associated with energy production.

Is the second assertion (R290 = Less efficient) actually true?

Here are extracts from the spec sheets for Mitsubishi R32 and Vaillant R290, both I would suggest state of the art consumer pumps.  The Vaillant pump (R290) is the more efficient although the difference is small.  Is the article more propaganda (like the 'high temperature heat pumps article a few days ago) by a manufacturer that does not have an R290 pump?

I always assumed it was marginally more efficient, and hence it requires considerably smaller charge volumes, but I’m no refrigeration engineer.

To be honest, I don’t think there’s much in them. Some of the tricks used to get higher temperatures on some heat pumps (for dhw charges) can be attributed to other techniques like EVI.

When I was having a good chat with Chris at Cool Energy, he said that r410 was actually a better gas than r32, and the EVI on the r32 machines was a requirement to get round the physics of that gas.

As soon as a drop in replacement for r410 was available, they were planning to switch back to that gas. Interesting….

The only practical downside (from a consumer point of view) of R290 appears to be its flammability and hence location constraints.  Meanwhile we happily pump methane into our homes and I can have 1 13kg cylinder of R290 in my boat/caravan.

Once you reach a cop of 4+ Im not sure a few points either way matters

Yeah, it’s all a bit ridiculous this obsession over 1kg of propane….

@hughf We have a Daikin and thus R32 refrigerant; I considered a Vaillant heat pump but the constraints on available siting due to doors and windows precluded them anyway. I have often wondered about the GWP, if the rules / guidance are adhered to, then surely it would only be the problem of leakage / scrapage then. Perhaps these factors are greater risks than I’d imagined - if the greater efficiency of  R32 is a significant factor, then isn’t this still a good choice? That is, until something better ‘comes along’? Regards, Toodles.

@toodles don’t worry too much about what gas your system uses. What matters is are you warm, can you afford to heat your house with your system?

Nothing wrong with r32 either, perfectly decent refrigerant….. that also happens to be flammable, but not to the extent of propane.

@hughf Very happy with the performance achieved; when we were experiencing -6 or -7 degrees C. OAT a week or so back, our desired 22.5 degrees C. was under by 0.7 degrees in the early morning in the living room and fully up to temperature by about 10:00. The COP during this chill period was approx 2.6 and at present, we are seeing 4.5 or 4.6 when it is + 8 degrees C. This translates to 1.5 kW/h when -6 and 0.5 - 0.6 kW/h when + 8; we are very comfortable and have no intentions of ever leaking any R32 to the atmosphere knowingly!;-) Regards, Toodles.

@jamespa I guess R32 could be more efficient but there's plenty else that can dictate the efficiency of a heatpump. The Vaillant may just be designed better with better compressor control or something. It certainly modulates down and achieves steady state far better than my Ecodan R32. I'm sure I read somewhere someone saying that R32 is better at lowest temps but again no idea if that's true, perhaps dependent on what temp each changes state

I have been pondering the significance of GWP. Exactly how much refrigerant is in a heatpump? If my Ecodan only had 1kg of R32 then that's what 675CO2e equating to something like 3,200 kWh of gas - that's less than half the gas I was using in a single year, that seems pretty sustainable by comparison assuming typically minimal leakage over say a decade

Posted by: @walkers-heatpump

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I have been pondering the significance of GWP. Exactly how much refrigerant is in a heatpump? If my Ecodan only had 1kg of R32 then that's what 675CO2e equating to something like 3,200 kWh of gas - that's less than half the gas I was using in a single year, that seems pretty sustainable by comparison assuming typically minimal leakage over say a decade

The charge is specified, typically 1-3kW.  Your view has always been my view, nice if you can get low GWP but, by comparison with the savings due to adopting a heat pump, not the environmental determinant.  Also the refrigerant shouldn't leak even when its disposed of (but of course we all suspect it does!).

Posted by: @walkers-heatpump

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I guess R32 could be more efficient but there's plenty else that can dictate the efficiency of a heatpump. The Vaillant may just be designed better with better compressor control or something. It certainly modulates down and achieves steady state far better than my Ecodan R32. I'm sure I read somewhere someone saying that R32 is better at lowest temps but again no idea if that's true, perhaps dependent on what temp each changes state

Yes, I dont know what the physics says, hence why I picked Vaillant and Mitsubishi to compare- two representative manufacturers operating at about the same 'level' in the market (ie good, solid, well reputed but still mainstream).  

Refrigerant efficiency is quoted in absolute terms with reference to the refrigerant properties. There are many more variables that determine the overall comparative ASHP unit efficiency. 

The refrigeration industry is moving back to pure refrigerants, which includes R290, CO2, R32, etc. Most pure refrigerants are flammable to some extent. The IEC-60335-40 charge limit on an internal use of R290 propane is 5kg. To put that in context, most domestic monoblocs will have less than 2kg charge externally. The actual GWP impact of any refrigerant is 0 if it properly handled, does not leak, is recovered at the end of the product life, and recycled or destroyed. Unless something illegal or accidental happens, that's the route appliances containing refrigerants will follow. When you think how much methane gas UK distribution utility companies lose a year just in leaky pipes and lack of infrastructure maintenance then 1-2kg of R32 @ 675 GWP is no big deal.

R410a has become a very expensive refrigerant, so has R134a, and R32 will creep up. That's due to the gradual draw down and phase out of higher GWP greenhouse gas refrigerants under the F-Gas regulations. F-Gas timelines project up to 2050 under EU 517/2014 latest F-Gas proposal, so it's a very long-term process. * But for the small quantities a monobloc ASHP needs, refrigerant cost isn't a huge concern.

More of an industry concern is the use of PFAS chemicals, so-called 'forever chemicals' as they don't degrade readily in the environment and there is increasing concern about their environmental and health impact. There is a proposal to draw down and ban their use tabled by several EU member states. That would have wide implications for the industrial heat pump market in particular, as they use HFO synthetic refrigerants quite extensively, such as R1234ze and R1234yf containing PFASs in their refrigerant blend.

* The UK currently adopts and aligns with the EU F-Gas legislation in full post Brexit.