What refrigerant would you opt for if purchasing today?

[CalvinHobbes]

Hello, which refrigerant would you opt for and are there any brands/models of ASHP that you would stay clear of?

 

[RobLe]

R290, propane.  Cheap, efficient, no f-gas restrictions on disposal as not a GWB problem.  First used in ac systems 100 years ago, so not exactly new!  Flammability is it’s only downside - not a big issue these days, as most heatpumps are mono blocks outside - just don’t site immediately by a drain or openable window.

Lots to pick from - I’d get a Vaillant Arotherm plus if I were buying a unit (I diy-ed my own propane gshp, there’s a thread on build hub somewhere).  Keep the installation simple for efficiency - only one zone, no TRVs.  Get weather compensation fitted and working!

[JohnMo]

  On 11/06/2024 at 06:12, CalvinHobbes said:

Hello, which refrigerant would you opt for and are there any brands/models of ASHP that you would stay clear of?

 

Expand  

Concentrate on system design, refrigerant makes little or no difference to system performance. Big coil cylinder (3m2+), design for no buffer and single zone. Unit sized as close to heating demand as possible.

 

If it can't do cooling out the box not interested, that would include lots of Daikin units, Vaillant etc

 

If I was buying new again as small a Panasonic R32 unit as I could get away with. Why, combination of decent price, spec and user friendly instructions.

 

I would avoid any heat pump, that makes me have an indoor unit, or ties me into the manufacturer cylinder, that includes all Bosch units, split units (of any kinds).

[LnP]

  On 11/06/2024 at 06:41, RobLe said:

R290, propane.  Cheap, efficient, no f-gas restrictions on disposal as not a GWB problem.  First used in ac systems 100 years ago, so not exactly new!  Flammability is it’s only downside - not a big issue these days, as most heatpumps are mono blocks outside - just don’t site immediately by a drain or openable window.

Lots to pick from - I’d get a Vaillant Arotherm plus if I were buying a unit (I diy-ed my own propane gshp, there’s a thread on build hub somewhere).  Keep the installation simple for efficiency - only one zone, no TRVs.  Get weather compensation fitted and working!

Expand  

For the same operating conditions (in heating mode, the flow temp and outside air temp), how do the COPs compare for R32 vs R290?

[SteamyTea]

  On 11/06/2024 at 14:27, LnP said:

For the same operating conditions (in heating mode, the flow temp and outside air temp), how do the COPs compare for R32 vs R290?

Expand  

It is not as simple as that.

To find that out you would need two identical units, both with the same parameters, with the only difference being the gas.

And that is not how heat pumps are made.

 

Pick the one that suits your needs.

[JohnMo]

  On 11/06/2024 at 14:27, LnP said:

For the same operating conditions (in heating mode, the flow temp and outside air temp), how do the COPs compare for R32 vs R290?

Expand  

Almost the same, best way to compare is SCoP not CoP,

SCoP comparison looks at efficiency over the year, not a small moment in time.

 

Both examples below are the same output size ASHP.

 

Vaillant (R290) at 35 deg flow 4.48 SCoP 

Maxa (R32) at 35 deg flow 4.48 SCoP 4.46

 

As said above system design is way more important, best heat pump in a poor system, becomes a poor performance heat pump.

[JoeBano]

Very happy with my grant aerona3 r410a, quiet getting cop of 4 and cooling with some parameter’s changed. Can get replacement parts from Wolsey’s 

[LnP]

  On 11/06/2024 at 14:45, SteamyTea said:

It is not as simple as that.

To find that out you would need two identical units, both with the same parameters, with the only difference being the gas.

And that is not how heat pumps are made.

 

Pick the one that suits your needs.

Expand  

Well, that is my question. All other things being equal, is there a difference in efficiency between R32 and R290? @JohnMo's info suggests there isn't. But comparing quoted efficiency numbers might not give a valid comparison, so I'm curious whether there's a fundamental thermodynamic reason to choose one over the other.

 

There are several reasons why a manufacturer might choose one refrigerant over another. R290 is preferred if you need a high flow temperature because its critical temperature is higher than R32. At a 70^o C flow temperature, R32 would be close to supercritical (critical term 78^o  C) in the condenser and supercritical fluids don't condense. Both have low enough boiling points at suitable pressures to be able to be evaporated in the evaporator in cold winter air. The Carnot engine is the most efficient heat engine theoretically possible. The efficiency of a Carnot engine is independent of the working medium of the engine. But the irreversibilities inherent in the vapour compression cycle cause the coefficient of performance of practical applications to depend on the refrigerant. A heat pump isn't a Carnot engine but the same principles apply.

 

If you're buying a car and are interested in fuel consumption, it will be handy to know that diesel engines are inherently more efficient than petrol ones because of their higher compression ratio. That's an inescapable thermodynamic fact and it will save you scrolling through petrol engine ones to find the best fuel consumption.

 

Considering an R32 vs an R290 heat pump in an application where both would be technically suitable (i.e. a 45^o C flow temp), is there a fundamental thermodynamic reason why you'd choose one over the other? COP, SCOP or something else? I'm curious 🙂

 

Edited June 11, 2024 by LnP

[PhilT]

  On 11/06/2024 at 19:07, LnP said:

Well, that is my question. All other things being equal, is there a difference in efficiency between R32 and R290? @JohnMo's info suggests there isn't. But comparing quoted efficiency numbers might not give a valid comparison, so I'm curious whether there's a fundamental thermodynamic reason to choose one over the other.

 

There are several reasons why a manufacturer might choose one refrigerant over another. R290 is preferred if you need a high flow temperature because its critical temperature is higher than R32. At a 70^o C flow temperature, R32 would be close to supercritical (critical term 78^o  C) in the condenser and supercritical fluids don't condense. Both have low enough boiling points at suitable pressures to be able to be evaporated in the evaporator in cold winter air. The Carnot engine is the most efficient heat engine theoretically possible. The efficiency of a Carnot engine is independent of the working medium of the engine. But the irreversibilities inherent in the vapour compression cycle cause the coefficient of performance of practical applications to depend on the refrigerant. A heat pump isn't a Carnot engine but the same principles apply.

 

If you're buying a car and are interested in fuel consumption, it will be handy to know that diesel engines are inherently more efficient than petrol ones because of their higher compression ratio. That's an inescapable thermodynamic fact and it will save you scrolling through petrol engine ones to find the best fuel consumption.

 

Considering an R32 vs an R290 heat pump in an application where both would be technically suitable (i.e. a 45^o C flow temp), is there a fundamental thermodynamic reason why you'd choose one over the other? COP, SCOP or something else? I'm curious 🙂

 

Expand  

Easy enough to find out there are dozens of articles and research projects comparing those two

[JohnMo]

  On 11/06/2024 at 19:07, LnP said:

 

Considering an R32 vs an R290 heat pump in an application where both would be technically suitable (i.e. a 45^o C flow temp), is there a fundamental thermodynamic reason why you'd choose one over the other? COP, SCOP or something else? I'm curious

Expand  

@RobLe stated one reason for h environmental plus a safety issue, flammability.

 

Reasonable write here. Note we are a moderate climate not a cold one

 

https://sprsunheatpump.com/Differences-between-R290-and-R32-Heat-Pumps-id46798837.html

[dpmiller]

  On 11/06/2024 at 19:07, LnP said:

 

If you're buying a car and are interested in fuel consumption, it will be handy to know that diesel engines are inherently more efficient than petrol ones because of their higher compression ratio. That's an inescapable thermodynamic fact and it will save you scrolling through petrol engine ones to find the best fuel consumption.

Expand  

 

Atkinson cycle needs consideration

[SteamyTea]

[HughF]

I’d pick the unit with the widest modulation ratio, ignoring the type of refrigerant used.

[PhilT]

  On 14/06/2024 at 11:24, HughF said:

I’d pick the unit with the widest modulation ratio, ignoring the type of refrigerant used.

Expand  

Where can you find the modulation ratio published for all the different makes and models?

[JohnMo]

  On 14/06/2024 at 12:29, PhilT said:

Where can you find the modulation ratio published for all the different makes and models?

Expand  

Data sheets normally. So a bit long winded

[HughF]

  On 14/06/2024 at 12:29, PhilT said:

Where can you find the modulation ratio published for all the different makes and models?

Expand  

Yep, manufacturers data sheet…

[PhilT]

  On 11/06/2024 at 06:12, CalvinHobbes said:

Hello, which refrigerant would you opt for and are there any brands/models of ASHP that you would stay clear of?

 

Expand  

The MCS database may be helpful, giving SCOP test results at different flow temps (typically 35 to 55) for most (possibly all?) commercially available MCS certified heat pumps, now including the new Octopus Cosy 6. https://mcscertified.com/product-directory/

While accepting that design and operation mode are most important, it is worth noting that, generally, the MCS tests show that R32 heat pumps have significantly better SCOPs than their R290 equivalents. You can see this most clearly by comparing like for like R32 vs R290 models, for example the Misubishi R32 6kW model PUZ-WM60VAA has SCOP of 4.81 at 35degC, compared to the Mitsubishi R290 6kW model PUZ-WZ60VAA (a much newer model) which has a SCOP of 4.39 at 35degC