In the international market place there are several systems that use an air source heat pump to provide space heating, space cooling and DHW.  Availability in north America is quite limited.  Some of the systems I've found are : Daikin Altherma, LG Therma V & Tritherma (China),Anhui (China), Rotoberg (China).  The outdoor unit is very similar to that typical of a "minisplit"  while the indoor unit has a refrigerant to water heat exchanger.  There also are systems where all the refrigerant hardware is in the outdoor unit these are called "monoblock" systems & require protection from freezing.   These systems work, at reduced output, down to -25c (-13f) in some cases.  They also seem to have higher capacities than most minisplits with capacity from 1 to 5+ tons being offered.  They all seem to use variable speed (inverter) scroll compressors and offer heating COP s above 4 at 45f. & some claim COPs about 2 even at zero f.  In all cases the package leaves much to be done by the installer, as they can heat or cool with radient tubing or fan coils.  radient floor cooling is very limited and can not dehumidify but add a fan coil or 2 and it looks more like a minisplit that can do DHW both summer and winter.  Anyway these seem like a reasonable way to get DHW in a net zero PV equipped house.     

That is what we build. The systems are A/W or W/W but we haven't got into the inverter systems yet, still in the design stage. The best systems in Europe have COPs of 6-7 and to get this floor heating is a must. Stay away from the Chinese stuff as there is little or no long term support.

Most of our stuff has been commercial/industrial but 20% is resi.

The best systems in Europe have COPs of 6-7

On a year-round basis?

Looks like I missed something in my research.

Which ones are you referring to?

Heliotherm and IDM are a couple of them. Their W/W units are in the 6+ range but it all depends on the installation. A/W is definitely less as expected. IIRC it can be in the 4- 4.5 range (perhaps on an annual basis). It seems that the real improvements have all been during the last few years. Inverter systems and weather compensation (outdoor reset) are big reasons. This is all second hand info BTW, I have seen the equipment but I have to rely on european industry people for the numbers.

I have to rely on european industry people for the numbers.

Industry people? Would those be people with an interest in selling the products? I see a lot of claims, but no third party corroboration and nothing indicating that they possess any different technology. BTW, they are now claiming COP of 8.4

A COP of 6 for an open loop ground source to large surface radiant floor with inverter driven compressor and outdoor reset sounds reasonable. Air source - not unless you have very mild weather.

Posted By ICFHybrid on 18 Aug 2012 09:51 AM

I have to rely on european industry people for the numbers.

Industry people? Would those be people with an interest in selling the products? I see a lot of claims, but no third party corroboration and nothing indicating that they possess any different technology. BTW, they are now claiming COP of 8.4

Those I talk to regularly would not believe an 8.4 COP and of course no manufacturer is talking about ancillary loads, only their equipment and we don't know at what temps are they measuring. They could be testing at really favorable temps.

It seems many  COP claims are BS because of bogus assumptions or ignored energy use, I've even seen a ground source heat pump that used solar preheated water.  Any way I've found one heat pump that claims a cop of 2.47 using -20c air to heat water to +35c & the same unit has a 4.85COP using +10c (50f) air to heat water to +35.  But it's cop is 3.69 heating water to +45c with air at +10c. That pretty well makes the case for radient floors.   The advance in heat pumps is directly related to the adoption of both inverter control and "enthalpy boost" AKA Enhanced Vapor Injection.  The EVI is what has allowed heat pumps to produce +60c water from -20c air at COP greater than 1.5 and operation with a COP above 1 below -25c (-13f).  Beware it does cost a bit more to use both inverters and EVI & lots of manufacturers do not!

Posted By Liebler on 18 Aug 2012 09:35 PM
It seems many  COP claims are BS because of bogus assumptions or ignored energy use, I've even seen a ground source heat pump that used solar preheated water.  Any way I've found one heat pump that claims a cop of 2.47 using -20c air to heat water to +35c & the same unit has a 4.85COP using +10c (50f) air to heat water to +35.  But it's cop is 3.69 heating water to +45c with air at +10c. That pretty well makes the case for radient floors.   The advance in heat pumps is directly related to the adoption of both inverter control and "enthalpy boost" AKA Enhanced Vapor Injection.  The EVI is what has allowed heat pumps to produce +60c water from -20c air at COP greater than 1.5 and operation with a COP above 1 below -25c (-13f).  Beware it does cost a bit more to use both inverters and EVI & lots of manufacturers do not!

True, in a way it doesn't matter what the makers claim because the installation will dictate success or failure. We are working on a solar preheat ASHP for those who want the HP but cannot drill or don't want to drill.

The dT is so important and while it is nice to be able to have -20A/60W performance, it is a tall order, we have to use much bigger evaporators to get the low temp performance, we need an EEV instead of the TXV to regulate refrigerant flow and if I use vapour injection I need 2 EEVs and a lot of programming so there is a definite cost disadvantage to using it. It is a limited market in North America.

For us, that is down the road. I will be happy if I can get a annual "system" COP of 5 with a solar/ASHP system. That will easily compete with the GSHPs.

I would think that an inverter controlled HP would be critical for a solar air application - you want it to run continuously while the sun is shining but at the minimum air flow rate needed (slower air flow means more gain from the solar collector). But you also want to predict the btus that will be needed at night. Air to water would make it much easier to store the heat for nighttime use.

There are more ways to get the extra heat out of a system than just an inverter but it does make like easier. The real problem for us is that most of the Europeans systems don't have is cooling . Most of their systems have no reversing valve so the relation between evap and condenser is much simpler and is is easier to optimize. It makes their systems look really good compared to our AC derived junk

I designed one ASHP with a very oversized evap that would be very efficient in the winter but simply didn't work in the summer for cooling as there was way too much refrigerant (even with an accumulator) and the fan speeds were fine for winter but way too fast for summer. An inverter would work better in that situation but it takes a lot of development.

All our A/W or W/W HPs have 120gal tanks for off peak storage and to keep cycling to a minimum. But it also adds to the cost so there is another tradeoff.

"Most of their systems have no reversing valve so the relation between evap and condenser is much simpler and is is easier to optimize. It makes their systems look really good compared to our AC derived junk"

  How do they handle defrost???  Defrost cycles are crucial to getting heat from of air below about 5c. The least energy defrost cycle is hot gas with the fan off & needs to be followed by a "drying" function where the evaporator fan is run hard. 

Posted By Liebler on 19 Aug 2012 09:44 PM
"Most of their systems have no reversing valve so the relation between evap and condenser is much simpler and is is easier to optimize. It makes their systems look really good compared to our AC derived junk"

  How do they handle defrost???  Defrost cycles are crucial to getting heat from of air below about 5c. The least energy defrost cycle is hot gas with the fan off & needs to be followed by a "drying" function where the evaporator fan is run hard. 

Hot gas bypass is one way and yes some do have reversing valves but not necessarily for cooling. My point was that they did not need to worry about cooling performance at all and it can be a compromise one way or the other to do both heating and cooling well. It just takes more work.