Anybody in northern europe/UK or other cold place running air source heat pump

[CatalinaWOW]

As OP says the performance depends heavily on the details.  I am NW US and at my location winter temps average around 0C for many weeks, with dips to -5 to -8 C.  All at high relative humidity.  So not too different from OPs conditions.  My house has older (I wasn't there when they were installed but they appear to be late 1980s to 1990s units) air source heat pumps and the cost of operating them caused me to switch to fuel based sources.  Way too much time was spent defrosting.  Might work better with newer technology pumps, but I couldn't prove it to myself.

They are handy for the few hot days of the summer which can't be dealt with with shade, good insulation, thermal mass,  overnight cooling and the like.  And because site details and the house efficiency details work for me the cost of operation is similar to what james_s mentions.

[Nauris]

Might work better with newer technology pumps, but I couldn't prove it to myself.

It certainly does. There has been very big leap forwards since '90. Like actually working defrosting, inverter driven twin rotary compressors, electronically controlled expansion valves, different refrigerants, oils that do not freeze in the evaporator, inverter driven outdoor and indoor unit fans, bigger heat exchangers and so on...

[CatalinaWOW]

Actually I should have said that I couldn't prove that savings in operating costs would cover the installation costs.  Or that I wouldn't be better off waiting for a few more years of improvements.  And I am not saying it wouldn't, just saying that with the amount of research I did it wasn't obvious to me.

[theoldwizard1]

Apologies for jumping in late ...

Heat pumps are a classic case of "BUYER BEWARE".  This is especially true with mini-split heat pumps !  You have to learn how to read the specifications.

Many heat pumps will actually supply heat from below -20C WITHOUT USING A RESISTIVE HEAT STRIP !  Cheaper models use resistive heat strips when the temp gets down to about 10C and your power bill goes up, A LOT.

Again, BUYER BEWARE.  Even the top brands (Mitsubishi, Fujitsu, etc) sell units that will work at low temperatures, but they also sell units that rely on heat strips.

[james_s]

There's no magic here, it's all a matter of the size and efficiency of the unit and how it's set up. If the heat pump is too small or the efficiency too low then it will require supplemental electric heat to keep up.

[kaz911]

Just a follow up:

Denmark - heat pump installed for 1 1/2 years. No issues at all even in -10c in February '18. Energy savings compared to old electric storage heaters - about 2/3- so TOTAL electric consumption is now 1/3 of what it was before with same avg. indoor temperature. One single Panasonic SZ9 for 80 SQM house with big windows and one outlet. Had to reset it ONCE during the summer probably due to a thunderstorm making it slightly confused.

UK - Daikin Ururu Sarara thing - over sized for the room but - kept my 25m2 lab  hot during winter and cold during summer. Savings > 50% less TOTAL electricity consumption in my lab over 1 year and 3 months. That is despite cooling running a lot this year! during summer and Ururu spends some extra energy pulling in "real" fresh air from outside. And since it is over sized next door have not even noticed it is there as fans run VERY silent - despite it being about 30cm from our fence in a terraced house and about 3 meters from neighbors outside "entertainment table".....

So thumbs up for heat pumps from me. They will earn their installed cost back in about 3-4 years worst case.

[cdev]

So heat pumps are much more efficient than resistive heating for heating?

Are you serious? How is this done? How does one tell the difference?

Apologies for jumping in late ...

Heat pumps are a classic case of "BUYER BEWARE".  This is especially true with mini-split heat pumps !  You have to learn how to read the specifications.

Many heat pumps will actually supply heat from below -20C WITHOUT USING A RESISTIVE HEAT STRIP !  Cheaper models use resistive heat strips when the temp gets down to about 10C and your power bill goes up, A LOT.

Again, BUYER BEWARE.  Even the top brands (Mitsubishi, Fujitsu, etc) sell units that will work at low temperatures, but they also sell units that rely on heat strips.

[cdev]

Nauris - could you summarize the gist of the report?

I have seen claims of 2 COP at -30C!

But typically you get COP of 3 at 0C including defrosting.
They are really popular here many houses even have more than one.

One big importer get some units measured by independent lab attached are some results (vertical axis is avarage output power/input power (COP))
First Mitsubishi Electric MSZ-FH35VE we have two of these in this house


Second MSZ-LN25VGW, the newest and greatest one.


Figures include defrosting, outdoor relative humidity about 80%, units are operating at partial load above aprox. -10C outdoor temperature, room temperature 20C
Further details are in the report but it is in finish.

Here is more graphs and models(in finish):
https://www.scanoffice.fi/fi/tuotteet/tuoteryhmat/ilmalampopumput/raportit-ja-sertifikaatit/vttn-testiraportit

[AndyC_772]

So heat pumps are much more efficient than resistive heating for heating?

Are you serious? How is this done? How does one tell the difference?

Yes, absolutely. The search term you'll need is "Coefficient of Performance", or COP, which is the ratio of useful heat output to energy consumed.

The COP for a good domestic air con / heat pump system is around 4 to 5.

[bingo600]

We have a Swedish IVT Air/Air pump in the summerhouse in SE , COP = 5+  ,  Efficient to -25
IVT Nordic Inverter 12 KHR-N


Our choice was based on "Get one made for the Cold climate, by the Swedes" , and the 10C - "keep house at standby heat".

Lot's of "Cheap" pumps can not go below 18C , but that's only an issue in a summerhouse i guess.



Bosch - Bought IVT in 2013 , and our's is now a : 8000 AA

https://www.bosch-thermotechnology.com/dk/da/ocs/compress-8000-aa-758044-p

Others to looked as was

Daikin & Mitshubishi.  Where Daikin prob was #2


/Bingo

[james_s]

So heat pumps are much more efficient than resistive heating for heating?

Are you serious? How is this done? How does one tell the difference?

Yes that's the whole point. For 1kW of electricity in you get about 3kW of heat into your house. 1kW comes from the electricity, the other 2kW comes from refrigerating the outdoors. Not to be confused with some kind of free energy scheme, there's no energy being created from nothing, you're just consuming some energy to shove other energy around to where you want it. While electric resistance heat is 100% efficient at turning electricity into heat, that's only part of the process. Generating and transporting the electricity is far less than 100% efficient and dumps a lot of heat into the atmosphere and a heat pump can be thought of as recovering a portion of that.

[coppice]

So heat pumps are much more efficient than resistive heating for heating?

Are you serious? How is this done? How does one tell the difference?

Yes, absolutely. The search term you'll need is "Coefficient of Performance", or COP, which is the ratio of useful heat output to energy consumed.

The COP for a good domestic air con / heat pump system is around 4 to 5.

4 to 5 is a bit optimistic. 3 to 4 is more like the figure you usually get.

[woodchips]

Good luck!

We have an old GEC Nightstor electric boiler running wet radiators. It is brilliant, but we also get through 16MW electricity per year, that is everything, heat, domestic, workshop. It seemed sensible to look,again, at a heat pump.

After spending a long time searching, there are many websites to look at, from the UK posting feedback and comments ASHP is not a great way to go. This means the total cost not only of running, but also buying and maintaining it.

Doing the sums I came to the conclusion that I could save more money by running a diesel generator into the Nightstor. It seems that diesel is available for £0.70 per litre, so £0.075 per kWh. Diesel is 11.6 kWh per kg, sg of 0.8. The genset is about 60-70% efficient but the losses are heat, so you put it in a shed and plumb the radiator into the house. If the shed is insulated then it to will be warm, like my workshop! It would be cheaper if you can use heating oil in the engine, but savings might be more illusatory than real.

The one unknown in these ASHP calculations is how much they cost in maintenance. The Nightstor costs nothing per year in maintenance, unlike a gas or oil boiler. I once cansidered a log gassification boiler, we have a wood so the fuel is free, other than the cost of felling, shifting and cutting up, which is significant. The cost of buying the gassification plant was horrendous, can't really remember, £10k? And then you have the chimney sweeping etc etc. Simply didn't add up.

[timgiles]

Currently living in a small village in the middle of Sweden on the East coast (Umeå). We have a small heat pump by Mitsubishi and it manages ok down to about -15oC and stops working at -30oC. It is stated that it is an 'extended temperature' model - the normal ones stop providing more than they consume around -15oC if I remember. Air source works well but ground source works better.

Ground source work well but if you need to heat a large house you are looking at multiple units, where each unit requires an internal large heat transfer unit and an externally mounted radiator / fan unit. As stated, if you are going to get properly cold weather, you need to make sure you purchase an extended temperature model - that has a better compressor. Else when it is cold, you are basically switching over to standard resistive load type costs. Ground source will normally have a single hole bored 150m (ish) deep and requires only a single unit mounted inside. Since winter cold only penetrates about 35 meters - they are effected by changes in surface temperature as much.

[james_s]

The diesel generator idea has some appeal, at least as supplemental energy. If all you want is heat then it's going to be more efficient to burn the diesel in a boiler but if you can use the electricity and pipe the heat into the house then it could start to look pretty favorable. On top of that you could recover a sizable amount of heat from the exhaust.

I wouldn't go out and buy a new genset to do that but in parts of the world where diesel passenger cars are common it ought to be easy to get an engine from a salvage yard and couple it to a surplus alternator. Could be a fun project.

[NiHaoMike]

What about a CHP generator plus a heat pump to extract the last bit of heat that can be realistically extracted from the exhaust?

[Nauris]

What about a CHP generator plus a heat pump to extract the last bit of heat that can be realistically extracted from the exhaust?

Does work, that is sometimes used to boost heat recovery from exhaust washing units in smaller biomass fired district heating plants, profitability depends on things like return water temp, fuel moisture content and electricity price.

[soldar]

I am running heat pumps in central Spain and they definitely produce much more heat than a resistive space heater. It is cheaper to heat each room as needed than to heat the entire house with the central boiler.

They do have one problem, if I can call it that, and it is that condensation on the outside coil freezes solid and then the unit goes into a defrost cycle which is inefficient (ice outside needs to be melted) and uncomfortable because you are not getting any heat during that time.

It could be that colder air is dryer and the problem diminishes as the air gets colder but if the air is slightly above or below freezing and humid then you get a lot of defrosting.