Advancements in cold climate heat pump efficiency.

[Brian26]

Mini splits are starting to achieve some incredible efficiencies in some pretty extreme cold. This new LG unit can maintain a COP of 2.88 at 5 degrees at full output. It can turn down to a crazy low 561 btus using only 60 watts even at 5 degrees with a COP of 2.74.

The 47 degrees specs are just as impressive. It can output almost double its rated capacity with 20,472 btus with a COP of 4.55.

I went through the engineering manual and even at -13 it still has an impressive COP of 2.56 and still has close to 90 percent of its capacity.

So this LG unit will have an effective efficiency of 288% at 5 degrees and 455% at 47 degrees.

ASHP

ashp.neep.org

 

[CaptSpiff]

Is that a 9000 btu unit ? That's amazing.

 

[DBoon]

My recollection is that my Fujitsu RLS2H (capability of providing heat down to -17 degrees F) has comparable performance. I recall that the rated capacity for my 15 kBTU unit is around -5 degrees F. Having operated it as a primary heater in a house during renovation, I can tell you that it produces a nice, warm heat below 0 degrees F.

 

[Highbeam]

I believe the new advancement is that it makes full rated output at -5 AND does so with a COP of nearly 3.

 

[peakbagger]

I agree, normally the COP and output drops significantly as the temps drop. Many companies did not routinely supply low temp performance and it caused some issues with various state incentive programs in northern New England. There is non profit linked to Vermonts program that lists the preformance at lower temps a bit more typical of the region. They have a website but I cant find it right now.

 

[Brian26]

Is that a 9000 btu unit ? That's amazing.

It is listed as a 9k unit. Most mini splits share the same compressor and its the software that limits the output. If you look at the submittal sheets usually the 9 and 12k and 18 and 24k units have the same compressors.

 

[Brian26]

I agree, normally the COP and output drops significantly as the temps drop. Many companies did not routinely supply low temp performance and it caused some issues with various state incentive programs in northern New England. There is non profit linked to Vermonts program that lists the preformance at lower temps a bit more typical of the region. They have a website but I cant find it right now.

Its the Northeast Energy Efficiency Partners directory. The current AHRI testing only requires performance specifications at 47 and 17 degrees. This directory got the manufacturers to submit the data for performance at colder New England temperatures such as 5 degrees.

ASHP

ashp.neep.org

 

[Brian26]

I believe the new advancement is that it makes full rated output at -5 AND does so with a COP of nearly 3.

Just as important are the turn down ratios between the minimum and maximum output. That LG at 47 degrees can modulate from 1000 to 20000 btus. No fossil fuel source of heat has anywhere near that kind of variable range of btu output.

 

[peakbagger]

Since I am up in an area where cold weather temps can go below even the 5 degree temps I have thought of getting a functioning used one and removing the outdoor coil and replacing it with a water to refrigerant heat exchanger and try a small scale geothermal setup. Ground water temp is consistently in the low forties and my guess is the minisplit compressors performance is better than a typical geothermal. Whenever I run into geothermal reps at trade shows its obvious that they are focused on whole house high end custom systems or lower efficiency units for middle atlantic and down south.

I have participated in a couple manufacturer webinars of late and across the board they still recommend having a alternative source of backup heat from the middle atlantic north.

 

[Brian26]

Since I am up in an area where cold weather temps can go below even the 5 degree temps I have thought of getting a functioning used one and removing the outdoor coil and replacing it with a water to refrigerant heat exchanger and try a small scale geothermal setup. Ground water temp is consistently in the low forties and my guess is the minisplit compressors performance is better than a typical geothermal. Whenever I run into geothermal reps at trade shows its obvious that they are focused on whole house high end custom systems or lower efficiency units for middle atlantic and down south.

I have participated in a couple manufacturer webinars of late and across the board they still recommend having a alternative source of backup heat from the middle atlantic north.

LG has an air to water heat pump now that I think is available here. It uses a new more efficient compressor and the new r32 refrigerant that is going to replace r410a. It is an all in one unit and only water lines need to be run to it. The specs claim it can provide 149 degree water temperatures all the way down to-13.


LG THERMA V R32 Monobloc is an all-in-one unit equipped with an innovative and eco-friendly R1 compressor and R32 refrigerant. This unit can operate at extremely cold weather like -25℃ and heat water up to 65℃.

Monobloc AWHP | Products | Air Solution | Business | LG Global

LG's Monobloc utilises heat generated by the outdoor unit via heat exchange with external air transferred to the domestic hot water tank. Learn more now.

www.lg.com

 

[peakbagger]

That is good to know if they are importing them. If you look at John Siegenthalers stuff he is major advocate of low temperature radiant emitters supplied from a thermal storage tank heated by an air to water heat exchanger with a wood or pellet boiler for backup. To date the offerings for these have been pretty slim less known companies.

I took a quick look and do not see any for sale in the US

 

[Highbeam]

LG has an air to water heat pump now that I think is available here. It uses a new more efficient compressor and the new r32 refrigerant that is going to replace r410a. It is an all in one unit and only water lines need to be run to it. The specs claim it can provide 149 degree water temperatures all the way down to-13.
View attachment 270231

LG THERMA V R32 Monobloc is an all-in-one unit equipped with an innovative and eco-friendly R1 compressor and R32 refrigerant. This unit can operate at extremely cold weather like -25℃ and heat water up to 65℃.

Monobloc AWHP | Products | Air Solution | Business | LG Global

LG's Monobloc utilises heat generated by the outdoor unit via heat exchange with external air transferred to the domestic hot water tank. Learn more now.

www.lg.com

This is what we need. Okay, what I want.

 

[peakbagger]

Similar to several other firms, they just dont seem to want to import them in the US.

Several companies sell inverter based refrigerators in Mexico but not in the US.

 

[DBoon]

I believe the new advancement is that it makes full rated output at -5 AND does so with a COP of nearly 3.

Agreed that a COP of nearly 3.0 at 5 degrees F is a pretty nice advancement in a broader-market (lower-priced) unit.

I reminded myself what my nearly 10-year old technology Fujitsu unit could do. Take a look at the RLS2H Design Technical Manual (link here https://manualzz.com/doc/7776927/rls2h-design-technical-manual, extracted image attached). At an outdoor temperature of -17 degrees F the input power is 2.28 kW and the output is 15.4 kBTU/hr (4.51 kW/hr) or a COP of ~2.0 with indoor temperature at 65 degrees F. At -5 deg F, COP is 2.17 and at 5 deg F COP is 2.37. I could expect some de-rating from this (it is a Total Capacity, not actual Output/Hr rating, so there must be some defrost cycle lost). But still, this was a pretty good COP for its day (nearly 10 year old technology).

Where these units historically suffered was that their COPs at higher temperatures weren't nearly as good (COP of this one only 3.25 at 47 degrees F). as units that don't have the cold-heating capability.

I recently installed Mitsubishi MXZ-2C20NAHZ2 splits in a condo. See attached datasheet. That unit at 5 degrees F outputs 22 kBTU/hr (6.44 kW/hr) with an input of 1.45 kW (COP = 4.44) and COP of 5.85. It can't modulate as low as the LG unit (only to about 25% of full output). I can't remember if this is capable of operating below 5 degrees F, but it is not so critical for it to do so in that southeastern NY climate.

So it is good to know that other manufacturers are gaining capabilities for great COP at low temps. Fujitsu and Mitsubishi need some competition in that area. Their prices have been a little ridiculous (Mitsubishi more so than Fujitsu). Maybe that is why the Mitsu unit came in a lot lower than expected when I asked for a quote a year and a half ago.

 

[begreen]

That Fujitsu is a remarkable unit. I can't forget when several years ago I visited a local old farmhouse that had one sitting next to the entry steps. It was running, but very quiet. When the owner opened the door, the heat blasted out, even though it was 14º outside. I asked if they also had a woodstove going and they said no, just the mini.

 

[Brian26]

That Fujitsu is a remarkable unit. I can't forget when several years ago I visited a local old farmhouse that had one sitting next to the entry steps. It was running, but very quiet. When the owner opened the door, the heat blasted out, even though it was 14º outside. I asked if they also had a woodstove going and they said no, just the mini.

The Japanese invented mini splits and they had to be reliable, quiet, and energy efficient as electricity was and still is expensive in Japan. If installed correctly the refrigerant loop is airsealed and the compressor oil is never exposed to outside contaminates. The compressors can last for decades. I know of someone with a 15 year old Mitsubishi split that has been running pretty much nonstop for 15 years. Inverter driven compressor also have the huge advantage of soft starting at low rpms and gradually ramping up.

Despite what people think of the electronics on these they are extremely reliable. These units were designed to be used mainly in Asia and China were the power can be dirty. My Chinese Gree mini split said right in the brochure it has stable operation under a wide voltage range.

Also interesting is the reason for the flare fittings on the refrigerant lines was due to the huge fire hazard in Asia. There are a lot of poorly built extremely flammable wood structures there. Here in the states brazing refrigerant lines with a flame is common practice.

 

[Brian26]

I have electricity monitors on both my mini split's. Its amazing to see them operate and how little power they use. I have seen them ramp up responding to me opening a door to go outside or a cold front coming through. They will lock on the temperature set point with extreme precision and modulate to the exact heating load.

Here is a snapshot yesterday of my downstairs Midea 12k spilt that carries most of my heating load. Those brief electrical spikes at the end of the graph are designed into the software for oil control. When the compressors are near their minimum speed they briefly ramp up to send oil to the compressor.

 

[Corey]

Interesting numbers. Curious how the 'defrost cycle' plays into those - is it already included with the rated COP? Maybe they've found some way to get rid of it?

I recall that was the slightly unsettling thing about one house I was in, which was primarily heated with a heat pump system (besides the constant draft of barely warm air). The heat pump would run with some nominal efficiency...maybe COP of 2.0 back in those days. But every so often, it would 'defrost' the outdoor coils, so basically switch back into 'air conditioner' mode, kick on the electric resistance heat and pump that hard won heat from the house right back outdoors. So while it could run efficiently, it seemed some amount of time was in 'anti-efficient' mode, pumping heat the wrong way.

 

[Brian26]

Interesting numbers. Curious how the 'defrost cycle' plays into those - is it already included with the rated COP? Maybe they've found some way to get rid of it?

I recall that was the slightly unsettling thing about one house I was in, which was primarily heated with a heat pump system (besides the constant draft of barely warm air). The heat pump would run with some nominal efficiency...maybe COP of 2.0 back in those days. But every so often, it would 'defrost' the outdoor coils, so basically switch back into 'air conditioner' mode, kick on the electric resistance heat and pump that hard won heat from the house right back outdoors. So while it could run efficiently, it seemed some amount of time was in 'anti-efficient' mode, pumping heat the wrong way.

Traditional heat pumps used a wasteful timer for the defrost. Mini splits use software driven algorithms for the defrost cycle. They can detect the coil icing up based off the amp draw on the variable speed outdoor DC condenser fan. As the outdoor coil ices up they can see the the airflow dropping by an increase in the outdoor fan speed amp draw. I can see my outdoor condenser through my window and the defrost controls are extremely energy efficient.

 

[DBoon]

which was primarily heated with a heat pump system (besides the constant draft of barely warm air).

The classic "heat pump" is a pile of garbage. I was happy to replace mine at the condo with two mini-splits. The old heat pump seemed to spend half its time in electric resistance mode anytime the temperature was close to freezing or if you nudged the thermostat up a half degree. It was really an electric resistance heater, in my opinion, that also provided air-conditioning in the summer.

 

[mcdougy]

These mini splits are starting to gain nterest here in Ontario. The old school heat pump disasters caused a slow climb for them to catch on....I have a project coming up and the current shop house has in floor heat. The client has indicated that they are not interested in trying to tie into the existing system, nor interested in doing infloor at all. There is no basement or a/c. This points directly at a mini split in my opinion. Since I have no experience at all with a mini split I have a couple questions.....
I understand that you can have one outdoor unit and multiple thru the wall units supplied by the lone outdoor unit......Does each bedroom need its own thru the wall unit to supply a comfortable bedroom?
This shop house is currently a 1 bedroom 1 bath and largish open kitchen/family room. Currently is 1000sqft total. Built by me in 2009, well insulated and airsealed. The addition they are wanting is 2 more bedrooms and another bathroom, as well as enlarging the main space for a total addition size of approx. 600sqft. Bringing the totals to 3 bedroom.,2 bath and sq footage of 1600.
I have a great hvac contractor that I have worked with for over 18years, but I'm thinking he does not have alot of real experience with mini splits. He did indicate that he can get LG units. There appears to be many here with first hand experience and others with large knowledge of these systems.....What do you folks think would suit this retrofit scenario?? Since there is a lack of a/c in the current building and they are requesting a/c, I believe they will be fine with abandoning the current l.p.boiler radiant heat system. Its a white Roger's combo tank that they would still use for d.h.w..

 

[Brian26]

These mini splits are starting to gain nterest here in Ontario. The old school heat pump disasters caused a slow climb for them to catch on....I have a project coming up and the current shop house has in floor heat. The client has indicated that they are not interested in trying to tie into the existing system, nor interested in doing infloor at all. There is no basement or a/c. This points directly at a mini split in my opinion. Since I have no experience at all with a mini split I have a couple questions.....
I understand that you can have one outdoor unit and multiple thru the wall units supplied by the lone outdoor unit......Does each bedroom need its own thru the wall unit to supply a comfortable bedroom?
This shop house is currently a 1 bedroom 1 bath and largish open kitchen/family room. Currently is 1000sqft total. Built by me in 2009, well insulated and airsealed. The addition they are wanting is 2 more bedrooms and another bathroom, as well as enlarging the main space for a total addition size of approx. 600sqft. Bringing the totals to 3 bedroom.,2 bath and sq footage of 1600.
I have a great hvac contractor that I have worked with for over 18years, but I'm thinking he does not have alot of real experience with mini splits. He did indicate that he can get LG units. There appears to be many here with first hand experience and others with large knowledge of these systems.....What do you folks think would suit this retrofit scenario?? Since there is a lack of a/c in the current building and they are requesting a/c, I believe they will be fine with abandoning the current l.p.boiler radiant heat system. Its a white Roger's combo tank that they would still use for d.h.w..

The multi split units that have one outdoor condenser with multiple indoor heads usually have a big flaw. The minimum heating or cooling output is often way too much and they short cycle which kills the efficiency

An example would be a 36k btu Mitsubishi that can be connected to 3 indoor 12k heads. The minimum heat output might be 9k btus. With a 1 to 1 unit you get much better turn down ratios such as the LG that can turn down to just 500 btus.

 

[mcdougy]

The multi split units that have one outdoor condenser with multiple indoor heads usually have a big flaw. The minimum heating or cooling output is often way too much and they short cycle which kills the efficiency

An example would be a 36k btu Mitsubishi that can be connected to 3 indoor 12k heads. The minimum heat output might be 9k btus. With a 1 to 1 unit you get much better turn down ratios such as the LG that can turn down to just 500 btus.

Ok, this is the type of info I am looking for. So for a all in one units.....how many do you think a place of their size need? Do bedrooms suffer if you don't have one unit per room?

 

[stoveliker]

Ok, this is the type of info I am looking for. So for a all in one units.....how many do you think a place of their size need? Do bedrooms suffer if you don't have one unit per room?

You would have to do the calculation of buying multiple (at $2000 each?) outdoor units versus the power savings over the (20?) years as compared to one outdoor unit and multiple indoor ones.

 

[JRP3]

Similar to several other firms, they just dont seem to want to import them in the US.

Several companies sell inverter based refrigerators in Mexico but not in the US.

I don't know much about them but this company sells an air to liquid unit. https://www.chiltrix.com/chiller-technology.html
Rather pricey as I remember, I think $4k just for the outdoor unit.