by Gerry Wagner
The North American consumer has generally thought of mini splits as strictly cooling equipment but that narrow view is soon to change. The heating capability of the inverter mini split has been evolving quickly over the past decade and the technology is now at a point where these systems are being used as primary heat sources, (sole heat sources) in the most traditionally cold climates…like Mongolia!
GREE has developed what they are calling a “three cylinder, two stage compressor of variable volume ratio”…in simple terms, a three cylinder compressor with a two stage compression cycle that expands the heating performance range down to -31F°
The above essentially represents the recent history of GREE compressor evolution.
The new GREE UltraHeat, three cylinder, two stage compressor allows for a range of performance from
-31F° to 115F°…WOW!
The heating range will be from -31F° to 75F° with 100% of rated HEAT capacity down to -4F°, 80% of rated HEAT capacity down to -22F° and although not published yet, somewhere in the 70% range of rated capacity down to -31F° is expected.
This is not a re-work of an existing compressor but rather a completely new technology. GREE was able to scrub impressive heat performance numbers from the two stage compressor but its limitation was in overall capacity, (limited to 2 ton). The new three cylinder, two stage compressor will bring these impressive heat performance numbers stated earlier, to systems up to 4 tons and beyond!
Where this new compressor will really make an impact is in the multi-zone market.
Currently, the GREE Multi21+ has a minimum operating outdoor air temperature limitation of -4F° but we really need to look a little closer to completely understand just how that piece of equipment will perform in the HEAT mode.
Let’s take a look at the GREE Multi21+ model MULTI18HP230V1CO on the AHRI Directory. It says that
this model will give you 19,000 BTUH of heat at 47F° outdoor air but at 17F° outdoor air it will give you
11,400 BTUH, (or only 64% of rated capacity).
Suffice it to say that the closer we get to -4F° the amount of heat provided continues to fall at a fairly
steep rate until there is no performance at all.
That same system with the new GREE UltraHeat three cylinder, two stage compressor will provide 100%
of rated heat capacity, (18,000 BTUH) down to -4F°, 80% of rated heat capacity, (14,400 BTUH) down to
-22F° and at -31F°, somewhere in the neighborhood of 12,600 BTUH, (1,200 BTUH better than the
current MULTI18HP230V1CO at just 17F° outdoor air)
Impressive by anyone’s standards…including the United Nations!
The United Nations assisted in funding a project led by Dr. Kirk R Smith, Professor of Global
Environmental Health, School of Public Health, University of California, Berkeley, fellow of the National
Academy of Science and winner of the 2007 Nobel Peace prize.
The GREE UltraHeat product was installed in residential applications in Ulaanbaatar, Mongolia where
chronic illness among citizens was an ongoing dilemma for generations due to poor climate control in
living spaces in a geographic area that sees outdoor air temperatures as low as -40F°.
Look at where Ulaanbaatar, Mongolia sits in the world…
Pretty amazing that this technology that we will soon be enjoying here in the United States, where in my
neck of the woods, (New York) the design temperature is 0F°, has already been beta tested you might
say, in a climate which sees -40F° and has achieved a level of success recognized by the United Nations!
I always mention in my GREE Mini Split Design & Installation curriculum the old joke in the boiler
business from back in the 1970’s that said, “you should never install a heat pump north of Richmond,
Virginia.” It was a joke, but a joke based in reality as heat pumps back in the ‘70s had a minimum
operating outdoor air temperature of 45F°…that was it…it wasn’t derated at 45F°, it was OFF!
Here we have a technology that is not only changing the HVAC industry but the world! I’m proud to be a
part of it!
ABOUT THE AUTHOR: Gerry Wagner is the Vice President of HVAC Technical Training for Tradewinds
Climate Systems. He has 38 years in the HVACR industry working in manufacturing, contracting and now
training. You can contact Gerry by email: and also please visit our website: