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Old 09-24-16, 09:28 PM   #11
Xringer
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Here's Gree video that shows the 2-stage compressor..

https://youtu.be/givgAL48lOo?t=2m57s

May not be accurate, since the video is PR, or an ad..

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Old 09-25-16, 07:10 AM   #12
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That video is somewhat revealing, yet still vague and non-descriptive. Luckily, I am good at hunting down stuff like this... I found this chinese patent that describes the operation and intended performance of the manufacturing utility model. Between the video and the patent, it looks as if Gree has put a massive amount of r&d into this design. It obviously works well enough for them to include in production machines.

The compressor assembly has two rotary cylinders on a single shaft that are always working, with no switching of cylinders. The lower cylinder moves more volume than the upper cylinder. The compressor has three ports: suction, intermediate, and discharge. The intermediate port is connected as a tee between the two cylinders. It looks as if the intermediate port is being used as a suction line, and capacity and compression ratio of the compressor is varied by manipulating what goes into the compressor (at intermediate pressure) between cylinders. This is the same operating principle employed by the Acadia / Hallowell heat pumps. The main difference being that the Acadia used two separate compressors, where Gree has integrated two compression chambers into one shell.

At low dT, nothing is injected at intermediate pressure, and the two cylinders provide maximum BTU throughput at "normal R-410a" compression ratio. As working conditions change, some control (outside of the compressor) starts injecting gas into the intermediate port, which forces a shift in the way the compressor behaves. The interesting part is that the change in behavior can be tailored for an intended purpose! If the unit was designed for low ambient conditions, the compressor would shift into "bulldog gear", moving about the same BTU's at higher compression ratio (higher output pressure and/or lower suction pressure). OTOH, if the unit was designed for medium ambient conditions, the output pressure could be boosted without a major shift in suction pressure. This would lead to an increase in BTU throughput without much sacrifice in energy efficiency, if any. It all depends on what concoction exists OUTSIDE OF THE COMPRESSOR.

Now that I have an idea what the new compressor really is, it is obvious that Gree (and whoever is collaborating with them on this project) is breaking into ground that others have failed miserably at trying to conquer before. Hopefully the decade of design and testing they have done has yielded a product that is super durable. It needs to be to survive thousands of operating hours.
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Old 09-25-16, 07:52 AM   #13
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Quote:
Originally Posted by MN Renovator View Post
"Please tell you are joking.
-AC"

Which part? COPs run into the sub 2 COP range when things are actually cold. Not to mention defrost cycle losses.



I'm not sure how well the Gree units handle deep winter. I see specs provided by a manufacturer but it's hard to compare that when it's not a third party testing multiple units with the same method. I'm looking at the Fujitsu and Mitsubishi units.
Looking into these types of air-source units has made me aware of some general practices the manufacturers follow. Widely published specs will be inflated to impress the average consumer. If the units are designed to operate in frigid outdoor conditions, their sell sheets will boast this element. If not, this information will not exist in public. If you look at the installation instructions, service manuals, and/or "extended" data sheets not usually included on reseller/distributor websites, most manufacturers publish performance figures in a range outside the standardized test conditions required by the authorities. These charts and graphs are not so inflated, and if you know how to read them, you can fill in the blanks as to what data is included with relative confidence.

Looking at the Gree units, the NEO line doesn't include any low-temp data (below 5 degF). The CROWN units have this data published in their submittal sheets down into the sub-zero (-22 degF) temperature range. This looks fine to me, since the Neo line is not optimized for heating operation below about 15 degF, whereas the Crown line delivers its rated capacity down to zero. At -22, the max capacity of the crown 9kbtu is only 700 btu below its rated capacity.

For most customers, the Neo system cited is an exceptional deal. For more demanding customers, the Crown system belts out the heat when it gets really cold out (at least on paper).

Last edited by jeff5may; 09-25-16 at 08:50 PM.. Reason: info and links
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Old 12-07-16, 09:39 AM   #14
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Since I'm on the ComfortUp mailing list, I'm getting a LOT of emails about sales lately..
Not seeing the same info on their website.. If you are looking for a sale, you might want to sign up on their list..


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