Who should I believe?
I’m going to heat the “pretty good” house I’m just starting to build with cold climate mini-splits. I’m building in Kentucky and my heat loss estimate is 23,000 BTU/h @ 0F I’d prefer to use 2 single zone duct-ed systems. There are now several alternatives to Fujitsu and Mitsuishi” that promise full capacity at 5f or -5f and continued heating down to -23f at reduced capacity. Some claim 75% of rated capacity (the Carrier 38GRQ un-duct ed) at -22f . Some are even “Energy Starr” rated. I looked up the energy star data and it sure doesn’t match what the advertising says! The energy star data has it’s lowest temperature performance data point at 17f and the 38GRQ series only shows about 75% of rated output there. FWIW the Carrier and several other less well known brands all use Toshiba vapor injected dual rotary invert er driven compressors. Some of the “off brands” offer single zone duct-ed systems, which is what I’d like to use 2 of rather than a 2 zone multi-split which is the only way to get “hyper heat” duct-ed indoor units from the big ” M” or big “F”
So I checked the energy star ratings of the pioneering units from Fujitsu and Mitsubishi, at 17f they are also about 75% of rated heating capacity and they definitely are much better than that but they use there own proprietary compressors so I’m not sure it’s a test protocol issue Why is the energy star heating performance data simply wrong?.
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Replies
Jerry,
Can you give us some links?
One of the Energy Star web pages for Energy Star rated minisplits provides links to two resources for performance information:
The AHRI directory for minisplits (That web page shows performance at 17 degrees F)
The Excel spreadsheet developed by Northeast Energy Efficiency Partnerships (That web page shows performance at 5 degrees F)
Or are you referring to another list of performance specs that I am unaware of?
Martin,
I used the AHRI link. FWIW the NEEP data is NOT third party test data but manufacturer supplied. But the NEEP data includes some data from which part load COP can be calculated. Another "link" is the manufacturers that have Energy star certification advertise an AHRI report # and that is the data I found at the site I linked too from Energy star.
Jerry,
It's a lot of research to verify what you are saying. I'm starting by looking into your question about the Carrier 38GRQ.
Here is the spreadsheet from AHRI on that model.
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Finding information from Carrier on the 38GRQ model is difficult -- perhaps a GBA reader can find it. I did find the graph reproduced below (from a Carrier brochure), and that graph does indeed seem to claim better performance than shown in the AHRI spreadsheet.
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The Carrier 38GRQ looks remarkably similar in it's physical details to a Gree Crown or Crown + (and probably is, under the paint), with fairly similar lo-temp specifications.
http://17uo7e27w1attiybs22of10v.wpengine.netdna-cdn.com/wp-content/uploads/2017/02/Gree_Crown_Submittal_18KBtuH_230V_020517.pdf
The statement "The energy star data has it's lowest temperature performance data point at 17f and the 38GRQ series only shows about 75% of rated output there." is simply can't be the case. The HSPF protocol tests the efficiency the RATED output at +17F and +47. If it doesn't have sufficient capacity at +17F to test it's efficiency there,
The short-sheet brochure on the 38GRQ series lives here:
http://s7d2.scene7.com/is/content/Watscocom/Gemaire/carrier_38grqb18---3_article_1420814188023_en_datasheet.pdf?fmt=pdf
Here is the link to the energy star data for the attachment and it's cousins
https://www.ahridirectory.org/ahridirectory/pages/vsmshp/cee/defaultSearch.aspx
This is a unit I'm considering which shows the strange data 17f "capacity" 13400 BTU while the HSPF is 11 and the manufacturer, in the attachment, claims 19000TU output at 5 f.
Another interesting bit about this pairing of a duct ed indoor and outdoor units is that it gives better HSPF than the same outdoor unit paired with an un-ducted indoors.
I added a second attachment, which I got from Midea, when I asked about output at lower temperatures. I believe Midea is the source of the Carrier line of mini-splits, which probably have different software.
I encourage take a good look at some of the conventional heat pumps look for variable speed compressors and electronic expansion valves.
The advantages are
1 You will find the contractors will be comfortable installing them and price them fairly. Yes they will give you a quote for a mini split but it comes with an I do not want this job price tag.
2 It will come with back up electric heat that you can program to only run when it is below XX° outdoors.
I have been very pleased with my new Rheem RP17. The heat pump does all heating above 10° and most of it below. I think I can set it even lower
At this moment we are in a cold wave, but on average how many hour per year do you spend below 10°
Attached are some screen shots from a cold morning.
Please note I did have a board replaced to get the latest software and lost some historical data.
Walta
Walter,
I'm spending plenty to build an energy efficient house, well within the capacity of current mini-splits. There is simply no reason for accepting a COP of 1 ( resistance heat)! You are certainly right most HVAC contractors have serious problems both with competence and GREED. I'll do the design and installation myself, even if I have to get a damn licence to do it. I've always been able to find a licensed technician who'll do the " commissioning" part for a reasonable cash fee and that's enough to satisfy the warantee requirements of ethical manufacturers.
Hint! For those trying to solve this "puzzle" In reading about the AHRI test protocol I noticed that the testing requires a unit modified to permit the testers to externally set the compressor speed.
Jerry - the mfr's choose a compressor speed for the AHRI rating that meets their marketing goals for nameplate/nominal sizing along with SEER/HSPF ratings. Most mini-splits (and especially the ones designed for cold climates) have significant additional heating capacity available, and typically a small amount of additional cooling capacity available. Generally, the mfrs' expanded engineering data is what you should be looking at (not the AHRI data), though sometimes there's misleading marketing BS...even in the engineering data.
I don't understand why you're going down this path of investigating ductless units when you state that you'd prefer to use a pair of single zone ducted systems. The Fujitsu AOU/ARU series is easily the best available slim-duct system on the North American market (though it's far from perfect).
John,
THANK YOU! Why? Doesn't testing "performance" at fixed speeds eliminate the influence of the "control system" not only on capacity but efficiency as well? Yes I'll probably use mini ducts but the performance data is all in the same place. Regrettably Fujitsu doesn't offer a single zone mini duct with XLTH (extended low temperature heating) . Mitsubshi and Midea appear to be the only "brands" offering substantial low temperature heating in single zone mini duct.
Jerry -
Fujitsu's AOU/ARU 9 provides 14,000Btu/hr heating at -5F (117% of it's 47F AHRI rated capacity...I'd call that "extended low temperature heating"). Fujitsu does not publish an outside temperature cut-off for these units. I have colleagues who have seen them operating as low as -25F. You state your load is 23,000Btu/hr at 0F. A pair of the AOU/ARU 9k would give you 28,000Btu/hr at -5F. A pair of the 12k units would give you 30,000Btu/hr at -5F.