Mini-split models with least derating at low temperature
ranson
| Posted in Mechanicals on
I’ve been looking at mini splits, and I’ve noticed that some seem to have much less capacity falloff at low temperature. Specifically, I would like 8kBTU/h at 7F from as small a unit as possible. Any thoughts on which models to consider?
–John
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As an additional question, should I trust the performance numbers provided by cheaper minisplit manufacturers? I was looking at Gree, and they claim a small unit can achieve the same low temperature performance as a bigger Mitsubishi unit. Admittedly, they don't publish electrical power usage, just heating output.
Mitsubishi MUZ-FH15NAH:
21.0kbtu @ 55F outdoor, 70F indoor
8.6kbtu @ 5F outdoor, 70F indoor
Gree TERRA09HP230V1A
10.8kbtu @ 55F outdoor, 70F indoor
7.9kbtu @ 5F outdoor, 70F indoor
The reason I'm asking these questions is I want to minimize my excess capacity during the swing seasons. I would like the mini-split to operate continuously, rather than on-off, for as much of the year as possible. My thinking is that if I size a unit for my 99% design heating, and it has 2x or 3x the heating capacity during the swing seasons, it won't be able to modulate low enough for continuous operation
The Fujitsu 9RLS3H can hit this mark pretty easily and will heat at temperatures far below +7F. With such a small load, turn-down ratios are maybe more important than just going with the smallest size unit.
Hopefully Dana can chime in as he is our resident expert.
I'm not an expert- I just make it up as I go along! :-)
The Fujistu 9RLS3 (and _H and _HY) is really more like a 1-ton. The choice to test it's efficiency as if it were a 3/4 tonner seems largely a marketing decision, getting marginally higher efficiency out of the lower modulated output levels. It's capacity numbers are very close to those their 1-ton, the 12RLS3. The max heating capacity numbers (tested at 47F) of BOTH is 22,000 BTU/hr, as specified in their submittal sheets:
http://www.fujitsu-general.com/us/resources/pdf/support/downloads/submittal-sheets/12RLS3.pdf
https://www.master.ca/documents/regroupements/1fujitsu_submittal_9RLS31.pdf
Independly of what the engineering manual's capacity tables state, with a load that low it's pretty safe to go with the Mitsubishi FH09NA:
http://meus1.mylinkdrive.com/files/MSZ-FH09NA_MUZ-FH09NA-1_ProductDataSheet.pdf
Mitsubishi's capacity tables worst-case it. Under some outdoor humidity conditions it might not quite keep up at +7F but under most conditions it will. The minimum modulation @ +47F is barely more half that of the beefier 9RLS3, which will give it a much higher modulation range. Your load at +47F is about 3000 BTU/hr, which is barely below the minimum output of the 9RLS3- it' won't be modulating much at temps above 47F, whereas the FH09NA should be able to modulate well into the 50s F.
Midea Premier Hyper is almost 1:1 see
https://us.midea.com/dam/jcr:46dc6a93-ff69-45a0-8ae6-546bc7456f5d/US_PP-RAC_PROD_PREMIERHYPER-HIGHWALL_specsheet.pdf
Also, you can find every model on the market at
https://www.ahridirectory.org/ahridirectory/pages/vsmshp/defaultSearch.aspx
Anon3,
I hope you can get a chance to update your profile to change the way your user name is displayed.
Here is a link to an article explaining how to do that: How the GBA Site Displays Readers’ Names.
Okay, I'm a little confused. I'm looking at the MUZ-FH09NA in the M series engineering manual at https://www.ecomfort.com/manuals/mzfhengineering.pdf
In the Specifications section, it quotes a maximum capacity of 18kBTU/h at 47F, and 12.2kBTU/h at 17F.
In the "Performance Data" section, it quotes a capacity of 11.2kBTU/h at 45F and 6.7kBTU/h at 15F.
In the "Maximum Heating Capacity in Low Ambient Temperature" section, it quotes a flat 100% of heating capacity down to 5F.
Now, from the Specification section, it's clear that the maximum heating capacity is not flat with temperature. My best guess, is that the "Maximum Heating Capacity..." chart is indicating that the unit can meet at least 100% of the rated 47F "rated" heating capacity (10.9kBTU/h) across temperature. And I guess "Performance Data" is essentially rated performance, but not actually indicative of the maximum limits.
Can anyone tell me if I'm reading this right?
--John
It looks like the LG LA090HYV1 might be a better fit than the FH09NA. It has a max heat capacity of 11.2kBTU/h at 5F, and a minimum heating capacity of 1kBTU/h at 47F.
--John
Rated capacity gives you the efficiency rating. Max capacity is very inefficient and will cost you a bundle. That LG unit has humidity issues in AC mode btw.
The minimum modulation of the 3/4 ton Midea @ 47F is 4500 BTU/hr. If the heat load is 8000 BTU/hr @ +7F out, 70F in, the heat load at 36F will be less than the minimum modulation of that unit, which means it only modulates more than half the time during the coldest weeks of the winter, and not at all during the shoulder seasons.
The 3/4 ton LG Art Cool Premier would be a good fit though. It's a bit noisier than the Mitsubishi FH09. According to the heating capacity tables (like the FH09) it won't be able to deliver that max 11K capacity at all outdoor humidity conditions when defrost cycles are factored in, but it's not that risky. According to the capacity tables in the engineering manual, at a wet bulb temp of +5F, dry bulb temp of +6F (=77% relative humidity) it's only guaranteed good for net 6140 BTU/hr @ 70F indoors, even though it's max capacity while not defrosting would still be the ~11K number. LGs have a "sump heater" near the drain port on the outdoor unit, but there is no description of it's operation or function in the English version of the manual- I'm assuming it's for managing defrost ice buildup, but that should be verified with the installer/distributor if you go that route.
http://www.lg-dfs.com/art-cool-premier.aspx/Download?filename=EM_SZ_ArtCoolPremier_ALL_01_17.pdf&id=188
Like most mini-splits, the LGs can be operated in a dehumidifying mode on days when sensible cooling loads are low but it's still sticky outside. The as-used SEER is lower in dehumidify mode than when in a standard cooling mode, but that's physics for you! :-)
Dana,
The LG models have an built-in drain pan heater. It's another reason I'm considering them.
Are you saying that the "Maximum Heating Capacity" number at 5F WB / 6F DB excludes the defrost cycle?
--John
Maximum means maximum, and not the net heat put averaged over defrost cycles. Capacity tables are usually the net heat output, but read the fine print- the conditions used aren't always the same, and not always the net output. (IIRC Gree's capacity tables are always max, not net.) Some manufacturers only spec a capacity at wet bulb temperatures. LG's heating capacity tables specify both dry bulb & wet bulb conditions in the table itself, and stipulate:
"1. All capacities are net, evaporator fan motor heat is deducted. "
Ooh Ooh
For specific models with the least derating at low temperatures, you may want to consider Mitsubishi Electric's Zoned Comfort Solutions series, such as the MXZ H2i or the FH Series. Keep in mind that technology and product offerings evolve, so it's advisable to check the latest models and consult with HVAC professionals or the manufacturer for the most up-to-date information on mini-split systems designed for optimal performance in cold climates.
If for some reason you still think Mitsubishi is expensive then you can get Cooper and hunter mini split-brand https://southminisplits.com/collections/2-zone/products/18-000-btu-2-zone-9k-9k-ceiling-cassette-with-installation-kits-sophia-series-21-3-seer-1-5-ton-dual-zone-ductless-multi-mini-split-air-conditioners-1?variant=41209944080499