Helpful? 0

Best minisplit system in Zone 6A for a 2-story home?

Experts, Dana and all...

I propose best system might be

1 outside unit hyperheat etc... I only know what you all post...
2 indoor heads that are large enough to one at a time heat the home from 1st floor
and cool the home from 2nd floor most of the time with worst case scenarios taken care by the fact
that there is a "reserve" head.

Question... can this system be built and installed for$5-10,000 and will it be as efficient as 1 head designed to 1 outside unit?

1500-2000 sqft PGH home will add solar in the future to go net zero... built 50% better via Recheck than the 2012 energy code.

Can you crunch some numbers Dana?
Thank you

(Alex Wilson, something similar to your home but adding an upstairs cassette is my question. i have a feeling that your upstairs is not going to do too well during a prolonged hot spell may be just fine. Let us know this summer if you would blog about that.)

Asked by aj builder, Upstate NY Zone 6a
Posted Mon, 02/10/2014 - 16:17
Edited Mon, 02/10/2014 - 17:06


17 Answers

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Helpful? 0

Have you read this article? Just Two Minisplits Heat and Cool the Whole House.

Answered by Martin Holladay, GBA Advisor
Posted Mon, 02/10/2014 - 17:05

Helpful? 0

Thanks Martin, need to reread that thread.

And start a notebook as to my future use of mini splits.

Answered by aj builder, Upstate NY Zone 6a
Posted Mon, 02/10/2014 - 22:48

Helpful? 0

Without heat load numbers it's hard to get specific on costs. The Mitsubishi MSZ-FE18NA, MSZ-FH15NA, and Fujitsu -15RLS2-H all put out roughly 15,000BTU/hr @ -13F, but that won't quite cut it if that's your 99% outside design temp and your heat load is 25,000BTU/hr at that temp.

A pair of any of those should come in under $10K, but not by much. one-off singles that size will be under $5K. A mostly-DIY installation, with only the final refrigerant charging and commissioning testing performed by a qualified tech could bring a pair of those down to the ~$6-7K range.

Pairs of the 3/4 ton units in those series could be under $6K turn-key, in a competitive local market, ~$4K as a mostly DIY.

In a snowy zone 6 climate bracket-mount the outdoor units on the wall, well above the historical snowpack depth, protected by roof overhangs (rake preferable to eaves) or a small shed roof to prevent it from getting buried in snowdrift or clobbered by cornice-falls/roof-avalanches. I pass a house on my daily commute with a pair of mini-splits mounted at grade level- it seems the owner has to dig them up at least 1-2x /year after bigger nor'easters.

Answered by Dana Dorsett
Posted Tue, 02/11/2014 - 12:09

Helpful? 0

Dana, are you listing 2 single systems? What about 2 head 1 compressor set ups, advantage disadvantages?

For me one reason to use mini splits here is to not hook up to natural gas. Gas base delivery is $300/yr. If going gas cogen along with a NG vehicle hookup is interesting ... But the cost is higher than mini splits wood stoves and grid tied solar.

Anyway 2 to 1 compressor still gives 3 COP?

Answered by aj builder, Upstate NY Zone 6a
Posted Tue, 02/11/2014 - 14:30

Helpful? 0

What effect does line set length have on performance's?

10' verses 50'

Answered by aj builder, Upstate NY Zone 6a
Posted Tue, 02/11/2014 - 14:32

Helpful? 0

Yes, I'm talking about pairs of singles, which as a rule operate more efficiently than multi-splits, and it sometimes even costs less up front.

Take a look at the HSPF numbers of the 3/4-ton and 1-ton units, and compare that to a 2-head multi-split of a similar series from the same manufacturer. That number is the average BTUs delivered per watt- hour under a standard set of test conditions, and you can work backward from there to come up with relative COP:

An HSPF of 9.3 means you get 9.3 BTU/watt-hour . At 3.412 BTU per watt in a resistance heater, that means the COP of (9.3 / 3.412=) 2.7 Similarly an HSPF of 12 is a COP of (12 / 3.412= ) 3.5. Your climate will vary from the tested condition averages so your in-situ COP will vary a bit, but the comparative efficiencies will track the rated efficiencies.

Note: The new -FHxxNA series Mitsubishi units take a hefty HSPF step above the -FExxNA, or Fujitsu XLTH series units. If that's real, it's setting new efficiency standard for cold-climate mini-splits.

There is also some variation in efficiency related to oversizing factor- you get a slight gain in seasonal efficiency if you oversize it slightly, say 25%, but if you oversize it too much that turns around, giving up too much to cycling losses in the shoulder seasons.

SFAIK line set lengths have very little effect on overall efficiency or capacity, but as I understand it there are limits to the line lengths and total system refrigerant volume that will work at all. eg.: A 200' lineset would either have too much volume if the diameter is large, or too much pumping head to if it's too skinny.

Answered by Dana Dorsett
Posted Wed, 02/12/2014 - 17:58

Helpful? 0

My Mitsubishi FE18NA manual gives the following figures:

25 feet: 100% cooling capacity
40 feet: 95.4%
65 feet: 87.8%
100 feet: 77.1%

Unfortunately it says nothing about the effect of lineset length on heating capacity.

Answered by Nick Welch
Posted Wed, 02/12/2014 - 18:10

Helpful? 0

Thanks Nick! I'm guessing the pumping head of the lines limits the volume that can be delivered for a 1.5 tonner like the FE18, which should roughly correlate to it's impact on heating capacity. I've read of hacks using fatter linesets to overcome some of these limitations, but at some point they find other limitations. I'd be curious if the capacity break points in the -FE09 aren't considerably longer, since it's the same line set, but only needs to move half the volume.

Interpolating on that small table, a 50' line set on the FE18 would cut capacity by about 10%, but anything up to 25' would be able to deliver full rated capacity.

Answered by Dana Dorsett
Posted Wed, 02/12/2014 - 19:05

Helpful? 0

Dana, the FE09 and FE12 give the same numbers, except that the 100 foot option is not supported.

I wonder if you have a less than 25 foot lineset, would you get an undocumented capacity boost?

Answered by Nick Welch
Posted Wed, 02/12/2014 - 20:35
Edited Wed, 02/12/2014 - 20:36.

Helpful? 0

Logic prevails... I had an idea that line length could be quite meaningful. We need to keep adding to our mini split knowledge base here at GBA.

Has the Mini split book for dummies been written yet? I am ready to buy a few books... Dana.... FHXXNAs are not priced or shipping till Spring? trying to keep this all in me head... notebook time.

Edit add; Wes Diskin Barron Green Team... lots of info has quite a bit on youtube too... this is the page I am reading right now,

Daiken has 12 HSPA Fujitsu... Wes uses all the brands and at of late likes the new super multi head Daikens... Northwest climate area... milder than here in 6A.

Answered by aj builder, Upstate NY Zone 6a
Posted Wed, 02/12/2014 - 23:12
Edited Thu, 02/13/2014 - 13:55.

Helpful? 0

The -FH series are at all the relevant trade shows with "2014 release" all over them, but I don't know if they're in the distribution chain in any quantity yet.

Daikin typically only specifies output down to -20C/-4F and not on all models. You'd have to see the extended temperature range output tables to know if it would work in your location. (Though it's fine for most zone 5 locations.)The Fujitsu XLTH and Mitsubishi H2i "FE" and "FH" are the only ones I know of that are fully characterized at -25C/-13F or lower.

Answered by Dana Dorsett
Posted Thu, 02/13/2014 - 15:21

Helpful? 0

For my personal install i have a large 1980s great room 1.5 story. My thinking is a highly rated upper system that is good for zone 5 or 4 used for summer AC and for some extra cold season btus. Lower system would be main heat source for temps to 0 degrees, best rating one for 0-30 degrees. Am below zero very little during daytime hours and have back up wood heat.

Dana,,, are there performance charts with all the choices plotted on one chart for hspa per temperature?

As to any new mini splits you mention coming soon, have googled for nada so far.

Answered by aj builder, Upstate NY Zone 6a
Posted Thu, 02/13/2014 - 15:59

Helpful? 0

I'm new to this site and have been reading a lot of info on mini split. Could anyone tell me witch size Mitsubishi FHxxNA series or Fujitsu model I should get for my house 24000sf split level home in zone 7. The cold weather gets to -30F or so in Dec and Jan so it would need to be the better heat efficient one. I have a Pacific energy wood stove here is the TECHNICAL INFORMATION
Heat Output Cord Wood (BTU)72,000 BTU
Heat Output EPA (BTU)36,600 BTU
Emissions3.4 gm/hr
Firebox Size2.1 cu.ft.
Log Size (recommended)18 in.
Log Size (max.)18 in.
Burn Time (max.)8 hrs.
In the -30F temp it works but burns a lot of wood per hour.
So with that said could anyone help me on choosing the right mini split unit for my application ust don't want to get it to small or to big. I would just use the wood stove when it would be extremely cold. Thanks for your help in advance.

Answered by Perry Comeau
Posted Thu, 02/13/2014 - 16:03
Edited Thu, 02/13/2014 - 16:06.

Helpful? 1

Perry, you need a heat load calculation done on your home. There are so many details about a home that can drastically affect how much heat is required, that just knowing the square footage and climate zone is nowhere near enough information. Your home needs to be carefully measured and evaluated by someone such as an energy rater.

Answered by Nick Welch
Posted Thu, 02/13/2014 - 16:33

Helpful? -1

No interest in this thread a" Perry"... mini splits have my interest. The olympics are on some good hockey... Go USA.

Add to the fun and tell us what your regular posting handle is... better yet, add something useful, I really am trying to just learn more about mini splits myself, many of us are.

Answered by aj builder, Upstate NY Zone 6a
Posted Thu, 02/13/2014 - 16:41
Edited Thu, 02/13/2014 - 17:00.

Helpful? 1

Thanks Nick I will look in to that. Sorry AJ for bumping in your thread first time on this site and don't really know anything about mini split or all that jibber you guys are talking about.
Just learning here.

Answered by Perry Comeau
Posted Thu, 02/13/2014 - 19:07

Helpful? 0

There is no way to graph the outdoor efficiency with temperature without knowing what fractional load is at each point on the chart. The COP of the -FExxNA Mitsubishi running full-speed at -25C/-13F is about 1.8, but it would be somewhat higher if running slower than full speed.

The bench testing on the -FE12 and 12RLS2 (the most recent antecedents of the FH12 and 12RL2H) has a lot of graphic information about how efficiency degrades with temperature and compressor/blower speeds, which should give you a pretty good feel for how those curves play out:

The -FE12NA has a rated HSPF of 10.6, which is about 13% lower efficiency than the -FH12NA's 12.5. The -12RLS2-H rated HSPF is 9.3, fully 27% behind the -FH12NA, but again, that's under one set of test conditions, which may not correspond to your operating conditions and how you're using it..

Note the 12RLS2 beat the FE12NA on efficiency in that Ecotope bench test, and they were unable to replicate an HSPF 10.3 in in their lab under the standard conditions, but in-situ monitoring of about a dozen FE12s installed in occupied homes in the Idaho Falls area (US climate zone 6B) under the NEEA program averaged a COP of 2.96 (= HSPF 10.1), which is pretty respectable real-world efficiency performance for a cold climate, under a somewhat tougher set of climate averages.

Answered by Dana Dorsett
Posted Fri, 02/14/2014 - 15:05

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