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Which Ductless system??

Posted by teedjvt (My Page) on
Mon, Aug 11, 14 at 23:25

Trying to decide between Mitsubishi and Trane Split Ductless AC. Need a 30,000 BTU compressor with 3 zones (6, 9, and 18 BTU's).

Any recommendations on Mitsubishi vs Trane? Fairly similar cost. Similar warranties.

What's the big difference?

Thanks!

This post was edited by teedjvt on Mon, Aug 11, 14 at 23:36


Follow-Up Postings:

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RE: Which Ductless system??

I was unaware Trane made ductless systems. I would ask if Trane's system is just a rebadged brand and if true, what brand?

IMO


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RE: Which Ductless system??

this is the unit...

http://www.trane.com/residential/en/products/heating-and-cooling/ductless-systems/multi-split-outdoor-unit/4txm6.html


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RE: Which Ductless system??

I take Mitsubishi.


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RE: Which Ductless system??

From my research (from a few years ago) Trane was only just coming into the market and couldn't get their specs up to par--not as efficient as Mitsu. Mitsubishi has a LONG proven history in ductless. If they are similarly priced, I'd go Mitsubishi.


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RE: Which Ductless system??

I signed up specifically to add to this thread. I strongly agree with kirkhall - Mitsubishi has a long, long history of manufacturing DFS. Go with the experience.

Have you compared Mitsubishi with Gree at all? Gree isn't well known in the US, but very large worldwide. Something like 1 in 3 AC units is manufactured by them.


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RE: Which Ductless system??

Thanks!
No, haven't heard of Gree. Live in VT so some of our options are limited as far as manufacturers go.

Pretty much decided to go with Mitsubishi. Have 3 quotes to install a system.

now, wondering about BTU size. some seem to overestimate and one seems to underestimate.

My condo is 3 levels (very open) with 2 bdrms. I want 3 zones.

total sq ft is about 1800 so I estimate a 30 BTU Compressor and a 18 BTU in the large open/ living area, 6 BTU in the small bedrom and 9 in the large.


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RE: Which Ductless system??

30,000 BTU might be a little bit undersized for 1800 square feet, though if the floor plan is very open, that might work. I'd probably suggest a 36k compressor to ensure you're not over-working the system.

I've seen this chart cited elsewhere, and it's a good estimate without doing an actual load test with an HVAC contractor: http://www.thermospace.com/ductless_split/faq.php

Mitsubishi doesn't give a chart, but does explain the risks of under-sizing: http://mitsubishicomfortdealers.com/info/what-size-system


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RE: Which Ductless system??

You are in VT so you are sizing the system for heat and it will be oversized for cooling?

Oversized for a fully variable speed system might not be such a big deal, but I think there is one factor that is, apparently, overlooked in mini split planning. I am not a refrigeration expert so take this analysis with a grain of salt. I don't know how it could be wrong, but I'll take reasonable criticism.

These variable speed compressors will throttle back to 20-30% of their full capacity and then they have to start to cycle. If you have a 9000 BTU 1:1 system you can throttle back to 3000 but using the 30% figure. If you have a 6000 or 9000 BTU indoor unit hooked to a 30,000 BTU compressor, you only get to go back to 10,000 BTU on the compressor end. That means that if you are only running the 9000 BTU unit at night in a bedroom with the door closed, you can't get the full benefit of the variable speed.

Given those constraints, you might want to consider pricing out two outdoor units to go with your three indoor if you have a good site to put two outdoors.


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RE: Which Ductless system??

Because this is a condo and I have limited space I don't think 2 units are possible. But this is the dilemma I am in. I don't want to go to big OR to small. This unit will be primarily for cooling as I have a natural gas fed furnace for heat.

One of the estimates was for a 24 K BTU compressor with two 6k BTU and one 12K BTU for the inside. For the reason you are listing above. However, everywhere I read about sizing (and all the other estimates) says I need at least a 30 K BTU Compressor. Not even close to being an air conditioning expert here but feel like I have to have some knowledge in order to sort through the different estimates.

Condo is 1800 square feet with a basement (doesn't need a/c) and it is a very open space with two enclosed bedrooms and a bathroom. The rest of the space is open with a loft above.
Do you really think 24 K BTU compressor would be enough?


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RE: Which Ductless system??

Lots of variables to consider. How big is the condo if you're not counting the basement? Does it face North, South, etc? Do you have double-paned windows?

24k sounds undersized to me, even with an open space. I agree with ionized that a slightly oversized won't be much of an issue with a variable speed system.


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RE: Which Ductless system??

You should match the compressor as best as possible to the indoor unit capacity. There may be some decisions to be made there. I don't know how that handle that in Mitsubishi school. I believe that I have seen that the compressors can be under the capacity of the indoor units. Don't hold me to that because I don't remember where I might have seen that. It could have been another brand too. It may mean that you can't get full capacity out of all the indoor units at the same time. You'll need a knowledgeable installer to get the best system, but it does not hurt to ask the right questions.

If you are oversized, the humidity control might not be as good, but it might be so much better than with conventional AC that you might not notice. Are you on the coastal plain or inland? My experience in the NE tells me that inland humidity will not be as big a deal as coastal plain.


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RE: Which Ductless system??

I represented Fujitsu in Vt for 13 years. I would not hesitate to size at 650-700 fsq ft per ton on cooling. The caveat to this is whether you have a lot of W-NW windows giving direct gain into the space in the summer afternoon when the sun is low and drives the load. Vt rarely requires a great deal of temperature reduction but regularly requires dehumidification. Slightly undersized is better than oversized for dehu. Unless you have that direct gain mentioned, if it was my place I'd go with the 24 and run it.

FYI, trane does not manuf mini-splits. They don't have the technology. they private label I think it is toshiba units out of Japan. I would not buy a Trane mini-split. Stick with Mitsu, Fujitsu, Daikin. there are a lot more Fujitsu's sold in VT than Mitsu's. I'd check them out as well.


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RE: Which Ductless system??

I have had two Gree products, not heat pumps, and am not impressed…I am trying to make a decision on a Mitsub. ductless system. Everything I have read, and people who have the Mits. are very pleased.


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RE: Which Ductless system??

My neighbor has a Gree 2 zone heat pump and he raves about it. I don't own one, so I can't comment personally, but he's said he's really happy with his choice. I know his operational noise is very minimal, both indoor and outdoor.

Mitsubishi definitely has a lot of experience in the ductless space, and I think probably either brand (or Fujitsu) would be a good bet.


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RE: Which Ductless system??

what is the heating performance for these units? I was informed that there is a unit out there which will give 2:1 performance at 0 degrees outside temperature,
and 1:1 at -30 (i.e. at -30 it's just like resistance head). Any comments?


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RE: Which Ductless system??

MTVhike, you may have to just find the details about this aspect by finding the data yourself. Keep in mind two things.

Historically the multi indoor unit systems do not perform as well as the 1:1 systems (one indoor:one outdoor).

As you approach heating performance of 1:1, you have a very expensive heater based on equipment costs.


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RE: Which Ductless system??

MTV, Each manuf has a chart showing performance at specific temps. Even at the very low temps as the performance declines you have to look at a seasonal overview. It is design condition in most locales less than 1/2 of !% of the total heating season. The NOAA maintains what they call Binn numbers. It is a compilation of hourly weather statistics.


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RE: Which Ductless system??

trane units are rebranded Gree units. Have put some Trane in and have installed mitsubishi as well.kinda like both but mitsubishi is kinda the big dog in the fight to me. just my opinion.


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RE: Which Ductless system??

Agreed with harlemhvacguy - Gree is actually the OEM for a bunch of the major players (Trane, Mitsubishi, Daikin, etc). They only make parts for some of these guys, but they do the full on product for others.


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