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Old 12-29-10, 02:26 AM   #1
Telstar
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Default Any experience with 3-zone mini splits?

Greetings all! I am seeking advice regarding a couple of different mini split 3 zone heat pump/ac systems that I'm looking at installing in my 100 year-old home. I've been looking at several different posts, on different sites but have yet to uncover much info based on experience, rather than informed speculation and/or prejuducial responses from HVAC pros that seem to have little actual experience with these. My basic home stats are as follows:

My home is located in memphis, TN. It has 2 stories plus a semi-finished attic room. The exterior walls are uninsulated (and probably won't be anytime soon), balloon 2x4 frame, with plaster walls and approx 4-5-inch thick limestone facing on the exterior of the first floor, slate tiles on the 2nd floor (which doesn't get nearly as cold as the 1st floor in winter!). The attic is insulated, and I have r-30 insulation under the ground floor (crawlspace, which incidentally has a plastic sheeting for a vapor barrier over the dirt).

The rooms I'm looking at for the 3 zones (what we can afford right now) are downstairs -room 1 is 15' x 15' with an 11' ceiling (2 exterior facing walls), room 2 is 14' x 14' x 11' (2 exterior facing walls), room 3 is 18' x 12' x11' with one (8' x11') exterior (south facing) wall. All of the windows are single pane, wood set in masonry, 3' x 6'.

I did a rough estimate of my whole house heat loss using the caclulator located at builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htm and came up with a heat loss figure of about 117,000 and some change. This doesn't take into account our current heating, as we'd like to use that as little as possible once this other system is in. The total heat loss (according to the calculator, which I suspect may be on the high side) for the 3 rooms we're looking to heat is around 40k BTU.

We have 2 gas logs at present, which aren't really doing the job, probably partially because we have such high ceilings and standard-height (80” -ish) openings between rooms, as well as a front room staircase that may as well be a chimney for the way that it funnels heat from one of the gas logs upstairs. And in spite of MLGW's laughably fictitious claims to the contrary, using natural gas here is insanely expensive, so we'd reaaally like to get off the stuff if possible. The two outdoor units we've been looking at are the LG and Mitsubishi multi-zone units (36000 BTU) with a matched combination of (2) 18K BTU indoor units and (1) 12k BTU unit. (see typical online package offers below)

e-comfortusa.com/products/lg-lmu365hvlmn125hvlmn185hvx2--wall-mounted-tri-zone-heat-pump36000btu/3492

e-comfortusa.com/products/mitsubishi-mxz4a36namsza12namsza15nax2wall-mounted-tri-zone-mini-split-32400btu/3436

Is there anyone out there who has experience with this type of system in a multi-zone application and can give me an idea if this would be a decent heat setup for my type of house and climate? I have a friend who is an HVAC guy who highly recommends mini splits and has installed several single zone systems, but he hasn't installed a multi-zone system before. He will be helping me pressure test and evacuate the system. Also, any advice regarding the heating performance of ceiling cassette units vs wall mount units?

I'm pretty set on putting a mini split system in, as having a central unit put in isn't really an option, nor is it something I'm really interested in due to the mess that installing the ductwork would make of the walls, floors, and/or ceiling (not to mention the 3 x 6' hole in the 100 year-old foundation I'm told would be required to fit the main trunk for a package unit).

I'd love to hear from someone who has installed one or more of these multi zone units in a similar scenario(s) and can give me an idea of how well they work for heat...Thank you in advance for any information that y'all can provide, and please hit me up if I can provide any additional information about my home...

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Old 01-19-11, 12:57 AM   #2
AC_Hacker
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Hello,

First off, I do not have the multi-zone experience that you are seeking.

But I did install an single-head minisplit at my home and I have had no trouble at all with it in the two years that I have owned it. I have been very pleased and consider it to be money very well spent.

I think that your climate is an excellent one for mini-split heating and if you size it even close to right, I think you'll be very happy with how quietly and economically it works.

But I think the most pleasant bonus will be how well it works as an air conditioner.

I would, however advise you to take a bit of care where you locate your outdoor unit, because on hot days it will be blowing out even more hot air... and on cold days, it will be blowing out even more cold air. Something to consider if you plan to use your yard for entertaining.

Good luck with your install, and I'm sure that I speak for others here in inviting you to share your install experiences with us, in words and in photos.

Best Regards,

-AC_Hacker
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Old 01-19-11, 03:31 PM   #3
benpope
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Hey Telstar, we're practically neighbors! I faced a lot of the same problems in my old house as you do now: exterior that is hard to insulate because of stone/brick facing, high rate of heat loss/gain, etc. The previous owners paid up to $500 a month for utilities during the winter. It may get hot in Memphis, but the major expense is winter heating.

From what I have seen, the cassette units max out at about SEER 13 (not sure about the HSPF rating) while the wall mount units go up as high as SEER 21. Also keep in mind that the single units have a higher efficiency than the three zone units because they have smaller pumps and fans. However, there are two fewer compressor units to go bad--and only one to replace--if you have the 3 zone system.

Also, have you looked at the LG Art Cool? It is a bit more aesthetically pleasing than the regular mini splits (no offense to the artistic sensibilities of AC Hacker and Xringer, but some of us have picky SWAMBOs).

Also, MLGW (for non-Memphians, that is our power, gas, and water "non profit" utility) offers an in-home energy audit program. Don't worry--the inspection is done by a subcontractor who should know what he is doing. I didn't have time to do it, but a neighbor did and she was pleased. They can help you with air sealing and weatherstripping, which when you have an old house you can almost never do enough of. An aside on air infiltration, check out Daox's interior storm windows so that you can keep the original windows but reduce losses through them.

MLGW has a huge infrastructure devoted to gas and they want to be sure that it is used. They came through on my block last summer and replaced the 80 year old buried gas line and they want to be sure to make that money back. I also get the feeling that they don't get along well with TVA--there are a lot of TVA programs that they aren't a part of--so they want to push as much business as they can away from TVA. That is just my unsubstantiated opinion, though.

What was the original heating system for the house? Coal fireplaces, radiators, or a gravity furnace? I'm surprised you don't have a partial basement, but maybe they just put those in for boilers or gravity furnaces.

It sounds like you are a step ahead of the rest of us if you have a real HVAC contractor who can help you with it. All of the guys I've talked to have no idea what I'm talking about. Here is a thread that covers an LG 3 zone install. Good luck.

Last edited by benpope; 01-19-11 at 03:39 PM..
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Old 01-20-11, 09:17 PM   #4
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I have a Grunaire 4-zone heat pump that I installed a couple months ago and we're pretty happy with it. I'm about an hour north of Philly and have a 90 yr old brick house with original windows with storms.

One floor was heated with hydronic oil, top floor was heated with electric baseboard. I haven't run either since I installed the mini-split and my electric bill has been lower then last year, even though average temp has been lower. If I continue to use no oil throughout the year I'll save about 500 gal ($1500+) this winter plus cheaper electric.
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Old 01-21-11, 08:06 AM   #5
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I don't mean to high jack this thread or anything but Stefanc how do you keep your basement warm with the heatpump ? I have virtually the same heating situation as you. I'd love to dump my $1800 a year oil heat.
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Old 01-21-11, 08:34 AM   #6
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The house is actually a duplex-

unit 1- First Floor, heated with gas furnace in the basement with some electric baseboards.

unit 2- Second and third floor, Mini-split


So the basement stays pretty warm with the gas furnace but even without it I don't think it would be a problem being that it's not a living space and it's 90% underground.

Last edited by stefanc; 01-21-11 at 08:37 AM..
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Old 01-21-11, 08:43 AM   #7
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I picked up my mini-split from GoDuctless and have been very pleased with the purchase there. Shipping was quick, customer support has been really great and everyone is very helpful. I had a warranty issue (control board on outdoor unit was cooked, not allowing one of the indoor units to work) and had no problems getting help from them troubleshooting and repairing.

Price was good too!
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Old 01-21-11, 10:24 AM   #8
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Cool! Yeah I'm feeling better and better about the mini splits on my house. I think that's the way I'm going to go with maybe a pellet stove as backup for really cold days. I'm only 15 miles north west of Philly so it's not brutal cold in the winter.

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