Author Topic: What ductless multi zone mini split system to get ?  (Read 1370 times)

tristan15

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What ductless multi zone mini split system to get ?
« on: January 23, 2021, 06:18:49 PM »
Hi everyone,

I just bough a house in western NC, current heat is provided by 40+ yr old oil boiler, no AC. I would say that the min winter temperature is probably 5/10 degrees Fahrenheit and summer can get up to 85. House is about 1700 SF.

I want to get rid of the boiler for many reasons and would like to install a 5 zone mini split system for heating and cooling. I started doing research and got very overwhelmed, seems hard to find un-biased information.

What are the best brands to look for? What system would you recommend ?

Thank you

Mr. Green

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Re: What ductless multi zone mini split system to get ?
« Reply #1 on: January 23, 2021, 06:47:11 PM »
I watch a YouTube channel of a couple in West Virginia building their own house. They used a Mr. Cool mini split system. It comes precharged so there's no adding refrigerant. The husband is an electrician so he goes into some details during the installation. Here's the video of their install. I think it might be the first video and there's a second one where they wrap up this particular project on the house.

https://youtu.be/zwIqB7yiTeo

uniwelder

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Re: What ductless multi zone mini split system to get ?
« Reply #2 on: January 23, 2021, 06:59:52 PM »
Fujitsu, LG, Mitsubishi are supposed to be good brands.  You can look around at websites like ecomfort.com or acwholesalers.com to get an idea of selection and pricing.  There will be a huge difference in actual price if you have a contractor buy and install the system.  For 5 zones, it will probably cost more for the mini-split setup you're asking about than to have ductwork run and a central heat pump system installed.  A 2 zone mini-split costs about the same as 2 individual mini-splits, so you don't really save any money, just less outside units to make space for.

If you can describe the house layout, we might be able to give better advice.  You might get away with two zones.  One wall mounted unit in the central living area and another short-ducted unit that can placed up at the ceiling of a closet or laundry room that is sandwiched between other bedrooms. 

I live in a similar area to you--- Blue Ridge mountains of Virginia.  Our house is 800 sq ft and heated/cooled with one 1.5 ton Mitsubishi wall unit and it is fantastic.  In another house (rental for now, soon to become primary home) last year, I installed a 2 ton LG wall unit that takes care of a 1,700 sq foot ranch, though the two bedrooms at the far end are about 10 degrees cooler in the winter and the doors need to stay open.  This spring I'm going to be installing a 1 ton Fujitsu short ducted unit to serve those two rooms.  For the Mitsubishi, a contractor purchased and installed for about 2x the price ($4,000 total cost, 5 years ago) of what I could have done myself.  I did the LG myself and hired a technician to do the final connection and vacuum, saving me probably $3,000.  I'll do the same again when hooking up the Fujitsu.

edited to add--- as Mr. Green said, Mr. Cool is an option, though I don't know much about their quality vs the brands I mentioned.  I also have the idea that Mr Cool isn't as efficient in low temp operation as others.  If you were to the DIY route, I'd recommend finding an hvac tech that's willing to work with you and get a professional brand.  My guy charged $300 for his work.  And make sure you find someone first, before deciding on going that route.

Also, the brand you end up with will likely be dependent on what the contractor is most familiar working with.  Options like hyperheat (mitsubishi) aren't necessary for your climate.
« Last Edit: January 23, 2021, 07:10:52 PM by uniwelder »

tristan15

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Re: What ductless multi zone mini split system to get ?
« Reply #3 on: January 24, 2021, 06:37:38 AM »
Thank you for the answers, that was very helpful. I live in the blue ridge mountains as well, at about 3400 ft elevation.

Here is the layout, the house had two level, the main level living with three bedrooms, one bathroom, a corridor leading to the kitchen, dining, living which is fairly open, the house has 8' ceilings thorough the house.
Then there is a basement level downstairs which is mostly the garage but which also has a finished bathroom and open area for a future bedroom/office. I do not know that a ducted system would be easily installable as the main floor is framed with 2x10 meaning that the ducts would have to run below that rendering the space below unusable as the ceiling height would drop significantly. The roof has a low slope roof so the attic is pretty tiny, maybe 4 ft height.

I will definitely plan on calling local AC companies to know which system they use and see if I can find someone willing to do the final connections as I was planning on installing the mini split system myself to save some money and have someone do the final hookup. I just got our service upgraded from 100 amp to 200 amp for the house.

After looking at the floor plans, let me know if you have any other feedback ,I also marked where I was planning on installing each of the 5 zones.



« Last Edit: January 24, 2021, 06:48:56 AM by tristan15 »

uniwelder

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Re: What ductless multi zone mini split system to get ?
« Reply #4 on: January 24, 2021, 07:09:58 AM »
Do the bedrooms have closets?  If so, where?  Does the closet in your drawing open up to the hallway or one of the bedrooms?  Do you keep bedroom doors open or closed when occupied?

Regarding DIY and having a tech do final hookup, you probably don't want to call a company directly.  They get pretty pissy about that.  Might need to find someone that does independent work.

Wall units are usually placed along exterior walls to run copper lines to the outside unit.  Where are some accessible places you can put the outdoor units?

edited to add--- how much do you care about resale?  Mini-splits really turn some people off.
« Last Edit: January 24, 2021, 09:11:38 AM by uniwelder »

tristan15

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Re: What ductless multi zone mini split system to get ?
« Reply #5 on: January 24, 2021, 09:26:58 AM »
All bedrooms have closets, I omitted drawing two of them which are small and are pretty much back to back in between bedroom 2 and 3. The closets only open up to the bedrooms. They are all about 3 to 4 feet deep.

Well we just moved in so we do not have any history of how we have been doing things but we are open to leave some doors open if needed.

Yes I did talk to some companies and indeed, they want to provide the units and do everything. Any advice on how to locate an Ac guy that would be willing to do this? Even if I have to pay extra to have him/her drive from the closest metro, it'd still be worth it but as you mentioned, I would love to find that person first to decide on the system brand.

Outdoor units will probably sit at the back of the house (back wall is wall connection bedroom 1, bathroom, kitchen, dining) I was thinking. I originally wanted to have it on the left side (wall outside of bedroom 1 and bedroom 2) but I am worried that the lines will not be long enough to go all the way to the farther unit. Is there a typical max length from the compressor to the farthest indoor unit?
I was thinking about running all the lines on the ext wall to the attic and then spread it out to the different indoor units that way, would that be a bad idea?

We plan on keeping it as an investment so I do not anticipate ever selling it. Most old houses around here (this house is from the 70's) do not have AC and run just old, clunky boilers, so I actually think a mini split would be an upgrade compare to similar houses.

Thanks a lot !
« Last Edit: January 24, 2021, 09:28:38 AM by tristan15 »

KarefulKactus15

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Re: What ductless multi zone mini split system to get ?
« Reply #6 on: January 24, 2021, 09:39:32 AM »
I have some questions.

How did you determine load capacity? (Manual J is the correct formula for this. You can find some online. I have an excel version if you want.)
How are you powering all these units? Are you sure your power supply can handle the aux heat kicking on(if you need that option in your climate zone)
When I look at the upstairs there are like 3 major rooms that won't have air flow and will have uneven temps.
Are you using 1 outdoor condenser unit? (Most new systems are variable and can handle 5 or more indoor units.

Ducted package / split systems are the gold standard in this area so their may be a cost benefit to using that as contractors are more familiar.  Do you already have natural gas supply at this house?

With all that, mini splits have come a ways and I think there's a good chance the future goes that way. If you have any attic space, the flush ceiling mounted indoor units would be good aesthetically. Look "ceiling cassette" paired with your brand of choice should bring it up.

Again I think ducted is usually cheaper. Mini splits excel cost wise on a house that absolutely can't retrofit to ducts due to 100 year old brick construction or similar.

tristan15

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Re: What ductless multi zone mini split system to get ?
« Reply #7 on: January 24, 2021, 12:57:58 PM »
I am unsure how to calculate the load capacity. I am just looking at the square footage and the BTU needed.

I have upgraded my electrical system from 100 amp to 200 amp. Yes it would be one condenser and 5 indoor units. I would say that the min temp around here would be 10F, most day time winter temperature are usually 20F-40F.

No natural gas available at the house, current system is an oil boiler which I want decommissioned especially that is has a buried tank, we got soil sample and it does not appear that it is leaking but I just want it out.

It is correct that the bathrooms will be significantly colder and the the temperature might not be homogeneous.

I am going to get a couple of local AC companies to price some options and get their 2 cents on the pros and cons of a ducted system vs mini split in my area. Obviously, it's going to come down to cost, if they quote me 10k+ for a ducted system but that the DIY mini split is 5k... I am willing to be somewhat cold in my bathroom to save that much money and maybe just have a small space heater to put in the bathroom if it's really that bad.

Thanks

uniwelder

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Re: What ductless multi zone mini split system to get ?
« Reply #8 on: January 24, 2021, 01:12:18 PM »
As Kroaler mentioned, the cassette units may work well for your case.  I looked up a 5 head unit and price isn't bad.  One head per bedroom just seems overkill from a capacity standpoint, though mini-splits run very efficiently to about 25% of output supposedly. 

The alternative that I brought up originally, that may work in your case, is to use a short ducted unit for the 3 bedrooms.  It would mount in one of the bedroom closets with the return bringing air in from the hallway, then run some short ducts through the closets at ceiling height to the bedrooms.  You'd have to create a chase to get over to/from bedroom #1 if your closet layout is what I imagine.  You'd still need another unit for the living room area and basement.

Not sure how to find a hvac guy for the hookup.  Ask around to any contractor type people you're friendly with and see if they know someone that does work on the side or has their own small independent service.  If you're doing DIY, how competent are you?  Did you do the electrical service upgrade yourself or hire that out?  There are definitely things with the mini-split you don't want to screw up, like kinking the copper lines or getting the condensate drain to slope properly. 

You'd need to look at a spec sheet for the unit for max run of lines.  I think 50-65 feet is the typical, but that might just be for the amount of precharge in the unit.  That info is on the websites mentioned once you look at a particular unit.

Something else to consider is that this doesn't all have to be done at once.  If you have a functional oil boiler, just keep using it for now.  Add a wall mount mini-split unit along the dining/living room wall so it blows toward the kitchen and hallway, so it becomes the primary heat source except for the coldest temps.  Or maybe you end up with a two head unit, so another interior location could be in the basement, and these can tie in together with the outdoor unit in the back of the house behind the dining room.  The bedrooms can be figured out later on once you see how you like the setup.  If you had to locate two exterior units, would this be reasonable?

edited to add--- oversizing a mini-split isn't too bad since they throttle down very efficiently to its low end of capacity, and I'm going to guess you'd end up needing something around 2 tons.  You should do a manual-J for each room, particularly if you will end up a with a head in each, and if you plan to DIY, I just feel like you should have a good grasp of why you're doing what you're doing.  I get the impression HVAC guys just wing it most of the time.

Bathroom doors stay open most of the time and your's are pretty central, so I don't think it would matter.  I have a friend whose house has mini-splits in each bedroom and he's mentioned he doesn't feel any difference in the bathroom which does not. 
« Last Edit: January 24, 2021, 01:23:58 PM by uniwelder »

KarefulKactus15

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Re: What ductless multi zone mini split system to get ?
« Reply #9 on: January 24, 2021, 01:56:05 PM »
Sorry for my bad typing. I'm on the phone.

I meant load calculation not capacity. More is not better even on variable systems.

I looked at your plan again, where's the water heater? Does it stay in the garage?   

Your plan looks like a split system would work. Put the indoor unit in the basement. To do the upstairs rooms you seemed concerned about giving up joist space below.  To get around that I'd sacrifice some closet space on the main level hallway closet and use it as a utility run for supply ducting into the attic, that way you only need room for flexible ducting up there and your unit is in the garage in a nice serviceable location. 

If not, alot of purpose made  ducting fits nicely between joist of all sizes and you could do floor level vents.

Like I said before most contractors do ducted systems.  I'm sure you already know this, but for mini split make sure you find someone who proudly and prominently advertises they do mini splits as their primary and doesn't shy away from them so you get a nice clean install.
« Last Edit: January 24, 2021, 02:12:56 PM by Kroaler »

KarefulKactus15

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Re: What ductless multi zone mini split system to get ?
« Reply #10 on: January 24, 2021, 02:09:06 PM »
Just realized with a boiler there is no water heater.  Feel kinda dumb for that....

tristan15

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Re: What ductless multi zone mini split system to get ?
« Reply #11 on: January 24, 2021, 02:39:55 PM »
Kroaler,

There is actually an electrical water heater in the bathroom downstairs, I still do not know if it is part of the boiler system or independent.

Uniwelder, not going to lie, I am not that knowledgeable about ac and mini split. I guess I have seen people put together their Mr Cool systems and figured out I would do the same with the five zone system. I am a structural engineer by trade so I feel that it is not completely out of reach but I would probably make some mistakes, I do not doubt it. I did hire the service upgrade. I will do a manual J to see what it comes up with.

Thank you
« Last Edit: January 24, 2021, 03:49:07 PM by tristan15 »

Bradfurd

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Re: What ductless multi zone mini split system to get ?
« Reply #12 on: January 25, 2021, 07:17:07 AM »
FWIW, I just hired a company to install a 2 zone system in a finished basement. I also work in an educational/commercial environment where ductless systems are installed a lot. We stick with Mitsubishi or Daikin. Mitsubishi now makes the MLZ indoor unit that fits in between traditional ceiling joists at 16" O.C. However, it only blows one way. The square ceiling cassettes will not fit in a recessed fashion unless you have a bulkhead. They blow four ways. The ceiling units will have a condensate pump, which is OK, but it's another thing that may fail down the road. The wall units, although less attractive, typically expel condensate via gravity. LG has a wall unit that you can mount photos or artwork on so it isn't as much of an eyesore.

I did a lot of research on ecomfort and acwholesalers, and although the prices seem great, I got sketchy vibes about the potential equipment's newness and the likelihood of it ever showing up. Reviews also stated that their support was almost non-existent. In short, the Mistubishis of the world have relationships with contractors, and you are likely not going to be the benefactor of wholesale pricing on the equipment unless you have a unique relationship or take some risk from one of the online outlets. If you can find a licensed tech who does side work, that is a decent option.

I had a lot of firms that wanted to sell me three indoor units, when I knew (based on my own calcs) that two units were sufficient, which they have proven to be. I added a small baseboard heater in the room in question just in case. $75 vs. $3k.

I am very happy with the performance of the system thus far. Good luck! I have no regrets about hiring this work out.
« Last Edit: January 25, 2021, 07:20:06 AM by Bradfurd »