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Master Brian 05-20-2013 03:58 PM

split mini??
I have been trying for 5yrs to figure out how to cool/heat the 2nd floor of my 1915 bungalow. I think I've finally settled on a split mini setup, but I need help trying to decide how large to go.

I live in South Central Kansas. The 2nd floor is about 600sqft total with 3 rooms. A bedroom, an office and a master bath, they are about 150-200sq ft each +/-. The main floor is 1300 sqft and the basement is about 1000sqft, they are both serviced with a 3ton central unit, though the basement isn't fully ducted.

The online guides seem to say 1 1/2 ton units will service about 600-1000sqft, but my understanding is I want to upsize an upstairs unit since the cold will fall to the main floor. So, would a 1-1/2ton unit be too small and should I look at a 2 ton unit? I like the idea of the ducted ones, so I can place a few ducts in each room, but it sounds like I'd loose some efficiency, so may just do the units with a seperate air handler in each room.

I've been seeing these used on This Old House and other shows, but what really caught my eye was a flyer at Home Depot with the Mitsubishi unit. Are there any of these to stay away from? Are they really difficult to install? ....and will I really loose much efficiency if I go with a ducted version? I have easy attic access above. I should also state, I'm looking at one that can heat, so likely would be the heat pump and I do have baseboard and will have gas fireplace for auxilary heat if need be.

Thanks for any direction on this! And though I probably won't hire a professional to do the install, due to bad luck in past getting any quotes on this space, I do have several licensed people that will likely help me on the side if need be.

yuri 05-20-2013 04:21 PM

1st of all you can cool 600 sq feet with 12,000 BTU window unit easily so the 1.5 ton minisplit is just fine. Going bigger and it will definetly short cycle and not remove enough moisture. Excess starting/short cycling will drastically reduce the life of the compressor just like starting/stopping a car at every light. They are designed to run long cycles or continuos. Not that much air settles so I would not try use it to do the main floor as all the heat from there rises so they equal out. They make ducted ones but you can go with 3 blower units/heads that will give you individual control and IMO be a better unit. Efficiency does not get lost as it is the compressor/outdoor unit that is efficient/SEER rated. Drainage is usually a big problem so if it is too difficult to drain 3 heads then 1 ducted unit may be better and drain it straight out thru the attic/wall. May cost more for the ducted unit and I would only trust Fujitsu or Mitsubishi when buying them as they are very high quality. These units are not easy to install but if your buddies are qualified and you carefully read the install info and use the proper wirng etc can be done. Fujitsu makes a cassette system.

Master Brian 05-20-2013 06:14 PM

Yuri, thanks for the info, that is very helpful.

I have heard very good things about the Mitsubishi and some about the Fujitsu. One thing was that unless installed by their certified installers no warranty, I guess I'll have to find out more about that....

I currently have an 18,500 BTU window unit and I suppose it does an ok job at cooling the space, but I haven't thought it did it easily, but maybe that's because of the breakup of the rooms. Drainage could be a bit tricky, but it's probably something I could figure out as all rooms have outside walls. I understand it gets to be a fine line on being too small and being too big that's the tricky part!

yuri 05-20-2013 06:22 PM

window units are notorious for the condenser coil getting plugged with dirt and then they lose capacity BIG time. You have to take them apart and to the car wash and wash all the dirt out, yeah seriously. You will be sorry with an oversized unit. window units do a fair job but they use the same fan motor for the cooling coil and condenser and are a compromise and nobody expects great results from them anyway. They are meant for apartments/condos/mobile homes etc. You cannot blame manufacturers for not warranting DIY units as how do they know it was done properly and no moisture or dirt got in the system. Personally I would get a Pro to do it or your friends if they are qualified. Mini splits are NOT as easy as a regular AC and are critically charged with Freon. Meaning a ounce or 2 extra will cause it to not work properly so it has to be exactly measured in etc. with a regular resi unit we can be out few ounces and not big problems. NOT so with minisplits. If you pay lots of $$ for it I would want it to work 100%. I am sure lots of them are done by DIYers but few are charged properly but they won't know any different anyway as they don't know what it really should work like. You get what you pay for.

Master Brian 05-20-2013 08:58 PM

The work I'd do would like it only be cutting holes, hanging, wiring, etc. Anything to do with Freon, etc, would be left to someone knowledgeable on the subject. I suppose you are correct on the window units, which is why I don't want to keep it. It should be working fine as its not even a year old.

yuri 05-20-2013 09:13 PM

I am sure the minisplit would be much better as it will throw the air better and circulate it better. Not hard to sell the window unit on E-Bay etc. Probably use a lot less electricity too. As long as it is charged up properly by a Pro and a proper vacuum done then they may warranty it. Need to check with them as to what they want. If you snoop around enough you may find a install manual for a Fujitsu or Mitsubishi online. Like I said draining the condensate from the indoor unit is usually the biggest logistical problem so you may want to research the install thoroughly. Those tiny condensate pumps for them are very unreliable and we have had lots of failures and leaks with them. Gravity drainage is the best way. You don't need a fan unit/head for the bathroom so a 2 head setup is your best bet.

Good Luck

Master Brian 05-20-2013 09:28 PM

I will l see what I can find for manuals, I thought about that as well. The problem with not putting a unit in bath is it might be the biggest room on the 2nd floor. I also have easy access to two main floor bedroom closets for chases to get drain lines down. I'd only use 3/4" pvc or pex for the drains and take down to sump pit.

yuri 05-20-2013 09:39 PM

Normally we don't cool a bathroom but I see your point. BUT you REALLY don't want to get HIGH humidity into the head as there is a VERY expensive circuit board in there. As long as you are not showering in there fine but if there is a shower then it will kill that head/board unless you can suck the steam out as fast as it is being produced. Go with nothing less than 3/4 for the drain and it should be fine. 1/2 is too easy to get dirty/plugged or air locked.

Master Brian 05-21-2013 11:58 AM


Originally Posted by yuri (Post 1183741)
Normally we don't cool a bathroom but I see your point. BUT you REALLY don't want to get HIGH humidity into the head as there is a VERY expensive circuit board in there. As long as you are not showering in there fine but if there is a shower then it will kill that head/board unless you can suck the steam out as fast as it is being produced. Go with nothing less than 3/4 for the drain and it should be fine. 1/2 is too easy to get dirty/plugged or air locked.

Hadn't thought about that! Yes, there is a shower that we use every day. I do have a fan, but being as it currently isn't vented outside, only into the attic, I rarely use it. One of these days, I plan to remedy that and do it right, as I didn't install it.

I guess with my current window unit, which is in the bathroom, the other rooms don't fair too badly, so it should get some airflow. I'll have to look into wether or not I can get two heads, with one of them being capable of having some duct work I could run into the bath! The big problem with the bath NOT having a unit is that it is north facing, so in the winter it gets the coldest, but it does have a baseboard heater, which I plan on keeping. The other thing is it has a skylight which bakes the room in the summer. I've been placing a shade in there in the summer, but it still lets LOTS of heat in.

Thanks for the great info, this really helps me in my searches. I was given a name of a company that installs these locally, so I think I'll give them a call soon and see what they have to say!

yuri 05-21-2013 02:43 PM

Sounds Good.

There are different combos like fan coil units that Fujitsu has and those cassette units ( meant for offices and suspended ceilings ) and I am sure Mitsubishi has similar units so a contractor has more info on that than I do. What about putting an airhandler in the attic and running ducts to those rooms. You can get high quality airhandlers with ECM motors/variable speed fans which can slow down a lot to keep the air flow down with a 1.5 ton unit. Have to run the Freon lines up an outside wall ( they have cosmetic covers which look very good for them) and it would be a lot better and possibly cheaper than a minisplit and a LOT less expensive to fix in the long run. Minisplits work great but once they have problems are expensive and difficult to fix and very few guys know how unlike a regular resi unit.

I can guarantee you the shower will kill that unit and sooner or later some one will turn the exhaust fan off too soon and moisture will wreck it. VERY bad idea and if they see a corroded board will void the warranty on it.

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