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Old 09-15-2011, 08:11 AM   #1
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mini-split systems for larger houses?


We recently moved in to an older house (built in 78) that has electric baseboard heating. The options for running duct-work for a central system like a central heat pump aren't very good. We had a couple quotes for around $13K that would run ductwork in the attic and have a heat pump to service the upper floors, but the lower floors wouldn't have any duct work to them.

I am interested in putting some mini-split systems in, which I could run the lines to cover the whole house, but I get conflicting information on sizing all over the web.

Here is a floor plan for our house (We live in central PA). It is a split level, so it is really 3 elevations even though it lists it as two floors on here:




The attic has blown in cellulose insulation (R30 I believe). Walls are vinyl siding with fiberglass, but I'm not sure the R value. For windows:
Upper floor: 7 36" windows
Lower floor: 2 36" & 1 72" bay window, 1 french door, 1 door to garage, sits on concrete pad
Main floor has a 95" bay window, 2 sliding doors, 6 36" windows, unfinished basement below (with fiberglass insulation between floor/ceiling)


What I'm trying to figure out is how many outdoor units I would need, and how many indoor units I would need.

My thought originall was to have two 36K BTU outdoor units, and put 3 12K indoor units on the main floor, and then the second outdoor unit could service the upper and lower floor with 2 9K indoor units on each floor.

But I don't know if this is too much or not enough BTU (mostly concerned with heating).

Is putting in mini-splits even a viable idea for this house?

Thanks for your help...

Nate

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Old 09-15-2011, 09:03 AM   #2
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mini-split systems for larger houses?


It would cost the same for a mini-split, as it does for the hvac. Review the bids, and if needed, get back to them, to clarify exactly what they are doing, entails. Did any of the bids figure in replacement and repair of any drywall? If wanting to do the upstairs, it is easier up there, or else you are talking of repairing the ceiling on the first floor, if not wanting a separate unit on the 2nd floor. How many square feet is this house, and how many tons for the a/c & btu/hr for the furnace, or were any bidding in a heat-pump hybrid?

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Old 09-15-2011, 09:23 AM   #3
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mini-split systems for larger houses?


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Originally Posted by gregzoll View Post
It would cost the same for a mini-split, as it does for the hvac. Review the bids, and if needed, get back to them, to clarify exactly what they are doing, entails. Did any of the bids figure in replacement and repair of any drywall? If wanting to do the upstairs, it is easier up there, or else you are talking of repairing the ceiling on the first floor, if not wanting a separate unit on the 2nd floor. How many square feet is this house, and how many tons for the a/c & btu/hr for the furnace, or were any bidding in a heat-pump hybrid?

The house is about 2700sq ft. The reason I want to go mini-split is I can do the work myself.
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Old 09-15-2011, 11:07 AM   #4
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With inverter driven condensers you'll be running partial load, oversizing doubtful in our opinion.

Estimating about $6k to $6500 in equipment alone with any of 3 reputable brands.
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Old 09-15-2011, 11:41 AM   #5
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With inverter driven condensers you'll be running partial load, oversizing doubtful in our opinion.

Estimating about $6k to $6500 in equipment alone with any of 3 reputable brands.

I'm not sure I understand what you mean by your first point. I've seen the number 518sq ft/ton, which would work aout to be about 5.25 tons. If I wanted to put an indoor unit to cover the unfinished basement, it seems like having 6 tons would work out well, but I don't know how accurate that 518 sq ft/ton number is...

As far as your second point, I was looking at the 36K btu LG mini split systems, so I had estimated about $8K in indoor/outdoor units + piping/controls. I could do almost all the work myself with a mini-split system. I could install the indoor/outdoor units and run all the cables necessary, and then just pay an HVAC contractor to come and charge/connect/activate everything.
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Old 09-15-2011, 12:01 PM   #6
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Fujitsu , LG , Samsung , Sanyo...For a little more, Mitsubishi...take your pic.

Careful on your capacities , some LG 3-ton condensers only yield 32,300 cooling brush on nonducted type ahus ( LMU366HV) their larger 3-ton only yields 34,000 and a minimum btu cooling of 20,396 cooling due to inverter.
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Old 09-16-2011, 07:05 AM   #7
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mini-split systems for larger houses?


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Originally Posted by bignateyk View Post
I'm not sure I understand what you mean by your first point. I've seen the number 518sq ft/ton, which would work aout to be about 5.25 tons. If I wanted to put an indoor unit to cover the unfinished basement, it seems like having 6 tons would work out well, but I don't know how accurate that 518 sq ft/ton number is...

As far as your second point, I was looking at the 36K btu LG mini split systems, so I had estimated about $8K in indoor/outdoor units + piping/controls. I could do almost all the work myself with a mini-split system. I could install the indoor/outdoor units and run all the cables necessary, and then just pay an HVAC contractor to come and charge/connect/activate everything.
Just a blurb, it's not that easy to charge/connect/activate everything.
Could be many problems due to diy installation and the contractor will charge many$$$ if something is not right somewhere in the system.
No Warranty on start up.
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Old 09-16-2011, 09:07 AM   #8
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mini-split systems for larger houses?


first off, ductless is a great way to go because you will have zone controll and your house should be very comfortable. as far as sizing..there is no set sizing based on square footage. there are other factors that go into it. if you are going to do it yourself go with six tons because you will be oversized. the inverter technology will help you compensate for the oversize. as far as placement and size per area...you can do that as you like. your plan for that soulds ok. cant be positive without looking at it myself. you have to consider your condensate drainage too. the water will need to get removed from each unit. i think you cost to just have a pro do the job wouold only be around 10k. you are not saving that much by doing it yourself. than you will get installation and start-up warranteees.
www.cascadehvac.com

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