Time to Buy some Mini-Split A/C systems, your thoughts?

solar_dave
solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
in Energy Use & Conservation #1
OK so it is time to buy my mini split for my new shop/home office building. Here are the conditions:

3 rooms to cool separately, the small one will be occupied daily as a work from home office with some heat load from a couple computers. The other 2 are a work shop and plus size garage bay and I just want to control run away temps in those most of the time with occasional reasonable working temps. The Location is PHX and the building will be 2X6 construction with spray foam insulation and 2 inch foil faced radiant barrier iso-cyanate foam panels attached over the sheathing.

room 1 ~120 sq ft. 2 windows, 1 exterior door.
room 2 ~240 sq ft 2 window, 1 exterior door.
room 3 ~350 sq ft with insulated 7X10 north facing garage door.

Here is what I propose

1 - CM3172 ground unit 30,600 unit.
1 - KMS0772 wall unit 7,000 BTU
1 - KMS1272 wall unit 11,900 BTU
1 - KMS1872 wall unit 17,500 BTU

Is this overkill ???

PS not worried about heating at all.
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Time to Buy some Mini-Split A/C systems, your thoughts?

    Solar Dave,

    I have moved your post to its own thread...

    Regarding your systems--You have lots of insulation, double pane windows, energy efficient computers/appliances in the rooms?

    By the way, why are you not worried about heating with heat pumps?

    -Bill "Conservation First" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #3
    Re: Time to Buy some Mini-Split A/C systems, your thoughts?
    BB. wrote: »
    Solar Dave,

    I have moved your post to its own thread...

    Regarding your systems--You have lots of insulation, double pane windows, energy efficient computers/appliances in the rooms?

    By the way, why are you not worried about heating with heat pumps?

    -Bill "Conservation First" B.

    Midday winter temps here are just really rare occurrence that need heat. it is pretty rare that we even turn on the main house heat.

    The insulation will be overkill, compared to the local building standards, all low e coated double pane windows, a Mac Mini, macbook both with multiple heads for the Computers and maybe one Intel Atom for a file server.

    I have not found anyway of figuring the heat load, but the office can probably be warmed by the five 24 inch flat panel displays.:blush:

    Thanks for my very own thread! ;)
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: Time to Buy some Mini-Split A/C systems, your thoughts?

    You can start with a kill-a-watt meter for your plug-in computers/appliances.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #5
    Re: Time to Buy some Mini-Split A/C systems, your thoughts?
    BB. wrote: »
    You can start with a kill-a-watt meter for your plug-in computers/appliances.

    -Bill

    Got one, the computers are all real low energy users, more interested if the system I spec'd is over kill for my needs.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #6
    Re: Time to Buy some Mini-Split A/C systems, your thoughts?

    I cannot remember the name of one of the big building energy calculators--but from a Federal Government Website, there are a bunch listed (they have the free ones highlighted).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #7
    Re: Time to Buy some Mini-Split A/C systems, your thoughts?
    BB. wrote: »
    I cannot remember the name of one of the big building energy calculators--but from a Federal Government Website, there are a bunch listed (they have the free ones highlighted).

    -Bill

    Thanks Bill some are limited to windows but found one that runs on MAC.
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  • LucMan
    LucMan Solar Expert Posts: 223 ✭✭✭
    #8
    Re: Time to Buy some Mini-Split A/C systems, your thoughts?

    Looks like overkill. 710 sq ft total
    600-800 square ft per ton ( 12,000 BTU) is the rule of thumb for normally insulated homes. (R38 ceiling and R19 walls)
    To be sure do a manual J, (heat loss heat gain) calculation and enter all your insulation, infiltration,windows, doors, & your weather conditions etc.
    Try HVAC calc. it is available for purchase as a 1 time use, very easy to use and will get you spot on as to heat gains and loss.
    room 1 ~120 sq ft. 2 windows, 1 exterior door.
    room 2 ~240 sq ft 2 window, 1 exterior door.
    room 3 ~350 sq ft with insulated 7X10 north facing garage door.

    Here is what I propose

    1 - CM3172 ground unit 30,600 unit.
    1 - KMS0772 wall unit 7,000 BTU
    1 - KMS1272 wall unit 11,900 BTU
    1 - KMS1872 wall unit 17,500 BTU

    Is this overkill ???

    PS not worried about heating at all.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #9
    Re: Time to Buy some Mini-Split A/C systems, your thoughts?

    Dave,
    Why would you not consider evaporative cooling for most of the year and use the heat pump for Monsoon season? If you are looking to save energy that is what my buddies in Tucson do? Much better climate with the right moisture content!
    Good Luck!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #10
    Re: Time to Buy some Mini-Split A/C systems, your thoughts?
    Dave Sparks wrote: »
    Dave,
    Why would you not consider evaporative cooling for most of the year and use the heat pump for Monsoon season? If you are looking to save energy that is what my buddies in Tucson do? Much better climate with the right moisture content!
    Good Luck!

    Yeah got evap planned for garage room but the AC has to cover the 2 months of monsoon at least. In the other room I don't want that high humidity because of what will be there. Evaps are a PITA BTW, they take a fair amount of maintainence, require some water filtration to keep calcium deposits down on this nasty AZ water. I will know at the end of the month how much overkill I built into my PV system.

    My only concern with this 3 way mini split is it over kill if I use closed cell foam insulation on the 2X6 exterior walls, with an added 2 inches of iso-cyanate foam board over the sheathing, then the stucco.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #11
    Re: Time to Buy some Mini-Split A/C systems, your thoughts?

    With the Sanyo brand I believe you could add the air handlers later as long as the compressor was sized right!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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