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Community and Q&A

Mini split sizing

Bert Matter | Posted in Energy Efficiency and Durability on

We are looking to add a mini split to replace electric  baseboard heating . Located in Langley  BC.
January February mean daytime temperature is 36 F, night time 33F, night time  temperatures go below  freezing maybe 15-20 times all winter and only to the high 20’s F.

We live in a 2nd floor  in law suite around  750 – 800 square feet , open concept  kitchen family room, an additional  bedroom  is not heated as it stays between  58-65F.
Presently heated with2-500watt and 1- 1250 watt electric  baseboard  heaters (3413×2.25=7679btu).
Night time setback to 62F, daytime 69F, however  it generally takes2-3 hours to bring it back up in the  morning. Only  a  few times a winter does it get somewhat cold into the low to mid 20’s, then a plug in electric heater is used to bring the temperature  back up quicker  in the  morning. 

So I am looking at Gree 9000 btu and a Gree 12000 btu .Specs for 9000btu: cooling cap;1535-12966,heating  cap:2388-13648, seer:38 hspf;15.

12000 btu specs:cooling cap:3,100- 13,000, heating  cap: 3,071- 18,766, seer: 30.5, hspf :14

When I look at hvac internet  sites they recommend 9000btu for less than 400 sq feet , 12,000 btu 5-600 sq feet.

Am I missing  something  here? I think  either one would do as they  both modulate  quite low in heating (2388 &3071) .

Any thoughts  would be appreciated!

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Replies

  1. William Morse | | #1

    You need to figure out your heat loss before any decisions. See many other posts here on how to do it.

  2. Expert Member
    Dana Dorsett | | #2

    At your fairly temperate -5C heating design temp just about any 9000BTU mini-split would cover the entire load, as you correctly surmise from the maximum output numbers of your existing baseboards that are doing the job.

    For reference, Vancouver Airport's 99% design temp is +25F/-4C :

    https://higherlogicdownload.s3.amazonaws.com/ACCA/c6b38bda-2e04-4f93-bd51-7a80525ad936/UploadedImages/Outdoor-Design-Conditions-1.pdf

    With a mini-split it's less efficient to use deep overnight setbacks. Using set backs it'll use a bit less than half what the baseboards use, but if you "set and forget", tweaking it up or down only a degree or two at a time it'll use just a third or less.

    1. Bert Matter | | #3

      Thank you for the confirmation Dana, I have read many Q&A columns over the years and I have read many times yhe importance to size it correctly.
      So the 9000 btu model would be the better choice over the 12000 btu model as the seer &hspf is higher?

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