sizeing a mini split

[AC_Hacker]

Originally Posted by ecomodded

Nokiasixteth I have found a calculator for sizing mini-splits...

I agree, this calculator is way off.

There are so many questions it should ask, but it just doesn't.

A much better tool is the Home Heat Loss Calculator that is free and over at Build it Solar website. It's actually based on Manual-J.

The one Nokiasixteth found is misleading, to put it mildly.

Best,

-AC

[ecomodded]

That calculator you posted Ac is very in depth , im going to give it a try , find all my info , I know my walls are a weak R12 not sure what my ceiling is, probably R24 or R30 something.

Glad to hear your enjoying your new mini split Nokiasixtech , sounds like I will be fine using a 12,000Btu heat pump for my upstairs.

[WyrTwister]

Originally Posted by ecomodded

Wiretwister I suspect big brother is watching grow shops and supplies (lights & high tech hydroponic plant food ) and not the air conditioning retailers who may get infrequent farmers every so often looking for air-conditioners.

You are right , but the sites I was referring to obviously were targeting / marketing to the indoor farmers , growing the funny tobacco . I left them promptly in search of other vendors .

God bless
Wyr

[nokiasixteth]

Originally Posted by AC_Hacker

I agree, this calculator is way off.

There are so many questions it should ask, but it just doesn't.

A much better tool is the Home Heat Loss Calculator that is free and over at Build it Solar website. It's actually based on Manual-J.

The one Nokiasixteth found is misleading, to put it mildly.

Best,

-AC

Dont you mean the calculator found by ecomodded . . I used the calculator that you sent to me in an earlier post.

[nokiasixteth]

Originally Posted by ecomodded

That calculator you posted Ac is very in depth , im going to give it a try , find all my info , I know my walls are a weak R12 not sure what my ceiling is, probably R24 or R30 something.

Glad to hear your enjoying your new mini split Nokiasixtech , sounds like I will be fine using a 12,000Btu heat pump for my upstairs.

I gotta say i like it a whole lot better than the old radiator heater. And actually stays warm . My walls just some have insulation on outside . In process of remodeling everything. Main room i stay in has r13 on walls and r 30 in the celing . But for down here thats what they recomend having in celing and walls. Have no insulation on the floors yet . Doubt it ever will. Did do something that helped a lot when i was using a radiator heater . Have 2 winders in the room. Two nights with temps almost identical. First night i didnt have any thing on them . Second night i used the black out curtains with the thermal backing. Helped me out a few kws per day. Sorry i dont remember specifics.

[nokiasixteth]

The way that i sized my mini split was almost dead on for me . Way i sized mine . I picked 3 days with close to the same temp as i could. I put my kw meter on it. Left it on 70. Then checked the kws at 3 days . That was a day like our average cold night nothing major I checked the main room i stay in. 234 sq ft . Ran it for few days . 162 hours.
heres the figures

234 sq ft

average nights

162 hours 73.95 kw hrs

10.95 kw hrs day heating room

457 watts hour

1560 btu per hour whole room
6.666667 btu per ft per hour
7000 btu per hour whole house
---------------------------------------


So on average nights it keeps my whole house at 68-70 degrees . I used the a kw to btu conversion calculator.
Kilowatts (kW) to BTU/hr conversion calculator
457 watts was 1559.348894 avgd to 1560
And i used a percentage caclulator Percentage Calculator
Did 7000 what percent of 13000 (btu of the heat kozy kool) Avg 54% of its capacity it has to run on avg night.

Do keep in mind thoughI sized mine for the coldest nights we would see in the teens and keep 560sq ft at 70 degrees. And not work at full blast to maintain it i have the figures somewhere but i will have to find them. The figures i have is the average cold night that i get here. above freezing temps
That i think is the best way to size the mini split from all the calculators out there being it is your house your checking and not someone elses figures..

[nokiasixteth]

cold night in the 20s

152 hours and

141 kws

0.927632 kw per hour

3165 btu per hour 13.6(avg again) btu per hour per ft

7575btu for 560 sq ft

I used kw to btu calculator to find 0.927632 was 3165.2121077 btu per hour maintaining room temp. 234 sq. Divided that by the sq ft
Then multiplied the btu per sq ft by 560 sq ft. Gave me around 7575

I used percentage calculator did 7575 percent of 13000 btu gave me 58.269230769230774%
Thats about where i wanted to run under 75% of its capacity.

Kilowatts (kW) to BTU/hr conversion calculator

Percentage Calculator

[ecomodded]

Thanks for the great explanation.

My current house has baseboard heaters, 4,000w (13,648 Btu)for the 20x20 room and those heaters do not run continuously, I found it astonishing the Calculator I linked too suggested I needed a 24,000btu.to heat it.
One more method of sizing a mini split is adding one the equals your current houses heating systems Btu output. Although that would assume your heating system is not grossly overkill.

[nokiasixteth]

Originally Posted by ecomodded

Thanks for the great explanation.

My current house has baseboard heaters, 4,000w (13,648 Btu)for the 20x20 room and those heaters do not run continuously, I found it astonishing the Calculator I linked too suggested I needed a 24,000btu.to heat it.
One more method of sizing a mini split is adding one the equals your current houses heating systems Btu output. Although that would assume your heating system is not grossly overkill.

Id be pretty sure in saying that the 12000 btu would keep the room good temp. Mine has 13000 btu heating. 1020 watts. More heat less money with a heat pump vs the old radiator . If you had a way to measure the watts per hour they ran on a 24 hour . You could get pretty much what you need.

[jeff5may]

Originally Posted by ecomodded

Thanks for the great explanation.

My current house has baseboard heaters, 4,000w (13,648 Btu)for the 20x20 room and those heaters do not run continuously, I found it astonishing the Calculator I linked too suggested I needed a 24,000btu.to heat it.
One more method of sizing a mini split is adding one the equals your current houses heating systems Btu output. Although that would assume your heating system is not grossly overkill.

If your baseboard heaters do the job at 13,600 btu of capacity, then a 1 ton heat pump would do the same job. The main difference is energy usage. Where your straight electrics use 4 kw while running, a mini-split would use less than 1.5 kw. An inverter unit would most likely draw even less juice on average.

You may be able to get away with even less heat pump capacity. If your main purpose is heating, you might install a 9k btu unit and leave a single 1 or 1,5 kw baseboard heater in as a backup on those frigid February nights. The price difference between units is not that great, but the smaller unit working harder indoors (most small mini-split units have the same outdoor unit) would gain you some efficiency and draw even less power. During the 1% cold nights, both units would run, still only drawing 1/2 the power of what you have now.

Then again, once you install the mini-split unit, you may do like so many others have done and let it spill its love throughout the house at will. It all depends on what kind of heat you like.