Mini Split sizing or recommendation

[vrinner]

So I had another thread going on condensation in my 40X60X20 shop. R19 on the walls, R30 on ceiling and doors are also insulated. Located in SoCal. Temps inside on hot days (90-100) are I'd say low to mid 80's by mid afternoon but "feels" humid. Here is a link to that previous thread. After the contractor fixed the leak and leaving insulation down for a few weeks to dry the problem "mostly" went away but still have drops falling from ceiling daily...leaves about a 6" puddle by mid morning.

https://www.garagejournal.com/forum/showthread.php?t=436175

So reading through other threads I'm thinking a mini split might work for me but the size and height is a concern. The mezzanine area is currently open but the plan is to eventually close it off to the rest of the space...but dont think that will happen for a while so we can consider it part of the open space for now (but the flooring is on it already)

Does anyone have any thoughts or recommendations on mini split brand, number of units and placement? I was considering a big dehumidifier but reading through other threads I think it's better to go Mini Split.

I have 200amp service in the shop as well and way oversized solar for my house and shop.

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[ericm]

I had a longer reply which seems to have disappeared.

It's likely to be condensation on the outside of the roof which is leaking in through a hole or holes. The roof radiates to the sky making it cooler than ambient, so it can go below the dew point. Like a car parked out in the open. But inside will be warmer, so less likely for the ceiling side to go below the dew point. Is there condensation on the part of the ceiling with the insulation pulled back? Is there water running off the roof in the early morning?

 

[SALIV8]

I cant help much on sizing but i like my gree minis and for the warranty and price point they seem to be a decent bargain.

I would recommend the gree saphire models. Id probably look at one on each side.

 

[ericm]

For sizing you can use the manual J calculator here: https://loadcalc.net
and then once you have the heat and cooling needs, use the manual S on the same site.

You'll probably want at least two mini splits and a fan or two to circulate the warm air near the ceiling.

 

[vrinner]

There was originally a screw hole that was missed. The water coming down was a LOT. The contractor went on the roof and found the hole (also inspecting the rest of the roof as well) and didn't find anything else.

There is a lot of condensation dripping off the top of the roof on the outside. I need to check again to see if there is any on the bottom side of the roof if I pull back the insulation.

That calculator is pretty cool. Looks like I need about 7200 BTU for cooling.

 

[Black Oak]

40 x 60 in Calif. , you need more than 7200 btu for AC . Closer to 72,000 .

 

[ericm]

California has a lot of different climates. But I agree 7200 btus sounds low for the OP's shop in his location.

For my 36x44 shop design with R19 walls, R30 ceiling and insulated doors, I get around 18k btus for cooling from that calculator. That's with a target design cooling temp of 95 degrees, cooling to 78.

Check the design cooling and heating temps in the calculator. I had to fudge them as the city it picked for me from their database is closer to the ocean and at a much lower altitude. It's very different from my climate. The targets should be the 99th percentile- only 1% of the highs or lows would be above/below those values.

I live in Anaheim, not far from the OP, for a while. I know that it can get some ocean effect but can also get pretty hot.

 

[vrinner]

Im sure that I messed up on the calculator then. Here is what I put into the calculator.

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[ericm]

I had to do mine three times before i caught all my errors. At least I think I caught them all....

If your building's small ends face due east/west, then outside wall north and south (long sides) should be 1200 each. The east and west is the two walls added together, which would be 1600. If the building is closer to aligned nw/se then you need to use those spaces in the form instead of north/south/east&west. You also need to add the doors and any windows.

Are your design temps right? Needing 23k btus for heating and 9k for cooling is the reverse of what I would expect where you are. It gets a lot colder here and my heating and cooling requirements from the model are close to equal.

According to weatherspark Placentia's 90 percentile high in Aug/Sept is in the mid 90s. Just from glancing at wunderground it looks like this year the 99 percentile high is in the high 90s.

 

[dcg9381]

You'll probably want at least two mini splits and a fan or two to circulate the warm air near the ceiling.

40x60x16 - Texas. 2 x 24000 btu units get it done for me. These were partly chosen on price point - two units were cheaper than one 36k unit.

Foam insulation, but like R17, not R30.

They are directional, so agree with having fan(s) if you want the cooling to be even.