Mini Split Questions

For central valley 1 ton per 500 sq ft is generic starting point for hvac sizing.

Get bigger rather than smaller and look into multi-output.

House unit is 3 ton but has 2 speed compressor so it has lower output until needed so it runs cheaper on cooler days.

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I just watched a couple videos on installation of the DIY sets. One was Bozo the clown and the other was a very professional install by a diligent DIY fellow.
This Mini-Split install can be a bit difficult. I may just go with the pros on this one.
I have so many projects lined up, I need to remember this is not a race to the finish.
How was your install experience?
 
I had a local hvac guy install mine. I wired it as they are not allowed to do wiring and paid cash. I got a fabulous deal as the Daikin he put in was a discontinued model. Proper insulation on the lines and slopping condensate drain were important things to get done correctly.
 
I performed the mechanical and electrical installs myself, but used a licensed HVAC guy for the system vacuum, leak test, and refrigerant install. This ensured my warranty from the mini split manufacturer in the event of a compressor failure.
 
I did a load cal on the shop/garage.?. as you described and had to guess at the rest.

440 sq ft.
N wall, E wall, S wall, no W wall.
1 window each wall.
R30 attic insulation (If you don't have attic insulation, you'll have to have it).
No wall insulation (Difference is 2,800 btu less if you have R11).
Dark roof- no ducts- open attic and ventilated.
Concrete slab- no edge insulation.
Added 1,200 btu for person and tools- lights.
Sacramento, California conditions.

Heat gain= Sensible is 10,500, latent 100. I would go with 12,000 btu as a rule.
Heat loss= 18,000 btu. 20k would heat fine.

Mini splits have compressors that may run 80% of the time to control humidity and they use blower speeds and compressor speeds to ramp up and down.. It is easy and ok to oversize the unit because of this.

Under these conditions, if it were mine, I would choose a 14,000 btu unit. If I wanted a quicker response to change the temperatures, I would go 18,000 btu.

A heat pump won't do you well if you want to change the temps quickly. Electric heat is a better option. 5kw might work.

I've been at for over 44 years, but in Texas, so I'm not familiar with California's climate.
I can recommend Mitsubishi. I have fewer problems with them and their service back up is one of the best. Cost less in the long run.

HVAC Cal. load.
 
WalterC said:
I did a load cal on the shop/garage.?. as you described and had to guess at the rest.

440 sq ft.
N wall, E wall, S wall, no W wall.
1 window each wall.
R30 attic insulation (If you don't have attic insulation, you'll have to have it).
No wall insulation (Difference is 2,800 btu less if you have R11).
Dark roof- no ducts- open attic and ventilated.
Concrete slab- no edge insulation.
Added 1,200 btu for person and tools- lights.
Sacramento, California conditions.

Heat gain= Sensible is 10,500, latent 100. I would go with 12,000 btu as a rule.
Heat loss= 18,000 btu. 20k would heat fine.

Mini splits have compressors that may run 80% of the time to control humidity and they use blower speeds and compressor speeds to ramp up and down.. It is easy and ok to oversize the unit because of this.

Under these conditions, if it were mine, I would choose a 14,000 btu unit. If I wanted a quicker response to change the temperatures, I would go 18,000 btu.

A heat pump won't do you well if you want to change the temps quickly. Electric heat is a better option. 5kw might work.

I've been at for over 44 years, but in Texas, so I'm not familiar with California's climate.
I can recommend Mitsubishi. I have fewer problems with them and their service back up is one of the best. Cost less in the long run.

HVAC Cal. load.
Click to expand...
It looks like you hit that pretty well. Thanks for doing the calculations for Jeff. The only minor change is that it is the south wall that is missing (house is there.) North wall is the garage door. Probably does not change things much...
 
Can the inside unit be mounted on the ceiling?
@Janderso, I hope you don’t mind me asking.
 
All though I've never installed one, they do make ceiling mounted inside units for the mini split. They fit between 16" centered joists.
 
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WalterC said:
All though I've never installed one, they do make ceiling mounted inside units for the mini split. They fit between 16" centered joists.
Click to expand...
Is it OK to block them in so they can fit 24" joist spacing? Or ones designed for 24" joist spacing?
 
Is there a reason why one couldn’t mount a wall unit on the surface of the ceiling? Maybe condensation draining issues comes to mind?
 
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