mini-split(s) for new shop

[skipdup]

I'm about to start wiring my new 38'x39'x12' (interior) shop. Still bare studs on the inside. I realized I'd better consider a/c now...

After electrical, I plan to insulate. Right now, leaning towards plywood walls/ceiling. Front two garage doors are insulated. The back roll-up door is not. There are also 8 very small (1'x1') double pane windows along the two side walls (not on plan).

I was thinking maybe two 15,000 btu mini-splits, along the left side wall???

Any suggestions for heat? Just get the mini-splits with heat?

Can you plumb these units after the insulation and interior walls are up - without too much drama (it'd help with $$$ if I could push buying the units out a little)? I figure I can pre-wire electrical, assuming I decide the location of the units.

I will likely also add a couple ceiling fans or maybe a couple oscillating wall-mount fans.

I probably just want to maintain the shop at 85 or so degrees during the summer - and then cool it down only when I'm in there working on a project.

Does this all sound reasonable? Any advice?

Thanks!
Skip

 

[PurdueSD]

Electrical for mine consists of 40A outside service, the indoor heads get power from the outdoor unit via the multi conductor cable supplied with the units. The outdoor unit is the brain and controls when and how the indoor units perform on my multi head unit. My system came with it's own refrigerant lines which hookup via compression fittings. You cant gas weld the lines close to the indoor units like you can with a traditional heat pump. You will need to set up condensate drain lines also.

I dont see any way around purchasing the system before rough in. You could install later with conduit and surface mounting the drains i guess, but i wouldn't.

 

[justinjoyal]

cant gas weld the lines close to the indoor units like you can with a traditional heat pump.

You sure can.

I dont see any way around purchasing the system before rough in. You could install later with conduit and surface mounting the drains i guess, but i wouldn't.

Most installs we do are on existing buildings. We drill a 2.5in hole through the wall and everything is surface mounted on the outside, hidden with a color-matched aluminum cover.

Cheap and easy. Also makes future repairs easy if needed.

When working on new buildings where hvac’s already been planned the lineset can be ran inside the walls, but it is not something I prefer.


OP: if you want to size your unit(s) properly, you need a load calculation. Otherwise it’s all guessing.

 

[ghnl]

Any suggestions for heat? Just get the mini-splits with heat?

All the mini-splits I am aware of do both heat & A/C - they are heat pumps - they can either pump heat in or out. They are not very efficient for heating when outdoor temps get below ~ 30F. Some have built-in heat strips - they then function as electric heaters which can be costly.

Can you plumb these units after the insulation and interior walls are up - without too much drama?

Easily. Put in a disconnect for the outside electrical supply now - everything else will be easy to add later.

 

[justinjoyal]

All the mini-splits I am aware of do both heat & A/C - they are heat pumps - they can either pump heat in or out. They are not very efficient for heating when outdoor temps get below ~ 30F. Some have built-in heat strips - they then function as electric heaters which can be costly.

Wrong, wrong and wrong.

Not all mini-splits are heatpumps. There are still A/C-only units sold.

Most new heatpumps, even the cheaper ones, are efficient down to ~15F. The higher end units are very efficient even at sub-20 temps.

Mini-splits do not have heat strips as backup heat.

 

[skipdup]

Thanks guys.

How does one go about doing a load calculation? Does it take a pro? DIY?

And, is it better to go with one big unit or two small? The units won't (somehow???) compete with each other, or something like that, right?

Thanks again!

- Skip

 

[Brian_WK]

Fujitsu used to make a heat pump that had a small resistive heat strip in it (think 1 kw like a space heater) But it was really only there for the defrost. A small baseboards heater mounted directly below the indoor mini split head is what we would recommend now if you get very cold temps like -30F (you being in TX I don't think this is a issue).

Run the exterior electrical for the outdoor units now but don't worry about the the mini splits until you plan on purchasing them.

This quote is correct=

You sure can.


Most installs we do are on existing buildings. We drill a 2.5in hole through the wall and everything is surface mounted on the outside, hidden with a color-matched aluminum cover.

Cheap and easy. Also makes future repairs easy if needed.

When working on new buildings where hvac’s already been planned the lineset can be ran inside the walls, but it is not something I prefer.


OP: if you want to size your unit(s) properly, you need a load calculation. Otherwise it’s all guessing.

Brian

 

[skipdup]

Yeah, I think I’m much less concerned with heat than a/c. We get so few really cold days here...

 

[skipdup]

I just got my bid back from the insulation co. that did the house. Not much more to have them do it than diy. Will go with R19 walls and R38 ceiling. That sound right?

 

[skipdup]

So, I got a bit distracted.
But, finally played around with loadcalc.com. Everything seems pretty self explanatory, except the garage doors. I searched, but couldn’t find an answer...

How do I account for the garage doors? I’m sure it’s obvious, but I’m not seeing it...

Thanks,
Skip

 

[PurdueSD]

I just got my bid back from the insulation co. that did the house. Not much more to have them do it than diy. Will go with R19 walls and R38 ceiling. That sound right?

Thats what i did in mine exactly, its working awesome. Above all else make sure you use a vapor barrier and seal it up as good as possible. Air intrusion is a huge deal!

 

[PurdueSD]

So, I got a bit distracted.
But, finally played around with loadcalc.com. Everything seems pretty self explanatory, except the garage doors. I searched, but couldn’t find an answer...

How do I account for the garage doors? I’m sure it’s obvious, but I’m not seeing it...

Thanks,
Skip

I only did a heat loss calc online, can you enter them as windows and set the R values to what the doors are...?

You're in Texas so im guessing cooling load will be higher than heating... I would guess you'll end up in the 3 to 4 ton range. Minis (or any heat pump really) arent really meant to have quick recovery times. You might actually save money keeping the shop closer to you ideal temp than bumping them down so drastically. This was an adjustment in thinking for me personally. One benefit will be your shop humidity will be kept in check.