Mini split ac or package unit in 40x50x16 pole barn

[lente]

Hello
I am looking to cool my shop just to make it bearable. I do not need it super cold or hot just tolerable.
My question is if I went with 2 mini splits would the units need to be on opposite sides of the shop blowing at each other or could they be on same wall split evenly and be effective? I have two over head doors on the 50 side nothing on the 40 sides. Building is still all open with some thin insulation not the best.
I was also thinking of putting a 5 ton package unit heat pump in the middle of the 50 side in the rear also. I do not have NG or propane I am stuck with all electric. Thanks for any help or advice.

 

[jack stand]

My "not a professional" opinion would be to offset them about 10' in from the diagonally opposite corners on the 50' walls. I've been nothing but impressed with our mini splits heating or cooling, and it's seemingly zero effect on the electric bill. I haven't heard anything different from the few other people I know with them.

 

[kgasaway]

I have a 40x60x16, also in Oklahoma. I have 1.5” closed cell on the walls, and 2” closed cell on the ceiling. I am finishing up my install on a 5 ton Mr. Cool Universal heat pump, should be finished this evening. I will let you know how it works. I chose this system just for the heat because I have no natural gas service and didn’t want to deal with propane.

 

[shade]

I have 2 minis on the same 40ft wall blowing to the opposite side of the garage.
Works great in the 115* heat here in AZ

 

[theoldwizard1]

I have 2 minis on the same 40ft wall blowing to the opposite side of the garage.
Works great in the 115* heat here in AZ

How WIDE is your shop ?

I vote opposite sides for better distribution. At 50' long you really need 2 air handlers on each wall or some really powerful fans.

 

[Yankeefarmer]

I have a 40x60x16, also in Oklahoma. I have 1.5” closed cell on the walls, and 2” closed cell on the ceiling. I am finishing up my install on a 5 ton Mr. Cool Universal heat pump, should be finished this evening. I will let you know how it works. I chose this system just for the heat because I have no natural gas service and didn’t want to deal with propane.

When I saw your inside photo, I thought it was a picture of my installation! One thing I noticed, that you may want to change if it isn’t there, is to add a trap to your condensate drain line. Maybe you’ve got one outside? Reason for the trap is these air handlers have the coil upstream of the fan, and so operate at below atmospheric pressure. When the fan is running, there will be outside air trying flowing into the unit, which restricts the condensate flow out. I discovered this because I was watching my outside drain when the air handler shut off, and saw a huge rush of condensate out when that happened.

 

[yeldogt]

I have a 40x60x16, also in Oklahoma. I have 1.5” closed cell on the walls, and 2” closed cell on the ceiling. I am finishing up my install on a 5 ton Mr. Cool Universal heat pump, should be finished this evening. I will let you know how it works. I chose this system just for the heat because I have no natural gas service and didn’t want to deal with propane.

They did a nice job on that foam .... very nice

 

[kgasaway]

When I saw your inside photo, I thought it was a picture of my installation! One thing I noticed, that you may want to change if it isn’t there, is to add a trap to your condensate drain line. Maybe you’ve got one outside? Reason for the trap is these air handlers have the coil upstream of the fan, and so operate at below atmospheric pressure. When the fan is running, there will be outside air trying flowing into the unit, which restricts the condensate flow out. I discovered this because I was watching my outside drain when the air handler shut off, and saw a huge rush of condensate out when that happened.

Hello Yankee,

If you look close, the blue object in the drain line is a waterless trap. https://www.deschampstechnologies.com/products/n-series__air-trap.html I decided to use this in the case the regular P-Trap would dry up in the winter months. It looks like a slick design so I figured I'd give it a shot.

They did a nice job on that foam .... very nice

Agreed, I was pretty happy with the final product. It also helped that my little cousin worked for the company I hired and tried to make sure they/he did a good job.


I got it all going last night, but the temps in Oklahoma were only in the mid-low 80's. It did knock the humidity down from 66% to 47% in an hour. I set the temp to 74 and it no issue with that task within 1.5 hrs. We should be in the upper 90's in a few days so I'll get a better idea of how its going to work out.

 

[lente]

Thank you all for the replies this info helps.

 

[brianpgriset]

I have a 40x60x16, also in Oklahoma. I have 1.5” closed cell on the walls, and 2” closed cell on the ceiling. I am finishing up my install on a 5 ton Mr. Cool Universal heat pump, should be finished this evening. I will let you know how it works. I chose this system just for the heat because I have no natural gas service and didn’t want to deal with propane.

Sweet setup, I am finishing up my 3 ton Mr. Cool universal split now.

Question for you, did you make the discharge air plenum? I was looking how to adapt the square discharge to round like you did. Might steal your idea.

 

[Yankeefarmer]

When I did my 5 ton, I used a tapered plenum from these people. When I couldn’t get any local suppliers to sell to me, they sold it to me direct. There are other online suppliers as well.

https://metalshop.org/tapered-plenums

 

[kgasaway]

Sweet setup, I am finishing up my 3 ton Mr. Cool universal split now.

Question for you, did you make the discharge air plenum? I was looking how to adapt the square discharge to round like you did. Might steal your idea.

Thank you.

I just had a local HVAC sheet metal fab shop make mine. He charged $80.

I think the one Yankeefarmer used looks better and is similar in cost.

 

[brianpgriset]

Thanks guys. The link Yankee Farmer posted has an 11.5x20 that should just fit (Mr Cool discharge is 11-5/8x20 but Im sure it will work with a touch of massaging.)

Ill order one up tomorrow.

 

[nsula_country]

I'm cool and heat a 40x60x17. 5 ton heat pump split system. 5 ton is marginal, but effective.

Build in my signature.

CT

 

[brianpgriset]

Question for the folks on this thread with the Mr Cool Universal systems about thermostat wiring. I have a 3 ton unit, no auxiliary heating strips.

What am I supposed to do with the W1 terminal from the outside unit? It’s listed as “Defrost Signal”. Is this supposed to go back to the thermostats’ heater control terminal? This would seem to be incorrect since I’d think the W1 terminal from the air handler says it’s supposed to go to the heater control terminal.

All the others seem straight forward but this one has me confused.

Some pics attached. Outdoor unit, then air handler, then thermostat, then wiring diagrams for each in the same order.

 

[brianpgriset]

Here’s the thermostat, what it says for 4 wire heat pump without auxiliary heat.

 

[Yankeefarmer]

I‘m pretty confident I made no connection to the W1 terminal at the outside unit. Being labeled “defrost signal” tells me it’s purpose is to activate a relay to energize an aux heating strip when the outside unit goes into defrost mode. Since you don’t have an aux strip, the signal isn’t useful.

I failed to take a photo of my connections at the outside unit, but I do have one of my indoor unit, and it shows no wires connected to W1. I used only a 5 conductor thermostat cable, so there were no wires left in the cable to worry about!

 

[brianpgriset]

Well it's up and running! I still wired W1 back to the thermostat but it sounds like it won't do anything. Either way all looks good.

The only thing I still don't understand is, if W1 is for auxiliary heat, how does the thermostat know when to call for it? I'd assume for "normal" heat it will just energize the switching valve and not activate W1? How does it know when to do one or the other?

 

[Yankeefarmer]

Remember that your outside unit does not have a 24 vac power supply for control purposes. That’s why you have a red and common lead from the inside air handler unit to the outside unit. It completes the circuit necessary to close the contactor (relay) to start the compressor whenever the thermostat calls for heating or cooling. Your thermostat is also configured to send control voltage to the reversing valve (the B terminal) when heat is called for. Power to energize the aux heating strip would come from the thermostat if so configured whenever the tstat programming calls for it. The aux heating could also be commanded on by the outside unit during defrost cycles even if the tstat doesn’t deem it necessary. As I understand from reading elsewhere, different thermostats are able to be configured to call for aux heating in addition to heat pump heating based on the difference between actual inside temperature and set point. That’s why people will tell you not to do a large setback (or any at all) on systems with aux heat, because each time the set point is changed, aux heat will be turned on, increasing electric usage.

Congratulations on getting your system up and running!

 

[brianpgriset]

Thanks! One more question for you guys, something I didn't think about on these no vac line sets. I had about four of five extra feet on the line set. I didn't have enough room for a loop next to the condensing unit so I took the extra height above the indoor unit and then back down, effectively arching above the air handler a few feet. The air handler is about six feet above the condenser. Any issues with this routing?