Mini-split rough-in

[pgray007]

I'm planning on a 2-zone Daiken mini-split for my 24x20 detached garage with a room upstairs. I'm in SC and using an online calculator came to 9K btu for the upstairs and 12K downstairs, but will probably bump both measurements up since the cost is minimal. I'll do all the "pre-work" and have a buddy who is an HVAC guy to hook up the lines and do all the refrigerant voodoo.

The question I have it on rough in. Right now I'm running electrical and plumbing. I've roughed out the AC disconnect, but am not sure if I should drill the holes in the wall for the wall units before insulation goes in or do it after insulation and/or drywall. Basically I'm wondering:

1) Do holes now?
2) If so, do you stick a piece of PVC or similar in the hole so the drywallers can work around it?
3) Do something else or just wait and drill the holes after drywall.

Thanks!

 

[k_ross]

It's very easy to drill a 3.5" hole through the wall after drywall is in. I'd say it's easier than trying to drywall around a 3.5" piece of PVC sticking out. I just completed the installation of a DIY mini-split system last week and drilling the hole through the wall was no problem at all.

 

[bzinsky]

definitely drill the hole after the wall is complete

 

[Kaizen]

insulate and close up the wall. don't drill anything till you get the actual units. most you can go out either side of the unit. also they will have a template to make drilling the hole idiot proof. I highly recommend the line set enclosures. you can install the inside unit, hole, line enclosure backing, wall bracket or pad. my unit came with a 2 part wall sleeve which was nice and professional looking.

 

[andre3k]

Like others have mentioned I pretty much installed mine after drywall and insulation were done. I ran the power and ac disconnect while the framing was exposed. Install was super easy after that.

Sent from my SM-G935V using Tapatalk

 

[justinjoyal]

using an online calculator came to 9K btu for the upstairs and 12K downstairs, but will probably bump both measurements up since the cost is minimal.

Why would you do that ? Proper sizing = proper cooling. Don't oversize. Unless you like damp air, that is.

 

[fastjohnny]

Why would you do that ? Proper sizing = proper cooling. Don't oversize. Unless you like damp air, that is.

As long as the MS is variable speed you can get away with oversizing...

 

[Kaizen]

Why would you do that ? Proper sizing = proper cooling. Don't oversize. Unless you like damp air, that is.

another thing with these units is there is only x number of outlets. so on the exampled 2 zone it takes longer at 12k btu to cool the area then say a 15 or 18 due to the bigger indoor units. as opposed to a normal system where each room has one or many outlets thereby cooling more efficiently. agreed on the statement if we are talking about tons and outside units for whole house systems. I know that causes more problems then it solves.

 

[yeldogt]

In my case the insulated lines and all he electrical was installed in the walls prior to the insulation. My contractor attached a large rectangle of drywall in each mini-split head location and mounted the bracket for the head. The building was insulated and the drywall was done. The heads were attached after the rooms were painted. Everything very neat a tidy. I had two of the cassettes done this way also.

Make sure the rectangle is big enough so the joint lines are far enough away to properly finish -- my house was foamed. The is the way my contractor always does it. This way everything is in place -- you know it's going to fit and nothing is exposed.

 

[justinjoyal]

As long as the MS is variable speed you can get away with oversizing...

another thing with these units is there is only x number of outlets. so on the exampled 2 zone it takes longer at 12k btu to cool the area then say a 15 or 18 due to the bigger indoor units. as opposed to a normal system where each room has one or many outlets thereby cooling more efficiently. agreed on the statement if we are talking about tons and outside units for whole house systems. I know that causes more problems then it solves.

The inverter does help forgive some of the oversizing, but it is not a miracle solution. Oversize your mini-split too much and you will not have a comfortable home.

There is no reason to oversize. Unless you just want to have a bigger unit than your neighbor's.