Mini split coolant line penetrations

[NivenHuH]

I’m building a room-in-a-room, double stud (3” air gap), live room. For heating/cooling, I’m planning to use a Mitsubishi ductless mini-split system.

This mini split system comes with the copper coolant, return, and electrical lines all bundled together in a 2.5” foam conduit. The return line doesn’t need to feed downwards and the whole conduit can be bent and ran in wide angles.

I’m planning to make a penetration in the corner of the outer shell ceiling for the coolant line to enter, then run it down the length of the wall in the air gap, and then penetrate the inner shell to connect to the wall unit.

My question is around the penetrations for the conduit. How can I minimize flanking paths with the conduit?

Should I cut the hole slightly larger than the hvac conduit and acoustic caulk the penetrations? And will this work with a foam conduit, or should I run this inside of a larger firm conduit (like pvc)?

Thanks in advance!

[John Sayers]

A soundproof room within a room is air tight. How do you expect to get fresh air into the room?
cheers
john

[NivenHuH]

There will be an intake and exhaust vent between the two shells. I’m planning to build 4 duct silencer boxes, connected with a flexible connection in-between the walls where the duct boxes meet. The duct boxes itself will be made of mdf, and I’m planning to use some of the designs I found on this forum as a guide for how to build them.

On the exhaust duct box, I’m planning to run a fan (mounted on the exterior vent box) to pull air out of the room.

Thanks for the awesome site by the way!

[Paulus87]

I’m building a room-in-a-room, double stud (3” air gap), live room. For heating/cooling, I’m planning to use a Mitsubishi ductless mini-split system.

This mini split system comes with the copper coolant, return, and electrical lines all bundled together in a 2.5” foam conduit. The return line doesn’t need to feed downwards and the whole conduit can be bent and ran in wide angles.

I’m planning to make a penetration in the corner of the outer shell ceiling for the coolant line to enter, then run it down the length of the wall in the air gap, and then penetrate the inner shell to connect to the wall unit.

My question is around the penetrations for the conduit. How can I minimize flanking paths with the conduit?

Should I cut the hole slightly larger than the hvac conduit and acoustic caulk the penetrations? And will this work with a foam conduit, or should I run this inside of a larger firm conduit (like pvc)?

Thanks in advance!

Here's a tip from passive house builders (whose main priority is incredible air tight enclosures) :

If you can separate all those bundled lines then you can drill/cut holes that are just big enough for each one, this will allow you to perfectly seal around each with a non hardening acoustic caulk.

If they remain bundled together then it will be much harder to get a perfectly air tight seal around it, but you would just have to stuff some fluffy insulation in any gaps, use backer rod and then seal around everything with lots of caulk - messy and difficult to guarantee every gap is sealed.

Paul

[NivenHuH]

Thanks, I'll give that a shot! I figured I needed to seal up the hole(s) with acoustic caulk, but wasn't 100% sure about whether the foam sheathing would cause an issue.

[gullfo]

on the mini-splits, if you have an option to use flexible (typ stainless mesh over rubber) on the freon and drain tubes, that can help reduce the hard connection (even with foam conduit) between the rooms and any of the operating unit vibrations.