Mitsubishi Split Refrigerant Line Sweating

Morrison

Thanks to an earlier post on this forum (https://forum.heatinghelp.com/discussion/170700/mitsubishi-split-refrigerant-line-sweating-water), I discovered that line sweating is definitely not normal and that zip ties (not to mention rips in the line insulation) are signs of shoddy work. We inherited the mitsubishi system when buying our house a few years ago.

My question is: if this line sweating is happening in the laundry room on the 1st floor, could it also be happening inside the walls on its way up to the 2nd floor? I ask because toward the end of the summer, every summer, I've noticed a musty smell develops on the 2nd floor. I worry that line sweating is occurring inside the wall somewhere and only becomes apparent when mold begins to build up. Is that possible?

Again, thanks to NJhomeowner's post and ratio's repsonse, I now know that I could fix the issue in the laundry room with foam insulating tape (probably a lot of it). But if there is a bigger issue in the walls, then that would be a bigger deal.

Whatever thoughts/advice are appreciated.

EdTheHeaterMan

That is a very real possibility. Open the wall and replace the torn insulation. Your home looks like you may have plaster walls. If the insulated lines were slid thru the wall cavity, there are many sharp edges to catch and tear the rubber insulation.

If you don't do DYI wall repairs, then have a handyman cut the wall open for insulation repair. You can use new insulation that is split with an adhesive to maintain the vapor barrier. Also add line-set tape to the seams

pecmsg

The insulation can not have any rips or tears. Any rip will allow moisture to enter and condense. This condensed water saturated the insulation and makes it worthless. Unfortunately the only remedy it to reinsulate the entire line set.

EdTheHeaterMan

Closed cell insulation like the black stuff in your post is not going to get waterlogged. But it must have a good vapor barrier. Replace any that is missing and seal the seems and tears as explained in the thread you referenced in your original post

EdTheHeaterMan

Follow up: If you are going to the trouble of opening the wall, I would replace anything that may be suspect to failure.

HVACNUT

Have you checked the head?
Shut the unit(s) down at shine a flash on the fan(s). They seem to build mold very easily.
Check the coil, filters, drain as well.

JPL941

SuperTech

> @HVACNUT said:
> Have you checked the head?
> Shut the unit(s) down at shine a flash on the fan(s). They seem to build mold very easily.
> Check the coil, filters, drain as well.
>
>

THIS

It cannot be understated how much black biological growth can build up inside the head of mini split units. The blower wheel can become completely plugged with this stuff. It doesn't take long for this to happen either. I've seen it on systems that operated for only one summer. Its absolutely disgusting.

mattmia2

BTW, running Romex like that is questionable at best.

Morrison

Wow, this has been a really great response. I appreciate the feedback. Thanks Ed, for the original reply and follow-ups. I probably won't do a DIY wall repair but sounds like it's worth it to have someone come out and open things up. Reinsulating the entire line set may be my best option (thanks pecmsg), though I guess I can still use insulating tape as a stop-gap on the obvious rips and zip ties. I haven't checked the head, HVACNUT and SuperTech, but I'll do that first thing. I had no idea about the mold that can build up there so really good to know. Sounds nasty. JPL941, good to know, appreciate it.

And finally, mattmia2, I had a feeling that looked off as well. I'm not surprised. I've been meaning to have an electrician out here for a long time since I discovered that ~60% of the house's electric runs to a single breaker. This house seems to have a history of shoddy work. Live and learn. The longer story here is that we'd like to move in the next year but I still want to get this stuff sorted before that, for our safety, for resale $, and just because I don't want to pass the issues on.

Thanks again, all.

pecmsg

Minor rips can be covered with Foam or Tar tape. End seams contact cement. If there are areas where water has accumulated cut a small hole, drain it and seal the hole!

Cut the wire ties and use Electrical tape. DO NOT pull it tight, Loose fitting.

All Cabling should be Stranded without any splices or run next to high voltage!

Any Opening in the insulation will allow warm moist air to enter. the moisture Will condense back to Water. this is why maintaining the Vapor Barrier is so critical.

pecmsg

EdTheHeaterMan said:

Closed cell insulation like the black stuff in your post is not going to get waterlogged. But it must have a good vapor barrier. Replace any that is missing and seal the seems and tears as explained in the thread you referenced in your original post

I've seen it absorb water that collected in the lower sections and saturated the lines. For the record this was on a freezer that the contractor used 3/8" wall instead of 1/2 or 3/4" Wall.

bio_guy

I don't like the look of that nearly-horizontal run of drain either. JPL951 commented on the problem of uninsulated drain line already, but I think that needs more emphasis. I know that this job is probably already done, so I hope that any condensation on the drain was addressed at the same time.