Should I insist on a new line set for this ductless mini split replacement? How should I do the lineset cover given that the current setup can't be easily opened?

The ductless mini AC at our Cabin needs replacing (missing half its old R22 coolant, likely leaking). I am getting bids on a new 18,000 BTU system, but I am having trouble getting contractors to work with the lineset cover. It runs like so (~20 foot run).

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The lineset cover isn't the usual, purpose-built stuff. It appears to be simple aluminum flashing, the same shade as the siding. It's 3"x3" That's good because it hasn't faded (like lineset cover at our house). IMO, it looks pretty good (better than the rain-guttery lineset cover that's typical), but it cannot be taken apart.

I've pried and poked enough to figure out it seems to be made from this flanged U channel, attached underneath the J-channel that holds the siding next to it. (This specimen was found in the garage rafters.)

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That means it can't just be popped open like regular lineset covers, and removing it would, I think, mean tearing up the siding all the way up, not a reasonable option. It's not over the siding, it's flush with the wall under the siding. The siding ends at the channel edge. The flanges from this appear to be nailed down under the J channel, which is then of course nailed down and holding the horizontal siding pieces.

The first AC replacement bid came in with the caveat from the contractor that his team would cut off the old lineset cover and do nothing if they couldn't get it back on properly. That's a recipe for a mess, so I'm not using them.

The next bidder wanted to simply re-use the old lines after flushing them. That sounds reasonable-ish, except that the insulation on these is likely completely rotted away under there. (The stuff at the bottom was falling apart) and I don't trust the 20 year-old copper lines. Moreover, the unit needs to be raised up between 4 inches and 1 foot (depending which heat pump we choose to use) and it's going to be rotated 90 degrees to be parallel to the wall, fan blowing out. I don't think the current line set can be made to do that.

As I see it, I have these options:

  • Reuse old lines and leave lineset cover alone
  • Run lines next to existing raceway and put them in new lineset cover.
  • Take apart existing lineset cover, new lines in there, and patch up in some way.

The latter might work because I found in the rafters in the garage two 8-foot pieces of non-flanged U channel in the same shade. I think if I cut the face off the existing channel, I could then fit this U over it, seal it up with caulk, and be good to go. (The length of the sides of the U aren't equal, but I suppose some tedious trimming with the aircraft snips could fix that.)

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1 Answer 1


I like the option of opening up the existing lineset cover enough to facilitate replacement of the line set. It's bound to be a painstaking process though -- you may have to ask a contractor to remove the refrigerant and disconnect the existing lines, then remove and replace them yourself, and finally call the contractor back to connect and charge the new equipment.

It may not be necessary to entirely open the lineset cover. If you open the angled portion at the top and cut the line set at the bottom you may be able to lift the column of line set out without opening any of the vertical portion of cover. It's possible that the line set may be fastened to the wall at one or more points in the vertical section though. If it is, you'll have to open the cover enough to find and release such fastening. It may be possible to find the location of any strapping by inserting a "glow stick" or "fish rod" (wire pulling tools used by electricians) with an inexpensive USB or wireless borescope camera attached.

If the old line set can be removed semi-non-destructively a new set can surely be installed by reversing the steps. Attach a pull rope to the old line set before removal; that rope may come in handy for pulling in the new line set.

Open the lineset cover by cutting near its outer corner. This will leave you with an L or Z-shape section (the sides of the cover) still on the wall. The U-shape section you've found could be used in the repair: attach with blind ("pop") rivets or screws to the L/Z shapes on the wall.

A metal shear like this one may make the cutting easier (as compared to aviation snips). I've seen electric, pneumatic, and drill-powered versions of this tool. (credit to Harbor Freight for the image) metal shear

  • The whole system's getting replaced & all contractors now agree line set is part of that. I had considered seeing if a new set could be fished through w/o cutting. My guess is it's not strapped down in there, but a couple cuts and tugs will make it clear. I like some of those ideas I hadn't considered, like only cutting open along one side and pop riveting things back together. Might be a good idea to drill the holes before setting the lines back in just to make sure then don't get nicked. Also good idea on the sheers. I have HF bauer batteries already. maybe they have a cordless sheer.
    – user122950
    Jul 21, 2021 at 21:46

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