Thread: AC unit conduit.

Gentlemen
On yesterdays inspection I came across two condensing units which were relocated around the corner of the structure to make room for a pool and decking. The coolant supply was stubbed out of the wall through a typical metal collar. This was a dual zoned split package system. To create a conduit to facilitate the longer run of the supply lines, the A/C company (who did the re-install) used corrugated drainage pipe and sealed the end attached to the metal collar with foam sealant. The coolant supply then ran inside the drainage pipe, underground approximately 15 feet, bending around the outside corner of the home, and resurfaced at the base of the condensers. Foam sealant was then used again, sealing the 'conduit' around the supply lines. I can't say I have come across this before, but I'm sure plastic drainage pipe is not an approved conduit in this application. I called it out but as both units were re-located by an A/C company, question why they would have used drainage pipe if it was not an approved method/application. Any thoughts? Thanks.

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I'm not aware of any restriction of buried AC coolant lines. ( in or out of drainage or other types of conduit.)

Billy...my thoughts also, but use of the drainage pipe just didn't look a particularly professional application. I was also concerned that should moisture enter and collect in the pipe, either failure of the foam sealant or damage to the pipe, the coolant lines could be sitting in water, underground. I don't know what impact that might have overtime.
Thanks for the reply.

Originally Posted by Ian Page

concerned that should moisture enter and collect in the pipe, either failure of the foam sealant or damage to the pipe, the coolant lines could be sitting in water, underground. I don't know what impact that might have overtime.
.

Your describing the same impact and condition as just being buried unprotected in the ground.

Originally Posted by Billy Stephens

I'm not aware of any restriction of buried AC coolant lines. ( in or out of drainage or other types of conduit.)

There are no restrictions but it's not a good idea. Here is some stuff to chew on:

From Trane: http://home.comcast.net/~arundelhome...Compressor.pdf

Stay away from under ground refrigerant line sets when possible.
Liquid refrigerant will always migrate to the coldest spot in a system; this will likely be the line sets under ground. A vapor line full of liquid refrigerant will slug the compressor on start up—especially during long off cycles.

From Goodman: http://www.goodmanmfg.com/Portals/0/.../IO-GSX11C.pdf

Burying Refrigerant Lines
If burying refrigerant lines can not be avoided, use the following checklist.
1. Insulate liquid and suction lines separately.
2. Enclose all underground portions of the refrigerant lines in waterproof material (conduit or pipe) sealing the ends where tubing enters/exits the enclosure.

Ian, don't use the term, "coolant lines." You will not impress many HVAC professionals with that. Try, "line sets," or, "refrigerant lines."

Thanks Mike,

Manufactures Installation Instructions is the key to correct install.
*I'm a big fan of Scroll compressors as they can handle some liquid and keep ticking.

Scroll Compressor - YouTube

Mike..Thanks for the 'head's up' on the correct terminology and the references. So it would seem that though my concerns for using drain pipe as conduit are largely unfounded it's probably better than nothing. However, my concern that the 'line sets' being buried has merit but not with regard to using drainage pipe as conduit. I couldn't tell if they were wrapped or insulated inside the pipe or not. The rest of the relocation work looked good, so maybe they were. The alternative of re-routing the 'line sets' across the attic space and down an exterior wall is ideal but cost prohibitive. Okay, time to amend the report...Thanks.

How many times do you see the line set run correctly but thereafter the landscapers cover them with mulch? Still buried. When practicable I like to run the line set out high enough that it can be run down alongside the condensing unit to the low point of connection and close enough to the structure that it won't be an obstacle when maintenance is performed. Of course local weather conditions should affect the thought process when burying any pipe so that proper drainage of the area will not create rather than prevent problems in frigid ground freezing temps. Thus the depth regulations for pressurized water lines. I've seen many frozen line sets but have never seen one split open because of it. The block of ice is from condensation on the outside of the copper and usually when the ambient temps are high, thus the need to run A/C.

Thanks Sam for your insight. In this application and judging by the angle that the drainage pipe disappeared into the ground, it was clear the pipe was buried fairly deeply by the HVAC Co. and not (in error) by the landscapers. Fortunately the buyers, in this case, are a/c-oholics and likely to run the systems more frequently than others might (until they get the bill, that is). Thus reducing the 'slugging' impact but they have been suitably advised.