*very* long AC supply lines thru very hott attic


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Old 05-17-12, 01:29 PM
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*very* long AC supply lines thru very hott attic

The house i recently purchased had a retrofitted additional AC unit
installed in one attic. The compressor unit is outside at the other end of the house and the refrigerant supply/return lines wander about 50' through a
second attic into the cooling unit. But it's worse. The line goes from
the compressor 20' up to the attic (2 story house) external to the west-facing
brick wall although it is clad and inside a metal conduit (non-insulated).
The worst part. I am in central Texas!! So the attic is going to be hot
regardless ... (I have added insulation/radiant barrier to the rafters).

Question: How critical is it to further insulate the refrigerant line,
both in the attic and outside - and how best to do this?
Can I just encase both lines in a foil-coated box that I could make
out of 4'x8' sheets?

Thanks for your thoughts!
 
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Old 05-17-12, 03:41 PM
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There fine let them be. They are in hot attics all the time
 
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Old 05-17-12, 07:26 PM
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The insulation on the line is there so it does not sweat from condensation. It is after the coil in the air handler. It has nothing to do with keeping the line cold. It is the hot line that is doing all the cooling when it gets to the coil.
 
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Old 05-17-12, 07:37 PM
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Yes, but the large line carries the heat to the outside. If it absorbs more heat it makes the unit less efficient and makes the compressor work harder. Here in Indiana they just passed new laws where the insulation now has to be 3/4" wall thickness on new installations. Having said that, lines have been running through attics for a long time. Will you see ANY energy savings on your electric bills by adding more insulation? Most likely no, at most pennies.
 
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Old 05-18-12, 07:48 AM
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Thanks hvactechfw, Tolyn, airman,
for the advice - and saving me some work!

A follow-up question. The long supply lines here
also result in some long duct runs here. Ducts seem
to be sealed ok but have probably no more than an
1" of insulation inside the foil exterior. Would I benefit
from adding more - straight over the existing?
Even with the roof deck having 5" of blown-in insulation
between the rafters and 4"x8' sheets of foil-faced foamboard
covering the roof deck it is likely to get over 110F in there
during the summer.
 
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Old 05-18-12, 08:42 AM
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50 feet away, 20 feet up is NOT very far. Many houses in Texas has longer line than that. Also, as mentioned by Airman and HVACtech, the insulation of the suction line is not that important. I believe put more efforts on cleaning filter and coil, insulation and seal duct work, proper freon charge, etc. may yield more energy saving.
 
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Old 05-19-12, 07:40 AM
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Thanks for the responses guys!
 
 

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