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A/C suction pipe sizing

Posted by attofarad (My Page) on
Mon, Oct 17, 11 at 20:25

Looking at the table for my 5 ton Carrier 2-stage A/C (soon to be installed), it shows that using a 7/8th line instead of a 1-1/8 line would result in ~2% less efficiency when running at maximum, and maybe 1% less when running in low stage (approximately 3.5 ton).

Since the a/c will mostly run on low stage, are there other advantages/disadvantages in selecting the pipe size? I have read that one disadvantage to a larger pipe is reduced velocity, resulting is less oil carried back to the outdoor unit.

This is for an install with maybe 90 feet effective length, with coil in attic about 15 feet above the outdoor unit. Obviously, both materials and labor are lower with the smaller pipe.

thanks,
Gary


Follow-Up Postings:

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RE: A/C suction pipe sizing

Linset sizing is quite important to protect the compressor.

Your application has a longer than typical length, making it even more important.

I recommend consulting with the manufacture's distributor to have them calculate the recommended size for you application, along with equivalent length, and vertical rise/drop. Using an improper size may lead to warranty problems in the event of a failure. Additional refrigeration specialties, or a mixed size line or traps may be recommended.


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