Efficiency Question


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Old 09-15-02, 05:33 PM
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Question Efficiency Question

I have a new Goodman 3 ton 13 SEER Condensing Unit with 37 feet of new 3/4" Suction line, new 3/8" liquid line and a new All Style 3 ton coil. The installation instructions table for Refrigerant Line Length says for a 3 ton unit with 25 to 49 feet of tubing that 3/4" suct. and 3/8" works but 1 1/8" Suct. line is required for full ratings. If I have the line increased to 1 1/8" is it going to be a big increase in efficiency? This line size increase just seems to be a huge jump in size.
 
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Old 09-15-02, 05:40 PM
Nominal
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Hmm

I'm probably going to lose my good reputation here but I'm not sure I would change it for 37 feet. Provided this is the actual feet. What I mean is, For copper length you should add linear feet plus 3 to 5 feet for every elbow. Also, is this a horizontal run or vertical? Either way I probably would not go any bigger than 7/8 o.d. for the suction line for 37 feet.
 
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Old 09-15-02, 05:51 PM
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Question

My coil is about 10 feet above my condenser and the line length is 37 lenear feet with 2 elbows.
 
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Old 09-15-02, 05:59 PM
Nominal
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Again Hmm

Personnally, I don't think you will gain very much more efficiency with this unit by increasing the suction line. For a 3 ton with R-22 I would not go over 7/8. If unit has the new R-410a I would consider 1 1/8". I would be honest with the customer and show them what the book shows, but also explain that the extra expense may not be worth it.

Please others, don't yell at me too loud. This is a tough call.
 
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Old 09-15-02, 06:47 PM
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Lightbulb savings

I doubt you would save enough to justify having the system pumped down, new lines installed and recharged.
If you REALLY want to save $$$ check your ductwork for leaks and use mastic to seal it up.
Most ductwork has substantial losses due to leakage ...
 
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Old 09-15-02, 07:26 PM
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If the company re-installs the line it would be at no cost to me. I did not know if it was even worth the hastle of having them change it.
 
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Old 09-15-02, 07:36 PM
Nominal
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It would have been nice if you had posted this in your original message

Then by all means, have the contractor install according to manufacturers specifications. This way, if you ever have a warranty issue, no one can try and blame the copper line set. I still do not believe it will make to much of a difference on efficiency, however it probably will make compressor work less and last longer. And I know, by making compressor work less, it will help efficiency some, but probably not enough to notice.
 
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Old 09-16-02, 08:45 PM
bigjohn
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I sent your query to a Goodman tech rep and below in quotes is his answer.

"It doesn't really matter about the size of the suction line when an unrated coil is being used. If this were a matched system using a Goodman indoor coil the larger suction line would be required to achieve the full capacity due to the larger size of the properly installed coil. I have not a clue, and neither does anyone else, what the mismatched coil will do to efficiency or capacity"
 
 

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