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Old 11-29-2010, 12:45 PM   #1
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Mini-split install question


I will be installing a new ductless mini-split heat pump and hope to use the existing line set (1/2" & 1/4") since the new system specifies the same sized lines as the old one. The old system was only 4 years old, but after two control boards and a shorted electric expansion valve, I decided a brand change was in order. Old and new systems are both R-410a. Is there any reason to replace these refrigerant lines? Are there signs of contamination I should look for? The insulation is in fine shape and there were no leaks in the old system.

Also, these lines are only about 10 feet long. The new system comes charged for up to 25 feet. Any risk of an over-charge? Come to think of it, the old system was pre-charged for up to 50 feet of line. Might that have contributed to the bad EEV?

Thanks in advance.
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Old 11-29-2010, 01:37 PM   #2
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Mini-split install question


Mini-splits are great when they work....I warn all my customers when they do break..$$$$$

Overcharge is a Killer.....do you have a vacuum pump? No issue with reusing the linesets as long as the compressor is not a burnout. Charge must be weighed in per the instructions (or weighed out for the difference)
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Old 11-29-2010, 03:15 PM   #3
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Mini-split install question


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Originally Posted by Technow View Post
Mini-splits are great when they work....I warn all my customers when they do break..$$$$$

Overcharge is a Killer.....do you have a vacuum pump? No issue with reusing the linesets as long as the compressor is not a burnout. Charge must be weighed in per the instructions (or weighed out for the difference)
Amen on the $$$$$ warning! It was going to cost almost $1000 to fix the old system which I bought for $1600.

Yes, I have a vacuum pump. I've installed two ductless systems so far. One is still going strong (fingers crossed). I do intend to vacuum the new system before releasing the refrigerant from the outdoor unit. It comes pre-charged. Once the system is evacuated, you just open the two valves on the outdoor unit and you're ready to go. The charge is adequate for up to 25 feet of line between the indoor and outdoor units. Any longer and you have to weigh in more R-410a. But the instructions say nothing about removing any if the lines are shorter than 25 feet.

The old system was pre-charged for up to 50 feet. Maybe that was too much refrigerant for my 10-foot lines. But over-charge is just a risk for the compressor, right? I had no problems there.
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Old 11-29-2010, 03:20 PM   #4
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Mini-split install question


No, its also a risk for the EEV, and probably why it failed. Too much refrigerant probably caused it to over compensate.
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Old 11-29-2010, 05:44 PM   #5
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Mini-split install question


IMO the extra 3-4 ounces of refrigerant isn't going to hurt the system. Half to 2/3rds that will be stuck in your manifold and hoses since most mini splits only have one access port. In reality it's going to be overcharged an ounce or two when all is done. Not worth messing with for that little bit.
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