Line-set Diameters

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Line-set Diameters

Postby CEO1 » Sat May 24, 2014 8:13 pm

I see frequent questions relative to line-set lengths and diameters, particularly relative to R-410A equipment. The charts below, taken from a Rheem install manual, can be used as a guide.



The concerns with tubing diameter are pressure drop and velocity. Too small of a liquid line, could result in too much pressure drop between the condenser and evaporator, possibly affecting the metering device and evaporator performance.

With vapor lines, the tubing diameter is a compromise between capacity loses and sufficient gas velocity to return the entrained system oil back to the compressor. Too large and you might have oil return issues; too small and you might have excessive capacity losses.
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Re: Line-set Diameters

Postby AC480 » Sat Oct 10, 2015 2:55 pm

In 2009, Trane issued a service bulletin with updated line size recommendations for 6 to 20 ton split systems. This resulted in smaller lines that resulted in higher flow rates and increased allowable pressure drops. This seems to contradict what we had always been taught. The bulletin is detailed and explains the reasoning behind the update. One of which was to reduce total system charge to reduce refrigerant migration during the off cycle resulting in increased long term service life.
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