Author Topic: Ductless Split Pressures and Line Temp  (Read 4795 times)

Offline scarey8

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Ductless Split Pressures and Line Temp
« on: July 23, 2009, 04:25:53 PM »
Stupid question probably but it seems to baffle me, I have a sound understanding of the refrigerant cycle and pressures, Superheat and Subcooling on domestic split style air conditioners.  Had the joy of re-installing/installing correctly a 410A Ductless Split, thought to myself simple setup, charge by superheat or subcooling depending on application.  Manufacturer recommends charging my added length of line set.  Simple enough I thought,  added applicable refrigerant.  No where did the manufacturer detail the style of metering device.  Old timer technician told me that some models use the actual liquid line length as the metering device.  Can someone clarify most commonly used metering device on Ductless?  Running at 125 PSI Vapour 42F Saturation and 48F suction line = 6F Superheat,  275PSI Liquid (Forgot Saturation)  50F Liquid line, thats my issue.  All ductless splits i've worked on I've noticed a very low temperature liquid line at the line set connection of the unit.  End up with a subcooling measurement of over 40F, Subcooling will vary with manufacturer and efficiency, but how can there be such a low temp liquid line on what seems like such a basic system?  Probably something simple but its escaping me.


Any takers???


SCAREY8 

Offline scarey8

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Re: Ductless Split Pressures and Line Temp
« Reply #1 on: August 16, 2009, 07:47:11 AM »
Ok no replies to my last post, I have found out that most utilize a cap tube metering device at the outdoor unit, hence why the cold liquid line due to the pressure drop after the metering device.  Try to revamp this question, why have the metering device on the outdoor unit?  Only reason i can think of is that if the metering device were to have a restriction it would be easier to work on rather than pulling the indoor unit off the wall.  Most ductless splits don't have a port to measure high side pressure or a way to calculate Subcooling, i find them hard to diagnose.  Anyone else having the trouble or found a way around this????