I've been helping out my guys in the field and I'm trying to understand which of the two specs matter when it comes to new equipment subcooling design specs. The condenser will have its recommended subcool spec and the coil with TXV will have a different spec, both shown in their own installation manuals. Which one should be the dominant factor? I'm assuming the TXV specification because it's doing the metering but that's why I ask.
Charge subcooling per Condenser or Coil/TXV specs?
nikonat
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I've been helping out my guys in the field and I'm trying to understand which of the two specs matter when it comes to new equipment subcooling design specs. The condenser will have its recommended subcool spec and the coil with TXV will have a different spec, both shown in their own installation manuals. Which one should be the dominant factor? I'm assuming the TXV specification because it's doing the metering but that's why I ask.
Go with the condenser subcool rating, because subcooling is an indication of proper charge.
I think the "coil with different spec" you're referring to is the indoor unit which has it's own measurement called superheat.
These are two separate measurements that are both critical.
I think the "coil with different spec" you're referring to is the indoor unit which has it's own measurement called superheat.
These are two separate measurements that are both critical.
I was referring to the recommend subcooling for every evap coil that comes with a factory TXV. Example : Amana Condenser 8° subcooling is recommended & ASPEN Evap Coil with TXV 14° subcooling is recommended.
I appreciate the reply but yeah we're not lining up. I completely get that the evap is SH and the condenser is SC. What I'm trying to convey is that even though the evap is SH, the installation instructions that come with the coil that has a factory TXV installed will show a recommended subcooling to have the system charged to work optimally with the TXV.
Example from the Evap Coil instructions:
SUPERHEAT AND SUBCOOL CHART
85° Outdoor Temp recommends 20° SH & 14° SC
Example from the condenser instructions:
8° SC +/- 1°
The TXV does not care if too much refrigerant is in the system, only if too little.
The technician should follow the recommended SC on the condenser.
Once the SC is met at the condenser, the SH can be obtained by adjusting the TXV,TEV.
By any chance are you some type of engineer? Over complicating this one bud.
The technician should follow the recommended SC on the condenser.
Once the SC is met at the condenser, the SH can be obtained by adjusting the TXV,TEV.
By any chance are you some type of engineer? Over complicating this one bud.
Awesome! That's exactly what I was trying to get and your patience was a virtue ��. You guess it, Unfortunately being a mechanical engineer can come with some complications in over complicating things. Thanks for your time.
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My understanding is that entering liquid temp is a design factor for the valve along with delta p. Temps above or below the design entering liquid temp would decrease or increase the capacity of a given valve.
Unless there was some additional subcooler on the unit you're only going to get whatever subcooling you get with a proper charge at the given ambients.
I'd run with the condensing unit chart. As said the valve wouldnt care if the system had a proper charge only if it had a solid column of liquid entering. I'm sure others will chime in with more insight.
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Unless there was some additional subcooler on the unit you're only going to get whatever subcooling you get with a proper charge at the given ambients.
I'd run with the condensing unit chart. As said the valve wouldnt care if the system had a proper charge only if it had a solid column of liquid entering. I'm sure others will chime in with more insight.
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Felix F
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I have plans for a 2 ton (heat pump) split system HVAC Project in the Los Angeles Building Dept Plan Check and they have a correction comment. They want to know how much refrigerant is required in the
condenser and the indoor unit. Question: does the indoor unit come from the factory with a refrigeration charge or does the condenser refrigeration charge serve the indoor unit also.
New Guest
I have plans for a 2 ton (heat pump) split system HVAC Project in the Los Angeles Building Dept Plan Check and they have a correction comment. They want to know how much refrigerant is required in the
condenser and the indoor unit. Question: does the indoor unit come from the factory with a refrigeration charge or does the condenser refrigeration charge serve the indoor unit also.
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33,565 Posts
Aspen probably has different specs than amana. But also in my hvac school book if i remember right they talk about "evaporator subcooling" which is the condensor subcooling + any aditional cooling that happens due to cooler ambient around the liquid line by the time it hits the metering device.
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2,004 Posts
Condenser comes with a charge for a line set of 15 to 25 ft ( depends on brand ) ,evap & condenser but when installed and running it may need more & it might need some removed. Just give them a WAG.
I was taught in school & several mfg schools you charge based on condenser SC spec if txv. But way back in the 60's most of the senior techs just charged to a clear sight glass or if no txv till the suction line was too cold to hold on to.
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Just go with what the outdoor unit nameplate shows as a factory charge. Its an irrelevant question. You being in Cali, they are probably getting ready to implement a refrigerant amount surcharge, or tax of some-kind, or some other ridiculous nonsense.
-Also, in the future, start your own thread.
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Always default to the condensers charging recommendations for the application.
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http://aspenmfg.com/documents/faq/12.24-Install Charge.pdf
Says Add refrigerant until the subcooling measured at the outdoor unit liquid line matches the subcooling from the condenser manufacturer recommended temperature (ie 7o-10o). IF.....the condenser manufacturer does not specify a subcooling level, refer to the chart.
Says Add refrigerant until the subcooling measured at the outdoor unit liquid line matches the subcooling from the condenser manufacturer recommended temperature (ie 7o-10o). IF.....the condenser manufacturer does not specify a subcooling level, refer to the chart.
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