| HVAC PRIME SOURCE, LLC |
HVAC QUESTIONS FORUM
Please feel free to ask any technical HVAC questions in the forum here for readers of
this website to respond and share their experience.
Please feel free to ask any technical HVAC questions in the forum here for readers of
this website to respond and share their experience.
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QUESTIONS & RESPONSES
Question 1:
What is the replacement refrigerant for CFC Refrigerant R12 that is ozone friendly and permitted by EPA. We
have four centrifugal chillers with R12, and we would like to get away from all the EPA requirements that come
along with it and the high cost of R12.
Response:
The common replacement is R134a, which is an HFC and permitted by EPA. You also need to change the oil
and possibly the gasket material that are compatible. The chiller performance changes somewhat with the new
refrigerant, and you may also have to make some hardware changes. Most likely the chiller manufacturer should
provide the necessary service for the retrofit.
Question 2
What size air return does a 3 ton a/c unit require???
Response:
The nominal air flow per ton is approximately 450 cfm. Three ton unit air flow will be approx 1350 cfm, and size
of the return duct for this air flow should be 18" dia max (for residential) and 14" dia min (for commercial
application).
Question 3
How i can calculate the supply cable size for 20 ton package unit(cooling and heating)far away from electrical
panel board 30meter
Response:
For a unit of this size the power requirement will be typically ranging from 21 to 25KW. To be conservative use
the 25KW. The cable size will depend on the voltage of your power supply and the amps. Typical power supply
voltage to this size unit will range from 208 to 575 Volts i.e. 208V, 230V, 460V or 575V. Once you know the
voltage for your supply, you can determine the amps (amps = watts / volts). An electrician will be able to tell you
the cable size and specs for the given amps, volts and distance.
Question 1:
What is the replacement refrigerant for CFC Refrigerant R12 that is ozone friendly and permitted by EPA. We
have four centrifugal chillers with R12, and we would like to get away from all the EPA requirements that come
along with it and the high cost of R12.
Response:
The common replacement is R134a, which is an HFC and permitted by EPA. You also need to change the oil
and possibly the gasket material that are compatible. The chiller performance changes somewhat with the new
refrigerant, and you may also have to make some hardware changes. Most likely the chiller manufacturer should
provide the necessary service for the retrofit.
Question 2
What size air return does a 3 ton a/c unit require???
Response:
The nominal air flow per ton is approximately 450 cfm. Three ton unit air flow will be approx 1350 cfm, and size
of the return duct for this air flow should be 18" dia max (for residential) and 14" dia min (for commercial
application).
Question 3
How i can calculate the supply cable size for 20 ton package unit(cooling and heating)far away from electrical
panel board 30meter
Response:
For a unit of this size the power requirement will be typically ranging from 21 to 25KW. To be conservative use
the 25KW. The cable size will depend on the voltage of your power supply and the amps. Typical power supply
voltage to this size unit will range from 208 to 575 Volts i.e. 208V, 230V, 460V or 575V. Once you know the
voltage for your supply, you can determine the amps (amps = watts / volts). An electrician will be able to tell you
the cable size and specs for the given amps, volts and distance.