hennyh
07-03-2007, 09:54 PM
I installed a new matching 4T HP/AH that came factory charged with 155 oz R22. After pulling the lineset and evap. down to <500 microns I added 21 oz R22 which is exactly what the manufacturer required due to my lineset size. (weighed in with digital scale and double checked).
It started up fine and shutdown within a minute or two. The gauges said 65 psi low/300 psi high at about 55-60 degrees F ambient at shutdown. (well above specs.)
I recovered the charge and recharged it pretty close to the manufacturer's chart for heating mode. It's now about 40 psi low/200 psi high at about 50 degrees ambient and 70 degrees indoor dry bulb.
It produces about 25 degrees temp delta from cold air return to nearest heating vent at about 1350 - 1400 CFM.
It seems fine but I plan to go back and recheck/readjust the charge exactly per the manufacturers chart. Here are my questions:
1. The initial pressure reading suggested the unit was grossly overcharged from the manufacturer. Is there any other likely scenario that would expain both high suction AND high liquid while it was in heating mode?
(ie is there anything else I should check or be worried about). It has a TXV at the evap. Based on a capacity of 155 oz how much approx. R22 overcharge would have resulted in the pressures I initially saw?
2. It seems like superheat and subcooling calculations are only applicable for heat pumps operating in cooling mode. Is there any good way of checking subcooling in heat mode? (ie it's still winter here)
3. I do plan to heat up the house, put the HP in A/C mode and measure subcooling. However is this technique good in the winter? Should I block off the condensor fins?
4. Finally I want to measure the compressors current draw. How close to nameplate running amps is considered normal, high and low?
I'm kind of new to HP's and am paranoid after the pressures I saw upon start up. I'm looking for a systematic approach to adjust charge and assure everything is correct.
TIA!!
It started up fine and shutdown within a minute or two. The gauges said 65 psi low/300 psi high at about 55-60 degrees F ambient at shutdown. (well above specs.)
I recovered the charge and recharged it pretty close to the manufacturer's chart for heating mode. It's now about 40 psi low/200 psi high at about 50 degrees ambient and 70 degrees indoor dry bulb.
It produces about 25 degrees temp delta from cold air return to nearest heating vent at about 1350 - 1400 CFM.
It seems fine but I plan to go back and recheck/readjust the charge exactly per the manufacturers chart. Here are my questions:
1. The initial pressure reading suggested the unit was grossly overcharged from the manufacturer. Is there any other likely scenario that would expain both high suction AND high liquid while it was in heating mode?
(ie is there anything else I should check or be worried about). It has a TXV at the evap. Based on a capacity of 155 oz how much approx. R22 overcharge would have resulted in the pressures I initially saw?
2. It seems like superheat and subcooling calculations are only applicable for heat pumps operating in cooling mode. Is there any good way of checking subcooling in heat mode? (ie it's still winter here)
3. I do plan to heat up the house, put the HP in A/C mode and measure subcooling. However is this technique good in the winter? Should I block off the condensor fins?
4. Finally I want to measure the compressors current draw. How close to nameplate running amps is considered normal, high and low?
I'm kind of new to HP's and am paranoid after the pressures I saw upon start up. I'm looking for a systematic approach to adjust charge and assure everything is correct.
TIA!!