mlenco
27-12-2010, 01:43 PM
Hello
I installed a JT4BD R-410A (3 ton unit for a 1500 square ft 1939 brick home) Heat Pump July 3, 2010. It was "tuned" removing R-410A down to H/L 290/150 63.7 degrees suction and 12 degrees superheat at 3pm. For three weeks the A coils froze up, not a day under 90 degrees for that three weeks. The house couldn't get down below 88 degrees for that three weeks. I called someone over to add some R-410A, they added a little and the A coils stopped freezing up. The house cooled nicely. Fastforwarded to Dec 20, 2010. The heat pump couldn't keep up with a few days of nightime temps of 15 degrees F (Arlington, VA) and it was making a loud hissing sound quite a few times an hour. I called in Michael and Son HVAC. Tim, measured the pressure in the outside unit at 2pm. The hi pump psig @392 and suction at least 116 degrees F. Aside from needing a TXV inline to counter flow we opted to not add R-410A though on page 25 of the Refrigerant Charging Charts for Heating Mode of Operation call for 40 suction pressure, at 40degrees, a liquid pressure of 371, discharge temp of 131 and a suction pressure of 101. The tech said the measurements should be taken at 10pm when it is colder. Though the pressure was higher than recommended in the chart he said this will change later on in the night when the temperature drops. If we add pressure now then it drops to 20 degrees then adding pressure may not be advisable. So, what should we do?
Thanks!
Matt
571-332-6493
I installed a JT4BD R-410A (3 ton unit for a 1500 square ft 1939 brick home) Heat Pump July 3, 2010. It was "tuned" removing R-410A down to H/L 290/150 63.7 degrees suction and 12 degrees superheat at 3pm. For three weeks the A coils froze up, not a day under 90 degrees for that three weeks. The house couldn't get down below 88 degrees for that three weeks. I called someone over to add some R-410A, they added a little and the A coils stopped freezing up. The house cooled nicely. Fastforwarded to Dec 20, 2010. The heat pump couldn't keep up with a few days of nightime temps of 15 degrees F (Arlington, VA) and it was making a loud hissing sound quite a few times an hour. I called in Michael and Son HVAC. Tim, measured the pressure in the outside unit at 2pm. The hi pump psig @392 and suction at least 116 degrees F. Aside from needing a TXV inline to counter flow we opted to not add R-410A though on page 25 of the Refrigerant Charging Charts for Heating Mode of Operation call for 40 suction pressure, at 40degrees, a liquid pressure of 371, discharge temp of 131 and a suction pressure of 101. The tech said the measurements should be taken at 10pm when it is colder. Though the pressure was higher than recommended in the chart he said this will change later on in the night when the temperature drops. If we add pressure now then it drops to 20 degrees then adding pressure may not be advisable. So, what should we do?
Thanks!
Matt
571-332-6493