Just had a newer R-410A Heat Pump repaired during winter weather conditions and the tech had to evacuate the lineset. He deep vacuumed down to the 500 micron level then re-charged the system.
Since it was too cold outside, he was unable to verify charge using Subcooling Method. Unsure of the exact lineset length, he added refrigerant and then followed the Heat Pump Charging chart to check the lineset pressures vs. indoor & outdoor temps.
Without weighing the charge, I guess this got him pretty close and within the tolerances of the relationship chart. Since this system uses a TXV @ indoor coil, I thought the subcooling method (with superheat verification) is the most accurate way to check charge. I just want to make sure the charge is exactly right.. I know a few ounces in either direction can make a significant difference on these new high-efficiency units. I've noticed some horizontal frost bands on the outside coil at 35-40 degrees OAT that didn't happen before.
Should I call them back in the spring-late summer and request a proper subcooling check be performed or did he get it right using the heating mode chart??