Charging a Heat Pump

[ksspartan]

If a contractor is charging a heat pump in 40 degree weather is it true that he cannot get a sufficient charge on it to meet my summer high temp conditions? I know this was the case in the old compressors but wasn't sure if this was still the case. If I have a contractor install a heat pump in this weather do I need to have him come back and check the refrigerant charge when the temperature warms up?

[docholiday]

No, he can weigh it in. In other words he can calculate the amount of refrigerant needed and charge the system by the required weight.

[ksspartan]

Is this true with either R-410 or R-22? I assume it doesn't matter? When you say weigh it in what does that mean?

[karsthuntr]

Use a scale, calculate the requried oz.'s needed for system and open valve. Shut valve off when scale reaches required number.

[docholiday]

Really, it depends on the unit, some units allow charging at lower temps. You really need to consult the unit charging procedures (which only apply to a properly installed system).

[smokin68]

Yes you can weigh in a charge in cool weather, but you should always have it checked during a hot day for proper charge. The weight a manufacturor specs is for up to "15-25ft" lineset, so charge can be off a little with the weigh in method. Always best to use subcool/superheat per manu's specs in cool mode IMO.

[RoBoTeq]

Heat pumps can also be adequetly charged in cold weather using the hot gas discharge method. It is a bit of a pain, but quite accurate.

[souper phly]

Originally posted by RoBoTeq
Heat pumps can also be adequetly charged in cold weather using the hot gas discharge method. It is a bit of a pain, but quite accurate.

Never even heard of such a method. Please enlighten me sir.