charge on a R-410 system

[rob421]

I was starting a Tempstar 3.5 ton system with R-410 refrigerant. Outdoor temp was about 77 and head pressure was 259 with a liquid line temp of 75 which is exactly what the charging chart on the unit said I should have for an 11 degree subcool. But the suction pressure was about 101 with a line temp of 61. Thats a 30 degree superheat. Am I undercharged or will this suffice? I'm fairly new to charging the 410 units.

[jpsmith1cm]

Did the chart reference superheat?

20-30 degrees at the compressor is normal.

[beenthere]

Is the TXV adjustable.
If so, you missed an instruction in the install manual for checking charge.

[rob421]

The chart gives no parameters for superheat at all, just charge to subcooling. But if the subcooling is right on the mark without adding refrigerant, does that mean the charge is good? 30degree superheat seems high to me.

[just_opinion]

The chart gives no parameters for superheat at all, just charge to subcooling. But if the subcooling is right on the mark without adding refrigerant, does that mean the charge is good? 30degree superheat seems high to me.

First of all, you did not tell us if this is a TXV system. So let's assume that it is TXV

High super heat means: higher load than normal or the TXV does not open properly.

High load is easy to see.
TXV does not open will give you higher sub-cool. Like your case, if ID temp is mid 70's degrees, then you have bad TXV. The system runs at 32 degrees evaporator saturated temp and 30 degrees superheat

[AggieEngineer]

First of all, you did not tell us if this is a TXV system. So let's assume that it is TXV

High super heat means: higher load than normal or the TXV does not open properly.

High load is easy to see.
TXV does not open will give you higher sub-cool. Like your case, if ID temp is mid 70's degrees, then you have bad TXV. The system runs at 32 degrees evaporator saturated temp and 30 degrees superheat

If your Tempstar system is 410A then it is required to have a TXV on the ID and charged by SC. The longer the lineset the higher the SH at the compressor. Also, if the indoor was extremely humid, high temp or excessive airflow, it will drive up the SH. Just to cover the bases, where are you measuring the SH? 32 is too high at the evap and pretty high but possible in a properly operating system depending on proper conditinos and line length... Check the SH at the evaporator, you should have ~ 10F there if the indoor is in normal range (RH, °F, CFM).

The charging and check out basics are pretty much the same with 410 as with 22 but using a different PT chart.