Question about superheat.

[gagecalman]

I trying to understand the correct way to set superheat.

All new Goodman: GLXS5BA3010 condenser, CAPTA3026B3 coil on a GR9S960603BN gas furnace. R32.

The install manual states:
SH at compressor 10-12°F
SC at OD Liquid 7-9°F

Pressures and line temps taken at condenser.
Outdoor ambient 94°.
Liquid 340 psi/103°, line 95°. Subcool 8°.
Suction 130 psi/44°, line 56°. Superheat 12°.

Looks good to me but the very knowledgeable HVAC guy (friend) that helped me with the install says the superheat should never be that low for Copeland scrolls. Should be 15°-20° at the compressor. He says it should be checked at the evaporator coil but it doesn't look like anyone does that. Not even sure how it would be done.

So are Goodman specs wrong?
Is it okay where it is?

Thanks!

 

[danski0224]

Should be 15°-20° at the compressor.

This is a typical spec for walk in coolers, and while superheat is set at the TXV valve, it needs to be verified at the compressor, and that may change the settings at the TXV valve to satisfy compressor requirements.

For residential equipment, go with the data tag on the unit.

 

[TRWham]

The official Copeland guidance is still 20° F measured on the suction line 6" from the compressor inlet, but that is a very conservative number that was set many years ago (Copeland is very protective of their compressors). Having said that, if you have a stable 12° F, it should be fine as scrolls are pretty tolerant of liquid, as long as it's not enough to wash out the oil. Lower SH is generally better, and I would go with what Goodman advises.

 

[fitter30]

Super heat only works with a expansion valve. Bulb has to tight ( stainless hose champ) to the suction line at horizontal line 10-2 o'clock and insulated. Just before equalizer line. Suction temp at bulb and pressure should be at the equalizer line which very few taking sh would cut in a fitting so add about 2 lbs at condenser. Ex valves that have adjustment i always set sh where the sweat either stops at the commpressor body or very little into the body. Ccw for less more flow or cw for more less flow. Takes about 20 minutes after adjustment for valve to settle down.

 

[gagecalman]

Thanks for the replies and great info.

So I feel like the way I have everything set up is fine.

He does 99% refrigeration so I guess that's where his concern comes from.

 

[Aileron]

IMO 20+ is too warm for a 94* day. If your going by superheat on a fixed piston device, it is going to change depending on load and outdoor ambient as liquid gets stacked into the condenser on cooler days. Basically the condenser is going to **** up more liquid on cool days. A lot of times a system can be low on gas but have a stopped up condenser and seem like its working. When you clean that condenser is when you notice its low because the gas starts to stack. Your going to have a higher superheat when the outdoor temp drops.