13 Seer A/c

[ar4s1]

Does the 30 degrees above ambient still apply when calculating head pressure on higher efficiency? I'll run down some numbers as to what I recently experienced after installing my first split system that was higher than 10 SEER. This is an R-22 system.

Ambient temp was about 86 degrees, head pressure was about 206 psig which to me was a little low. The suction pressure however was hovering around 80 psig. This to me seemed quite high but my supply air temp was 55 degrees giving be a 17 degree drop across the evaporator. If I 'd removed refrigerant from the factory charge to try and achieve the 68 psig that I'm used to seeing, I'm afraid that my coil temp would have dropped to the point that it would freeze up. Unfortunately, I didn't take anything with me to do super heat and subcooling readings. If I had there probably would have been no need to post this question.

Also this was an older house that had never had central air so I had a great concern that the duct may have been undersized. I'm not used to seeing my gauges out of proportion that way, normally both are either high or low, never one high and one low. Could underszed ductwork be at the root of my problem?

[MichaelPaladin]

Does the 30 degrees above ambient still apply when calculating head pressure on higher efficiency? I'll run down some numbers as to what I recently experienced after installing my first split system that was higher than 10 SEER. This is an R-22 system.

Ambient temp was about 86 degrees, head pressure was about 206 psig which to me was a little low. The suction pressure however was hovering around 80 psig. This to me seemed quite high but my supply air temp was 55 degrees giving be a 17 degree drop across the evaporator. If I 'd removed refrigerant from the factory charge to try and achieve the 68 psig that I'm used to seeing, I'm afraid that my coil temp would have dropped to the point that it would freeze up. Unfortunately, I didn't take anything with me to do super heat and subcooling readings. If I had there probably would have been no need to post this question.

Also this was an older house that had never had central air so I had a great concern that the duct may have been undersized. I'm not used to seeing my gauges out of proportion that way, normally both are either high or low, never one high and one low. Could underszed ductwork be at the root of my problem?

Whats your wet bulb and dry bulb temps?

Also what subcooling does that unit require?

What is your Liquid Line temp?

13 SEER systems are charged and operate by subcooling and not by superheat.

You put those together, and most likely you will answer most of your own questions.

[beenthere]

30 above OD ambient was never a garranty that the charge was right.

You'll need to go back and check the charge with SH, and SC.

[beenthere]

Whats your wet bulb and dry bulb temps?

Also what subcooling does that unit require?

What is your Liquid Line temp?

13 SEER systems are charged and operate by subcooling and not by superheat.

You put those together, and most likely you will answer most of your own questions.
There are some brands that use pistons on their 13 SEER units, and they do get their charge checked by SH.

[t527ed]

no more "rules of thumb":eek:


only way to charge correctly is by following manufacturers instructions.:)

[catmanacman]

the thing i like about the rule of thumb the bigger the thumb the bigger the bigger mistake

[ar4s1]

no more "rules of thumb":eek:


only way to charge correctly is by following manufacturers instructions.:)

As I previously stated, the factory charge was retained, however the line set was relatively short, only about 12-13'. I thought if any thing, I'd have to recover some refrigerant. Also from what I'd been taught, an 80 psig suction pressure shouldn't equate to a coil delivering 55 degree air. All that aside, I'll pack along all of my temp probes on the return trip and do proper SH/SC readings. Thanks y'all!

[jligon3HVAC]

I'm assuming its a txv. . . on the inside.. go back and check air flow, then subcooling... newer designs often only run 20 degrees difference between oda and saturation temp (Derived from cond pressure) Sorry, but your going to have to go back and take more time...

[MichaelPaladin]

There are some brands that use pistons on their 13 SEER units, and they do get their charge checked by SH.

That may be true, but so far all 13 SEER (and up) systems that I've installed over the past year have used TXV's on the indoor coils. But I'll give you this one, I should have said "Most 13 SEER systems are charged by subcooling."

[BaldLoonie]

I started a new A-S 13 today. All A-S/Trane use TXV. This one had head of 175 which is around 94° saturation. My ambient was 80. Glad I wasn't looking for 30° over ambient! Had a nice 10° subcool, 18° temp drop.