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Old 07-03-2013, 08:56 AM   #61
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Please help me correctly size my A/C condenser


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Originally Posted by beenthere View Post
When the indoor temp is near the set point temp. take a wetbulb reading. Check outdoor air temp entering the condense. use a superheat slide chart and determine what the super heat should be. if the super heat is near that amount. Then the subcooling should be within 10 degrees of that.
A caveat to the above: Beenthere's numbers assume a matched system.

With a mis matched components you get as close to ten degrees as possible.

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Old 07-03-2013, 09:24 AM   #62
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Please help me correctly size my A/C condenser


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Originally Posted by hvac5646 View Post
A caveat to the above: Beenthere's numbers assume a matched system.

With a mis matched components you get as close to ten degrees as possible.
Thanks,

How are adjustments made to get closer to ten degrees?
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Old 07-03-2013, 12:02 PM   #63
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Please help me correctly size my A/C condenser


The A/C Tech came out today.
Said he wouldn't be able to check SC.

He did say:
"Compressor is drawing 9.45 amps (max is 16.0)
Motor is drawing 1.51 amps
Cooling is fine when air from vent is 10 or colder than temperature inside the house (today A/C output is 8 lower than inside house temperature."

If the condenser had run longer it would have put out air ~14 cooler than temperature inside house.
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Old 07-03-2013, 01:27 PM   #64
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Please help me correctly size my A/C condenser


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Originally Posted by Unicornz0 View Post
The A/C Tech came out today.
Said he wouldn't be able to check SC.

He did say:
"Compressor is drawing 9.45 amps (max is 16.0)
Motor is drawing 1.51 amps
Cooling is fine when air from vent is 10 or colder than temperature inside the house (today A/C output is 8 lower than inside house temperature."

If the condenser had run longer it would have put out air ~14 cooler than temperature inside house.
the tech is blowing smoke.

"cooling is fine" is not a diagnostic conclusion, just an opinion.

The ac could be excessively out of spec and on its way to failure it could still "cool fine".
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Old 07-03-2013, 03:19 PM   #65
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Please help me correctly size my A/C condenser


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Originally Posted by hvac5646 View Post
the tech is blowing smoke.

"cooling is fine" is not a diagnostic conclusion, just an opinion.

The ac could be excessively out of spec and on its way to failure it could still "cool fine".
Thanks,

Wish I could find a Tech to measure & calculate the SC.

At least the electrical is within specs.

Is it actually possible for the A/C to be excessively out of spec & still work fine?

Aren't there perceivable operational symptoms & indicators, in addition to the SC, which will show when this A/C is excessively out of specification?
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Old 07-03-2013, 03:59 PM   #66
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Please help me correctly size my A/C condenser


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Originally Posted by hvac5646 View Post
A caveat to the above: Beenthere's numbers assume a matched system.

With a mis matched components you get as close to ten degrees as possible.
Matched, or mis matched, wouldn't change SH on a fixed metering device system.
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Old 07-04-2013, 02:01 AM   #67
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Please help me correctly size my A/C condenser


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Originally Posted by beenthere View Post
Matched, or mis matched, wouldn't change SH on a fixed metering device system.
Is anyone willing to tell me how SC is adjusted, if found to be out of spec (less than 10)?

Thanks In Advance,
Uni
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Old 07-04-2013, 07:52 AM   #68
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Originally Posted by Unicornz0 View Post
Is anyone willing to tell me how SC is adjusted, if found to be out of spec (less than 10)?

Thanks In Advance,
Uni
You have to fix what is causing the SC to be out of spec. Since you hven't got the readings yet. No way to tell you.
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Old 07-04-2013, 10:01 AM   #69
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Please help me correctly size my A/C condenser


Quote:
Originally Posted by beenthere View Post
Matched, or mis matched, wouldn't change SH on a fixed metering device system.
I am referring to the specs on a matched system.

Individual equip model SH charts are not universal in their application. The superheat reading one mfgr is not identical to another.

RSC did a article on on mix matches and found that even though after hours of toying with the press they could never get the SH in specs or any where close.

The units cooled but at the cost of high energy consumption and poor
dehumidification.

SC would not come in line on any unit.
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Old 07-04-2013, 10:12 AM   #70
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Originally Posted by hvac5646 View Post
I am referring to the specs on a matched system.

Individual equip model SH charts are not universal in their application. The superheat reading one mfgr is not identical to another.

They are all close enough that a universal chart will still list a target that is very close to the manufacturers.

RSC did a article on on mix matches and found that even though after hours of toying with the press they could never get the SH in specs or any where close.

Several studies/test were done by several different companies. All results were pretty much the same.

The units cooled but at the cost of high energy consumption and poor
dehumidification.

Dehumidification problems occur when they try to keep the wattage in line with the matched evap coil.

SC would not come in line on any unit.

SC not being proper due to the mis match is common. And if someone wants it to be proper. that is where fixing the cause comes in. Which of course is installing a proper matching evap coil. In the case of a 6 to 10 SEER designed oil.
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Old 07-04-2013, 10:45 AM   #71
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Please help me correctly size my A/C condenser


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Originally Posted by beenthere View Post
SC not being proper due to the mis match is common. And if someone wants it to be proper. that is where fixing the cause comes in. Which of course is installing a proper matching evap coil. In the case of a 6 to 10 SEER designed oil.
Good ,,,than you agree I was correct. Thank you.
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Old 07-04-2013, 10:50 AM   #72
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SH will still be correct, mis matched or not.
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Old 07-04-2013, 11:30 AM   #73
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SH will still be correct, mis matched or not.
correct in what sense...? ...that the SH is as good as your going to get even though it's not correct or optimal?
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Old 07-04-2013, 11:37 AM   #74
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correct in what sense...? ...that the SH is as good as your going to get even though it's not correct or optimal?
If the indoor wetbulb and outdoor drybulb require 17F of SH. There is no problem getting that SH just because the condenser and evap coil are mix matched SEER ratings.


Got a lot of apartment complexes with 10 SEER evaps and 13 SEER condensers. Getting target SH(+/-3F) is no problem.
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Old 08-01-2013, 09:47 AM   #75
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Please help me correctly size my A/C condenser


An A/C Tech came out & measured the temp before the coil & after the coil.
He used a gauge with a probe & penetrated the aluminum ducting before & after the coil.
His probe left 2 small holes in the flexible aluminum ducts.

What should I use to seal these holes?

Thanks Again,
Uni

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