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Strange AC unit current draw

Old 09-30-2020, 10:43 AM
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Default Strange AC unit current draw

Electrician cleaning up bad wiring, installing new ground well, happened to clamp on the Goodman unit feeders, 11a per leg while running, but 5 a on both when not running. WhAt could that be? Will check if the air handler is supplied from the compressor unit but should be on a separate breaker me thinks?
Old 09-30-2020, 10:44 AM
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Maybe 1 breaker in main panel that feeds a subpanel that feeds both AH and Condenser unit.
Old 09-30-2020, 11:11 AM
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compressor heater maybe,
should turn on when compressor is off.
not sure if it is controlled by a low temp switch or not

Last edited by 99yam40; 09-30-2020 at 11:47 AM.
Old 09-30-2020, 12:09 PM
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Originally Posted by 99yam40 View Post
compressor heater maybe,
should turn on when compressor is off.
not sure if it is controlled by a low temp switch or not
yup, crankcase heater
Old 09-30-2020, 12:57 PM
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Don’t think a crankcase heater will pull 5 amps. .5 maybe
Old 09-30-2020, 01:29 PM
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Originally Posted by Chasinhoo View Post
Don’t think a crankcase heater will pull 5 amps. .5 maybe
I never measure the current of one, but I would think the same thing.
5 amps is too high.
I wonder if someone miss read the meter
not hard to miss that decimal
Old 09-30-2020, 02:17 PM
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Crankcase heater draws up to about .3 amps (300ma).
Old 09-30-2020, 04:45 PM
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Does unit have heat strips?
Did he go leg to leg or leg to neutral?
Old 09-30-2020, 07:01 PM
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Originally Posted by Edselectric1 View Post
Maybe 1 breaker in main panel that feeds a subpanel that feeds both AH and Condenser unit.
or a mobile home AC Pkg unit, with blower in the outdoor unit also....
Old 09-30-2020, 08:18 PM
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Originally Posted by Stim View Post
Does unit have heat strips?
Did he go leg to leg or leg to neutral?
you do not measure amps line to neutral or line to line
Old 09-30-2020, 08:30 PM
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Clamp on ammeter, was not the air handler, some jackass put capacitors across the 240v feeding each compressor trying to correct phase angle.
( a common scam here that has surfaced a number of times over the years, usually coupled with a meter leg bypass to show the Huge savings.......)
AC units were replaced, installer left the caps in place, probably failed long ago. Disconnected them. phantom consumption gone.
13A @240 x 24hrs/day, x 30 days/billing period. @ $.34/Kwh.
The shit i see...........
was 5a on one unit, 8 a on the other.
Old 10-01-2020, 07:36 AM
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Wow. I can't see how that could draw 13A though, unless those caps were sitting at 250 degrees?
Old 10-01-2020, 11:46 AM
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Originally Posted by Capt Odyssea View Post
13A @240 x 24hrs/day, x 30 days/billing period. @ $.34/Kwh.
The shit i see...........
Crazy situation.
But if the draw was constant it would be costing $763/month.
I would think the capacitor charges up then the draw stopped.
Old 10-01-2020, 12:08 PM
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Capacitors add reactive power. Don't really consume much power. Draw power on the rise of the sine curve, discharge on the downslope of the sine curve. Net consumption near zero except for resistive losses. Amp meters can't tell the difference between reactive power and resistive power, it's still just amps in either case. Not sure if kWh meters can tell the difference, I think they do.
Old 10-01-2020, 03:16 PM
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Originally Posted by 99yam40 View Post
you do not measure amps line to neutral or line to line
Only once
Old 10-01-2020, 04:03 PM
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Originally Posted by mikefloyd View Post
Only once
a good meter should have a fuse that will protect it
Old 10-01-2020, 04:10 PM
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Use clamp-on
Old 10-01-2020, 04:50 PM
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Originally Posted by round2it View Post
Use clamp-on
but how would you measure using that, line to line to or line to neutral as the guy posted we are talking about?
I agree most knowledgeable people would us a clamp on meter to do this measuring
Old 10-01-2020, 07:07 PM
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DC Current is measured in line (most meters limit this to 10A max), voltage across, for AC current a clamp on around the hot or neutral indicates AC amps.
Yes, the Capacitor itself indicated 5 A current, the other one 8A, but realized that might have been reactive. Or they are bad/shot. Probably a way to figure out actual watts drawn and it is probably less than the read value.
The 5 and 8 amp reading was when the compressor was not running.
Been reading up, phase angle correction (Power factor correction) can cause issues with surges and spikes if not done right.
Power co does it to balance resistive vs.reactive on substations and transmission lines but over here it's all disconnected no doubt.
Old 10-01-2020, 07:14 PM
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Originally Posted by 99yam40 View Post
but how would you measure using that, line to line to or line to neutral as the guy posted we are talking about?
I agree most knowledgeable people would us a clamp on meter to do this measuring
Got ya now. I wouldn't know how to measure between line to line to line with a clamp on ammeter. Certainly the phrase of doing it "only once" would come into play.

Certainly would troubleshoot the unbalanced line. Best method for that would be hiring an experienced electrician.



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