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Old 11-11-2012, 05:31 AM   #1
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121V to 108V ??

Hi All
Had to run 125 feet of 8/3 cable from my house box (30A breaker) to my class A, my Kill A watt reads 121V, when running an electric heater, my Kill a Watt reads 14.56 A and drops to 108 V, will this harm anything ??
AL
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Old 11-11-2012, 06:10 AM   #2
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Seems you have a 1.5 Kw heater and you dissipate 189 watts in the cable.
Have the cable layed out straight (no curls) so the heat from the cable
dissipates nicely into the air. Otherwise you can have the insulation melt.
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Old 11-11-2012, 06:49 AM   #3
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Hello, I would say if all you are running is your electric heater you are ok, just watch for "heating of plug ends" as that is a long run. I also would assume that the 30 amp. breaker is wired with #8 or larger wire? I think you will be fine.
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Old 11-11-2012, 07:03 AM   #4
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108v is ok to run the heater, power the converter and 12v control systems. The only thing I would caution you on is the AC. Going below 104v is not a good idea. Of course it's doubtful you would be pulling 15amps before you turned it on. An AC will pull about 13-14 amps, just figure that with other high amp appliances running.
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Old 11-11-2012, 07:16 AM   #5
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I agree with what others have stated in regards to using caution about how much load you put onto that very long cable. You don't want to overload its ability. Use your KaW to monitor your usage, do not relay on the 30 amp circuit breaker to fully protect you as they will handle more until they get old and cranky.

If you want to spend some bucks, you could purchase a PowerMaster Voltage Booster. I have a 50 amp one, VC-50 which is wired first in line with my shore power cable. That eliminates any voltage drops due to long runs and poorly wired RV Parks.

http://www.powermasterrv.com/

It will boost your voltage 2.5% or 12% whenever needed.

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Old 11-11-2012, 10:00 AM   #6
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The 108 isn't too terrible, but the fact that you are dropping 13v in #8 wire at that distance would be worrisome to me. That wire should be more than enough to deliver 15A @125 ft with little voltage drop, at most maybe 2-3 v, so I think you have a poor connection somewhere and that will heat up and eventually fail.
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Old 11-11-2012, 10:18 AM   #7
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Quote:
Originally Posted by Gary RVRoamer View Post
The 108 isn't too terrible, but the fact that you are dropping 13v in #8 wire at that distance would be worrisome to me. That wire should be more than enough to deliver 15A @125 ft with little voltage drop, at most maybe 2-3 v, so I think you have a poor connection somewhere and that will heat up and eventually fail.

I agree, your upwards of allmost 10% drop, which 3% is maximum on feeders. #8 shuld carry 30 amps at 125 ft with virtually no drop. you have a problem somewhere else
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Old 11-11-2012, 10:24 AM   #8
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voltage drop can be calculated by the following formula, which will take a code book to give circular mills, (outter area of conductor) and the resistance in a conductor

VD = 2XRXIXL divided by circular mills



R resistance
I amps
L legnth
CM circular mills


I do this for a living
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Old 11-11-2012, 02:44 PM   #9
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Seems like quite a bit of drop. I have similar, even longer, run to my workshop and then another ~20' to the RV recept. When running large electric heater only a couple three volt drop. I would double check all connections, suspect maybe the breaker, etc.
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Old 11-11-2012, 03:04 PM   #10
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Agree check all connections at breaker box pedestal sounds like the problem my run is like yours heater doesn't drop yes Ac does to 116
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Old 11-11-2012, 03:11 PM   #11
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Is that 30a breaker in the main panel or a remote sub panel?

Quote:
Originally Posted by AL Dot View Post
Hi All
Had to run 125 feet of 8/3 cable from my house box (30A breaker) to my class A, my Kill A watt reads 121V, when running an electric heater, my Kill a Watt reads 14.56 A and drops to 108 V, will this harm anything ??
AL
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Old 11-11-2012, 03:34 PM   #12
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Check the Kill-A-Watt. Mine reads about 2 volts below actual according to my Fluke meter.

ie your 108 volts may really be 110 volts. Still not great due to reasons mentioned already.
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Old 11-11-2012, 04:38 PM   #13
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Is the line copper?
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Old 11-11-2012, 09:03 PM   #14
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Do not have my calculator handy, but only 15 amps in #8 at 125 should not drop that much, you may have other problems.

Get a voltmeter and measure voltage at different points under load to confirm actual voltage at each end of the wire

If you do not have a meter harbor freight has them cheap, get an IR thermometer while you are there, you can turn on the heater and monitor connection and wire temperature.

A bad plug will get warm

The part with the highest voltage drop will generate the most heat, so a loose wire at a connection will get warm, the thermometer makes it easy to measure
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