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Old 06-17-2009, 07:16 AM   #1
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wiring problem


why does my lights brighten when well pump motor starts? This is an existing condition when I bought home.
Background:
1 1/2 HP motor
20 amp breaker 120 volt
14 ga. wire w/o grd. connected at recpt. ( I reaalize this needs changing)
can't see label plate data or view actual wire connections at motor unless removing pump assy.
3 wire 15 amp plug on motor


Last edited by nancy t; 06-17-2009 at 07:21 AM. Reason: additional info
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Old 06-17-2009, 07:47 AM   #2
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wiring problem


If the pump and the lights are on the same circuit, the lights will dim for a moment and then brighten back to normal after the pump starts.
If you don't like this, move the pump to it's own breaker.
If the lights actually brighten when the pump goes on, that would be odd.
Ron

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Old 06-17-2009, 08:03 AM   #3
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the pump is on its own circuit already. I have been wondering if the wiring at the motor end ( which I can' t see) could be connected for a 220V conection ?
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Old 06-17-2009, 09:16 AM   #4
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Lights brightening is a symptom of a loose neutral. The voltage is going up. This can be serious. If the voltage goes up too much it can seriously damage electronics. Get this looked at ASAP. The problem could be anywhere from you panel back to the POCO connection at the transformer.
I would start with a call to the POCO and tell them your lights are brightening and you think you have a loose neutral.
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Last edited by joed; 06-17-2009 at 09:16 AM. Reason: spelling
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Old 06-17-2009, 06:05 PM   #5
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Quote:
Originally Posted by nancy t View Post
20 amp breaker 120 volt
14 ga. wire w/o grd. connected at recpt. ( I reaalize this needs changing)

Were you referring to the unconnected ground, or the 14g wire? A 20 amp breaker should have no smaller than a 12g wire anywhere on that circuit. I don't think that's related to your problem, but it's something that stood out to me.
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Old 06-17-2009, 07:00 PM   #6
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Quote:
Originally Posted by Atroxx View Post
Were you referring to the unconnected ground, or the 14g wire? A 20 amp breaker should have no smaller than a 12g wire anywhere on that circuit. I don't think that's related to your problem, but it's something that stood out to me.
This may of been done to compensate for the surge at startup. When a motor starts up it needs an inrush in current to get it turning, once it's turning the amperage will go down.
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Old 06-17-2009, 11:11 PM   #7
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Quote:
If the lights actually brighten when the pump goes on, that would be odd.
Not odd at all. Electrical troubleshooting 101.

See Joed's post.
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Old 06-17-2009, 11:16 PM   #8
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Nancy t,
joed is correct, it is a symptom of a defective neutral connection. It could be a corroded or loose neutral connection in you panel, at the meter base, or the utility transformer. Your other problem with the 14g wire on a 20 amp breaker and no ground is minor compared to the hazard the bad neutral poses.

Last edited by hayewe farm; 06-17-2009 at 11:21 PM.
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Old 06-18-2009, 09:02 PM   #9
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A 1-1/2 HP motor operating at 115 volts will draw about 60-100 amps on starting. Running will be about 15-20. Before we get too carried away with the loose neutral idea, first consider the overall layout of the system.

1) How far is the utility transformer from the meter?

2) What size are the conductors from the transformer to the meter?

3) How far is the pump from the meter? Is the pump fed directly from the main panel?

4) Do all the lights brighten or dim? Is it just a little, or a huge amount of brightness or dimming?

5) Does anything else that has a motor cause the lights to brighten or dim? Like the washing machine, dryer, dishwasher, or disposer.

If the utility feed is overhead, and longer than 50', the situation might be normal. A 1-1/2 HP motor operating at 115 volts on a residential system is very close to abusive. The best solution here would be to re-connect the motor for 230 volts, and change the breaker to a 2 pole. (assuming nothing else is connected to the pump circuit).

If the motor were to be operated on 230 volts, the lights would not brighten at all, though slight dimming might be noticeable. #14 wire would be the code minimum, and a 25 amp breaker would be the code maximum. This would be one of the rare times when an oversized breaker is allowed by code.

We can help better with a bit more info.

Rob
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Old 06-18-2009, 09:17 PM   #10
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I have a 1.5 HP pool pump setup
Rated to draw Max 18.6a @ 120v
I switched it over to 240v, very good idea

Never saw the lights dim as the pump was always running before the lights went on
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Old 06-18-2009, 09:44 PM   #11
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Joed and 220/221 have it right on! I once worked on a subpanel while the NEUTRAL disconnected momentarily. All the lights brightened and 2 GFCI receptacles were damaged. Nearly got a heart attack!!! Don't Drink and Drive!!!
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Old 06-19-2009, 11:01 AM   #12
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It doesn't matter how far or close th transformer is. If some of the lights are going BRIGHTER, the only cause is a loose neutral. If all the lights are dimming then you have a voltage drop issue.
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Old 06-19-2009, 05:31 PM   #13
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It's a voltage drop issue in any case. 122v on one side and 118v on the other side means a 2v drop across your bad neutral connection.
How hot this bad connection gets depends on the watts dissipated in it and the surface area of the bad connection.
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Old 06-19-2009, 08:58 PM   #14
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Consider this; Suppose the transformer is 100' away. Suppose the wire is #6 AL. At 80 amps (reasonable starting current for a 1-1/2 HP motor on 115 volts), the voltage drop will be about 13 volts.

That's just the wire from the transformer, not to mention what's after the meter.

I bet I'd notice 13 volts.

Rob

P.S. I'm not stating that a loose neutral isn't the cause, it may very well be. I'm just introducing the possibility of other problems.

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