Motor loads brighten lights?

At a friend's house, I have observed the (incandescent) lighting noticeably brighten when a motor load is switched on. So far it will happen with any motorized power tool, and with the garbage disposal. It seems more intense with the bigger motors. The Milwaukee Hole Hog really turns them up. It only lasts about a second. Evidently corresponds with the starting surge. I'm thinking neutral problem. Any other opinions? The neutral bond appears to be intact, and the grounding has numerous paths into wet soil through pipes, and of course the #4 copper to the water main. Today I put a bond bushing on a piece of 3/4" GRC that runs about 60' underground. Bonded it back to the ground/neutral bar. Shouldn't be any "float" on the neutral, besides all the other houses grounding the neutral from that transformer.

Reply to
Long Ranger
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It does sound like a neutral problem. You could have a problem at the neutral service splice outside. Have the utility check it.

It has nothing to do with the grounding electrode(s). The neutral current returns to the transformer through the grounded service wire, which is metallic and therefore much more conductive than any path through the earth.

Ben Miller

Reply to
Ben Miller

Rust/corrosion in the meter pan; at the bugs; at the utility connection.

Ed

Reply to
ehsjr

What I was suggesting is that the transformer might be ungrounded at the neutral point, causing the voltage on each leg to bias with the applied load.

Reply to
Long Ranger

I was reading things into the post that are not there. My guess is that you have an Edison system. That is a neutral with two hot conductors at 120VAC from the neutral but out of phase with each other. (That is like true two phase as opposed to a four phase supply with two phases missing.) If, say, the sockets are on one phase while the lights are on the other, starting a motor will pull the neutral away from 0V toward the plugs' hot phase. That increases the voltage across the lamps. Incandescent lamp output is sensitive to small changes of voltage.

Bill

-- Ferme le Bush

Reply to
<salmonegg

Exactly right. But no amount of grounding electrode bonding, etc. is going to fix that. As long as the earth is in the only return path, you are going to have problems.

Reply to
Ben Miller

Reply to
Long Ranger

As long as the neutral conductor back to the transformer is open, you'll see lights brighten and dim as loads are switched on and off. This is because the voltage of the neutral at the panel (or whereever) changes to whatever it will be with what amounts to two loads in series with each other. Same thing but less so if the neutral path is high resistance. The grounds don't matter other than placing a relatively high resistance path in series with the neutral.

Reply to
Michael Moroney

"Michael Moroney" wrote in message news:dnffc4$h8s$ snipped-for-privacy@pcls4.std.com...

If the neutral is open back to the transformer, then the potential exists for 240 volts across the hot (120V) conductors of a 3 wire circuit, when loads are present on both.. If the ground is low resistance, and the transformer has an intact ground bond on it's neutral point, then this condition will be masked, and the errant 240 volts prevented. This is why I often get service calls after people have had plumbers work on the part of their pipes that carries the cold water bond. Usually an open neutral is to be found, and the plumbers have not reconnected the bond, or have loosened it, or placed PVC pipe, or whatever. Note that I'm not saying it is normal for the ground to carry the neutral current back to the transformer. Only that it will happen if the right conditions are at hand. Also, when a municipality requires a cold water bond, your neutral current can follow the pipes to another person's house, and their neutral conductor back to the same transformer. I think there is, in fact a high resistance path back to the transformer neutral, which is causing the problem at my friend's home. What I have seen in the past, is a small transformer without a bond on it's neutral point that will allow a drift of about twenty volts in either direction, depending on which leg is pulling more current. This has nothing to do with an open neutral. After a bond is placed at the appropriate point, the voltages are held nearly unwavering on both legs. That is what I was describing in my previous post, and what I was initially looking for in the cursory exam I gave the service. I'm going back over there on Monday and have a look again. In the mean time, my friend has discovered that the "alleged electrician" who worked on his remodel was known to have tampered with his overhead service conductors, therefore the evidence mounts in favor of a neutral splice being poorly done, if his other work is any indicator. Finally, I don't see where a ground is ever in series with the neutral conductor. They are separate, and parallel, (between the service and the transformer bond.) otherwise there would only be one wire present for both of them. Take a look at any power system one-line diagram, and you'll see what I mean.

Reply to
Long Ranger

I'm not sure what you're saying, I guess. The first sentence describes an open neutral at the transformer, but then you explicitly say it's not an open neutral. An open neutral at the transformer would cause the same symptoms as one at the meter or drip loop, but would affect every house on that transformer, and a heavy load switched on at one house will affect the other houses.

Also, I read your earlier post as a missing _ground_ at the transformer causing the symptoms. A ground connection at a transformer isn't going to offer the low resistance as a ground through the water piping since it will almost certainly _not_ be connected to the water piping there. It'll be just a ground stake.

It won't be in series, but in parallel (the ground in the panel/meter paralleling the neutral connection to the ground at the transformer pole) When the neutral is intact the ground path resistance is high enough to be unimportant.

Reply to
Michael Moroney

*I'm talking about the (ground) bond that has to be connected to the neutral. Any time you use a transformer over 1000 watts you have to apply a (ground) neutral bond. It is considered a new system at that point. If this is not in place you will experience a drift in voltage from leg to leg on a single phase 3 wire system, or a 3 phase 4 wire system, if there is a great enough imbalance on the system. This rarely happens to a transformer feeding different buildings, since each building has it's own neutral bond, and it is unlikely that the bond will fail on each building at the same time. Plus, each utility transformer has it's own bond connected to it's own rod. As I said, with enough imbalance, a drift of up around twenty volts can be experienced across the 120 volt legs to neutral.
*What I'm saying about the water piping is that in these older areas it is common for the water grid to be all metal. Since each home's service is connected to the pipe by it's neutral bond, there is usually a pretty good path back to the neutral point on the transformer (if your neutral is open) via the pipes and your neighbor's neutral wire.
  • You were the one who suggested that the ground and neutral were in series. But you make my point here about how a relatively good ground, or an alternate path for the neutral can mask an open or high resistance joint in the neutral path.
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Reply to
Long Ranger

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