Lights flickering in old house


Old 03-07-05, 08:39 PM
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Lights flickering in old house

The problem I am having is that all the lights in my house flicker simultaneously.

The details:
The house is 80 years old, and has an amalgamation of wiring from the different periods of the house, although none older than probably 50 years old (no knob and tube or anything, but I do have paper insulation on some things). It is all copper wiring except for the mains. There are several subpanels (3) which power different parts of the house. One is for the basement/garage, one is for the original part of the house, and one is for the addition completed in the 80s.

Most of the permanent lighting fixtures are controlled via low-voltage switches. I can't tell if only the lights on this system are flickering, but I think it's everything. They flicker more when there is a high load on the system. When the lights flicker, clocks don't reset and computers don't crash or anything.

I changed the subpanel for the original part of the house to a breaker panel instead of a fusebox a week or two before this started becoming a problem.

The attempts at a solution:
I've disconnected every circuit in the house one at a time, but each time the lights still flicker.

The utility company came and checked the mains into the house, everything appeared fine. He also tried metering the mains into the garage subpanel while the lights flickered, but didn't see a change in voltage. I suspect however that he wouldn't even be able to see this as the flickers are so quick.

I had two electricians out here for a few hours two months ago and we couldn't find anything. Tightened all the mains connections in the subpanels, but they were fairly tight already. While we were doing this, I had an old 240V window A/C unit cranked up to full heat, and it fried itself and freaked us out because it smelled like smoke all of a sudden. However, that was the source, and unplugging it solved that problem. They told me that this could have been the source of the problem if it were already somewhat fried inside and disrupting the neutral. We left it at that, since we couldn't find anything else.

Two months have passed now, and while the lights stopped flickering a week after the electricians were here (for no apparent reason) they have begun doing it again.


#1, what's going on? Also, most everything is ungrounded, but the things that are grounded are just grounded to neutral. The house I'm fairly sure is ungrounded. I'm going to change that, but would this be causing the problem?
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Old 03-07-05, 09:23 PM
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In poking around, I just now noticed what looks like the end of a grounding rod poking out of the cinder block in the basement with a single wire coming off of it that has been clipped off about 10 feet away. I'm not sure where the rest of it is, but would this be a valid ground?
Old 03-08-05, 07:34 AM
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Mild light flickering in older homes is sometimes unavoidable. It sounds like you've already addressed all the things that can be addressed, so you'll probably have to just live with it until some time in the future when you rewire the house.

You asked about a "valid ground". That's a difficult question to answer because there are different kinds of grounding for different purposes. But it doesn't sound like it's grounding anything at the moment. And it's certainly not an acceptable place to attach a grounding wire from an outlet. If this doesn't answer your question, then please explain more why you asked it.
Old 03-08-05, 09:52 AM
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Also, most everything is ungrounded, but the things that are grounded are just grounded to neutral
Please explain. Do you mean that ground terminals at outlets have been connected to the neutral wire? Or do you mean that large appliances such as the stove have only 3 conductors and that the ground and neutral connections are bonded together inside the appliance?

Doug M.
Old 03-10-05, 05:41 PM
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Well, some of the outlets have been "ghetto-grounded" I have noticed, where a "grounded" outlet is installed simply by replacing an ungrounded outlet with a three-hole one and tieing the ground terminal and the neutral side of the outlet to the neutral wire. My question about the grounding rod was whether I should connect it to the grounding bar in the panel. Right now, everything in the panel is either connected to hot or neutral, there is nothing on the grounding bar because it's not connected to anything to ground it. I would wonder why anyone would disconnect a perfectly good grounding rod and just wrap up all the wire next to it. Perhaps it was installed but never connected into the system in the first place? Or would there be a reason to disconnect the ground?

Secondly, I have a screw to bond the subpanel that I installed to ground, and I was wondering whether I should use that.
Old 03-10-05, 11:24 PM
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There are two independent grounding systems in your house. A connection to the dirt via a grounding rod is primarily for lightning protection. This connection to dirt is very important, but not necessary to make the outlet grounding system effective. Don't do anything until you fully understand these two systems and how they work.

You should immediately disconnect an connection of grounding wires or screws to the neutral at all outlets. This bootleg ground is more dangerous than no ground at all.

For subpanels installed in the same building as the main panel, you should never install the bonding screw.

I know of no reason to disconnect a grounding rod from the panel. It sounds like you need a complete overhaul. This grounding stuff is far more complicated than you currently imagine. Either study really hard, or better yet, get professional help. If you don't do it correctly, it won't work or might actually create hazards that didn't exist before.

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