Subpanel Repair

[John Keiser]

My pool pump stopped working. Power to the subpanel but not to the pump. Pulled the breakers, Tested good. Noticed carbon deposit near block where one of the hot lines connects. Removed the bakelite plate and the 2 hot blocks. One was very clean after 30 years of use; the other had carbon around and behind. The block is 2 pieces: literally a block and set screw that attaches to the hot line and a "L" shaped bracket [where the breaker fits] that sits under the block, held tight by a screw through the bakelite plate. The prongs on the "L" shaped bracket looked fine. I separated the block from the bracket and there was lots of carbon. I scraped off, cleaned up [but nothing special], reassembeld tightly. Put everything back together and all is working now. My question is: should I have doen anything special to make sure I have an optimal connection so this does not recur? Would an electrican have tried to "mate" these surfaces or used a special cleaner? Thank you for any comment.

[bob haller]

sub panels are cheap I would just replace it with everything new

[John Grabowski]

*Sometimes a little sandpaper is all that is needed to get everything clean. I am wondering what caused the problem. Was the screw terminal loose? That would cause arcing which would explain the carbon.

[clare]

As would MOST electricians.

[trader4]

Without actually seeing it, replacing it would be my advice too. Pool pump subpanels are often outside and after 30 years, you can expect problems.

[dpb]

One thought just in case...is the feeder Cu or Al? If Al, need to use anti-oxidant on the connections. Wouldn't hurt to redo the other even if still clean.

If there was any signs of pitting or other corrosion other than a surface coating, it's possible there may be service parts available. Then again, depending on the rating and the manufacturer, they may be as much or nearly so as a new box.

I see no need to replace a good box for just a cleanup of a contact, however. There are outside boxes on the farm here that are 50-60 yo that are still just fine...of course it's moderately dry here as opposed to areas farther east.

A relatively fine grit emery paper is the ideal tool for that; be sure to remove all debris after.

[Stormin Mormon]

The stores have grey paste, for aluminum contacts. I'm not sure if I advise it, one time I used it on .250 push in terminals, and it ate the teminals away. Not good.

There has to be an approved coating, but I'm not sure what it is.

Years ago, a friend had strange electrical flickers in his house. I had a look, and find that the power feed (through a 100 amp double pole breaker) was not right. Had to pry the breaker out, and sand the bus bars where the breaker clipped on. I may have used some kind of protectant, but can't remember.

For automotive use, heavy water proof grease works nicely to protect the wires.

[John Keiser]

The subpanel is in a shed and not directly exposed to the elements. Exterior and interior are clean, no corrosion. A replacement subpanel is cheap enough but would take me longer to rewire so I chose to try the repair. If it fails again, I'll source a new subpanel. Thanks to all responders.

[John Keiser]

No chemicals. Just 30+ years in Hawaiian humidity

[gfretwell]

Don't go nuts about this, just keep an eye on it.

One of those $30 IR non contact thermometers is cool for stuff like those. If the bus is cool, it is cool.

[John Keiser]

A good idea and a good use for the IR thermometer gather dust in the tool box. The bus checked out the temp same as all the other connections under load. Probably fixed for a few years. Thanks.