Replacing a main breaker

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jeff43222

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Minneapolis, Minnesota
I looked at a job today where the HO was complaining about flickering and dimming lights when the laundry machines were turned on. Load-wise, the 100A service was more than adequate (measured about 15A on each leg), and the BCs weren't overloaded. I opened up the panelboard and saw significant corrosion on the #2 Al conductor connected to the MCB (no one put on any antioxidant). I had her start the dryer, and I saw a spark come from the corroded conductor and saw the lights dim. The lug on the breaker was tight.

My plan is to replace the conductors from the meter socket to the panel, probably with #4 Cu to avoid future corrosion. My concern is if there's a lot of corrosion inside the breaker lug. If it's bad, is it possible to replace just the main breaker, or does this call for a panel swap? Other than the main breaker, the panelboard looks OK. It's a Sq.D. QOC-20M.
 
How do the buss bars look? I'd replace that main breaker in any event. If the lug is tight, it's likely "welded" in that positon.

Here's a tip... buying a new panel and taking the main breaker out of it is cheaper than buying a new main breaker. Just chuck the rest of the panel. The HOM and the QO panels use the same main breaker, so buy the cheaper HOM panel to take main breakers out of. If this panel is older and uses an old style main, you might have no choice but to buy that particular main breaker, but I thought I'd pass along the tip anyhow.
 
The breaker was one of those huge ones that spans the entire width of the CBs plugged into the bus. I'm not even sure how to plug such a breaker into the panel.

The Al bus bars looked OK.
 
Oh, backfed main? That one you describe sounds like the old QO1 breaker, that spanned 2 slots wide and 2 slots tall. The replacement is a QO breaker, with a different style hold down clip. A panel that old might deserve replacement, particularly if it's full and had a few non-CTL tandems installed over the years.
 
Yeah, it looked like the main was backfed. I could replace it with a standard 100A QO? How? I'm assuming the panelboard would need a new cover.

The 20-slot panel is full, and I don't know if there were any tandems installed previously. There is a little rust inside the panel, and the HO said she had no idea if there had been any water leakage in the vicinity of the panel. I suspect it might be rusty just from the humidity of the basement (I have some rust in my own QO panel, and there's no water leakage near it).

Otherwise, the panel is OK. I've seen plenty of worse ones out there. I'd like to avoid a panel swap if possible since that would run the HO $700-$800, and she's already indicated that she's not looking to spend that kind of money if it can be helped.
 
If it's a backfed main, and it's a QO1 breaker, you just unplug it (it's hard, since it's clipped in lots of places) and clip in a QO. You'll have two slots in the cover plate to fill with filler plates. Those old panels take the QO1FP (old style, grey metal) filler plates. They are still available.

If you go the route of getting a new old stock QO1 breaker, they are hundreds of dollars. There's no need to go that route.

EDIT... sorry... I've been saying QO1, when I really meant Q1. Look at this pic and see if this looks like that main:

http://img.photobucket.com/albums/v62/peterwaldman/Circuit%20Breakers/Square%20D/IMG_2664.jpg
 
The part number QOC-20M is for your trim, not the loadcenter itself. But you do have a 20 circuit 100A main breaker panel, if it is less than 14"w it is about 30yrs old.

As mdshunk said, the Q1 breakers were the ones that spanned the entire panel width. A Q1 main breaker could have been a back-feed design (both main lugs were on one end of the breaker) in which case a standard QO would fit in its place, although there is no mechanical retaining mechanism available. The other Q1 design was a top feed, where the main lugs came in on the top side of the breaker. Replacing the Q1-TF design with a QO would probably require the incoming cables to be "lengthened".

I vote: Replace the panel.
 
In this case, the lugs are on opposite sides of the breaker, and they are fed from the top. Considering the condition of the conductors, I was planning on replacing the conductors from the meter to the panelboard, anyway.

Sure, I'd like to replace the panel, but the HO is leery of going that route unless it's absolutely necessary. Is it even possible to replace just the QO-TF breaker?
 
mdshunk said:
If it's a backfed main, and it's a QO1 breaker, you just unplug it (it's hard, since it's clipped in lots of places) and clip in a QO. You'll have two slots in the cover plate to fill with filler plates. Those old panels take the QO1FP (old style, grey metal) filler plates. They are still available.

If you go the route of getting a new old stock QO1 breaker, they are hundreds of dollars. There's no need to go that route.

EDIT... sorry... I've been saying QO1, when I really meant Q1. Look at this pic and see if this looks like that main:

http://img.photobucket.com/albums/v62/peterwaldman/Circuit%20Breakers/Square%20D/IMG_2664.jpg
Click to expand...

Yep -- that's what the breaker looked like. Can it be replaced? Is it worthwhile?
 
It's becoming very obvious that you're not going to be able to do this lady a favor. She needs a panel change, and there's not much getting around it at this point.
 
Turns out the breaker was replaceable, but the guys at the supply house said the price is over $400. So much for that idea.

So today I installed a new panel for her. I was able to save her a little money by re-using the old CBs. She was happy with the job and the price, and she asked for a couple of my cards because her daughter needs some electrical work done.
 
jeff43222 said:
She was happy with the job and the price, and she asked for a couple of my cards because her daughter needs some electrical work done.
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See there, all that worry for nothing. :D

Glad it all worked out for you. Funny, people that don't seem to have 2 nickels to rub together seem to come up with cash when it looks like they're out of options. Keep that in mind.
 
What killed me is when I gave her the final bill, she actually responded with, "That's not so bad!" I hate hearing that. My translation circuit automatically kicks in on phrases like that, so my brain gets the message "You just lost money, Bonehead!"

The corrosion was pretty bad on that lug. I had to cut the #2 Al conductor to yank out the panel. The lug was corroded shut, and the screw head disintegrated when I tried to loosen it. I was able to just pull the whole conductor out. No wonder her lights were flickering.
 
jeff43222 said:
What killed me is when I gave her the final bill, she actually responded with, "That's not so bad!" I hate hearing that. .
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Jeff, if you made money, you should be happy. It's great to be known as a fair contractor. I'm glad it worked out for the both of you.
 
I have about 4 of those Q1-2100TF breakers in my stash at the shop. All of `em in good condition.

I keep wishing for a service call like yours so I could sell `em off "cheap"
 
Have you tried taking the wire off the lug and seeing if the lug is seriously corroded?

You might be able to just wire brush the end of the incoming wire and put some anti-oxidant on it and save her some money if the breaker is still OK.

I think once you go to the trouble of replacing the main it might not be all that much more to just replace the whole box. A 100A box with 20 breakers can be had for less than $200. IF it will fit in the same space.

I seems to me replacing the conductors is going to run a big chunk, and unless you absolutely have to I would avoid it.

but then I am just me.
 
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I couldn't open up the lug. The screw on it was corroded as bad as the wire itself. When I tried, the head of the screw pretty much melted under the pressure of the screwdriver.

The incoming wire was seriously corroded. A wire brush wasn't going to fix it.

Since the main was so expensive, I figured replacing the box was a better way to go. It did fit in the existing space, and I put in a slightly larger box so there would be a few extra slots in case there is any future need for more circuits.

The conductors had to be replaced. It wasn't actually all that expensive. I only needed about 24' of #4 Cu.
 
jeff43222 said:
What killed me is when I gave her the final bill, she actually responded with, "That's not so bad!"
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I get that comment quite often myself and I react the way you did. I'm sure the referrals you get from a happy customer will outweigh the few extra bucks you could have made. BTW, what did you charge her?
 
jeff43222 said:
A mere $575, including a $25 permit. The job took five hours, and materials cost me about $220.
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Jeff, I don't intend to tell you how to operate your business. What I will say is that I cannot understand how you made money on that job. I'm glad it's working out for you, but my price on a 5 hour job with $220 my cost on material would have been more like 700 or 800 bucks.
 
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