Lisa has experience working with cranky old electrical systems, even live ones. The old house in Mehama had a similar problem to what we were having in Fernley, even though it had a brand new 200A power drop and box from the local utility and nowhere near as much draw as we do in Fernley. In the Mehama case, a helpful local utility worker told Lisa that the two screws holding the feed line (you'll see the equivalent below here) were loose. He tightened it all right — so much so that he broke the breaker. Lisa's father had to buy a new main breaker, and Lisa installed it. So while working on a live circuit can be tricky, Lisa did know what she was doing.
This is the replacement (used) Zinsco-style circuit breaker that we bought on eBay. We were delighted that it arrived much more quickly than expected.
Here's what it looks like on the bottom. These two slots fit over the main service bar in the service box.
The lower end of the breaker has these two holes into which the heavy copper feed wires fit. These two wires run from the circuit breaker to the bus bars that feed the individual house circuits
With the replacement breaker in hand and several hours of daylight available, Lisa decided that we could try to replace the breaker on Friday evening. We shut down the computers, lights, and every other thing in the house except the refrigerator (which could take care of itself), and Lisa went out to the service box to face the challenge of working on a live electrical circuit.
Lisa opened up the breaker box and turned off all of the individual circuits (the breakers running from bottom to top along the two vertical feed bars), then the main 100A breaker (top left in this view). This box is very full. Technically, there is room for one more circuit breaker on the bus, but to make it happen, she would need to remove every circuit breaker from the bus, pull all of the wires, shorten them up to make enough space (there is way too much wire in here, making it difficult to close the box), then reinstall the circuit breakers slightly lower in order to make enough room for one more single-width breaker.
This is the old 100A master breaker. It fits onto the main service feed bars, which are the two horizontal metal bars shown here. This shows the tricky part. Although the main breaker is off, these two feed bars are live and there is no way for us to turn them off. (They are connected to the utility feed through the meter. The only way to shut them off would be for the utility to come out, break the seal, and unlock and remove the meter.) You can see the plastic covers that are there to try and prevent inadvertent contact with the 125A 220V service feed. One of the two has partially broken. Lisa says that she'd rather leave it alone, as working on it would be difficult, and as long as we keep the box closed, we should be okay.
At some point in the past, someone painted this box, and that got paint on the master breaker. That in turn made it difficult to loosen the two screws that hold the two heavy copper lines that run down to the house circuit bar. Lisa also removed the 30A breaker shown at the bottom of this photo (that's the circuit to the hot water heater that she installed some months ago) to give her more room to work, loosened the main feed wires from the 100A breaker, and attempted to remove the old breaker.
Removing the old breaker should have been as easy as pulling the old circuit breaker off the main service bus. But the old breaker was stuck, and getting a grip on it was very difficult. Remember that the main bus is live. You can't just reach in there and grab the circuit breaker any old way you want, not if you want to avoid accidentally touching that 120A power bus. When the old breaker refused to budge, you couldn't just reach in there with a metal pry-bar, not if you valued your life. And even if you didn't get fried, the box would possibly blow up if you short-circuited it, and that would have still left us in the soup.
I stood well back in case Lisa needed to jump clear, and I was wearing heavy gloves and a long-sleeve shirt in case I needed to try and pull her clear, which fortunately I did not. She used various wooden sticks to try and make the old breaker loosen its grip on the main service bar. Eventually she got it out, but at the expense of the breaker itself.
Hands and wooden sticks having proved ineffective, Lisa tried a pair of Vice-Grips grabbing the plastic frame of the breaker on the front. Unfortunately, this breaker, having been here for an unknown number of years in the hot desert environment, cracked under the strain.
It was back to wooden pry sticks, and the breaker eventually cracked into several pieces.
We had originally hoped we could retain the old breaker as a spare, but that wasn't going to happen. With the old breaker now removed (for good), we were at the Point of No Return.
You would think that installing the replacement would be relatively easy compared to the hassle of getting the old breaker out of the box, but it was not the case.
The replacement breaker needed to be connected to the multi-strand copper feed wires at the bottom, then snapped onto the service feed bars. The metal bracket between the wires and the two service bars acts as a pivot point. The bottom of the breaker fits onto it first, after which you are supposed to be able to just push the breaker onto the service bars.
The challenge here is that those heavy copper feed wires are not very flexible at all. Although Lisa could get the wires into the breaker (and the connections to the lower feed bar), it was very difficult to get everything to snap back together. Lisa had to laboriously adjust the feed wires to give her enough play to get everything to come together.
It took what seemed to be forever at the time, but probably was only 30 minutes or so, before finally the replacement breaker barely managed to snap onto the service bus. Lisa tightened down the connections to the breaker above and the house circuits below, and we were nearly done.
After a long struggle with persuading the replacement to fit where it was needed, it was time to button things up and turn the power back on.
I mentioned earlier that there is too much wire in the box. That makes getting the cover back on something of a struggle. With some help from me pushing where she said to push, Lisa was able to reinstall the cover. She then threw the main breaker. When nothing untoward happened, she energized the circuit that includes the front porch light and I went and turned it on. Light!
One at a time, Lisa energized each circuit, and I went to check to make sure everything worked. There were no problems. All was well. I restarted the computers, she turned the travel trailer back on, we closed the breaker box, I threw the shattered old 100A breaker in the trash, and we were done.
So there we are. We now have 125A service (the maximum feed possible on our line from NV Energy), which is 25A more than we did have. We still have more than 125A worth of circuits on the box, and if we were to turn everything on all at once, we'd blow the main breaker; however, we don't expect to do that. Besides the fact that we were running several circuits simultaneously that we rarely run at once when we started popping the 100A breaker, Lisa still thinks that we were experiencing voltage sags from NV Energy, which caused the amperage to spike over 100A, popping the old breaker. Now we have 25% reserve against that happening again. Also, this replacement breaker, while used, appears to be in better condition than the one it replaced, so we have some hope that it will last until such time in the future as we save up sufficient money to undertake the expensive (~$10K) and time-consuming (possibly multiple days) work of replacing the main service box and getting a more modern power drop from our utility.