electrical
Was digging out my final gate post hole and realized that the conduit carrying the main power supply into the house was corroded through. The cable sheathing does not appear to be compromised. I'm wondering what I am in for regarding repairs and cost… sheesh.
The NEC wants you to avoid overfilling a conduit so that the conductors can dissipate heat, and so you can remove a conductor without damaging it. See NEC 300.17.
There are only 9 single pole circuits (so 18 conductors?)
Ground conductors count for equipment fill, so you have more than 18 -- maybe 23?
Ironically, when you get close to a fill limit, the NEC actually wants you to increase conductor size, because that reduces heat.
Should I be worried or just put the cable through it anyways?
If this was my house, I would want to add a new conduit, if only because pulling the new conductor will be so much easier.
Do they make "reducing" hubs?
Yes. Here are some examples: http://www.thomasbetts.com/ps/endeca/index.cgi?a=nav&N=3819+598+4294951140&Ntt=
I've always found I needed 6" of conduit to make the transition between the reducer and the male fitting that connects to the box. Luckily my local hardware store will sell PVC conduit by the foot, so I don't have to buy a full stick for this.
As @Tester101 mentions, you can also make the hole bigger. A step bit is a nice tool, but 1 1/4" conduit requires a knockout that's actually ~1 3/4". The one he linked to only goes to 1 3/8", and I haven't seen bigger.
The professional way to make a larger knockout is to use a punch. They're a little expensive. Maybe you can find an electrician who will punch the hole for you in exchange for beer or a favor. Or maybe a tool rental place will have a bunch for you.
You don't have to bring the conduit in through an existing knockout - you could punch a hole on the side in a blank area, if that's more convenient for you. Alternately, if there's a good spot with 2 small knockouts, you can consume that whole area.
In your existing installation, I think the lock washer is upside-down. There are sharp edges that are intended to bit in to the metal, so it won't come loose. Unfortunately fixing this means undoing a lot of wiring.
Also, I think you should use a bushing to protect the conductor from the end of the conduit. Whether your inspector will require it is difficult to guess, but it's seems like cheap insurance. Something like this:
Also, I hope that if you're going through the trouble of pulling a big conductor to a new location, you're installing a subpanel at the other end. Because subpanels are awesome.
There's a decent discussion about making aluminum wire connections over here: What's the best way of replacing a plug or switch in a house with aluminum wiring?
If there is #12 Al wire on the circuit, the breaker should be 15A. #10 aluminum wire can have a 20A breaker, and you shouldn't normally see anything like #14 aluminum. Or you could just pull new copper wire and permanently disconnect the aluminum. Your home insurance company might not even cover you if they discover that you have aluminum wiring on your branch circuits. Aluminum is still common for the big feeders into your main panel, though, and that's fine because it's terminated appropriately by the electrician.
Any device that aluminum wire is connected to should be approved for connecting to aluminum wire, and any connections between aluminum and copper wire have to be made with special connectors. There are different types. Some are crimps that compress the wires very tightly to "cold weld" them together, some are special wire nuts, and you must use aluminum oxide inhibitor. The oxide inhibitor is included in the special purple wire nuts that are rated to connect aluminum and copper.
One of the issues is that aluminum and copper have different rates of thermal expansion and contraction. Combine that with the tendency for corrosion when aluminum and copper are in constant contact, and the fact that aluminum oxidizes (rusts) very rapidly if oxide inhibitor isn't used. All the inconsistent expansion and contraction and corrosion helps to loosen connections. Add the fact that aluminum oxide is an effective electrical insulator and you have a lot of potential for connections to go bad over time, leading to overheating and fires. Loose electrical connections get hot (and might also produce sparks), and heat starts fires (as do sparks, since they're hot), etc.
If you're going to leave the aluminum wire in place, though, maybe you want to avoid the twist-on connectors (wire nuts) and use the cold-weld crimp-on connectors, then seal the connections up really well with something like lineman's rubber splicing tape.
You don't want this in your walls:
Best Answer
It will not be cheap and it cannot be ignored. But if it is between the utility pole / vault and your meter, it might be their (the utility's) responsibility. That varies from place to place, but it certainly can't hurt to call them.