This is the main electrical box. Power from NV Energy comes into the top of the box from a transformer across the street that runs to a pole at the corner of our property.
I curse whoever put in this box, because he obviously decided that nobody would ever want to put in additional circuits, ever. The original power feeds out of the box to the circuits inside the house lead from a conduit going straight down. That means they're literally set in stone because of the decorative stonework laid right over the conduit. The electrical contractor proposed that he might have to tear out a channel to get at that conduit to redo everything, and I can see why. Had we been doing this from scratch, a sensible thing might have been to leave space for the conduits and cover them with a removable surface so you could get at it later.
From the side of the box extend three conduits added later. The ones on the right lead to the laundry room and a sub-box there for the south addition, and to another sub-box that covers the garage and the "granny hutch" apartment upstairs that we hope to be my office eventually. The leftmost conduit is the one we had installed that runs to a pedestal for the travel trailer. Any two of those three circuits outstrip the 100A master breaker; however, none of them actually carry anything near their total loads, and with only two of us in the house, we've not been too worried about actually popping the main breaker. Nevertheless, we'd like to replace the 100A master with a 125A master so we can have the maximum load that the drop from NV Energy can tolerate. (NVE says anything above that will take a 200A drop and that's likely to cost several thousand dollars all by itself, not counting the electrical contractor's work to replace the box with a 200A version.)
So anyway, Plan B was to run a length of suitable wire through this conduit down under the house from the box. She already knew that the lines come out there and take a turn to a different conduit leading over to the travel trailer pedestal, so if she could get the line through the conduit, more than half the battle was done, as running it under the house in a length of flexible conduit, then up through the floor of the bathroom to a disconnect box for the proposed electric hot water heater would be relatively simple.
Lisa got kitted up in coveralls and old shoes and took a flashlight and the coil of 10/3 wire under the house. She got the wire pushed about halfway up the conduit before encountering too much resistance to continue. She then came out and we tried pushing it down the conduit. This time she got past whatever was holding it coming up, but eventually it got stuck again. We spent several hours sweating and cursing over this, trying various things, but nothing worked, and Lisa finally gave up and just as the light was fading put everything back the way it was and we reactivated the main breaker.
Lisa now has come up with Plan C: We need a bigger conduit on the line she'd been trying to use. She wants to buy larger conduit, disconnect the "trailer" wire from its circuit, then run it and the new wire through the new conduit, using adapters at the top end to fit it into the existing hole in the electrical box. (There's enough room in the hole into the box to admit all of the wires if we could get them to all run through the conduit.) Lisa was there when the electrician laid the trailer circuit, and says digging out from around the conduit lines under the house (about 30-40 cm, she says) is easy and can be done with a hand trowel in the sandy soil. Perhaps today we'll go looking for larger conduit and adapters.
If this doesn't work, there is a Plan D: drill a fourth hole in the box and run a fourth conduit. We really don't want to do this as there is almost no space left to run more conduit without running afoul of the phone lines to the right of the existing box and conduit.
I was surprised at how tiring this was, considering that I mostly spent the time standing and waiting for Lisa to tell me what to do while she did the really hard work crawling around under the house with tools. However, I was completely fried by the time I went to bed and slept for eleven hours.