SHOP PRODUCTS
Houzz Logo Print
perel_gw

Old Touch-Plate rat's nest - how to trace?

perel
15 years ago

I have one of those old 1950s Touch-Plate relay panels in my house. I'd like to replace it with something modern, and reuse the existing wiring to light locations if possible.

That means I need to figure out what wire goes where in the existing box. Unfortunately, the original installer didn't bother labelling most of it, and I'm not sure if I can trust the few labels that are in there.

I have a lot of experience tracing telecom wires.. but this is quite different.

I know that one side of every fixture leg is connected to the common neutral. (It looks like either most or all of the box is on one circuit.) This would be simple if they'd used a busbar or something, but no.. it's five wires under a wirenut, jumpered to three wires in another wirenut, jumpered to two wires in another wirenut, jumpered to seven wires in another wirenut, etc. And that seems to be, in several cases, how BOTH ends of the wire are set up. Plus, there are a bunch of 14/3s coming in to the box, some with the red conductor chopped off, some with it in use. This makes me think that some of the fixtures may have been wired multiwire style, but with both hots on the same circuit/phase, just switched separately.

Is that how these systems were installed? How do I trace these? I really want to megger out some of the fixture legs BEFORE I do anything destructive to the old system, so I'd like to trace at least a few lines out while leaving the rest of the system hooked up.

The only way I can think of is pretty destructive - unhook EVERYTHING and then put a tone injector at each fixture box and trace it back to where it enters the relay enclosure. Leaving it hooked up, I'm concerned that the tone leakage to other conductors, or carried via the metal cable sheathing, would get in the way of pinpointing a specific conductor.

At the very least - can I be pretty confident that the original installers at least didn't steal neutrals from OTHER circuits, or was that commonly done in the 1950s on these systems? This was definitely a professional install, though decades of less-professional repairs have turned it into a rat's nest.

Comments (7)