Pulled a job ticket for a 1920s house and the old wiring was a real shock

I was working on a retrofit in an old neighborhood last week, trying to tie a new panel into the existing low voltage lines. I found out the original alarm wire from the 80s was run right next to the main power line for the whole floor, like inches apart. My meter was picking up crazy interference. I looked it up in an old trade manual and it said that kind of parallel run can cause false alarms for sure. Anyone else run into this in really old builds and have a good fix besides a full re-pull?

2 comments

2 Comments

moore.joel5d ago

Man, that's a classic old house problem. I had the same thing with a doorbell transformer wire running alongside a BX cable for years. The fix that worked for me was just pulling a new shielded alarm cable through the same hole and grounding the shield at the panel. It killed the interference dead.

nelson.kim4d ago

Wait, so @moore.joel, you're telling me the secret to peace and quiet is basically giving the wire a little metal jacket? That's hilarious, like we're putting the cable in time-out for being too loud. I guess my old house just wanted some fancy dressed-up wires instead of those old noisy ones.