Conductor tracing question

[ggunn]

We have been contracted to install a PV system on some buildings in an old facility where there are several buildings that have been built and added onto over the past 50 years or more. There is a central bank of transformers, meters, and disconnects which are labeled poorly or not at all; what paper documentation there is is in very bad shape and who knows how up to date or accurate. The custodian who has worked there for 28 years has no idea what is connected to what and neither does anyone else there.

In particular there is a 800A disco that feeds underground conduits, and there are two buildings 100' away where conduits emerge, one of which has a gutter feeding 4 or 5 discos and the other of which has an ancient MDP. We don't know which this disco feeds, or maybe it feeds both of them. The only thing our site assessor and project manager can think of is to arrange a time with the customer when they can go there, open the switch, and see what loses power.

This seems awful crude to me, but I am just an engineer, not an electrician. Isn't there a better way to trace these conductors, some way we can do it without shutting down power to large sections of the facility, which is, by the way, occupied 24 hours a day?

 

[tom baker]

There are circuit tracers that work well with branch circuits but I have not used with feeders - there may not be enough signal strength
I used to use a light bulb flasher with 100 W bulb and ampmeter to trace circuits it was a very positive indication. Perhaps something with a larger load you could cycle
But actually turning off the power may be the best solution

 

[ActionDave]

If turning off the power doesn't interrupt anything critical then that would be my first choice. It often ends up being the chosen method settled on after trying all the other tools and tricks anyway so why not cut to the chase.

 

[hillbilly1]

There are circuit tracers that work well with branch circuits but I have not used with feeders - there may not be enough signal strength
I used to use a light bulb flasher with 100 W bulb and ampmeter to trace circuits it was a very positive indication. Perhaps something with a larger load you could cycle
But actually turning off the power may be the best solution

Mine works fine on feeders, even through transformers. Line noise at the same frequency makes it a little harder to trace, so if there is a lot of electronics on the line, it can make it hard to trace.