Re: Causes of Ground Faults

["jewellfish" <jewellfish@xxxxxxxxx>]

Some of the causes of ground fualts I have run across:

1.  Cables that have been tie-wrapped to threaded rod--ALWAYS a bad
idea (unless you wrap the rod first, with elec. tape).

2.  Water penetration into backbox (assuming wiring is in metalic
conduit).

3.  Faulty batteries.

4.  I have seen installations where the installers used fire wire
inside EMT.  The problems was that the insulation on the individual
wire conductors tends to be very very thin.  Had several instances
where the wire was shoved into a 4" backbox and the insulation was
scraped off by the knock-out sluggs (the slugs were slightly indented
toward the inside of the boxes which left a small lip around the slug
which was enough to slice through the wires insulation).

5.  Our part of the country still uses "lease line" circuits to connect
the FACP to the fire dept.  These frequently get ground faults.

6.  Water penetration into conduit that is underground, in the slab,
etc.  Most insulation is water resistant not waterproof (esp old THW
wire)

7.  Cables nicked by steel steel studs (roped through knockouts with no
bushings--gosh, I love that).  Wires pulled tight across ceiling grid,
support wires, ducting, etc.



Hope it helps,

Jewellfish

jonlevis@xxxxxxxxx wrote:
> I have been asked to present a training seminar regarding fire alarm
> systems, in particular addressable systems. I am looking for common
> causes of Ground Fault Troubles that people have come across. Any one?