Re: Causes of Ground Faults

[G. Morgan <alarmpro@xxxxxxxxxxx>]

On 18 Dec 2006 12:12:04 -0800, 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?


I'd say the most common is nicking, skinning, and burring the wire
when it's being pulled.   Common hang ups are un-reamed EMT connected
to fittings (couplers etc.. ) , iron beams with sharp edges etc...

Pulling too hard or forcing the cable will often result in bad news
such as stretching and breakage.   Pull slack in multiple locations
around obstacles, with help if possible, to reduce the urge to
manhandle it.

Some installers still don't know how to strip the proper length of
copper for device termination and leave too much hanging out to get
grounded on the back box when the device is secured to it.


Even worse than not stripping the proper length of copper for landing
on the terminal:   is when guys strip the outer layer of a cable
jacket  (plenum is the easiest to muss-up) with their strippers and
use that first cut....  Why do you think the cat's hair is in there???
Use the cat hair!!  Pull the cat hair down the length of the outer
jacket and cut away the original jacket strip...  so there is no
chance of nicks, opens,  or shorts..  sheeze~!!!  Use the damn cat
hair...

On addressable sytems using isolation modules is a huge deal too..
explain them.








--

-Graham

(delete the double e's to email)