Re: Inductants/ground faults?

["Bill" <bill190nospam@xxxxxxxxx>]

The old relay control panels which were not grounded did not have problems
of this nature. Then electronic panels came along and these problems
occurred.

What you can do is use an isolated power supply (DC output not grounded) to
power a loop along with a relay. (Relay contacts go to electronic control
panel.) Then when door contacts open/close, the relay opens/closes as well.
Basically you are isolating the building wiring from the electronic control
panel.

What this does is two things.

1. More current is flowing through the wiring, so it is much less sensitive
to induced current such as caused by nearby lightning strikes. (Direct
strike, forget about it.)

2. When you have a retail business with an aluminum front glass/door frame
system and a customer attempts to enter the business after closing (thinking
the business is still open), they will sometimes place a lot of force and
"vibration" on the *locked* front door. This vibration can make a door
contact momentarily open and close. Some electronic controls will notice the
brief opening of the contact and trigger an alarm. A relay will require a
longer "open" of the circuit before it will trigger an alarm. Also you can
add a small value electrolytic capacitor to the relay for an additional
delay. A full second of delay time may be required to stop these types of
false alarms. (Symptoms of this trouble are retail store with aluminum front
glass/door system, and frequent false alarms shortly after closing time.)


"JW" wrote in message
>A couple of months ago (in one of the trade mags), I read about a company
>who had a new(?) product that reduced ground faults. My understanding was
>that you put them on the lines to clean up inductants. Also thought it
>suppressed ground faults that restored right away. Any insights?
>