justdavemamm
Senior Member
- Location
- Rochester NY
We have an enclosure in a Class I Division 2 area. It has a type Z purge with monitoring so we do not have automatic power cutoff when the purge is lost, just a local light and a relay from the pressure switch inside that has dry contacts (form 'C', both N.C. and N.O.) that are wired to a remote safe area for more monitoring.
We also have a number of dry contacts in the safe area wired to equipment in the purged enclosure. No problem here because power flowing through the contacts originates from the purged panel.
But what about the relays in the purged panel? Power to the contacts does not originate in the panel but rather at the remote safe area. With the purge lost & door open, even though the local disconnect if off, pulling a relay from its socket could produce an arc from the contacts that are powered.
There could also be the same type of problem in reverse. If I have local relay, whose contacts I use in some circuit, but the coil is powered from the remote safe area. The coil could be under power if it is pulled from its socket.
Is there a standard solution ? The only one I can think of is for the local panel to supply power to the remote panel, both to power the dry contacts and the remote coils. Either directly or to energize a relay in the remote safe panel to enable power to the coils and to the dry contacts.
We also have a number of dry contacts in the safe area wired to equipment in the purged enclosure. No problem here because power flowing through the contacts originates from the purged panel.
But what about the relays in the purged panel? Power to the contacts does not originate in the panel but rather at the remote safe area. With the purge lost & door open, even though the local disconnect if off, pulling a relay from its socket could produce an arc from the contacts that are powered.
There could also be the same type of problem in reverse. If I have local relay, whose contacts I use in some circuit, but the coil is powered from the remote safe area. The coil could be under power if it is pulled from its socket.
Is there a standard solution ? The only one I can think of is for the local panel to supply power to the remote panel, both to power the dry contacts and the remote coils. Either directly or to energize a relay in the remote safe panel to enable power to the coils and to the dry contacts.