Frank Bowick
New member
- Location
- Ottawa, Ontario
Overload contacts are always connected in the grounded control circuit conductor? Why aren't they in the ungrounded side like any other control?
Overload contacts are always connected in the grounded control circuit conductor? Why aren't they in the ungrounded side like any other control?
I have a hard time saying overload relay contacts switches are subject to Article 404 as they do not meet any of the Article 100 definitions of switches nor 404.3 or 404.15.404.2(B) is often cited to support not having the overload relay contact open the grounded side conductor. I tend to agree that a relay is a switch and this rule would apply if I built a control system from component parts, but I don't agree that it applies to the internal wiring of a listed motor controller.
In my first post I should have used the term "switching device" and not switch. It is my opinion that a relay contact is a "switching device".404.1 Scope.
The provisions of this article shall apply to all switches, switching devices, and circuit breakers where used as switches.
Your opinion versus my opinion. I contend that an overload relay contact, integral to a starter, does not fit under any of the sections of article 404.In my first post I should have used the term "switching device" and not switch. It is my opinion that a relay contact is a "switching device".
Actually, it is not uncommon to see panels with the overload relay mounted remote from the contactor (i.e. a separately mounted relay after a VFD). I have even seen multi-section panels where all of the OLR where mounted on a single rail.As far as 430.74, it does not use the term "remote control circuit". It says you can't install a control circuit "remote from the the controller" if a ground fault on that conductor would bypass an automatic safety shut down device. The overload relay is such a device. If you extend the conductor that is run between the overload relay contact and the contactor coil, a ground fault on that conductor would prevent the overload relay from doing its job. Like I said before, this would not be a common circuit.
Which is what I said in my first post.Your opinion versus my opinion. I contend that an overload relay contact, integral to a starter, does not fit under any of the sections of article 404.
Yes, and the NEMA document that I cited says this is the very reason that the overload relay contact is normally connected to the grounded conductor of the control circuit. It is very similar to the reason behind the rule in 430.74. An accidental ground on the conductor between the overload and the motor controller would not be noticed under normal operation, but would prevent the overload relay from doing its job.If the overload relay contact is located on the ungrounded side of the coil it needs to be protected against short circuit currents. A welded contact would not be readily noticed during normal operation.
...An extension from the line side is not a violation of this section.
Overload contacts are always connected in the grounded control circuit conductor? Why aren't they in the ungrounded side like any other control?
Smart,If both the extension and the overload relay are on the grounded side of the contactor coil, it is a violation. Doesn't matter whether it is on the line or the load side of the OLR.
Any fault to ground on the remote wiring cannot cause the coil to maintain or become energized.
Remote wiring and subsequent devices always have to be on the ungrounded side of the contactor coil, regardless of the location of the OLR in the circuit.
That is correct. A remote control circuit with device current paths parallel to the coil (and any device in series with it on the grounded side of the coil) are not a violation.Smart,
My post is about extending the conductor that runs between the coil and the overload relay contact. The extension of that one would be a code violation, however there is no issue with running the grounded conductor from the other side of the overload relay contact. This is done any time you have a pilot light at the start stop station. A ground fault on this conductor does not bypass the overload relay.