Hi all, just a quick question on control wiring and where it should be in a circuit. The facility I work at is going through an upgrade of our HVAC system. Recently I happened by a newly installed exhaust fan controlled with a single phase motor starter mounted on the wall near the entrance of the room it serves. With the switch in the on position the fan was not running, no big deal, however, upon further investigation, I found that the control wiring is installed on the line side of the starter as opposed to the being on the load side. Thus the switch is on, but there is no line voltage to it, this to me can create an unsafe condition with someone who does not realize how the system is wired. I have been an Electrician for 26 years and this is a foreign practice to me but I can’t find anything in the NEC to justify having the contractor change it. I would think proper wiring methods and general common sense would dictate that the controls go on the load side of any disconnect. What am I missing here? Code violation or not?
Question on Control Wiring and where in a circuit it should be.....
- Thread starter Ondarc
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OldSparks
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- Vacaville CA USA
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- Retired: Electrician, Submarine Electronics (21 years), Potable water system maintenance boss (21 years).
I am confused. At one point you say the control circuit is on the line side of the starter, then at the end, talk about a disconnect. Are they the same device?
Obviously if the control circuit is sourced from the load side of a motor starter, the motor will NEVER run. On the other hand, the control circuit definitely should be deenergized when the equipment DISCONNECT is open.
Thanks for your reply. To clarify, the control wiring, is located between the starter and the breaker. The relay that breaks the circuit is actually in another room. The starter is a manual motor starter, not disconnect (my bad), just a switch with a heater in it. My fear is that someone could see the switch in the on position, see that the fan is off, remove the switch thinking that something is wrong then have the control circuit turn the thing on and they get hit.
Ill check it out. Thanks.
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- Licensed Electrician
I'm still confused. A switch is not a motor starter.
Ignoring any confusion about terminology, controlling a motor in a remote room is not unusual and a disconnect, which could be a switch, in sight of a motor is required.
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Sorry for the confusion. A Manual Motor Starter is basically a switch with a slot for an overload built in. To look at it installed, a regular every day person would see a switch on the wall. Controlling from a remote location is not the issue I have though. My issue is with the contractor interrupting the line side of the Manual Motor Starter as opposed to interrupting it on the load side for his control wiring.
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You are looking at it backwards. The switch is there to disconnect the motor even when the contactor is closed. A normal everyday person should keep his hands off.
kwired
Electron manager
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- NE Nebraska
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- EC
You have a manual motor starter (the switch in question) plus a magnetic motor controller elsewhere?
If so why? Not necessarily a code violation but probably not the greatest design either.
That said - any reasonably qualified person would check voltage and not just assume there is none at the switch just because the motor is not running.
If so why? Not necessarily a code violation but probably not the greatest design either.
That said - any reasonably qualified person would check voltage and not just assume there is none at the switch just because the motor is not running.
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