I have a combination starter inside of which is a separate 120 volt control circuit. The control circuit enters the enclosure and lands directly on a Hand-Off-Auto selector switch. The starter breaker disconnects the 480 volt motor circuit. Can the HOA serve as the disconnecting means for the control circuit or should another toggle switch be mounted outside the starter to disconnect power to the HOA? If the HOA is considered part of the controller then I think we need an additional toggle disconnect ahead of it?
HOA as disconnect for control power
- Thread starter jckenner
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brother
Senior Member
In my opinion yes. The HOA is part of the controls. so a snap switch is needed.
mkgrady
Senior Member
- Location
- Massachusetts
Why would a disconnect be required at all? This control circuit doesn't feed a motor. It feeds the controller for a motor. The motor can't turn on if the motor disconnect is off.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
motor controllers are also required to have disconnecting means.
To me it's a fine line, but i would tend to agree with Brother. The HOA is part of the control circuit and 430.75 says disconnect the control circuit from its power supply.
On combination starters I have always preferred the factory optional switch which can be added to the disconnect handle.
On combination starters I have always preferred the factory optional switch which can be added to the disconnect handle.
The preferred method, but not required, is to disconnect both power and control with a single disconnecting means. If separate disconnecting means are used, they are required to be immediately adjacent to each other (with exceptions).
IMO, if the disconnecting means for the motor is the starter breaker and the HOA switch is mounted in the same enclosure, the HOA switch will suffice as the control disconnecting means.
I can't recall specifically why, but shouldn't there be a warning label on the cover stating in effect there is more than one source of energy?
IMO, if the disconnecting means for the motor is the starter breaker and the HOA switch is mounted in the same enclosure, the HOA switch will suffice as the control disconnecting means.
I can't recall specifically why, but shouldn't there be a warning label on the cover stating in effect there is more than one source of energy?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Not required by any general code, but it sure is a good idea. I think NFPA 79 discuss this, along with coloring the 'foreign' conductors orange (it used to be yellow).
OK, I do think it is imperative that the starter be labeled that more than one voltage source is present in the enclosure. I had thought that this was code, but when I tried to find it I couldn't. My question on the HOA came up because we were adding the Hand function to an auto-off selector switch, which also functioned as the control power disconnect. I couldn't think of any reason that the auto-off selector switch, when placed at the start of the control power in the enclosure, could not function as the control disconnecting means. And if that was the case, why would it not still be able to serve as the disconnect when we added the hand function? Maybe the HOA selector would just need to be labeled as the control power disconnect, so that people would understand that this does indeed switch off all control power to the circuit? I say this because there are other ways things could be configured such that the HOA is in the middle of the circuit, and in that instance it would not shut off all control power present in the enclosure. I do think it is good practice to inform people of how to kill all power sources to a starter, or any piece of equipment.
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
What about 430.101 & 430.102(A)?
Neither the starter breaker nor the H/O/A switch disconnect power from the starter enclosure. Those disconnects are located ahead of the controller, not in the controller. See diagram at beginning of Article 430...
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IMM_Doctor
Senior Member
Outside source conductors (Then Yellow / Now Orange)
Outside source conductors (Then Yellow / Now Orange)
NFPA 79 INDUSTRIAL
Just curious, does anyone know why or what wisdom, promoted, or elected to identify conductors that may be energized even when the main source power is de-energized, was changed from yellow to orange? (And Why?)
Outside source conductors (Then Yellow / Now Orange)
NFPA 79 INDUSTRIAL
Just curious, does anyone know why or what wisdom, promoted, or elected to identify conductors that may be energized even when the main source power is de-energized, was changed from yellow to orange? (And Why?)
I still think it comes down to whether you want to define the HOA as part of the controller or as the source point providing power to the controller. The disconnect switch on a combination starter is a legal disconnecting means for the motor circuit conductors. When this switch is off we still have live conductors inside the starter on the line side of the starter disconnect. How is it any different to have the control circuit disconnected at the selector switch? If the switch is off, the controller circuit is de-energized. I still think an on-off selector switch located at the start of a control circuit is a legal disconnect for the controller, whether it's inside or out of the starter enclosure. An HOA is (electrically) a double throw center off disconnect. I know it's nice to have totally deenergized enclosures to work in, but I don't think that's a code requirement.
Disconnects for motors and motor controllers can be a complex discussion if one does not refer to each disconnect by its specific purpose. There can easily be several disconnects associated with a motor. As you stated, a combination starter can be a code-compliant disconnect for the motor circuit conductors... but it may not be a code-compliant disconnect for the motor if it is not within sight of the motor.
Whether the H/O/A is code-compliant controller disconnect is debatable. My preference is to install an auxiliary switch on the starter disconnect mechanism. When connected properly, it will break the circuit no different than does your present H/O/A scenario... with the exception that it is done concurrently with the motor circuit conductors.
To match European standards.
Hand-Off-Auto selector switch is unlikely to be listed as a disconnect. Dry contacts are not considered safe in that application. The conductors must be physically separated when the disconnect is operated. Hence the nice big handle to physically pull the blades apart in a disconnect. I believe the term is "Positive Action" meaning it pulls the blades out or the handle can't be operated.
The control circuit typically operates a coil that pulls in dry contacts for the actual motor supply. Note that in 430.75(A) that it specifically mentions having a direct disconnect for the motor supply. Indirect disconnect by depowering the control circuit does not qualify.
... one of which disconnects the motor and controller ... and the other(s), the motor control circuit(s) ...
At best the HOA would qualify for the motor control circuit.
Orange wire is only required where the panel disconnect is pulled and there are wires that are still energized. Not because you disconnected half a motor.
The control circuit typically operates a coil that pulls in dry contacts for the actual motor supply. Note that in 430.75(A) that it specifically mentions having a direct disconnect for the motor supply. Indirect disconnect by depowering the control circuit does not qualify.
... one of which disconnects the motor and controller ... and the other(s), the motor control circuit(s) ...
At best the HOA would qualify for the motor control circuit.
Orange wire is only required where the panel disconnect is pulled and there are wires that are still energized. Not because you disconnected half a motor.
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