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#214573 - 12/22/14 02:42 PM Single Pole Control Switch On 240-v Motor  
02vito  Offline
New Member
Joined: Dec 2014
Posts: 2
CO
Installed a 20-a, 240-v, single-phase, dedicated branch circuit for an automotive lift.

The lift-installation instructions required that the lift-motor supply voltage (under load)and current be measured and recorded.

In doing this, we noticed that the lift-motor control switch is only a single-pole device. Other lifts we have worked on have had 2-pole switches.

We were surprised that a nationally-known, ETL-listed lift would use a single-pole switch on a 240-v device. Our local electrical inspector was also surprised when we informed him of what we found.

I'm wondering what others are seeing in this type application. I don't recall ever seeing a 240-v device operated from a single-pole control.


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#214575 - 12/22/14 03:38 PM Re: Single Pole Control Switch On 240-v Motor [Re: 02vito]  
gfretwell  Offline


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Joined: Jul 2004
Posts: 9,069
Estero,Fl,usa
You can use single pole "control" but you still need a 2 pole disconnect.

Quote
430.84 Need Not Open All Conductors.
The controller shall not be required to open all conductors to the motor.
Exception: Where the controller serves also as a disconnecting means, it shall open all ungrounded conductors to the motor as provided in 430.111.


Greg Fretwell

#214582 - 12/23/14 03:49 AM Re: Single Pole Control Switch On 240-v Motor [Re: 02vito]  
NORCAL  Offline
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Joined: Sep 2002
Posts: 869
HVAC equipment uses single pole contactors for 208-240V units & 2 pole ones for 3 units all the time.

As the code section quoted in the previous post shows, it's quite code compliant, but means any electrician needs to be on their toes & trust nothing.


#214603 - 12/24/14 03:45 PM Re: Single Pole Control Switch On 240-v Motor [Re: 02vito]  
02vito  Offline
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Joined: Dec 2014
Posts: 2
CO
Thank you both for your responses.

The circuit in question has of course a 2-pole breaker. The lift was furnished with a pigtail and twist-lock plug, so that serves as the local disconnect.

Most of my experience is in the power industry, and at the utility where I worked, we always used control devices that broke all hot circuit legs.


#214607 - 12/24/14 10:17 PM Re: Single Pole Control Switch On 240-v Motor [Re: 02vito]  
gfretwell  Offline


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Joined: Jul 2004
Posts: 9,069
Estero,Fl,usa
Breaking all ungrounded legs is actually pretty uncommon when they use solid state switching for controls.


Greg Fretwell


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