120V circuit from a verified 480/277V load center

C

clombardi66

Member
Location
Louisville, KY
Occupation
Maintenance Technician
It was supposed to be a simple job. Had a dead hand dryer, the job should not have taken more than 10 minutes. Had seen the breakers in a previous job, so I went out and flipped them. When I came back inside there was still 120V on the hand dryer. Nothing else was labeled as hand dryer, so I got out my circuit tracer. Got a few hits, but nothing was taking down power. Ran in circles looking for any panels I was not aware of, with no luck. I didn’t really see what happened, but somehow a jumper made contact between hot and ground on the hand dryer and tripped that breaker, so I thought at least we would be able to find the it now. Ran in circles and didn’t find anything, again. I had remembered seeing this store had a handful of circuit breaker locks and determined it had to be one of those. Checked every single lock and nothing was tripped. Finally went into a 480/277V load center and the first circuit breaker lock I removed was tripped. Sent a co-worker inside to confirm if this was our breaker, which it was. Only when that breaker was in the off position, it was still showing 19V. At that point I was so confused I went out and confirmed that the parking lot lighting that was fed from this panel was in fact @ 277V, which it was. After going back to the electrical room, I found a second panel schedule behind what was visible in the slot and somebody had hand written, “hand dryer?” in that exact breaker number. How is that possible? The only thing I can come up with was somebody made their day a heck of a lot easier by installing a step down transformer somewhere hidden, in place of tying that back to the correct breaker. 4 hours of running around for what should have been a 10 minute job.
 
clombardi66 said:
The only thing I can come up with was somebody made their day a heck of a lot easier by installing a step down transformer somewhere hidden, in place of tying that back to the correct breaker.
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Sounds like it was a 277 volt hand dryer. If you operated a 120 volt hand dryer on 277 volts is would only last a few seconds.
 
clombardi66 said:
It was supposed to be a simple job. Had a dead hand dryer, the job should not have taken more than 10 minutes. Had seen the breakers in a previous job, so I went out and flipped them. When I came back inside there was still 120V on the hand dryer. Nothing else was labeled as hand dryer, so I got out my circuit tracer. Got a few hits, but nothing was taking down power. Ran in circles looking for any panels I was not aware of, with no luck. I didn’t really see what happened, but somehow a jumper made contact between hot and ground on the hand dryer and tripped that breaker, so I thought at least we would be able to find the it now. Ran in circles and didn’t find anything, again. I had remembered seeing this store had a handful of circuit breaker locks and determined it had to be one of those. Checked every single lock and nothing was tripped. Finally went into a 480/277V load center and the first circuit breaker lock I removed was tripped. Sent a co-worker inside to confirm if this was our breaker, which it was. Only when that breaker was in the off position, it was still showing 19V. At that point I was so confused I went out and confirmed that the parking lot lighting that was fed from this panel was in fact @ 277V, which it was. After going back to the electrical room, I found a second panel schedule behind what was visible in the slot and somebody had hand written, “hand dryer?” in that exact breaker number. How is that possible? The only thing I can come up with was somebody made their day a heck of a lot easier by installing a step down transformer somewhere hidden, in place of tying that back to the correct breaker. 4 hours of running around for what should have been a 10 minute job.
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Was the hand dryer in a receptacle / cord and plug?

120V phase to neutral or phase to ground?

19V phase to neutral, phase to ground, or neutral to ground?

It sounds to me like someone doing the lighting might have tied together branch circuits thinking it was all 120V or something along the way. Either phases got crossed or grounds / neutrals.
 
Elect117 said:
Was the hand dryer in a receptacle / cord and plug?

120V phase to neutral or phase to ground?

19V phase to neutral, phase to ground, or neutral to ground?

It sounds to me like someone doing the lighting might have tied together branch circuits thinking it was all 120V or something along the way. Either phases got crossed or grounds / neutrals.
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The hand dryer was hardwired. 120V phase to ground. 19V phase to ground.
 
tortuga said:
Your looking for an autotransformer.
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That’s what I was thinking, but more importantly WHY would somebody do that? I’m in maintenance, that hand dryer is swapped and working. That work order is closed. Unless someone has a good reason that needs to be corrected, I made a note in the panel schedule and we’ll let it ride.
 
Probably the usual answer it was easier and cheaper for someone at that time I guess.
I saw some parking garage lights that were retofitted to LED but they left the old MH ballast transformer in the fixture and used it to generate 120 off a 277 circuit.
 
clombardi66 said:
That’s what I was thinking, but more importantly WHY would somebody do that? I’m in maintenance, that hand dryer is swapped and working. That work order is closed. Unless someone has a good reason that needs to be corrected, I made a note in the panel schedule and we’ll let it ride.
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Is there a hung ceiling in the room? Could be tapped off of the lighting circuit.
 
Whatever it is I would think replacing the hand dryer with a 277v model would probably be as cost effective as the material and labor to transform the voltage. I know there are many factors that could change that though
 
roger said:
Whatever it is I would think replacing the hand dryer with a 277v model would probably be as cost effective as the material and labor to transform the voltage. I know there are many factors that could change that though
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This is the way to go, especially with multiple units. XLERATOR, Mitsubishi Electric, World Dryer, Bobrick and Saniflow all have 480 volt versions as well. If you have three of them, it makes for a perfect 15A delta.
 
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