I have a site visit later today to assess an issue with an elevator not functioning when the elevator is running on generator power. The whole purpose of this one generator is to back-up one elevator. Apparently, the elevator runs fine on utility power but does not run AT all on generator power. My first thought is that there may be too high of a voltage drop due to the distance/under sized wires, my second thought is quality of power coming from the generator. In short, im just trying to see if there any ideas out there prior to making our site visit or if anyone is familar with this sort of problem. I don't know any other specifics as im going to be gathering any applicable information on my visit.
Elevator Low Voltage condition
- Thread starter Npstewart
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rcwilson
Senior Member
- Location
- Redmond, WA
Verify all of the elevator controls are also on generator power. Most likely the problem is voltge drop as you surmised. Could also be grounding / noise issues or reversed phase sequence.
A jail here had the motors in the penthouse powered from the penthouse Emergency DP and a portion of the elevator controls powered from the basement EDP. EDP's were on different transfer switch circuits. Worked fine on utility power but during an outage the elevator locked up. (A female guard got caught between floors for a few hours in the elevator with several male inmates. No problems occurred.) Wiring to the same power system fixed the problem.
A jail here had the motors in the penthouse powered from the penthouse Emergency DP and a portion of the elevator controls powered from the basement EDP. EDP's were on different transfer switch circuits. Worked fine on utility power but during an outage the elevator locked up. (A female guard got caught between floors for a few hours in the elevator with several male inmates. No problems occurred.) Wiring to the same power system fixed the problem.
I understand that in order to measure voltage drop that the elevator sees, you would typically measure the voltage when the elevator is running, but in this particular case the elevator isn't even starting so wouldn't the voltage have to be measured without the elevator running but on generator power? If the voltage at the elevator is too low, im assuming there would be some type of safety that doesen't allow the elevator to even start.
ptonsparky
Tom
- Occupation
- EC - retired
Does your elevator control have phase loss or phase reversal? Did it ever work?
From what im told, the elevator never worked on generator power, only utility power.
I also was just told that it is an extremely long run from the generator, to the electrical room, to the elevator.
I noticed that a few people have mentioned phase reversal. As you guys referring to for instance phase "B" at the generator is connected to phase "C" as the load?
I also was just told that it is an extremely long run from the generator, to the electrical room, to the elevator.
I noticed that a few people have mentioned phase reversal. As you guys referring to for instance phase "B" at the generator is connected to phase "C" as the load?
Joethemechanic
Senior Member
- Location
- Hazleton Pa
- Occupation
- Electro-Mechanical Technician. Industrial machinery
Yea there may be phase reversal protection in the control. It would stop the motor/motors from running in reverse rotation.
This could be as easy as just swapping two phase wires.
Is this a hydraulic elevator?
This could be as easy as just swapping two phase wires.
Is this a hydraulic elevator?
I hope to find out more specifics after our site visit. I don't even have the model number of the elevator yet. A phase reversal would be great otherwise if it is a voltage drop issue I think we would have to step up the voltage and step it back down prior to the load because the wires/conduit are existing.
kingpb
Senior Member
- Location
- SE USA as far as you can go
- Occupation
- Engineer, Registered
You say never worked? What does that mean? Lights are on, but push a button and doesn't move, or it tries to go but stops, etc.
First guess is load rejection, i.e. gen can't handle motor inrush, but without details, it could be many, many things.
First guess is load rejection, i.e. gen can't handle motor inrush, but without details, it could be many, many things.
Joethemechanic
Senior Member
- Location
- Hazleton Pa
- Occupation
- Electro-Mechanical Technician. Industrial machinery
Not to say it couldn't be a voltage drop issue, but it would have to be a pretty drastic voltage drop to make the elevator not function at all.
Do you know what nominal voltage this thing is running at?
What sort of drive is on the elevator?
Fixed speed or variable speed?
If it's variable speed or a soft start it might distort the supply from the generator sufficiently to make it not work.
The generator is likely to have a much higher impedance that the utility source and that would distortion worse.
Just a thought.
Joethemechanic
Senior Member
- Location
- Hazleton Pa
- Occupation
- Electro-Mechanical Technician. Industrial machinery
Yano,
Being that you haven't been there you really don't know if the transfer switch is transferring or even if the generator has any output at all.
You can't trust reports from the field. I find most times they contain more false information than correct info. For all you know the starting batteries in the generator could be dead, or it could be out of fuel.
Being that you haven't been there you really don't know if the transfer switch is transferring or even if the generator has any output at all.
You can't trust reports from the field. I find most times they contain more false information than correct info. For all you know the starting batteries in the generator could be dead, or it could be out of fuel.
Utility voltage is 208/3. The owner said the distance if he had to guess is approximately 400 feet. I think this generator and wires were sized by an electrician. Many electricians would take voltage drop into account but there are plenty who wont take it into account. I know if I was designing this 400 foot run, voltage drop would be #1 on my check list.
Joethemechanic
Senior Member
- Location
- Hazleton Pa
- Occupation
- Electro-Mechanical Technician. Industrial machinery
Well if that is a 12 lead machine, keep in mind that 416 or 480 volt connections are most likely possible at the generator.
480 you could use a delta/wye and 416 you could use a wye/wye at the load end.
480 you could use a delta/wye and 416 you could use a wye/wye at the load end.
Ain't that the truth. Just when you assume someone would check that, they don't. Heck, the whole generator could be sitting at the scrap metal place.:jawdrop:
It's good to get ideas before you go, but there is only so much you can do without checking things out for yourself.
Low voltage doesn't sound right unless the elevator at least tries to start. The voltage won't drop until the motor tries to start. If it did happen to be voltage drop, I'm thinking more along the lines of an generator not sized to handle the motor starting current than voltage drop along the wire. Again- just stuff to check for.
I suggest you probably need some type of phase rotation meter to see if the phases are swapped.
I also like the idea of some of the controls not being on the generator. That would explain the no attempt at starting. Most elevators have a 3 phase feed for the motor, and a 120V/15A supply for the elevator cab. You should see a disconnect for each just inside the door of the equipment room. I'm not sure which one provides control power for the control panel.
If its not an obvious fix on the supply end, you might have to have the owner get the elevator maintenance guy involved too.
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