What could cause intermittent voltage drops below 110v every couple of days?

[cityview]

I had another thread where I was wondering what was trapping people in my car wash. I discovered it has nothing to do with the doors and appears to be intermittent voltage drops.

I had technicians out three times and the voltage to the distribution blocks and controls are 119v. However, every couple of days, the voltage drops to multiple vdcs below 110, freezing the vdcs and locking the doors down until I reset.

I can't figure out how to reproduce the voltage drop. Anyone have any idea what could cause a voltage drop so I can test some scenarios? No new equipment besides repair and replacement of the the last two years.

The only thing I can think of is if the compressors, pumps, and drying fans all got at once? Hard to replicate... Could a short on some equipment somewhere call that could cause a voltage drop?

 

[GoBuckeyes]

Things like this are hard to diagnose when you can’t reproduce it. We had an undervoltage issue we suffered through for a month or two before we could figure it out. In our case it actually was a transformer issue on the pole and the power company came out and fixed it.

Are the door controllers the only thing at your wash that you’ve noticed a power issue with? Do you have cameras at your wash? You could buy a voltage monitor relay and tie it into your alarm system and/or wire it to a panel light so that you could go back and review your cameras when it triggers and see if anything else was running....like multiple bays or compressors etc.

 

[Eric H]

Agree with Gobuckeyes that it may be a transformer issue. I’d call the utility and ask them to test.
It is possible that only 1 leg is affected. Is it possible to pull the breaker and move it up 1 slot so the power is coming from a different leg?

 

[JGinther]

What does the voltage drop to while the door is operating? I doubt it is utility company related unless both drives fault out at the same time... If that happens, and both doors are pulling from their OWN 120V individual breaker, then it WOULD be very likely that there is a fault on the power grid that your drives are catching and going into error mode. Most often, you wouldn't have a low voltage issue as much as you would have a input phase loss detected error. I have had the experience of having 8 VFD drives fault out at once every time the city power utility would have a fault in their distribution. Once, they were replacing a substation switch and testing back and forth between stations. Every time they would switch, the drives would detect as a phase loss, and fault out. I had to change all the factory settings on all the drives on Belanger Vectors to be able to ignore and "ride through" the fault in order to stay open. It wasn't until 2 weeks later after inquiring with the utility engineer that they admitted to the grid switching and testing. Still to this day, I can tell before the utility company can that they have a fault, as the auto drives send an error, which the autocashier detects and text messages me that the equipment has faulted. Drives can be very finicky unless programmed to be less so.

 

[Ghetto Wash]

I’d call the utility and ask them to test.

That's where I'd start as well.

 

[sparkey]

Have you verified you are actually getting a voltage drop on the line with a meter or are you strictly going by a VFD error? Incorrect parameters in the drive can give you errors as well.

 

[cityview]

Things like this are hard to diagnose when you can’t reproduce it. We had an undervoltage issue we suffered through for a month or two before we could figure it out. In our case it actually was a transformer issue on the pole and the power company came out and fixed it.

Are the door controllers the only thing at your wash that you’ve noticed a power issue with? Do you have cameras at your wash? You could buy a voltage monitor relay and tie it into your alarm system and/or wire it to a panel light so that you could go back and review your cameras when it triggers and see if anything else was running....like multiple bays or compressors etc.

Im going to call them tomorrow. I get no voltage drop when testing... It appears to also correlate with the middle of the night.... Ie I can have a super busy day with all bays in full swing and nothing happens, but I get a phone call at 2 am that someone got stuck in the bay... Its never failed on when im on site, and I don't get a noticeable voltage drop even when running the motors.

 

[Main Street Carwash]

I had similar problems and it turned out to be a poor connection of one of the phases about a block away on a utility pole. Corroded crimp, aging utility infrastructure.