A local auto body shop has asked me to run a circuit for a spot welder that has been causing disturbances on the electrical system when it is used. The welder is rated 60A, 208V, 3 phase. It is supplied from a 100A subpanel. Every time the welder is used it causes the lights to flicker and the computers to falter. They now want to feed the welder from the 200A main panel instead of the subpanel, believing that this will alleviate the situation. I'm not so sure, and I'd hate to bill them for a new circuit and then discover that the problem still exists. Any ideas on what is causing this problem, and how best to fix it???
welder causing problems
- Thread starter JES2727
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mcclary's electrical
Senior Member
- Location
- VA
If the subpanel is very heavily loaded, and the lights and computers come off the subpanel, it might actually fix the problem. If the subpanel is lightly loaded, then there is likely another problem, and feeding from the larger panel is not going to help. So,,,,how loaded is the feeder to subpanel?
cadpoint
Senior Member
- Location
- Durham, NC
Sounds like several things, ask the owner if any of his technical people ever addressed any issues in the building, I’d start right there. Ask them in person so you can see their response!
The first thing you need to do is size the welder and make sure eveything right there, you might find out that fuses might be better, than a breaker.
This might be a rental place so anything I say or you might try might not be proper, cause the owner(renter) has to get a hold of the owner, if you determine any of the following.
I’d go to the owner (renter) and express your exact that you stated here, sounds like the building needs to be completely checked, or state that their existing service might be at its limit and thus to small; and that the upsize of this one piece is not the cure, light brown’n is usually a stain of existing service equipment or the dreaded loose neutral.
You can offer to check the Neutral through to the meter(depending on your POCO) but that you’ll need to express that they can pay you to open some service/circuits and check some things or not. As I saw here this weekend here someone shot a infred on the service riser and noted heat...
Tell them you need to add up all his numbers by Code anyways, “your requirement” to address a possible larger main service requirement. Do total load calculations (or summary) of all the equipment they have period, rent a recorder for a week, or ask for 1 year of electrical bills.
I’d walk in and quickly make observations of all equipment that’s running once at 10AM and at 2PM. I’d also do some AMP reading on the existing main service at those times as well. Or ask when is the crew all there and working, doing there thing, granted this is CA.
You can suggest that the owner purchase some battery backup UPS, so they will Beep instead of Blink! Which they should have any ways, JMO…
The first thing you need to do is size the welder and make sure eveything right there, you might find out that fuses might be better, than a breaker.
This might be a rental place so anything I say or you might try might not be proper, cause the owner(renter) has to get a hold of the owner, if you determine any of the following.
I’d go to the owner (renter) and express your exact that you stated here, sounds like the building needs to be completely checked, or state that their existing service might be at its limit and thus to small; and that the upsize of this one piece is not the cure, light brown’n is usually a stain of existing service equipment or the dreaded loose neutral.
You can offer to check the Neutral through to the meter(depending on your POCO) but that you’ll need to express that they can pay you to open some service/circuits and check some things or not. As I saw here this weekend here someone shot a infred on the service riser and noted heat...
Tell them you need to add up all his numbers by Code anyways, “your requirement” to address a possible larger main service requirement. Do total load calculations (or summary) of all the equipment they have period, rent a recorder for a week, or ask for 1 year of electrical bills.
I’d walk in and quickly make observations of all equipment that’s running once at 10AM and at 2PM. I’d also do some AMP reading on the existing main service at those times as well. Or ask when is the crew all there and working, doing there thing, granted this is CA.
You can suggest that the owner purchase some battery backup UPS, so they will Beep instead of Blink! Which they should have any ways, JMO…
The subpanel is pretty heavily loaded. It's in the shop, and it serves most of the shop equipment. At any one time they may be running welders, grinders, power tools, compressors, etc. The computers, however, are NOT served by the subpanel. The welder that is causing the problem is supplied by a 60A breaker, and a long cord. The cord is #6, so it's sized properly though it's length may introduce some voltage drop.
dbuckley
Senior Member
- Location
- Canterbury, New Zealand
When you connect that welder to the main panel, its supply impedence will likely be lower the the subpanel and long cord, so chances are the voltage dips will be greater once you've done the upgrade.
Putting the IT gear on a UPS sounds like an option more likely to deliver results, though it'll need to be a decent, on-line UPS, not a $9.99 ferromagnetic piece of junk. You can sell the customer on the value of the IT gear being UPS protected too
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