I recently started working as a maintenance electrician and gave up on the construction field. The whole factory is an electrical mess. The issue I have came across is we have a 480V switch gear that has been changed to 208V. The fuses are rated at 600V instead of 250V. I've done several searches on line and tried to find something in the code book , no luck either way. I've thought about this in a light bulb senerio , like 6V bulb in a 12V system or the other way around 12V bulb in a 6V system. Maybe this senerio is not apples to apples. What's your ideas.
How was it changed? Im going to assume they have 480 3 phase going to a step down with a wye secondary on the transformer to get the 120 line to neutral to run your 208 switch gear? I built this cabinet last night doing exactly that. This is taking 480 in, I tapped 2 legs and ran to the H1 and H4 on transformer and grounded x2 out to get my 208 output. But thats a single phase output. Is your 208 3 phase? Need more info.
Forgive my stupid question, I am not an engineer or an electrician, but I always thought all 480 volt inputs were 3 phase. At least going into a commercial electrical system.
Steve
------------------ Technology is great when it works, and one big pain in the ass when it doesn't
Forgive my stupid question, I am not an engineer or an electrician, but I always thought all 480 volt inputs were 3 phase. At least going into a commercial electrical system.
Steve
They are. Without any info on how its stepped down im assuming he has a transformer thats stepping it down to a single phase output. If that IS the case then the 600v fuses are fine as long as its on the high side of the transformer. I like to run the control transformers on 1 amp mini fuses on the 2 hot legs coming in but I know people who dont because the main fuse is already there (sounds like the case here)
It originally had a 480V 3ph coming in from the pole. At some point the transformer was changed to 208V 3ph 4w to first gear. It feeds a second gear that's rated 480V 3ph 3 w. Some idiot decided to use a ground rod to create a neutral. That has been changed now. Also many ungrounded circuits, as many as 7 circuits sharing one neutral. Just wondering about the fuse issue for now.
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85 GT 3.4 14.9 @ 90 1.9 60' Old TH125/3.06 Unknown New 4T60/3.42
It originally had a 480V 3ph coming in from the pole. At some point the transformer was changed to 208V 3ph 4w to first gear. It feeds a second gear that's rated 480V 3ph 3 w. Some idiot decided to use a ground rod to create a neutral. That has been changed now. Also many ungrounded circuits, as many as 7 circuits sharing one neutral. Just wondering about the fuse issue for now.
600 volt is fine. The clearing times are the same same and the 600V rating is for the re-strike and insulation ratings. NEC says you can run a 600V gear on a 280V system, ill try to find the quotation. In a nut shell, you can run under rated voltage for fuses but never over.
600 volt is fine. The clearing times are the same same and the 600V rating is for the re-strike and insulation ratings. NEC says you can run a 600V gear on a 280V system, ill try to find the quotation. In a nut shell, you can run under rated voltage for fuses but never over.
This is right. So you don't need to worry about the 600VAC fuses in a 208VAC system.
Originally posted by 87antuzzi: 600 volt is fine. The clearing times are the same same and the 600V rating is for the re-strike and insulation ratings. NEC says you can run a 600V gear on a 280V system, ill try to find the quotation. In a nut shell, you can run under rated voltage for fuses but never over.
Yes. "Over volt" fuse is OK.
You'll find this in many cases... Common to see low volt circuits protected with x Amp 200+ volts fuse.
Simple means Volts rating is stops current up to X volts.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Are you a licensed electrician? If not, ask the licensed electrician you're working under.
YUP !!!-------AND, get whatever he says IN WRITING. Then keep it forever.
I've fought THAT war as a tech manager a FEW times right up to battling the CEO of a comany. They dont like to take "no" for an answer but here at least ANY electrical wrk on a commercial building requires a licenced tradesman (lol, and those cost money )
As soon as ANYTHING ever goes wrong, the lawyers, investigators and everybody else will be hunting for both you (the tech who did the work) and your boss/ manager---and the corporate executive who forced the work will stand there saying "I never told you to do that" and you are hung-OUT-to dry.....if not just hung.
These days, ANYTHING in a tech field is a huge game of CYA.
600 volt is fine. The clearing times are the same same and the 600V rating is for the re-strike and insulation ratings. NEC says you can run a 600V gear on a 280V system, ill try to find the quotation. In a nut shell, you can run under rated voltage for fuses but never over.
Yeah when I read the O.P's original post this is what I was going to reply.
