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Old 02-15-2012, 11:28 PM   #21
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Quote:
Originally Posted by I_get_shocked
bringing in another circuit adds the likelyhood of failure to disconnect and shock
There's already over 8 ccts in the control box, but you're right.
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Old 02-15-2012, 11:29 PM   #22
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Originally Posted by Aegis View Post
There's already over 8 ccts in the control box, but you're right.


I used to work in a place like that. They'd sometimes ask me, "what all do you need to shut down to work on this". My answer was often, "the plant".
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Old 02-16-2012, 01:00 AM   #23
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Just replace the transformer, the more sources of power you have in a machine, the more of a PITA it can be to work on, especially with everybody getting more strict with energized work.
Like everybody else said, fuse the primary and secondary. You don't have to fuse the secondary by NEC on a transformer that small but I can't think of a reason in the world not to.

And like Marc said, the more you split up the secondary loads and fuse them separately the easier it is to find a fault in the future.
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Old 02-17-2012, 02:36 PM   #24
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Thanks, I'm going to replace the transformer, but because it's only 500VA I have to protect it with 2 Amp Fuses?
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Old 02-17-2012, 04:31 PM   #25
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... So naturally they have a 2p 40A breaker going into this control box and is feeding this 500VA transformer! lol
There's your problem right there. Virtually no primary protection. There was a time when you didn't need to have it, so they may have been grandfathered in, but now this would get red tagged.

Read this, there is a chart on page 3, makes it easy. You need 3-2/10A primary fuses, dual element (time delay) for a 500VA CPT.

But remember, this is why it CAUGHT ON FIRE, not what caused the initial problem. The fire was just because there was nothing that was going to take it off-line before the flames started. Check out everything else in the circuit very carefully to see what cause the overload of that transformer in the first place.
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Old 02-17-2012, 06:49 PM   #26
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Quote:
Originally Posted by JRaef

There's your problem right there. Virtually no primary protection. There was a time when you didn't need to have it, so they may have been grandfathered in, but now this would get red tagged.

Read this, there is a chart on page 3, makes it easy. You need 3-2/10A primary fuses, dual element (time delay) for a 500VA CPT.

But remember, this is why it CAUGHT ON FIRE, not what caused the initial problem. The fire was just because there was nothing that was going to take it off-line before the flames started. Check out everything else in the circuit very carefully to see what cause the overload of that transformer in the first place.
Thanks JRaef! I'm looking at pg 3 and I see 500VA @ 208 volts it says 4A Fuses, where did you see 10A?
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Old 02-17-2012, 07:13 PM   #27
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Thanks JRaef! I'm looking at pg 3 and I see 500VA @ 208 volts it says 4A Fuses, where did you see 10A?
Not 10A, 3-2/10A (3.2A) and I was looking at 240V, I thought that was what you had.

If you have 208V and you had a 240-120V transformer, you would have had only 104V on the output, that is likely what contributed to the demise of that transformer. Every time a coil pulled in under low voltage conditions like that it would have caused an additional voltage drop, your primary current would have shot up.

PS:
Derrr... it was right there in the same post I had quoted before:

Quote:
Whoever installed everything didn't bring a neutral from the transformer to the panel. So there's only 208 in the tub. They need 120 in the control box.
Sorry, missed it.
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Last edited by JRaef; 02-17-2012 at 07:17 PM.
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Old 02-17-2012, 10:34 PM   #28
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here a little software for fusiong sizes on transformer and motors
http://factorymation.info/fuses/saf.exe
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