3 phase load wiring

I have a 480v 3 phase heating element.. it only has 2 wires and a ground..?

It's just two legs and a ground... not much more it could be.

It's single phase.

plchris said:

It's single phase.

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You are right!

I just assumed they were 3 phase since the faceplate said 480v.

Umm. I’m not to familiar with 480v single phase? The control panel service is 480v 3 phase

HereForBeer said:

You are right!

I just assumed they were 3 phase since the faceplate said 480v.

Umm. I’m not to familiar with 480v single phase? The control panel service is 480v 3 phase

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Call an electrician. Maybe offer him a beer.

Any 2 legs will be 480 single phase. You have 3 phases to choose from.

keithkyll said:

Any 2 legs will be 480 single phase. You have 3 phases to choose from.

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Any leg to ground 277v and from leg to leg 480v!

damica1 said:

Any leg to ground 277v and from leg to leg 480v!

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Technically true, but to be clear, you cannot use the ground as a current carrying conductor like that, you would have to have a separate neutral (even though it is grounded at the source) AND a ground conductor. So this is definitely a single phase 480V line-to-line circuit for those heaters, which means that if you have 2 or 3 heater elements, the only way to connect them would be in series. That may not get you the desired effect here...

jraef said:

Technically true, but to be clear, you cannot use the ground as a current carrying conductor like that, you would have to have a separate neutral (even though it is grounded at the source) AND a ground conductor. So this is definitely a single phase 480V line-to-line circuit for those heaters, which means that if you have 2 or 3 heater elements, the only way to connect them would be in series. That may not get you the desired effect here...

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Yeah, the poster should have said "any leg to neutral".

I ran into a mess last Christmas where the equipment manufacturer modified and old 110 volt design to 220 volts. They still used the same color code for the second hot leg (in other words, they applied 110 volts to what was marked as the neutral, the white wire).

In addition to that, they wanted the secondary of the step down transformer left ungrounded. They couldn't wrap their head around how a wire (the ground) would be necessary since it only went to ground. Good lord...

We went around and around with them telling me that this was an approved design (which it most likely was for 110 volts), and that they had reviewed the design and found no problems. I smacked them upside the head with a few sections of the NEC, and they saw things my way. They sent out a tech to re-wire it properly.

And in the other side of the plant, on the exact same equipment, the electricians got confused (largely based on the bad prints that they got, but they should have known better) and wired that heater from hot to ground. Nothing like using your conduit (and flex) as your return path. In an explosion-proof environment no less...

damica1 said:

Any leg to ground 277v and from leg to leg 480v!

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Not always true. It is always true for a 480 Y connection, but not a 480V Delta connection. I worked at a plant that had a 480V ungrounded delta, it always threw maintenance guys for a loop when they didn't see 277V to ground.

So if the service is 480v Y, any phase, neutral, and ground?

Or

Any 2 phases, and a neatural ?

Any two phases and ground.

KB1GNI said:

Any two phases and ground.

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Huh?
Read what I already posted. That would be illegal. Plus, depending on the context of the question, probably wrong.

I'm not suggesting that ground be used as a current carrying conductor. That would be illegal, immoral, and unsafe.

To power that heater the original poster is holding in his hand, each black line goes to one phase of a 480Y circuit and the green and yellow goes to chassis ground. What's wrong with that?

KB1GNI said:

I'm not suggesting that ground be used as a current carrying conductor. That would be illegal, immoral, and unsafe.

To power that heater the original poster is holding in his hand, each black line goes to one phase of a 480Y circuit and the green and yellow goes to chassis ground. What's wrong with that?

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Ah, context is everything... sorry, I misinterpreted.

And to continue with my litany of errors, I also blundered when I said earlier that the only possible connection that will work is to have all three in series from phase to phase, which may not put out the desired heat. Now that I think about it more, all three in parallel from phase to phase would be possible, IF the heater elements themselves are actually rated for 480V line to line. In a lot of 3 phase 480V heaters, you will find that the elements are actually rated for 277V and intended to be connected in Wye, because true 480V heater elements are harder/more expensive to make. So it's going to boil down to the exact details of those heater elements.

Ground is only for safety grounding.