208v vs. 240v

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funseebee

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If the main switchboard rating is 120/240v, 3-ph, 4-wire, will it matter if a panelboard was ordered at 120/208, 3-ph, 4-wire? Please help. Thanks. :-? :-?
 
Wouldn't a panelboard that is rated for the higher voltage also be rated for a lower voltage?
 
infinity said:
Wouldn't a panelboard that is rated for the higher voltage also be rated for a lower voltage?
Click to expand...
sounds ok to me, but why would you have a panel 3 phase rated at 120/240? That would mean the B phase would be the high leg (208 volts to ground) right?
 
infinity said:
Wouldn't a panelboard that is rated for the higher voltage also be rated for a lower voltage?
Click to expand...
With 208, ALL phase conductors have 120 to "neutral" the center of the WYE. With 240, you will have 2 phase conductors to a centertap that are 120V, the 3rd will be the high leg. I've never thought how that 3 phase panel would be wired, but balancing the 120 load would seem to be impossible.

NOTE ... this is an engineer talking, and I may be even more stupid than I may seem.
 
GeorgeB said:
With 208, ALL phase conductors have 120 to "neutral" the center of the WYE. With 240, you will have 2 phase conductors to a centertap that are 120V, the 3rd will be the high leg. I've never thought how that 3 phase panel would be wired, but balancing the 120 load would seem to be impossible.

NOTE ... this is an engineer talking, and I may be even more stupid than I may seem.
Click to expand...
the panel gets wired the same. it's just that from the B phase to ground is 208volts to ground so you don't want to put any circuits that are suppossed to be 120 volts on the B leg buss in the panel.
 
steelersman said:
the panel gets wired the same. it's just that from the B phase to ground is 208volts to ground so you don't want to put any circuits that are suppossed to be 120 volts on the B leg buss in the panel.
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I wish I had my camera that day I saw exactly that

A - in .......... A - in
B - blank ...... B - blank
C - in........... C - in
A - in........... A - in
B - blank....... B - blank
C - in........... C - in
.
.
.
 
cadpoint said:
I wish I had my camera that day I saw exactly that

A - in .......... A - in
B - blank ...... B - blank
C - in........... C - in
A - in........... A - in
B - blank....... B - blank
C - in........... C - in
.
.
.
Click to expand...
What do you mean? What did you see?
 
GeorgeB said:
With 208, ALL phase conductors have 120 to "neutral" the center of the WYE. With 240, you will have 2 phase conductors to a centertap that are 120V, the 3rd will be the high leg. I've never thought how that 3 phase panel would be wired, but balancing the 120 load would seem to be impossible.

NOTE ... this is an engineer talking, and I may be even more stupid than I may seem.
Click to expand...

You only have to "balance" the center tapped transformer
 
steelersman said:
What do you mean? What did you see?
Click to expand...

A 120/208, 3-ph, 5-wire panel

Originally Posted by cadpoint
I wish I had my camera that day I saw exactly that

A - in .......... A - in
B - blank ...... B - blank
C - in........... C - in
A - in........... A - in
B - blank....... B - blank
C - in........... C - in
.
.
.
Click to expand...


in = a breaker
blank= no breaker
All 120 volt loads... on a 120/208 panel 3 Phase 5 wire.
 
Isn't that the infamous delta connection you are describing in which there are very dangerous wires you do not want to disconnect unless you are very aware of what you are doing?

I would say that a panel that says it is approved for 120/208 V is not rated for 120/240 V.
A 120/240V panel MAY be appoved for 120/208 V depending on the connection styles.
Kinda like a 208V stove element for an appartment stove is not safe in a 240V stove but a 240V stove element is acceptable in a 208V environment it just won't heat up quite as quickly or quite as hot.
 
cadpoint said:
A 120/208, 3-ph, 5-wire panel




in = a breaker
blank= no breaker
All 120 volt loads... on a 120/208 panel 3 Phase 5 wire.
Click to expand...
I believe the proper name for it is a 120/240 3 phase center tapped delta. because the only way you get 208 is from B to ground, not phase to phase. So it is called a 120/240 because you get 240 phase to phase and only 208 from B to ground.
 
alfiesauce said:
Isn't that the infamous delta connection you are describing in which there are very dangerous wires you do not want to disconnect unless you are very aware of what you are doing?

I would say that a panel that says it is approved for 120/208 V is not rated for 120/240 V.
A 120/240V panel MAY be appoved for 120/208 V depending on the connection styles.
Kinda like a 208V stove element for an appartment stove is not safe in a 240V stove but a 240V stove element is acceptable in a 208V environment it just won't heat up quite as quickly or quite as hot.
Click to expand...
I beleive that there is no danger in connecting a 208 stove lelment to 240volts.
 
Many apartment buildings have 208 volt services and of course most single family homes have 240 services. Because of that as far as I know, all electric stoves and dryers are dual rated 208 or 240.

Like these specs from GE range

KW Rating at 208V: 8.3

KW Rating at 240V: 11.0
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I think the only equipment I have seen rated 208 instead of 240 would be metering and distribution equipment - but in terms of panel-boards there is very little to differ - 3-phase is 3-phase reguardless of flavor. With metering equipment it really matters as the jaws for the meter are different.
 
cadpoint said:
A 120/208, 3-ph, 5-wire panel




in = a breaker
blank= no breaker
All 120 volt loads... on a 120/208 panel 3 Phase 5 wire.
Click to expand...

Guess the EC wasn't too bright. :rolleyes:
 
infinity said:
Guess the EC wasn't too bright. :rolleyes:
Click to expand...

Originally Posted by cadpoint
A 120/208, 3-ph, 5-wire panel




in = a breaker
blank= no breaker
All 120 volt loads... on a 120/208 panel 3 Phase 5 wire.

Well it depends on how you look at it. Maybe the 208/120 was all he had to work with. He had no 208 loads. And he was bright enough not to land any 120v circ. on B phase.
 
steelersman said:
I don't understand why you would say that?
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Well, if you skipped every B phase than one would think that you thought the panel was fed from a 4 wire Delta system when is wasn't, it was from a 208Y/120 volt system. The electrician should know the type of system he's working on, which was the point I was trying to make.

If I'm reading this wrong please fell free to correct me. I'm not trying to slam anyone just pointing out that someone has seemingly made a mistake. My original post did contain this: :rolleyes: indicating that my response was sarcastic.
 
infinity said:
Well, if you skipped every B phase than one would think that you thought the panel was fed from a 4 wire Delta system when is wasn't, it was from a 208Y/120 volt system. The electrician should know the type of system he's working on, which was the point I was trying to make.

If I'm reading this wrong please fell free to correct me. I'm not trying to slam anyone just pointing out that someone has seemingly made a mistake. My original post did contain this: :rolleyes: indicating that my response was sarcastic.
Click to expand...
I see now, I didn't even notice that it said 120/208, for some reason I thought it said 120/240 and was assuming it was a delta high leg. :)
 
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