Trouble finding straight 240v breaker vs 120/240 breaker

[kwired]

I looked at one job, brand new store (takeover existing building) someone put in an entire 208 volt switchgear on 480 volts! Gear had to be less than 10 years old. How they got it past inspections and energized I don’t know, unless the inspector didn’t know it was going to be 480. Had to give a quote on ripping it out and replacing.

I was going to say maybe he didn't know the actual voltage, but then there likely was step down transformer(s) to get 120 volts somewhere and that should have at least been a clue.

 

[hillbilly1]

I was going to say maybe he didn't know the actual voltage, but then there likely was step down transformer(s) to get 120 volts somewhere and that should have at least been a clue.

What was real strange, the original service was an old 208/120 three phase, this service was ADDED along with another poco transformer. So it had to have an inspection. Big city too.

 

[kwired]

What was real strange, the original service was an old 208/120 three phase, this service was ADDED along with another poco transformer. So it had to have an inspection. Big city too.

I could see that happening easier if both are service supplied than if there is SDS's for the 208/120. Code inspectors don't generally take voltage readings so unless there is more obvious reason to suspect one of those is 480 volt system seeing 240 volt panel/breakers they might assume it is 240 or 208 volt system.

 

[tortuga]

Interesting discussion, the OP seems to have left the building, but send me a PM if you need a plug on Siemens, we stock them as more and more of the 3 phase work we do is 240 delta.

I think Winnie nailed it with this:

If you have a 120/240V system, for the breaker to see a 240V fault, the fault is very likely flowing in series through _two_ breaker poles.

Just like the old plug fuses were only rated 125 volts, early breakers were probably only tested to 125V to ground faults and the listing standard never changed.

 

[Birken Vogt]

I just looked in the Eaton catalog for a single pole breaker that could work on the 208 high leg out of curiosity. Listed as a BR120H. Said it was for high mag but still rated at 120/240 volts. So it seems it might be hard to find single pole breakers for using the high leg for lighting. Just a crazy idea of mine.

 

[tortuga]

I just looked in the Eaton catalog for a single pole breaker that could work on the 208 high leg out of curiosity. Listed as a BR120H. Said it was for high mag but still rated at 120/240 volts. So it seems it might be hard to find single pole breakers for using the high leg for lighting. Just a crazy idea of mine.I

For lighting on a delta I just use a 3 pole (or a 2 pole) breaker and connect the lights L-L. I just balanced the single phase load among the phases. That helps move some of the lighting load to the b phase.

 

[kwired]

I just looked in the Eaton catalog for a single pole breaker that could work on the 208 high leg out of curiosity. Listed as a BR120H. Said it was for high mag but still rated at 120/240 volts. So it seems it might be hard to find single pole breakers for using the high leg for lighting. Just a crazy idea of mine.

That breaker is intended for cases of high magnetic inrush currents, like motors and such. Has higher magnetic trip rating than the standard breakers have. More common to see them used with Square D QO and Homeline series though as their standard 15 and 20 amp single pole breakers have lower magnetic trip setting than many other manufacturers typically have.

 

[norcal]

Only breaker that would "work" for a 208V high leg is a 277V single pole breaker, but from what I understand the high leg is not intended to be used on it's own.

 

[kwired]

Only breaker that would "work" for a 208V high leg is a 277V single pole breaker, but from what I understand the high leg is not intended to be used on it's own.

It complicates how the transformer gets loaded.

Full delta the return path has two possible directions it can flow.

Open delta it can only flow one way.

Either case it is additional current on source windings that you don't normally account for with conventional load connections

 

[tortuga]

It complicates how the transformer gets loaded.

Full delta the return path has two possible directions it can flow.

Open delta it can only flow one way.

Either case it is additional current on source windings that you don't normally account for with conventional load connections

Right and using that 208 to neutral does not help with the common issue of balancing single phase load on a hi-leg delta system where the A-C phases have the center tap. Your better off using A-B and B-C windings for 240 loads such as a water heater. I think the only thing wrong with these systems is they are uncommon and people don't know the tricks to optimize them, like setting the panelboard bottom section only with A-C phase stabs so you dont end up with unused spots that give people ideas like oh let me put a 277V breaker in there.

 

[jim dungar]

Only breaker that would "work" for a 208V high leg is a 277V single pole breaker, but from what I understand the high leg is not intended to be used on it's own.

Its not that it is not intended as much as it is not advised.
Any loading on the 208V 'high leg to neutral' also flows through the "A to neutral' windings of the transformer, thereby reducing the amount of traditional 120V loading you can support.

 

[tortuga]

Also worth mentioning is its important to know if you have a "hi-leg open delta"
If the OP puts his 240V single phase waterheater load across B-C legs
since there is no B-C winding the effect would be similar to the 208-Neutral.

 

[electrofelon]

Also worth mentioning is its important to know if you have a "hi-leg open delta"
If the OP puts his 240V single phase waterheater load across B-C legs
since there is no B-C winding the effect would be similar to the 208-Neutral.

I don't really think that is an issue, I put 240 single phase loads across the "open " legs all the time.

 

[LarryFine]

I don't really think that is an issue, I put 240 single phase loads across the "open " legs all the time.

Same here. I'll try to make it the smallest of the L-L loads if I can.

 

[tortuga]

Any loading on the B-C also flows through both windings (B-A-C) of the transformer, sill reducing the amount of traditional 120V loading you can support.

 

[electrofelon]

Same here. I'll try to make it the smallest of the L-L loads if I can.

How do you even know which legs are the open ones?

 

[LarryFine]

How do you even know which legs are the open ones?

Voltage measurements, sometimes, or visually trace the line from the open end if possible.

 

[tortuga]

How do you even know which legs are the open ones?

If the phase tape is correct it would be Orange - Blue.
This got me thinking (and I probably should make a different topic for it) how does one calculate the phase (winding) current for the load across the open jaw?
And to complicate things the hi-leg pot is usually about 1/3 the size of the lighting pot so figure a 25 and a 75kva.
If say the OP put the water heater across the B-C and say its a standard 4500W 50 gallon water heater ?

 

[jim dungar]

If the phase tape is correct it would be Orange - Blue.
This got me thinking (and I probably should make a different topic for it) how does one calculate the phase (winding) current for the load across the open jaw?
And to complicate things the hi-leg pot is usually about 1/3 the size of the lighting pot so figure a 25 and a 75kva.
If say the OP put the water heater across the B-C and say its a standard 4500W 50 gallon water heater ?

There is no real derating necessary for using the 'open' phase.

Typical formula for sizing the unequal transformers are:
Power pot = .58T
Lighting pot = .58T + S

Where T is the total three phase load and S is the total single phase load.
Note how the transformer sizing takes into account the open delta versus closed delta derate.

 

[electrofelon]

If the phase tape is correct it would be Orange - Blue.
This got me thinking (and I probably should make a different topic for it) how does one calculate the phase (winding) current for the load across the open jaw?
And to complicate things the hi-leg pot is usually about 1/3 the size of the lighting pot so figure a 25 and a 75kva.
If say the OP put the water heater across the B-C and say its a standard 4500W 50 gallon water heater ?

I think it is unlikely one can count on the utility coordinating the color coding at the service point in any particular way.