Simple answer: Definitely not.If you have a 3 phase 120/240 center tapped delta high leg service, giving you 208V to neutral on the high leg, is this an acceptable way to feed a single phase 208V load using only a single pole breaker?
If you have a 3 phase 120/240 center tapped delta high leg service, giving you 208V to neutral on the high leg, is this an acceptable way to feed a single phase 208V load using only a single pole breaker?
I'm not sure, as I don't have my NEC available right now, as my D drive isn't in my tower; I'm 'hosting' PJ's D drive while her tower is "on vacation." :roll:So let me ask, Larry, is there a code prohibition against such a branch circuit? If so, can you tell me where it might be found?
But it doesn't have to be with the right size transformer. I don't see why it could not be used in limited capacity but I don't recall ever having seen an application that did it.No, I believe the reason is because that 208V to ground is "unstable" I was told to never use that voltage on a delta transformer.
~Matt
But it doesn't have to be with the right size transformer. I don't see why it could not be used in limited capacity but I don't recall ever having seen an application that did it.
Seems I remember Jim Dungar posting about there not being breakers rated for this or something like that.
Yes, even the ones we use on 208Y/120 volt systems are rated for 240 so that is not an issue. The only issue is a single pole breaker rated at 208 or above that will fit in the panel.Well first if you have a 120 /240 volt system how would one install a 208 volt breaker in the panel in the first place all the panels are rated at 240 volts ? ...
Both smaller windings would share the load, along with the lighting pot winding.Well first if you have a 120 /240 volt system how would one install a 208 volt breaker in the panel in the first place all the panels are rated at 240 volts ?
But let me try explain why its not done in a three phase delta the winding C is larger than A or B winding ampacity wise due to it carrying a larger current load it has the three phase loads and the 120 volt loads to handle .
If one added a high leg load to B phase and C had to carry that excess load its a increase current flow on the neutral which is a magor unbalance on transformer it can burn out not only the center tap but puts a extra load on the smaller windings on B . Its bad news B for bad
Both smaller windings would share the load, along with the lighting pot winding.
Any tranformer will burn up if overloaded enough, even with standard connections. Using the high leg would be fine if you considered the reduced capacity, much the same way you have to take into consideration the single phase loads on a three phase bank.
That said, it is not the best way to get things done.
The windings in a delta connection do not suffer reduced voltage. They see the voltage they are designed to see.with a delta two windings suffer reduced voltage while one is 208v meaning hi leg a wye connected load sees this and there would be a unbalance
If you overload the transformer, it will be a problem. With the properly sized transformer, you could serve a 208 load from the high leg without damaging the transformer or causing significant issue with other loads served by the transformer. But that is the case with any transformer and mixed loads.Well just a tought
A WYE connected winding delivers the same power with less line current than a delta connected system meaning balanced wye .
Line voltage is equal to phase voltage line current is equal to phase current balanced.
with a delta two windings suffer reduced voltage while one is 208v meaning hi leg a wye connected load sees this and there would be a unbalance .
Resulting load burn out! one leg current is lower two legs current is higher balance is a problem on load and transformer .
But iam not a engineer so please help me out thats my way of looking into the future it may work but not effective way to go and thats why ?
Hmm... I consider that rather vague on the matter.I believe using the high leg would be a violation of 110.3(B) as the transformer does not list 208 as one of it's voltages.
If we have a 208V supply (I don't see where it is required to be a nominal 208V supply) and a 208V load, it's a 208V circuit... and with the equipment rated 240V or better, there's no problem here.110.4 Voltages. Throughout this Code, the voltage considered
shall be that at which the circuit operates. The voltage
rating of electrical equipment shall not be less than the
nominal voltage of a circuit to which it is connected.