Delta panel quick calc

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Toros

Senior Member
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Tujunga, CA
Hi
i am trying to find ways for a quick calc in my head on 120/240v, 4w, Delta, red leg panel board , without going through tailored calcis.

The loads are;
3ph load: elevator , 60 FLA
1ph, 2pole load: garage exhaust fan, 20 FLA and
line to mitral loads: light- plugs.... 25A
lCL @ 25%: 15A
LML @ 25%:15A
 
Are you sure the elevator has a load of 60 per phase. It looks high. Assuming its correct the load
would be 60 amps on each phase.(including wild leg)
The remander of the single phase load would be balanced on the other two
phases, not wild leg.
 
bob said:
Are you sure the elevator has a load of 60 per phase. It looks high. Assuming its correct the load
would be 60 amps on each phase.(including wild leg)
The remander of the single phase load would be balanced on the other two
phases, not wild leg.
Click to expand...
The two-pole load can be across any two lines, either of which can be the wild leg... which would actually help balance the system if it is a full delta. If open delta, may be better on A-C.
 
Smart $ said:
The two-pole load can be across any two lines, either of which can be the wild leg... which would actually help balance the system if it is a full delta. If open delta, may be better on A-C.
Click to expand...
For an open delta, depending on the size of the stinger pot, it may be OK to put it on BC (if AB is the open leg). But if that pot is only large enough for the three phase load, then yes putting it on AC is the proper choice.
 
GoldDigger said:
For an open delta, depending on the size of the stinger pot, it may be OK to put it on BC (if AB is the open leg). But if that pot is only large enough for the three phase load, then yes putting it on AC is the proper choice.
Click to expand...


Absoulutely correct, and knowing more about the whole situation helps one understand this better. Out here in rural areas open deltas can be fairly common to reduce costs of primary side infrastructure. I can think of several places where a facility has single phase primary running both ways from the facility but the line to the left is a different phase then the line to the right - allowing them to derive a three phase system via open delta for that facility, but with simpler and less costly line construction methods compared to bringing all three primary phases plus neutral to the location.

The load may still be there that a full delta or even a wye system would be preferred if all three primary phases were present, but they choose to save some costs in line construction and instead increase the transformer sizes over what would be there if a full delta so they can handle the load.
 
Smart $ said:
The two-pole load can be across any two lines, either of which can be the wild leg... which would actually help balance the system if it is a full delta. If open delta, may be better on A-C.
Click to expand...


Just be careful and make sure your 2pole breaker is rated 240v if you are using the high leg.
(not 120/240 slash rated)
 
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