Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
Feeder Sizing
- Thread starter Alwayslearningelec
- Start date
- Status
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Do you have some kind of point that you wish to make? Seems to me they are asking for three conductors per phase.
It looks like they called for (2) neutrals... So I think they didn't note for the parallel sets properly.
Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
But wouldn't you need (3) sets of #600?
yes
- Location
- Illinois
- Occupation
- retired electrician
Yes, it calls for three sets of 600 kcmil so you have 1260 amps of conductor and is code compliant.
The grounding conductor shown as 3/0 is really a supply side bonding jumper and is too small. 3/0 is 167kcmil, but this circuit requires the supply side bonding jumper to have an area 12.5% of the ungrounded conductors. That would require the use of a 250 kcmil supply side bonding jumper. It appears that the designer used Table 250.122, but that only applies on the load side of an OCPD. This is on the secondary of a transformer and Table 250.102(C) applies.
There are additional problems unless all of the conductors are in a common raceway such as a wireway or cable tray.
If there are 3 conduits, each conduit would require three 600 kcmil ungrounded conductors, one 400 kcmil grounded (neutral) conductor, and one 1/0 supply side bonding jumper.
The grounding conductor shown as 3/0 is really a supply side bonding jumper and is too small. 3/0 is 167kcmil, but this circuit requires the supply side bonding jumper to have an area 12.5% of the ungrounded conductors. That would require the use of a 250 kcmil supply side bonding jumper. It appears that the designer used Table 250.122, but that only applies on the load side of an OCPD. This is on the secondary of a transformer and Table 250.102(C) applies.
There are additional problems unless all of the conductors are in a common raceway such as a wireway or cable tray.
If there are 3 conduits, each conduit would require three 600 kcmil ungrounded conductors, one 400 kcmil grounded (neutral) conductor, and one 1/0 supply side bonding jumper.
Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
It doesn't call for (3) sets. It calls for one set w/ (3) hots for each phase.
- Location
- Illinois
- Occupation
- retired electrician
Three sets = three hots per phase. Three hots per phase has an ampacity of 1260 amps without any ampacity adjustment or correction.
I read it as 3#600MCM+2#600MCM Neutral.... To me... that means (3) #600mcm, one for each phase. Typically when we write plans... we say "3 sets: (4) 600MCM". I'm with the OP that they didn't write the conductor requirements properly. The OP should go back to designers and get the correction.
- Location
- Illinois
- Occupation
- retired electrician
Most drawings I worked with would look like this where they wanted 3 sets...it was rare to spell out "sets" on the drawings I worked with.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
It could have been done better but I think it is pretty clear they mean (3) 600 MCM per phase.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I see one set of conductors not three.
- Location
- Connecticut
- Occupation
- Engineer
Me too. They may have intended 3 sets, but that's not what they called for.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Yes a simple (3)- in front of the 600 would make it correct. The " GND" is a SSBJ and could be smaller a #1/0 is sufficient.
3 per phase... by why do they only use 2 neutrals?
The transformer is a K-13 transformer. It looks like they are requiring a 200% neutral. Which would mean that they aren't requiring multiple sets for the feeder. It looks like there are some issues with that feeder that an RFI would clarify.
- Location
- Illinois
- Occupation
- retired electrician
It could be a 1/0 if the sets are in multiple raceways. If the sets are in a wireway or a cable tray, it would be 250 kcmil.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Agreed. I was referencing (3) sets of what is written which says "IN 4" C".
- Status