article 250.30 question
- Thread starter steveng
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JohnJ0906
Senior Member
- Location
- Baltimore, MD
Is metal conduit being used?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
This can be a difficult question to answer because more info is needed. Are you saying the building is detached, a separate structure from where it is being fed??steveng said:
Dennis Alwon said:
the xfmr is located inside the bldg where the service is coming from, the panel is located outdoors near a pond supplying the service for the fountain pumps and lights...
bldg service which is 480/277 3 phase wye 4 wire.
the xfmr feeding the outdoor panel is a 15kva 480/240 single phase, the transformer is not grounded , there is no ground rod attached at xfmr...
the ungounded condutors supplying the panel are 2- #6 thhn
the grounded conductor is #6 thhn
no equipment ground conductor
voltage L1 to L2 238volts
load on panel L1 15a
L2 14a
there is a ground rod at panel with the equipment ground bar attached.
should the neutral and equipment bars be bonded with bar, wire, etc....?
is this a seperately derived system? according to art 250.30?
Last edited:
- Location
- Bremerton, Washington
Yes this is a separately derived system, a system bonding jumper is required at the transformer or first disconnecting means
Depending on where the SBJ is, determines if a green and white wire is run from trans. to panel, or if a white wire with an imaginary green stripe is run.
Think about the purpose of the white wire and green wire.
if the SBJis installed at the panel, we are returning fault current and unbalance current to the transformer windings on one wire-white with imaginary green stripe
If the SBJ is installed at the transformer, fault current and unbalanced current stay separate until they reach the transformer.
This question gets a bit muddy as we want to apply the rules in 230.23 for separate buildings. I have not thought of this application before and I hope some others will assist me if my explanation is wrong,
Depending on where the SBJ is, determines if a green and white wire is run from trans. to panel, or if a white wire with an imaginary green stripe is run.
Think about the purpose of the white wire and green wire.
if the SBJis installed at the panel, we are returning fault current and unbalance current to the transformer windings on one wire-white with imaginary green stripe
If the SBJ is installed at the transformer, fault current and unbalanced current stay separate until they reach the transformer.
This question gets a bit muddy as we want to apply the rules in 230.23 for separate buildings. I have not thought of this application before and I hope some others will assist me if my explanation is wrong,
tom baker said:
This is a single phase 3-wire secondary xfrmx and would need ocpd with in the first 10'. The sbj would be made like you said. If there isn't any metallic systems between the building and outdoor panel,a 3-wire feed could be run and a new gec would be established there..
Rick
Rich Elec.
Senior Member
- Location
- Pennsylvania
A new gec would be established and it would be bonded at the new panel, correct?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Yes--Rich Elec. said:
should the neutral and equipment bars be bonded with bar, wire, etc....?
you would bond the neutral and ground bar as you would a new service and drive a ground rod. A main disco is also required which could be part of the outdoor panel, i.e. main breaker weatherproof panel. No grounding conductor is necessary
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
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- Electrical Contractor
Yes. What sentence brings you to that conclusion?steveng said:
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Not always right, but never in doubt. :roll:steveng said:
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
This is an interesting installation, one I would not normally see, so I would not normally think about.
1. yes this is an SDS.
2. would you need to install a separate EGC? In my opinion, I think this is a good example of where using 250.32(B)(2) would be fine as the chances of having a metallic path between the two locations is remote...but...(see #4)
3. Some type of grounding electrode is required, either at the transformer or the panel located outside. (personally I like the termination at the transformer)
4. Most likely [more or less educated guessing based on the post(s)], you will need protection on the secondary side of the transformer within 10 or 20 feet, as per 240.21(C).
1. yes this is an SDS.
2. would you need to install a separate EGC? In my opinion, I think this is a good example of where using 250.32(B)(2) would be fine as the chances of having a metallic path between the two locations is remote...but...(see #4)
3. Some type of grounding electrode is required, either at the transformer or the panel located outside. (personally I like the termination at the transformer)
4. Most likely [more or less educated guessing based on the post(s)], you will need protection on the secondary side of the transformer within 10 or 20 feet, as per 240.21(C).
Bea said:
BEA. Unless this xfrmr is pad mounted and the conductors go directly undergound below concrete, there not considered outside conductors.The other problem with the OP is that he doesn't have a main in the panel if the conductors where considered outside.
Rick
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