Advice on sub panel configuration

[jform]

Hi folks,

First, thanks to the members on this site. Your knowledge and advice has been an invaluable resource.
I have a question regarding the electrical system of a property I recently purchased. It was primarily used for bluegrass gatherings, people would bring their campers and travel trailers to stay on the land, so the infrastructure may be unconventional for a typical residence.

There is an aerial service entrance at the road which brings 240v single phase power through the meter into a 200 amp breaker. This panel (panel #1) is the main service disconnect, with neutral and grounding bus bars connected via a main bonding jumper and a grounding electrode conductor connected to the bus bar and to a grounding electrode. There is a green grounding screw with an equipment bonding jumper for the enclosure, but this has been disconnected from the bus bar (would this be a violation of 250.24(C)?). Panel #1 has feed-through lugs with two wires under each lug. One set of wires are 6/2 NM-B with ground run in a 1” PVC conduit about 100’ underground to a small concrete pad where the conduit comes out of the ground and terminates. The cable has no connections, just wire nuts on the conductors. These wires have no OCPD and are not being used so I have them disconnected at panel #1.
The other set of wires under the feed through lugs in panel #1 are 4/0-4/0-2/0 AL URD which run in 2” PVC conduit about 350’ underground to a pole mounted enclosure (panel #2) where they terminate at a 150 amp breaker. Panel #2 directly feeds three branch circuits, a 15 amp circuit that powers a pole mounted light, and two 20 amp circuits that each power a single duplex receptacle mounted underneath the panel. Panel #2 also has feed-through lugs with two wires under each lug, both sets are 2-2-2 AL SEU. One set runs underground in 1” PVC conduit approximately 30’ to an indoor enclosure (panel #3) inside a cabin, the other set runs underground in 1 1/2” PVC conduit about 120’ to a small enclosure (panel #4) that has four 30 amp branch circuits and four TT-30R receptacles, and also feeds a duplex receptacle about 50’ away. Panel #4 has no main breaker.

Panel #2 does have a grounding electrode system, and the grounding electrode conductor and all the equipment grounds are bonded together with the neutral bus bars. It does not have bonding screws from the bus bars to the panel enclosure installed.
Panel #3, inside the cabin, has a 100 amp main breaker and seven 20 amp 120V branch circuits for receptacles and lighting, plus two 240V branch circuits, a 30 amp circuit for the water heater and 50 amp circuit for the stove. There is also a 40 amp double pole breaker of which one leg was used to feed 120V to a stage located about 100’ from the cabin, but I have disconnected and removed the stage’s sub panel and the wires running to it. Panel #3, like panel #2, has grounds and neutrals bonded together. Panel #3 does have screws bonding the panel enclosure to the neutral/ground bus bars. It has no grounding electrode system, nor does it have an equipment grounding conductor that feeds it, only the grounded conductor and two ungrounded conductors.
Apologies for the lengthy preamble, I wanted to give an explanation of the situation in case there are implications to my questions, which do pertain to a garage.
I had a 26’x40’ metal building built about 75’ from panel #2, which houses the 150 amp breaker. The plan is to use panel #2 to feed a 100 amp sub panel (panel #5) that will power the garage. Panel #5 has isolated grounds and its own grounding electrode system. I trenched from the pole where panel #2 is mounted to the garage and laid a 1 1/2” PVC conduit through which I ran 1-1-2-6 AL XHHW-2 wires. Those wires terminate at the garage in the 100 amp panel #5 enclosure and have a 100 amp breaker installed at panel #2, but I am waiting to connect until I have some clarity on the panel configurations, particularly panel #2 which feeds the garage.
I have read Article 250 and looking specifically at Section 250.32(B)(1), it appears that there is an exception for panels supplied by 3 wire feeders that allows for re-grounding the feeder’s grounded conductor if certain conditions are met. In this case it IS true that:

1) An equipment grounding conductor is not run with the supply to the structure.
2) There are no continuous metallic paths bonded to the grounding system in each structure (bonded water, or gas piping, other conduit, etc.).
3) Ground-fault protection of equipment has not been installed on the supply side of the feeders.

Does this indicate that panel #2 is acceptable the way it is and there is no need to separate ground and neutral busses and run a grounding conductor from panel #1 along with the supply conductors? I do plan on reworking panel #3 inside the cabin since the allowable ampacity for 2AWG AL conductors is less than the 100 amp OCPD they serve. I assume it is better to have a separate grounding conductor and not use the grounded conductor as the ground-fault return path. That said, I would appreciate any input from those wiser and more experienced than myself. What would you do if you were in my position?

My property is unrestricted so I don’t have to worry about inspections, my main concern is safety for myself and those who come after me.

 

[wyliesdiesels]

wow a lot to unpack here and go over. I wont get to all of it in one swoop but i will start...

There is an aerial service entrance at the road which brings 240v single phase power through the meter into a 200 amp breaker. This panel (panel #1) is the main service disconnect, with neutral and grounding bus bars connected via a main bonding jumper and a grounding electrode conductor connected to the bus bar and to a grounding electrode. There is a green grounding screw with an equipment bonding jumper for the enclosure, but this has been disconnected from the bus bar (would this be a violation of 250.24(C)?).

typically the neutral bar is bonded to the enclosure as its not set on plastic insulators. hard to say if what you have isnt an issue without seeing pictures of your panel. please post pics.

Panel #1 has feed-through lugs with two wires under each lug. One set of wires are 6/2 NM-B with ground run in a 1” PVC conduit about 100’ underground to a small concrete pad where the conduit comes out of the ground and terminates. The cable has no connections, just wire nuts on the conductors. These wires have no OCPD and are not being used so I have them disconnected at panel #1.

NM-b not permitted underground. this should be replaced if its ever needed. also a bare neutral is not allowed so this #6 feeder can only be used for 240v or 120v but not both. depending on when this was installed, the 3-wire feeders are not code permissive either and even if they were i would not want them should something happen to the neutral, which is entirely possible at your property with the next issue below.

The other set of wires under the feed through lugs in panel #1 are 4/0-4/0-2/0 AL URD which run in 2” PVC conduit about 350’ underground to a pole mounted enclosure (panel #2) where they terminate at a 150 amp breaker. Panel #2 directly feeds three branch circuits, a 15 amp circuit that powers a pole mounted light, and two 20 amp circuits that each power a single duplex receptacle mounted underneath the panel. Panel #2 also has feed-through lugs with two wires under each lug, both sets are 2-2-2 AL SEU. One set runs underground in 1” PVC conduit approximately 30’ to an indoor enclosure (panel #3) inside a cabin, the other set runs underground in 1 1/2” PVC conduit about 120’ to a small enclosure (panel #4) that has four 30 amp branch circuits and four TT-30R receptacles, and also feeds a duplex receptacle about 50’ away. Panel #4 has no main breaker.

most lugs are not rated for 2 wires. this should be fixed.

SEU is not permitted underground. that bare neutral is gonna turn to mush, causing you to have an open neutral which then creates several possible dangers.

Panel #2 does have a grounding electrode system, and the grounding electrode conductor and all the equipment grounds are bonded together with the neutral bus bars. It does not have bonding screws from the bus bars to the panel enclosure installed.

since its a 3-wire feed it should have bonding screw but the feeder needs to be replaced with suitable underground wire and 4-wire so then bonding screw should be removed.

Panel #3, inside the cabin, has a 100 amp main breaker and seven 20 amp 120V branch circuits for receptacles and lighting, plus two 240V branch circuits, a 30 amp circuit for the water heater and 50 amp circuit for the stove. There is also a 40 amp double pole breaker of which one leg was used to feed 120V to a stage located about 100’ from the cabin, but I have disconnected and removed the stage’s sub panel and the wires running to it.

without addl overcurrent protection and assuming the stage just has #12 wire for receptacles, this is not kosher.

Panel #3, like panel #2, has grounds and neutrals bonded together. Panel #3 does have screws bonding the panel enclosure to the neutral/ground bus bars. It has no grounding electrode system, nor does it have an equipment grounding conductor that feeds it, only the grounded conductor and two ungrounded conductors.

needs grounding electrodes and the 3-wire feeder should be replaced along with removing the bonding

Apologies for the lengthy preamble, I wanted to give an explanation of the situation in case there are implications to my questions, which do pertain to a garage.
I had a 26’x40’ metal building built about 75’ from panel #2, which houses the 150 amp breaker. The plan is to use panel #2 to feed a 100 amp sub panel (panel #5) that will power the garage. Panel #5 has isolated grounds and its own grounding electrode system. I trenched from the pole where panel #2 is mounted to the garage and laid a 1 1/2” PVC conduit through which I ran 1-1-2-6 AL XHHW-2 wires. Those wires terminate at the garage in the 100 amp panel #5 enclosure and have a 100 amp breaker installed at panel #2, but I am waiting to connect until I have some clarity on the panel configurations, particularly panel #2 which feeds the garage.
I have read Article 250 and looking specifically at Section 250.32(B)(1), it appears that there is an exception for panels supplied by 3 wire feeders that allows for re-grounding the feeder’s grounded conductor if certain conditions are met. In this case it IS true that:

1) An equipment grounding conductor is not run with the supply to the structure.
2) There are no continuous metallic paths bonded to the grounding system in each structure (bonded water, or gas piping, other conduit, etc.).
3) Ground-fault protection of equipment has not been installed on the supply side of the feeders.

Does this indicate that panel #2 is acceptable the way it is and there is no need to separate ground and neutral busses and run a grounding conductor from panel #1 along with the supply conductors?

depending on when this was installed, the 3-wire feeder could have been code permissive (prior to 2008 code cycle). having said that, I do not like 3-wire feeds to detached buildings because if theres ever an issue with the neutral in the feeder you can have potential for shock.

If it were my property and I could run an EGC with the feeder, I would do it.

I do plan on reworking panel #3 inside the cabin since the allowable ampacity for 2AWG AL conductors is less than the 100 amp OCPD they serve. I assume it is better to have a separate grounding conductor and not use the grounded conductor as the ground-fault return path. That said, I would appreciate any input from those wiser and more experienced than myself. What would you do if you were in my position?

My property is unrestricted so I don’t have to worry about inspections, my main concern is safety for myself and those who come after me.

that is correct. 4-wire feeder is better than 3-wire.

 

[jform]

Wyliesdiesels thank you for your reply.



Attached is a picture of the service entrance panel #1 when I first opened it. I’ve since removed the cut wire stubs from under the lugs and am going to remove the entire feeder cable. The bus bars are on plastic insulators and you can see the disconnected bonding jumper on the right.


What I’m understanding from the rest of your reply is:


1. It would be best to run a EGC from panel #1 to panel #2 and then to separate grounds and neutrals at panel #2.


2. Remove the underground SEU cables from panel #2 feeding panel #3 and panel #4 and replace them with 4-wire feeders suitable for burial. Additionally only have one set of wires terminate under the lugs.


3. Install a grounding electrode system for panel #3 and, once it has its 4-wire feeder, remove the bonding.


Since panel #3 in the cabin has a 100 amp breaker and the calculated load is about 95 amps, I was thinking about using 1-1-4-6 AL XHHW-2, the same wire I used to run to the shop except with neutral downsized based on load calculation. This would be pulling through a 1” conduit as opposed to 1 1/2”. It’s a short (~30’) run with two 90 degree bends. Do you think this is a doable pull or would it be better to go with a smaller wire size and downsize the breaker The conduit runs under the concrete foundation so it’d be difficult to increase the size here.

Again, I really appreciate you taking the time to read and reply.

 

[dscheidt]

1-1-4-6 XHHW will not fit in a 1" pvc conduit, at least not per code. (that's ~50% fill, you're allowed 40%.). I wouldn't want to pull it, either. for 30', consider doing it in copper. You can use 3 awg thwn (figure $2/foot), which will fit in 1" pvc.