I am setting up a 39′ camper on a permanent foundation and electric subpanel. Here is my electric set up. 3 wire underground feeder 2/2/4 to a subpanel outside the camper. Subpanel has ground/neutral bonded and a #4 copper to a ground rod, and 2 50 amp breakers. This feeds 2 factory installed 50 amp subpanels in the camper which have separate ground/neutral (not bonded). These were designed to be plugged into 2 separate 4 wire receptacles at a camp site. What to do in these panels? Do I bond ground/neutral or leave as is? Thanks
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Skim-coating with joint compound covers texture, renews old drywall and plaster, and leaves smooth surfaces ready to paint.
Featured Video
Highlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
2/2/4 not legal
2/2/2/4 legal
Is it possible that this could be interpreted as an "outbuilding", meriting its own ground and bonding strap?
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
I saw a similar discussion a while back on a different forum.They say that the code reads separate Structure not building. But I have no looked it up.The discussion in that case was the meter and a disconnect was on a pedistal some distant from the home.The home was a separate structure from the pedistal so that it could be treated as a main panel.
The criterion for a separate building is that it's more than 5 ft. from the main building.
-- J.S.
The question is whether the situation under discussion should be considered a "subpanel" or not. If it must be considered a subpanel then 3+1 cable is needed and no bonding in the panel. If it can be considered to be a separate structure then only 3 wire/no ground cable is needed, but a ground electrode system must be installed and the neutral-ground bond strap must be installed in the panel.I don't know the answer in this situation, where the "building" is a trailer pedestal.Beyond that, there likely are some special paragraphs in the Code regarding trailers ('scuse me -- modular structures), though for consistency they're no doubt buried in some unrelated section.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
a seperate structer is five feet and nothing metal connecting each bldg, no tv coax, no telephone wire, no carport, awning walkways. but also local inspector required everything south of meter is sub panel, no matter if in a seperate bldg or not. and all subpanel gets 4 wires. the seperate bldg requires a ground rod but netrual and ground cannot be bonded.
Simply being south of the meter doesn't force something to be treated as a subpanel (in the sense of not having a bonding screw). In fact, the code appears to REQUIRE that a separate building have it's own grounding electrode system AND be bonded to the "grounded" (neutral) conductor. (And, by implication, not be bonded to the incoming grounding electrode.)Unfortunately, the code section that applies here (250.24 in my ancient copy of the NEC) is fairly difficult to interpret.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
There is an NEC section on mobile homes. But I have never looked at it and don't know the RV would fit that or not.That is why I did not bother replying to the question.
I don't think the sub-panel outside the camper should have the bridge in place. And certainly 2/2/2/4...
-- Brooks
OK, I guess I left out a part of the set up. Sorry. The 3 wire feeding the 1st sub-panel at the outside of the camper comes from a 100 amp main disconnect at the power pole and has separate ground/neutral. It then runs 80' to the camper. Does this shed a different light on the question, and in my part of the country (very rural) where there is not much of an inspection on anything built, I guess I am not much concerned with code, but will it work safely. Thanks
till its burns down
Why would you see it as unsafe? When the detached structures main panel is supplied by a feeder that has no equipment grounding conductor run with that feeder, from the main structure to the detached structure (as in my case), then the neutral bar and equipment grounding bar must be joined or married together as one entity. Article 250-32-B-2 & 250-102-E The neutral bar must be married or joined together with the metal of the panel box and also the equipment grounding bar. Article 250-32-B-2.
If there is no grounding electrode system serving the detached structure (as in my case) then you must install a new grounding electrode system as described in Article 250-50. (as in my case). If you know something that I don't, please let me know. Thanks
You say "3-wire" and you say "separate ground/neutral". Enumerate the wires.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
Guys:Last week I had a conversation with a master electrician in Michigan who has worked on the code. He said that code does require an equipment ground, hence, 4-wire for 240 power. I didn't ask him, but was under the impression that the grounding bus is only bonded to the neutral wire at the main box, and at other locations, if there is a grounding electrode, it is just that, ground. According to them as knows, to reground the neutral at a separate building can cause real problems.Anyway, I am not an electrician, just a guy with barns and outbuildings who trieds to get advice to do it right. If I am confused, I'd like to hear about it.J
JoeWhat he said is not absolutely true. That is unless MI has modified the NEC in that area. I understand that WA has.But the code allows for 2 cases.If there is no other metalic connections (such as water pipes, tv cable, phone) between the two structures then the sub-panel in the 2nd structure can be treated as a service enterance with only 3 wire feed and the neutral bonded to the ground.Now a 4 wire feed and unbonded neutral is more flexible for future needs and as I said some place always require it. But not in the NEC.There are also some special grounding rules for animal barns, but I really don't knwo what they are.
Actually, Bill, my conversation with the master electrician was in connection with animal barns. Someone o this website warned me, and I talked with the electricial as a result of the warning. Seems under the wrong circumstances, a regrounded neutral can result in shocked or dead livestock on concrete floors. I am not the best one to try to eaplain this, but perhaps whoever warned me in the first place will chime in.
However, he strongly advised me to change out the present 3-wire 240 feed to my garage and workshop, and I thought he said code called for it.
In any event, code or no code, four conductors is a better way, if not a required way, wouldn't you agree?
J
"When two or more buildings are supplied by a grounded system from a single service equipment [ie, meter], each building shall have a grounding electrode connected to the ac system grounded circuit conductor on the supply side of the building disconnecting means.This appears to say that the building ground should be bonded to the neutral ("grounded conductor") in the building's panel. There's no mention of a separate grounding conductor. The diagram in the section shows three buildings with no ground wire between, only hot/hot/neutral.There is an EXCEPTION to the above, in that buildings without livestock are permitted to have the fourth (ground) wire and forgo the grounding system (though the ground wire must still be bonded to any pipes, etc, in the building).
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
There is a definite exception for outbuildings. When and how it should be applied is the fuzzy issue.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
Separate ground/neutral is at the power pole/meter/100 amp main disconnect location. From there 3 wires 2/2/4 run to sub panel.
Sorry on that last post. My error. Ground/neutral are bonded at main panel.
That is fine for you appliacation.But I don't know anything about mobil home connections so I will not comment past the panel.
Well, first off there would be some question whether #4 is adequate for a neutral in a #2 circuit.That question aside, it sounds like you should install a grounding electrode system at the pedestal and treat the incoming cable essentially like a service entrance, with bonding screw installed on the panel. This would appear to be in compliance with code, absent something to the contrary in the trailer section of the code.But this is a fuzzy area.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madisonqu