Want to add 230V outlets to my barn

[Farwell]

Eric,
I have had around 10 very serious discussions over the past several years with different electricians about the bonding of the neutral and ground in a panel in a detached building with a three wire supply (two hots and one neutral). I do not know where they get their information or mis-information but one would say absolutely no and the next would say absolutely yes. I know that if four wires are run (two hots one neutral and one ground) no bonding at the panel.
This topic has been discussed here on TBN several times and I think that the agreed upon method here on TBN is that the panel in the detached building is considered a sub-panel so according to the NEC, no bonding at the sub-panel and drive a ground rod or two near the sub-panel and run a ground wire to them.
This topic always gets things going here on TBN.
In my opinion the 130' of number 8 copper wire is fine if you do not plan on running anything that draws a lot of current.
Farwell

 

[ericbx1500]

David I understand what you are saying on all the different opinions from different electricians out there. On my set up I ran two hots and a neutral to the barn. I also drove two grounding rods (used to be you only needed one) six feet apart at the barn. I guess the question here is why do we even need to bond at all. They never did this practice years back. In fact I had my main panel updated four years ago and my old panels neutral was isolated from my ground now it’s bonded on the new panel. My old panel was 100amp service with a 60amp main for plugs and lights. So I change it out to a 100amp main 30 slot for more room. Another question would be if I didn’t bond my sub panel in the barn wouldn’t my neutral bar in my barn still be in a sense bonded because the main panel is? I think leaving my sub panel bonded wont hurt anything. Maybe an electrician out there could chime in on this one.

 

[ericbx1500]

found this on a electricians message board. if you use metal conduit dont bond. plastic conduit you need to bond the sub.

question:Well I was just told that if I don't include a equipment ground (green) wire with the feeder, then I have to bond the neutral to the panel/ground at the shed. Reason being is that there is no metallic connection between the house and the shed since I am using non-metallic conduit. Is this right??

answer: yes

250.32(B)(2) Grounded Neutral Conductor. When an equipment grounding (bonding) conductor is not run to the building or structure disconnecting means, the building or structure disconnecting means can be bonded to a grounded neutral conductor installed with the feeder conductors. This is only permitted where there?s no continuous metallic path between buildings and structures, and ground-fault protection of equipment isn?t installed on the supply side of the feeder.

Where the grounded neutral feeder conductor serves as the effective ground-fault current path, it must be sized no smaller than the larger of:

(1) The maximum unbalanced neutral load in accordance with 220.61.

(2) The available fault current in
accordance with 250.122.

CAUTION: Using the grounded neutral conductor as the effective ground-fault current path poses potentially dangerous consequences and should only be done after careful consideration. Even if the initial installation doesn?t result in dangerous objectionable current on metal parts, there remains the possibility that a future installation of metal piping or cables between the buildings or structures could create unwanted parallel neutral current paths.

Author?s Comment: The preferred practice (or at least my preferred practice) is to not use the grounded neutral conductor as the effective ground-fault current path, but to install an equipment grounding (bonding) conductor with the feeder conductors to the building or structure in accordance with 250.32(B)(1).

 

[EddieWalker]

Is your concern based on having 50 amps for a welder?

I'm only running 30 amps on my AC/DC arc welder. I use 1/8 rod without any trouble. It's really hard for me to imagine you'd need more power than this.

My generator puts out 20 amps that I plug into for emergancy work and that's too light, but will get the job done out in the field.

Eddie

 

[Keoke]

Hi Folks, here are some of the reasons for separating the neutral from ground at sub panels.

If the ground and neutral were the same conductor, then cutting only the neutral wire (for example by accident) would cause the grounded metal case of the equipment to be on mains potential (gnd wire is now the neutral) just because there is only live connected to equipment and that voltage can go through the equipment to the cut neutral cable and from there to equipment case.

When ground and neutral are separate, then cut neutral causes only the equipment to stop working and no dangerous situation. If ground gets cut by accident, there is no danger caused before some equipment gets damaged. So when there is separate wires for neutral and ground, a singe wire fault (cut or short circuit to other wire) on any wire going to outlet does not cause immediate danger to the user of the equipment:

Live shorted to ground or neutral: fuse blows immediatly. When fuse is blown then the dangers of electricity are gone.

Neutral shorted to ground: No immediate danger to use, just nasty ground loop problems start to occur. This is the same as running the gnd screw on neutral bar to panel shell or gnd. If there is GFCI or other ground leakage detector in wiring, it will cut the power to the outlet.

Live or neutral cut: Equipment just stops getting the power
Ground wire cut: The safety ground to equipment is lost.It continues to work nicely and there is no danger as long as there is no fault inside the equipment. Potentially as dangerous situation as using ungrounded outlet in same place, bur no immediate danger.
So any single failure does not cause great danger. So the for safety sense separate ground and neutral wires are a very good idea.
Also, ground loops are caused when are two separate gnds for a house. The difference in conductivity between the two grounds can cause audio and videio equiptment to hm or put horzion bars on the screen. This is especially true if the equiptmet used above is not all seeing the exact same ground.

cheers,
keoke

 

[SPIKER]

Eric:

while I have not looked into the bonding neutral in a sub panel in the 2005 nec yet so I can't definatly answer that, but I CAN difinatly say that the old 2002 book stated that when running a SUB-Panel the N was not to be bonded to the panel but that a sepperate ground system/rods were to be run and bonded to the panel and all grounds in that building bonded to the panel via the ground lugs. ok reason being for this is the N is a return path to the elec feed for the 120vac loads. if a 4 wire is run which is fine a ground rod is still required due to the fact that each structure requires it's own ground for the simple fact stated elsewhere that ground over at the house is not the same ground you are standing on 500' away holding a power device in you're hands thinking that the case of the thing is the same voltage potencial as the earth you are standing on... also as noted above by?? ( "Keeokei" sorry forgot his screen name )

anyhow the new regs and you're locations may varry a LOT so ask the local inspector if you have any REALLY concerning problems such as smoke rolling out of the panel box /forums/images/graemlins/blush.gif /forums/images/graemlins/crazy.gif

Mark M

 

[ericbx1500]

Hello mark, my last reply was based on a 3 wire feed(two hots and a neutral) not a 4 wire feed 2 hots a neutral and ground wire. With a three wire feed you need to bond your sub panel as long as there is no metelic path connecting the two structures(home and detached structure). With a four wire feed your neutral and ground need to be isolated(not bonded). Also if one only has a 3 wire feed threw metal conduit the conduit acts as a ground(do not bond). In this situation(my 2 cents)I would run a seperate green insulated ground wire back to the main panel. Like you said in both cases you still need seperate ground rod's at any detached struture.

 

[rambler]

mwood, I had (still have) computer issues & couldn't get to this site for a spell. Sorry for dredging up an older thread, but thank you for the pics.

I would consider you have a 50 amp service in your house, based on the 50 amp breakers. I just had my farm rewired, with 200 amp service total, 100 amp service in the house, & 60 amp service potential to all 9 outbuildings. You would have a 50 amp service, based on the 200, 100, & 60 amp breakers I got?

It is not really correct for you to have a 50 amp service (the top main breakers) and then pull a 50 amp sub-load (the bottom breakers out to the barn...) from it. There should be a step down, you should really replace that with a 40 amp breaker - no matter what wires are invlved. That still only leaves 10 amps for your house, if you weld hard! /forums/images/graemlins/smile.gif

A #6 copper wire could be good for a 60 amp service - if you have a very short run of wire. For over 100 feet, you will harm your electrical motors if you try to pull more than 40 amps through that wire for that length. Voltage drop will get you. If it is aluminumn wire, then you really should limit it to 30 amps. As others say, 40 amps probably will work out ok, but that is not to code & you do face insurance issues, and you can harm your electrical motors, etc. That is your call. I myself would _not_ be running a 50 amp service out to your barn with the current wires and main panel. That is asking for trouble in my view, and quite a bit beyond code. Red flags.....

In your barn box, since you have the possibility of more than 5 breaker cuircuts, you are by code supposed to have a main breaker there too. This was not always the case, so is grandfathered in as it is, but if you upgrade, would be nie to follow code & put a 30 or 40 amp double throw main breaker. As someone else said, do what you can sleep with at night, I'm just mentioning it.

Also, this building is always called a 'barn'. If livestock is involved, the service box on that building must be an outdoor rated box hung outside the building. As I'm in a rural ag area, we do not interchange the name 'shed' with 'barn' or you get all types of added restrictions. /forums/images/graemlins/smile.gif I assume you have a shed, actually.....


Three months after I had my wiring done, the inspector showed up. I had electricians do my service work. The inspector looked at about 1/2 of my buildings, slapped a few labels here & there, jotted down some notes, and left, all apporved. Never did look at the other stuff. If I had tried to do my own work, I think it would have been much rougher.

So, good luck with it. I sure wouldn't want to put more than a 40 amp double breaker out of your main, and I'll bet only 30 is to code.

Some others were talking about bonding & so forth. Dairy barns brought about those issues, and the mass of confusion. Stray voltage, just 5-10 volts, will totally mess up a cow & keep her from drinking water. Super sensitive. Several lawsuits for millions of dollars due to lost milk production caused a big change in how equipment is bonded, loads are balanced, and the confusion. I won't try to say what is right or wrong - I don't understand it, but today if you mention the word 'barn' then everyone becomes hyper-sensitive & all that bonding stuff comes up. It depends if there are shared water lines between buildings, etc...... But then to be honest, in my situation (real farm, livestock in one building, 2 others set up for livestock, water lines between 4 buildings including the house) all that was ignored. The livestock barn wasn't even inspected, and I have 1 ground rod at each building, 3 wire service. Never was looked at. Was real important to see the bonding wires of the pipes in the house - but all pipe leaving the house is plastic. Go figure?

What's right or wrong is what passes the local inspection......

--->Paul