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Advice on Installing 100 amp sub panel in worshop?

63K views 35 replies 16 participants last post by  yellowcat 
#1 ·
I have a new 100 amp main circuit panel I am going to use as a sub panel going out to the storage building. I ran three 2/0 wires from the house to the storage building and planned on using a grounding rod next to the storage building instead of running an extra 150' of copper 2/0 to the house to be used as a ground there. I have 2 links below showing the box I am going to use and I am using the left hand side buss to be used as the grounding side where the ground wire will be going to the grounding rod outside. I know the metal tab with the green screw on it is for bonding...do I need to do it on this setup since I am using a separate buss solely for all ground wires?


http://i45.tinypic.com/v41f0n.jpg


http://i48.tinypic.com/av1xxx.jpg
 
#2 ·
i'm not sure if the code requires it(i think it does) but you NEED to run the 4th wire, without it you will have a difference in ground potential which attracts lightning as well as causes all sort of headaches with various electronics. you still put in your ground rods, but they must be tied back to the main ground system.

and since this is a sub you don't want the bond screw in.
 
#4 ·
2/0 is way oversized,
Ken, you missed he's in Texas you know, Everything is bigger in ......:sidelaugh

P.S. When I build my house I use 1/0 to bring power in from pole underground to house. Wiring inspector was like [Why] :dunno:, it's bigger than what is run overhead to the street, once I told him what I payed for a 1000' roll he was like :eek: :biglaugh:
 
#8 ·
Here the chart shows a 4 wire cable going to the main...I only am using 3 wires which are 2/0 going from the main to my sub panel. Why do you need a separate ground going back to the main if you have a separate grounding rod for the sub to be used for all the grounds outside the storage building. Pretty confusing...I already got about 50 different opinions from different places and all have different opinions on if my way is safe. :crybaby:


P.S. As for the 2/0 wire all storage buildings I built and have to go 150' to tie in to some electrical panel its a normal size if your going to use a welder.
 
#10 ·
I think this answered my question:

It is number 2 above which is of concern to home inspectors. It is common for home inspectors to
examine detached garages in which there is a separate panelboard (a subpanel) supplied from the the
main panel (SES), at the house. If, upon removing the cover from the subpanel in the detached
building, you determine that ALL of the following conditions, 1 – 4, are present:
1. An equipment grounding conductor has not been run with the feeder (supply) wiring coming
from the main panel (SES),
2. There are no shared electrically continuous metallic systems such as plumbing or fuel gas
piping from the house to the separate building that are bonded to the grounding system for
the main panel (SES), and
3. Ground-fault protection of equipment has not been installed on the common alternating
current service,
then, the grounded/neutral conductor that has been run with the feeder (supply) wiring to the separate
building must be connected to the detached building disconnecting means and to a separate grounding
electrode/grounding electrode conductor system. This is because when an equipment grounding
conductor has not been run with the feeder (supply) wiring from the main panel (SES) to the separate
building, then a separate grounding electrode/grounding electrode conductor system for the subpanel
must be used to provide the required effective path for short duration, high electrical current events
such as lightning strikes. As ProSpex subscriber and licensed electrician, John Branham, points out,
the additional grounding electrode/grounding electrode conductor system bonded to the grounding bus
and to the subpanel enclosure in the subpanel in the separate building are necessary to create a
completely separate and independent path to ground.
 
#11 ·
I'll make one more post here. :dunno: Why

You can ask questions about electric and you'll get guesses, you'll get links to different ways and different interpretations to the NEC code.

I suggest that either you ask the local code official (if required to get permits and inspections) or get a copy of this book or the current edition (2011) http://en.m.wikipedia.org/wiki/National_Electrical_Code and read it.

Or if no inspections are required just pick any suggested way and hope your ok.

One more option is to hire a licensed, insurerd electrician from your area to do the job or give you the proper advise.

"Wiring is not a hobby" I had that bumper sticker on the service van I drove for an electrical contractor I worked for 15 years ago. I've been out on my own ever since then, as a licensed, bonded and insured electrical contractor.
 
#12 ·
I'll make one more post here. :dunno: Why

You can ask questions about electric and you'll get guesses, you'll get links to different ways and different interpretations to the NEC code.
I suggest that either you ask the local code official (if required to get permits and inspections) or get a copy of this book or the current edition (2011) and read it.
Or if no inspections are required just pick any suggested way and hope your ok.
One more option is to hire a licensed, insured electrician from your area to do the job or give you the proper advise.

"Wiring is not a hobby"
It would be a lot easier just to tell him what he wants to hear :fing20:
 
#13 ·
This might make no sense to some but I hear some wanting to run a ground all the way back to the main panel ground.....where the neutral bus and ground are both on the same side......this would then send the neutral to the separate ground on the sub way out in the workshop....This kinda makes no sense if you want to have a separate ground in workshop sub panel.:dogrun:




:lalala:
 
#14 ·
this would then send the neutral to the separate ground on the sub way out in the workshop....This kinda makes no sense if you want to have a separate ground in workshop sub panel.
don't take this wrong as i'm not downing you, but this statement alone tells me you need to hire this job out. you don't even have a basic understanding of current flow and without that you are more likely to do harm than good.
 
#17 ·
Just another thought here...

If you ever want/need to sell the house down the road not properly wiring the sub panel may well cause you some amount of grief. IIRC I ran 2-2-2-4 AL to my subpanel several years ago (yeah, I know it's 'rated' at 95A, not 100A with a 3% drop). I'd have to check on the ground rod, can't remember if I installed a second one or not.

Anywho, as most are saying, per code the ONLY place that it is permissible to bond ground and neutral is the main panel (and it is MANDATORY there!). There are many reasons for this, lightning, wire failures (digging accidents), short circuits, etc., and I leave the exact science of it up to those creating the NEC; after all, even if we don't agree with it that is the code we must measure to at the end of the day.

The ONLY way one should make shortcuts is if one TRULY has the proper engineering knowledge/experience to certify that said change is better/safer than the original spec. And even then if something were to happen you may have to prove your case to some governing body or court of law.
 
#18 ·
Unless you REALLY know what your doing, i.e. your an electrical engineer or journeyman wireman, you need 4 wires from the main to the subpanel. Since you asked the question, I must assume you don't know enough to do this correctly. Put in the 4th wire or hire an electrician to help you.
 
#19 ·
Thanks for all your help with my question on the sub. I know going by the book says run 4 wires back to the main...even though its a 150feet away. But I also was told by certified electricians that 3 going back to the main...2 hots and a neutral....with a separate grounding rod for the sub outside the storage building for all separate ground wire side bus would be fine also. Just wanted to get some others input on it. :thanku:
 
#21 ·
I live in Texas in a small town where there is no such thing as inspectors coming out to look at an electrical job. Also I did plan on having the grounding rods like you mentioned . By the way..here is the last main panel I installed a few weeks ago.





 
#25 ·
I live in Texas in a small town where there is no such thing as inspectors coming out to look at an electrical job. Also I did plan on having the grounding rods like you mentioned . By the way..here is the last main panel I installed a few weeks ago.
I guess there are still many places in the country that do not require permits or inspections.

But all the states I've worked in (11) require them. And a License and insurance is also required to do work for others.

BTW, the panel installation in your photos, would fail inspection here.
 
#22 ·
I went to tech school to be an electrician and found out it wasn't for me, but it did leave me with a good general knowledge of residential wiring and do all of my own work, except when it comes to stuff I know I am in over head with. My town has strict inspectors and building officials so when the time came for a service upgrade came last year I hired it out to a local company, pricing is very competitive now and when it comes down to other peoples safety is relying on your work sometimes a pro needs to be called in. This was my nightmare of a service that was in the house when I bought it, those are all minis on a 100 amp service....







The guy who used to own my house was a lineman for the power company and thought he was doing everything right, before we even before we could buy the house the city made them spend over 5K bringing the wiring up to code before we bought the house because no permits were ever pulled for work and showed the original 60 amp service on town records, there were many things in my house that could of killed people, The big thing was the in ground pool not grounded with the underground wires powering it doubled up on the main with no breaker. I'm sure he meant well but just didn't have the knowledge a licensed electrician has. Be careful.
 
#28 ·
I don't know much about electrical and the extent of my knowledge usually ends with wiring up an outlet or a light, but what is wrong with the picture and why would it fail inspection?
 
#29 ·
Several things jump out immediately -

1) Strip length on main lugs
2) Black wires on ground/neutral buses.
3) Odd box - two grounding strips, no actual neutral bus. (Not saying it's not ok, just that it could never be used as a sub-panel).
 
#30 ·
I hate this subject. Everyone is a pro and everyone knows the right way to do it, except everyone says to do it a different way. Makes it VERY confusing.

This is what i did, i called the local electrical inspector. Asked him if i needed to run 3 wire or 4 wire to my pole barn. He said 3 wire was fine, so thats what i did. I separated the neutral and ground at the panel and then drove in two ground rods. DONE

I used 1/0 1/0 2awg direct burial wire. I work for the power company and got it for $1.13 a foot. I only used conduit for entry into the buildings, I did not use it for the entire run. People always say to use conduit for the whole run, I don’t see the point, we as a power company do not use conduit for under ground service unless its under a driveway or parking lot other wise its direct bury.
 
#32 ·
Was the pole barn a separate service or a sub panel? I mean electrically the way you did it will work just fine either way, it just not what most inspectors require today if it's a sup panel. I agree on the direct burial cable, never understood that no matter how many services I've put in, but up here that's the way the inspector expects it to be done. The dang power company doesn't even spec conduit "underground" if using direct burial cable, but if you want it passed here it better be in conduit! lol

Like you say always a good idea to call your local inspector and see what they require, because in the end he's the one who is going to pass or fail it.
 
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