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A little puzzle about grounding feed back is welcome

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Blog entry by sandhill posted 901 days ago 3964 reads 0 times favorited 17 comments Add to Favorites Watch

As you can tell in this video I am a little puzzled and working to a solution for grounding of equipment.

-- Bob Egbert AKA Sandhill http://www.sandhillwoodworks.com/



17 comments so far

View ajosephg's profile

ajosephg

1840 posts in 2158 days


#1 posted 901 days ago

Your electrician friend is correct, 10-2 with ground is all you need for your outlets. The machine mfg will have the metal frame of the equipment connected to the ground wire.

-- Joe

View bigfish_95008's profile

bigfish_95008

250 posts in 1700 days


#2 posted 901 days ago

Joe is correct, and so is your electrician friend is right. use the bare safety ground throughout your system and your circuits should be fine.

-- bigfish "I am always doing what I cannot do yet, in order to learn how to do it." Vincent Van Gogh

View brtech's profile

brtech

664 posts in 1519 days


#3 posted 895 days ago

In a house, neutral and ground are close, but not the same thing. They are exactly the same thing at the service panel (they are tied together). From that point, however, they are considered different, and in every install I’ve ever seen, you have a separate insulated conductor for neutral, and a ground wire.

If you have a separate ground rod for a sub panel, you can bring just 10-2 in for the two hots, and tie ground to neutral at the sub panel. I think you need a separate ground rod if you do that. I understood that a sub panel without a ground rod needs 10-3 for 220V service, leaving the neutral to ground tie at the main panel and isolating neutral from ground at the sub panel.

For a 110V service outlet, you have neutral, one hot and ground, 3 conductors.
For a 220V service outlet, you have two hots, no neutral, and ground, 3 conductors
Having the neutral (4th wire) in a 220 tool isn’t useful. You need the ground, but not the neutral.

View sandhill's profile

sandhill

2102 posts in 2521 days


#4 posted 895 days ago

@brtech- I just spoke to the electrical inspector the other day and here is what I understood him to say. I had to bring a Neut & ground from the main panel to the sub panel ”to use a ground rod outside at the building would cause a ground loop”. So with that said I will run 4 each #2 aluminum conductors from the Main, two of which will be 120VAC at a 100 AMP breaker and the remaining two will be connected to the Ground buss on the left and the Neutral on the right which are connected together at the back by a green bar bonding them together electrically. in short everything must originate at the main and return to the main. Does this make sense? And yes all the 30 AMP 220 VAC runs will be 10-2 with the bare wire as ground (neutral).

-- Bob Egbert AKA Sandhill http://www.sandhillwoodworks.com/

View brtech's profile

brtech

664 posts in 1519 days


#5 posted 895 days ago

We’re probably not seeing the same picture. I understand code allowing a sub panel to have just 2 conductors from the main panel (not even a ground), with a ground rod. It’s then really just another service entrance. Claiming you get a ground loop from two ground rods not otherwise connected is like saying you can get a ground loop from your neighbors house and yours.

But, he is the one who signs off, so who am I to argue?

So you are putting in a 100A subpanel? Sweet! When you were talking 10-2 I was thinking 40A. And we’re back to Aluminum wire? I must really be out of it.

Now there is one part of your explanation I don’t understand

“Ground buss on the left and the Neutral on the right which are connected together at the back by a green bar bonding them together electrically”

Where is that “green bar”? In the main or the sub? If it’s in the Main, great. If it’s in the sub, problem. Then you have a neutral to ground connection in the main, two conductors and another neutral to ground tie in the sub. That’s a no-no the way I was taught.

And there is just a minor quibble:
“And yes all the 30 AMP 220 VAC runs will be 10-2 with the bare wire as ground (neutral)”
No! The bare wire is ground but it’s not neutral.

View sandhill's profile

sandhill

2102 posts in 2521 days


#6 posted 895 days ago

???? I miss stated that, that would be the same as putting the white wire to the same place as the bare copper wire. Big oops! The bar is in the MAIN.
I think you have to make a change in the Sub panel to make it the same as the Main but I have not clarified that yet.
I am sure he said NO GROUND ROD at the sub panel funny thing is there is one there now for the existing 120 VAC sub panel Which is all coming out because there is no 220 and the supply line is to small.

-- Bob Egbert AKA Sandhill http://www.sandhillwoodworks.com/

View brtech's profile

brtech

664 posts in 1519 days


#7 posted 895 days ago

Okay, that makes sense: no ground rod, 4 conductors, no ground to neutral tie in the sub panel. Ground to Neutral tie at the main. Yep, that’s it.

It may be that code changed. You used to be able to run 2 conductors from the main (2 hots), and have a ground rod at the sub, with neutral to ground tie at the sub. That way you only needed 2 conductors between the sub and the main instead of 4, at the cost of a ground rod at the sub.

View sandhill's profile

sandhill

2102 posts in 2521 days


#8 posted 895 days ago

Whatever the inspector wants me to do is what I will do being he has the final say, LOL I am buying the materials at Home Depot because the guy that works in electrical is a master electrician and said he will guide me through any areas I need help so between the two of them I should be in good shape. I had one guy quote me $1000.00 to do the work and said he would only bury the cable 12” (Not Code) and another $200.00 if I wanted it 24” this was just for the sub panel! what are we talking a one day job? I can do the whole garage for less than he wanted for the sub panel alone, inspected and signed off.

I think your right about the code being changed because as I said there is a ground rod in use there now for the current set up.

-- Bob Egbert AKA Sandhill http://www.sandhillwoodworks.com/

View Ken22F's profile

Ken22F

23 posts in 1861 days


#9 posted 890 days ago

Bob
Your friend was right
Let me explain, shop equipment (motors) wired for 220V because alternating current
AC different cycles opposite of each other can operate with the two hot Leeds (do not wire from the same pole you must use a two pole breaker).
And use the bare wire as frame ground “AND ALLWAYS GROUND”
And wire to the ground block in your sub panel not the neutral.
Note that you might be required to paint the wire ends black or red not white.
Outlet use 3prong twist lock.

Now for 110V because of the one wave cycle equipment uses the neutral,
Standard outlet Black+ White- Ground bare

I can explain further but
This is the short of it.

Ken F
Engineer

View Ken22F's profile

Ken22F

23 posts in 1861 days


#10 posted 890 days ago

Now for running a 220v sub panel
3 wires or 4 wires

3 wire:
Two positives
One neutral
Ground rod at the subpanel
Bond the ground and neutral together at the subpanel too.

4 wire: (preferred)
Two positives
One neutral
One ground
Do not bond at the subpanel

Ken F
Engineer

View sandhill's profile

sandhill

2102 posts in 2521 days


#11 posted 889 days ago

In our county they required 2 ground rods bonder together going to the sub. I decided to only go 18” not 24” and use pipe because I don’t want to dig another 6” for 20 feet, it don’t sound like a lot more digging but after I got down about 14” – 16” I was worn out so tomorrow I will finish up the dig and run the pipe and call it a day. I am running 8 ea. 220VAC – 20AMP dedicated outlets with twist locks and 8 quads 120VAC on 3 ckts then the lighting will be 15AMP with 6 ea. 6 tube hi bay T-8 lamps for the lighting and that should do it. The inspector will be here on Tue or Wed next week.

Thank you everyone for your help and advice could not have done it with out you.

-- Bob Egbert AKA Sandhill http://www.sandhillwoodworks.com/

View sandhill's profile

sandhill

2102 posts in 2521 days


#12 posted 884 days ago

Hey guys all the 220VAC outlets are in except for one and I have about 8 120VAC outlets to wire into the panel. The sub panel is in and has 100 AMPS to it. I ran 4 #2 aluminum wires from the main and 2 ground rods to the sub. I also rand the light 6 in all but need to power them as well. I need to find out if I can put boxes in the ceiling and run plugs from each light I think I can but need to use twist locks by code but not sure I guess I will ask the inspector when I call him to come out it should only take about a half hour to an hour so it should be done before he gets here. Thanks to all for the help, if you know weather I can put boxes in the ceiling for the lights to plug into post your response please. And thanks again.

-- Bob Egbert AKA Sandhill http://www.sandhillwoodworks.com/

View Ken22F's profile

Ken22F

23 posts in 1861 days


#13 posted 874 days ago

Bob,
Sounds good,
Grounding the sub with ground rods or rebar & rod are correct but
make sure (on a 4 wire system that is with the grounding leg) the sub-pnel is not bonded to the
neutral take the bolt out of if it has one.

View sandhill's profile

sandhill

2102 posts in 2521 days


#14 posted 873 days ago

Not sure what you mean Ken? Why have a 4th wire if its not bonded to the main? Unless you are talking about the ground and neutral not bonded together at the sub.

-- Bob Egbert AKA Sandhill http://www.sandhillwoodworks.com/

View Ken22F's profile

Ken22F

23 posts in 1861 days


#15 posted 871 days ago

We are talking about 220V Single Phase.

At your main panel (the one coming from the pole or street) there
Are two positives and one negative going into your main panel,
The main panel is grounded by a rod 8ft deep (or gas line),
The ground and negative gets bonded together at that location (some have a bolt option).

Some people make the mistake of bonding the ground to the negative at the
Sub Panel too (some sub panels have that option).
With a 4 wire system (with ground wire) having two Bonding points in a system causes a loop and can be DANGERIOUS!

On a three wire system (no ground wire) into the sub panel you
Can bond the ground and negative) do not use a this three wire
system too a metal Building.

There should be ground rod at each panel if they are in different buildings.

showing 1 through 15 of 17 comments

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