Grounding questions

[burleymike]

Now that the price of wire has come down so much I have decided to run 100 amp service to my barn (conversion to shop in progress). Since in Idaho we have adopted the 08 NEC I understand it that I need to use UG cable that has a ground.

I know I am supposed to keep the neutral and ground seperated since this will be a subpanel.

Question 1: is since my pole barn is metal do I need to keep the panel isolated from the barn?

Question 2: I have a irrigation pump in the barn that has a ground lug. Since this pump is connected to a steel pipe that is buried will connecting this ground lug effectively bond the grounding system of the house to this pump and it's piping which would act as a ground rod?

Mike

 

[Torque1st]

The panel does not have to be isolated from your pole barn. The enclosure would be grounded and I would certainly ground the pole barn sheeting. The sheeting will always get grounded somewhere and I prefer a good ground in several places. The neutral will be isolated in your panel.

While some inspectors may feel that the pump would be a good ground I do not consider it a permanent ground. Most inspectors I know would agree with my assessment. It could be disconnected during pump service. Some inspectors may allow the connection of the ground to the irrigation pipe. Use a ground rod permanently bonded to your sub panel ground bus and enclosure.

 

[Stuart in MN]

The well casing should be tied to your panel ground, but it can't be used as THE grounding electrode.

 

[burleymike]

Thanks guys for the info, now for the fun part digging the trench with a bad back.

 

[kbs2244]

If it is a recient well it may very well have a PVC caseing.
If you use the ground rods place them at least 10 feet apart and try to put them in a damp place.

 

[sberry]

The well casing or underground steel pipe at least 10 ft long is the primary grounding electrode, the rod becomes secondary. One of the more studious will be able to address the wire size per 100A, when the pipe or well is used for 200 it must be number 4 while the rods can be 6 for 200 or 8 for 100. I am not sure if they allow for less than 4 with 100????? The sheet should be bonded to the electric ground, as I recall this is to be number 8. It needs this bond for a couple reasons, one being step potential so its at the same plane as the ground you are standing on and as fault protection should something short to it.

 

[Aceman]

1. Is your barn a steel building or just sided with sheetmetal?
2. Do you have a metal well casing or an underground steel waterpipe in contact with the earth for at least 10 feet?

If you use the ground rods place them at least 10 feet apart and try to put them in a damp place.

The code says I can put rods at least 6' apart and wherever it's convenient.

 

[walrus]

wherever it's convenient.

I don't think it even says that. Put'em downtown if you want as long as you have 2,6ft apart, there isn't much that can be said.

 

[burleymike]

The barn is wood frame with steel panels. The well is a shallow well 16 foot steel pipe. The last 8' of the well casing is in saturated sand year around.

When I ran new 200 amp service to the house inspector told me to use #6 solid copper to the 2 ground rods at 6 foot apart. I will ask if #8 will work or 100 amp.

Thanks again

 

[Torque1st]

AFAIK #6 solid is the standard for grounding.