2 ground rods required?

[junkhound]

Nothing written, but most inspectors here will let you by with just one rod for a remote building/shed.

LOL, here in WA the first thing inspectors ask if you have ground rods or concrete encased electrode.

 

[Joethemechanic]

Back when barns and outbuildings used three arial conductors for feeders (two hots and a neutral) and had a ground rod, was it correct or incorrect to have a N-G bond in the barn's panel?

I'm talking about systems where the service was usually at the house

 

[petersonra]

Back when barns and outbuildings used three arial conductors for feeders (two hots and a neutral) and had a ground rod, was it correct or incorrect to have a N-G bond in the barn's panel?

I'm talking about systems where the service was usually at the house

there used to be an exception that allowed for this in many cases.

 

[jaggedben]

Back when barns and outbuildings used three arial conductors for feeders (two hots and a neutral) and had a ground rod, was it correct or incorrect to have a N-G bond in the barn's panel?

I'm talking about systems where the service was usually at the house

It was allowed.

there used to be an exception that allowed for this in many cases.

The exception still exists for installations that were compliant when they were installed.

 

[Electrical Geek]

Most (not all) jurisdictions around here are fine with one rod and water pipe, or sometimes even two rods if you don't use the water pipe. I think few understand that the code says you still need a 2nd rod even if you have the water pipe. Detached buildings I frequently find done wrong in various ways, I think many inspectors are just not aware of those rules. The biggest AHJs around here enforce things thoroughly.

I find it funny that 250.53(D)(2) states 'A metal underground water pipe shall be supplemented by an additional electrode...'which is singular so we only need one, but then refers us to 250.53(A) for the installation, one would think. If you follow the entirety of that code then you are essentially supplementing the supplemental, which doesn't make sense to me.

 

[infinity]

I find it funny that 250.53(D)(2) states 'A metal underground water pipe shall be supplemented by an additional electrode...'which is singular so we only need one, but then refers us to 250.53(A) for the installation, one would think. If you follow the entirety of that code then you are essentially supplementing the supplemental, which doesn't make sense to me.

A single rod is not an electrode until it meets the 25 ohms or less test. That's why most guys just install two.

 

[Electrical Geek]

A single rod is not an electrode until it meets the 25 ohms or less test. That's why most guys just install two.

The 25 ohms or less test only applies to whether the supplemental is needed or not, not whether the supplemental needs a supplemental, or am I reading it wrong and why?

 

[jaggedben]

The 25 ohms or less test only applies to whether the supplemental is needed or not, not whether the supplemental needs a supplemental, or am I reading it wrong and why?

250.53(A)(2) requires the rod to have a supplemental electrode of a type specified in 250.52(A)(2) thru (8). That notably excludes 250.52(A)(1), which is the water pipe. So the water pipe cannot supplement the rod.

250.53(D)(1) requires the water pipe to have a supplemental electrode that, if a rod, pipe or plate, complies with entirety of 250.53(A), which in turn requires the additional supplemental electrode that is not the water pipe.

In other words, they very deliberately wrote it to require two rods to supplement the water pipe if you don't have one of the other things like a ufer. Not easy to follow, but very clear once you do.

 

[Electrical Geek]

250.53(A)(2) requires the rod to have a supplemental electrode of a type specified in 250.52(A)(2) thru (8). That notably excludes 250.52(A)(1), which is the water pipe. So the water pipe cannot supplement the rod.

250.53(D)(1) requires the water pipe to have a supplemental electrode that, if a rod, pipe or plate, complies with entirety of 250.53(A), which in turn requires the additional supplemental electrode that is not the water pipe.

In other words, they very deliberately wrote it to require two rods to supplement the water pipe if you don't have one of the other things like a ufer. Not easy to follow, but very clear once you do.

Ok, so, the code requires that, with an underground water pipe, you have to supplement the supplemental. I kind of figured that was how it's being interpreted. Thank you.

 

[Joethemechanic]

there used to be an exception that allowed for this in many cases.

Yeah, but should the barn fed by 3 wires from the house have a N-G bond? I always felt that it should because it provided a low impedance path in the event of a hot falting to ground. Ground rod alone isn't low enough impedance to blow even a 15 amp fuse

 

[LarryFine]

Yeah, but should the barn fed by 3 wires from the house have a N-G bond? I always felt that it should because it provided a low impedance path in the event of a hot falting to ground. Ground rod alone isn't low enough impedance to blow even a 15 amp fuse

Yes, it must be bonded, just like a service, and for the same reasons.

 

[infinity]

Ok, so, the code requires that, with an underground water pipe, you have to supplement the supplemental. I kind of figured that was how it's being interpreted. Thank you.

You have to supplement the water pipe with another electrode. A single rod can be the other electrode but it requires testing to prove 25Ω or less.

 

[jaggedben]

Yeah, but should the barn fed by 3 wires from the house have a N-G bond? I always felt that it should because it provided a low impedance path in the event of a hot falting to ground. Ground rod alone isn't low enough impedance to blow even a 15 amp fuse

Absolutely it needs to be bonded. Lack of bonding at outbuildings, one way or the other, is by far the most dangerous condition that I seem to encounter in the field once a year or so.