Conduit grounding multiple circuits

[plout99]

I have started running the conduit in my shop and got to thinking about grounding the circuits. Code says the conduit is sufficient for grounding however would pulling a single ground be a better practice for 3 circuits since code is the minimum? I also already have the 12 stranded in green. The conduit is also painted black from the manufacture does this change anything in its ability to ground sufficiently.

 

[dogdog]

you can test your conduit with a continuity meter no? all the way to the panel to make sure the connection is sound ?

 

[wyliesdiesels]

seeing as how the conduit would be thicker than the wire, Id say the conduit, when installed properly and continuous to the panel, is a better EGC...

 

[exranger06]

you can test your conduit with a continuity meter no? all the way to the panel to make sure the connection is sound ?

Continuity doesn't tell you anything about solid connections or current-carrying capability. It tells you that SOME (unknown amount) of current is able to flow through. It doesn't tell you how much. For example, you can test the continuity of a piece of 14 gauge wire. Then test the continuity of a 4 gauge wire. You'll get the exact same results. Does that mean a 14 gauge wire can carry just as much fault current as a 4 gauge wire? Nope.
To test wire and connections, you need to actually put the wire under full load, or close to it. If a wire is supposed to be able to handle 30 amps and you want to test it, you need to actually put 30 amps through it. It's just like plumbing: If a pipe is supposed to be able to handle 60 psi of water, and you want to check it for leaks, you pressurize it to 60 psi and then check for leaks. You don't put only 5 psi in it and assume it's good because it's not leaking at 5 psi.

 

[dogdog]

Continuity doesn't tell you anything about solid connections or current-carrying capability. It tells you that SOME (unknown amount) of current is able to flow through. It doesn't tell you how much. For example, you can test the continuity of a piece of 14 gauge wire. Then test the continuity of a 4 gauge wire. You'll get the exact same results. Does that mean a 14 gauge wire can carry just as much fault current as a 4 gauge wire? Nope.
To test wire and connections, you need to actually put the wire under full load, or close to it. If a wire is supposed to be able to handle 30 amps and you want to test it, you need to actually put 30 amps through it. It's just like plumbing: If a pipe is supposed to be able to handle 60 psi of water, and you want to check it for leaks, you pressurize it to 60 psi and then check for leaks. You don't put only 5 psi in it and assume it's good because it's not leaking at 5 psi.

It have everything to do with how the conduit is connected, if you make sure that a solid connection is done at each joint. Continuity is a way to verify. Now your argument about full load to test the capability of the ground connection? That might be a far fetch. I want to hear how you do this test .




BTW you don't pull a 10Ga for ground if your expected load is 30AMP either...

 

[jayrush13]

seeing as how the conduit would be thicker than the wire, Id say the conduit, when installed properly and continuous to the panel, is a better EGC...

I would not be so sure. Most emt installed indoors would be using set srew connectors and couplings I would say a solid properly sized EGC would be a much better choice. I would never use emt conduit as an EGC just for the fact of how easy it can be pulled apart at joints accidentally. Ridgid conduit with threaded joints I would but pull EGC 99% of the time even with Ridgid. Just how I was taught by many of my journeyman. Not pulling a ground was just Hack work.

BTW you don't pull a 10Ga for ground if your expected load is 30AMP either...

What size would you pull?

 

[dogdog]

I would not be so sure. Most emt installed indoors would be using set srew connectors and couplings I would say a solid properly sized EGC would be a much better choice. I would never use emt conduit as an EGC just for the fact of how easy it can be pulled apart at joints accidentally. Ridgid conduit with threaded joints I would but pull EGC 99% of the time even with Ridgid. Just how I was taught by many of my journeyman. Not pulling a ground was just Hack work.



What size would you pull?

#2 size to fit


Pretty sure it says something in those doc. but the prerequisit is

In order for RMC, IMCand EMT to perform effectively as equipment grounding conductors, it is crucial that they are installed properly with tight joints

https://www.nema.org/docs/default-s...ven-to-meet-the-nec-reg.pdf?sfvrsn=c4ea5e08_3

 

[Norcal]

If a EGC is pulled in the conduit, it needs to be bonded at each termination point, not doing so will make it a poor performer in a fault situation.

 

[jayrush13]

#2 size to fit


Pretty sure it says something in those doc. but the prerequisit is



https://www.nema.org/docs/default-s...ven-to-meet-the-nec-reg.pdf?sfvrsn=c4ea5e08_3

#2 wire? For the ground on a 30amp load? Maybe I am not following what you are getting at with that. And yes it has everything to do with the connections and not so much the conduit itself. I know it is code compliant to use it as the EGC but I was taught otherwise. Just something that has always stuck with me guess I have seen to many old buildings with conduit pulled apart or damaged somehow makes that the extra step of pulling a ground wire seem like good practice.

 

[dogdog]

#2 wire? For the ground on a 30amp load? Maybe I am not following what you are getting at with that. And yes it has everything to do with the connections and not so much the conduit itself. I know it is code compliant to use it as the EGC but I was taught otherwise. Just something that has always stuck with me guess I have seen to many old buildings with conduit pulled apart or damaged somehow makes that the extra step of pulling a ground wire seem like good practice.

JK...

I don't see any merit or demerit with each methods... it all dependents on the person installing it..

 

[exranger06]

It have everything to do with how the conduit is connected, if you make sure that a solid connection is done at each joint. Continuity is a way to verify. Now your argument about full load to test the capability of the ground connection? That might be a far fetch. I want to hear how you do this test .




BTW you don't pull a 10Ga for ground if your expected load is 30AMP either...

If you make sure each connection is solid, then you don't need to check for continuity. That would be like checking continuity on every wire you wirenut together or every connection to a switch or outlet. If you know you've made a solid connection, why would you need to check the continuity? My point was that simply checking continuity without checking the connections doesn't tell you anything. You can have poor/loose connections and the meter would still show that you have continuity. And I wasn't suggesting that he actually try to put current on the conduit to test. I was just saying that, generally speaking, if you suspect you have bad wiring or connections, and you want to test it, you need to actually put some significant current through it. You can't just measure voltage or continuity when the wire is not under any load and assume it's good if it passes those tests.

 

[Jim greengo]

If a EGC is pulled in the conduit, it needs to be bonded at each termination point, not doing so will make it a poor performer in a fault situation.

What he said,lots of extra work.

 

[Terry D]

My own opinion, I know the conduit can serve as the equipment ground, but I always pull in a EGC. With your 3 circuits, as long as they are all 20 amp, a single #12 green EGC will be fine. The EGC should connect to the metal box, the devices and other EGC(s) leaving the box.

 

[sparky 1971]

I never pull a ground with EMT unless it is in the spec's, and it's very rare that I do a job that has a print, let alone spec's. That being said, I like it when the guy before me pulls a ground. That gives me a pull wire for adding a circuit.

 

[alfredeneuman]

The conduit is also painted black from the manufacture does this change anything in its ability to ground sufficiently.

The manufacturer uses a conductive coating that doesn't affect grounding.
(EDIT: With "Uncolored" EMT the coating is just clear.)

 

[dscheidt]

I would not be so sure. Most emt installed indoors would be using set srew connectors and couplings I would say a solid properly sized EGC would be a much better choice. I would never use emt conduit as an EGC just for the fact of how easy it can be pulled apart at joints accidentally. Ridgid conduit with threaded joints I would but pull EGC 99% of the time even with Ridgid. Just how I was taught by many of my journeyman. Not pulling a ground was just Hack work.

if the emt is installed properly, with the set screws tight, and lock rings wrench tight, the conduit is a vastly lower impedance path to ground than a puny little ground wire. Even if you run a ground, in the case of most faults, the fault current will be carried by the conduit, and not the wire. People who understand this lots better than I ever will have studied this, done measurements, and that's what they tell us. That's why the NEC doesn't require it. It can still make sense to run a ground, because if the conduit is damaged, the ground conductor will be used. Most EMT is pretty well protected from damage, so it's just a waste of money.

 

[alfredeneuman]

the fault current will be carried by the conduit, and not the wire.

The fault current will be split between the conduit and the wire, according to their respective impedance. The impedance of the conduit is less than the wire so it will carry most of the fault current.