[jculber]

Today I was helping another crew of the company I work for on a new addition to the hospital. I have never done any kind of work with hospitals and other similar projects. I was in charge of devicing out all of the receptacles and switches and while doing the recepts. I noticed a little green triangle on them. Looking further into it I found that this meant the recept. had an Isolated Ground. Now I wasn't able to just go and ask the supervisor what this meant but I am really curious as to what this means and how it works.

Hope I am not being too naive about this and thanks.

 

[BryanMD]

In hospitals, doctors offices etc (see section 517) there is a requirement for an additional grounding method beyond what every other device would have (why is a whole other discussion to have).

It's accomplished one of several ways but basically you'll either have 2 green wires (the second should have a yellow stripe), or there will be a bonding strip within the MC, or if in conduit they'll pull a green. (I'll assume you understand all the above)

At the device, the *second* grounding method attaches to the receptacle or switch and the first to the J box. if you are doing the devicing be sure you know which is which (not always clear) and NEVER mix the two.

Similar is done in IT applications but that is a another whole other discussion.

The only dumb question is the one not asked.

 

[nap]

if installed properly, there will be a seperate EGC which is isolated from the other EGC via standoffs in each panel it passes through all the way back to the service disconnect.

the iso ground is not to be connected to any normal grounding connections whether it be part of the conduit run (boxes etc. ) or as joints. The only place it is to be connected is on a device that is scheduled to have an iso ground.

hopefully the only place you landed that ground was on the ground terminal of the receps and you did not connect it to the normal EGC that should be in the conduit right along with the iso EGC.

 

[BryanMD]

Nap, I deliberately didn't get into the panel end
Far too often that is where the problems between theory of IG and practice are.





I still prefer the term "redundant" for that reason.

 

[nap]

In hospitals, doctors offices etc (see section 517) there is a requirement for an additional grounding method beyond what every other device would have (why is a whole other discussion to have).

It's accomplished one of several ways but basically you'll either have 2 green wires (the second should have a yellow stripe), or there will be a bonding strip within the MC, or if in conduit they'll pull a green. (I'll assume you understand all the above)

At the device, the *second* grounding method attaches to the receptacle or switch and the first to the J box. if you are doing the devicing be sure you know which is which (not always clear) and NEVER mix the two.

Similar is done in IT applications but that is a another whole other discussion.

The only dumb question is the one not asked.

I have to disagree with you here Brian (edit; sorry, I know, it's Bryan). The iso ground is not required and is not intended for the reason you post. A hospital uses the iso ground for the same reason you use it in an IT application. It is used on circuits used to power critical electronic equipment.. There is a requirement that the patient area receps are fed with an insulated EGC but it does not need to be iso.

and this is a sticking point with me but MC is not used in the application and is not constructed in the fashion you post. It is AC cable that has the redundant bonding wire.

 

[BryanMD]

The iso ground is not required and is not intended for the reason you post.

I didn't post any of the reasons. I tried to limit myself to addressing his basic Q about what was behind the device he saw. I believe I did that.

and this is a sticking point with me but MC is not used in the application and is not constructed in the fashion you post. It is AC cable that has the redundant bonding wire.

fair point. We should be more careful to not refer to all of that type as MC. fwiw Southwire (and others) do make an HCF MC .

 

[nap]

=BryanMD;30560]I didn't post any of the reasons. I tried to limit myself to addressing his basic Q about what was behind the device he saw. I believe I did that.

my point is that is not what the iso ground is for. It is not the reduntant ground required by the code in patient care areas. It would acutally be a third ground conductor where used in patient care areas. The first being the cable wrap itself, the second being the normal EGC and the iso being the third.

fair point. We should be more careful to not refer to all of that type as MC. fwiw Southwire (and others) do make an HCF MC

I have not dealt with the HCF-MC and no of no supply houses that carry it although I presume it could be special ordered. While it appears to meet the requirements, something somewhere along my travels, it seems there was a problem with it in medical facialiies applications. Could be remembering incorrectly so I cannot say no with any confidence. Could have been simply a stubborn inspector I was talking with. Not sure.

 

[BryanMD]

my point is that is not what the iso ground is for. It is not the reduntant ground required by the code in patient care areas. It would acutally be a third ground conductor where used in patient care areas. The first being the cable wrap itself, the second being the normal EGC and the iso being the third.

Oh! Now I've gotcha (I think. LOL).

That mention of 'redundant' should have been deleted before I posted. It was far off point and I meant to but didn't. That discussion could go on to 300 posts (and has) by folks far better versed in theory than I'll ever be.

But what is this **3rd** ground conductor you speak of Kemosabe? I've done plenty of patient care areas and IT related IG's but never anything in an actual hospital room (if that is the application for a 3rd grnd wire). 'splain yourself Lucy.

 

[JohnJ0906]

Patient care areas have redundant grounding - metal conduit/cable sheath (517.13(A)), AND an insulated EGC (517.13(B).

IG receptacles in a patient care area - see 517.16. See also the FPN.

 

[Speedy Petey]

We should be more careful to not refer to all of that type as MC. fwiw Southwire (and others) do make an HCF MC .

Yes, they do. And it is NOT cheap.
I think I paid over $1/ft last job.

 

[Bkessler]

I think nap is talking about the metal jacket as the 3rd ground. BMD

 

[nap]

I think nap is talking about the metal jacket as the 3rd ground. BMD

yes.

If there is no iso ground, there still must be 2 EGC's. The conduit (sheath with the bare solid bond wire) or solid metal conduit (emt, imc, rmc) and the insulated EGC conductor.

If you also need an iso ground in that same area, you would end up with a third EGC.