Over kill bond bushing

[Shawn pavich]

I'm a electrician transition to solar about 2 yrs ago .fyi solar pays really good I just don't understand why. my first solar company I worked for used bond bushing everywere even the 240 volt AC side I ask my boss about it he said that's what the sub contracter wanted fair enough. So now I work for a company that sells there own solar I don't use bond bushing only on ringed knock outs and the box connecters we use have a lock rings with teeth I have worked all over ca but obviously not in every jurisdiction I try to tell the other guys you are over doing it with the ground bushing wast of money if we don't need it I have guys bond bushing the AC side there excuse is in the city Fontana are whatever city,they make you put bond bushing. I've never not passed a inspection because not having a bond bushing were it was not needed so is there excuse valid can the AHJ make you put bond bushing were you have a a means of bonding already that is listed in nec 250.92 thanks

 

[luckylerado]

... can the AHJ make you put bond bushing were you have a a means of bonding already that is listed in nec 250.92....

Probably, however generally speaking if you have code on your side and can make a case without being standoffish it has been my experience that AHJ will back off if they realize they are asking for more than is required.

I very often find that those guys that go way overboard on things like this often do so because they lack knowledge of what the code actually says.

 

[petersonra]

how much more does a bonding bushing cost over a standard lock nut?

I don't know much about solar installs but maybe there are some locals that think it is necessary and it is cheaper to add 50 cents to the cost of a job in hardware rather than fight it and spend thousands of dollars in time.

 

[Smart $]

...the box connecters we use have a lock rings with teeth...
...listed in nec 250.92...

FWIW, "lock rings with teeth" are still standard locknuts and among the listed items in 250.92(B). The closest item is a bonding-type locknut, which has a set screw. After tightening the locknut in the normal fashion, you tighten the set screw to "bite" into the enclosure metal.

 

[Shawn pavich]

The last job it was about 60 dollar loss just on ground bushing it was about a 3 day project we do about 3 jobs a week that is a whole lot of money at the end of the year like I said I've never been Called on it I had a Inspecter ask me were my ground bushing was on a bell box haha I really don't think its the AJH it's the installers that's the way they were taught

 

[Shawn pavich]

I have been known to be wrong more then being right. We use Bridgeport box connecters the set screw type and compression type both state that for connecting and bonding EMT to box are enclosure the lock nuts come with it they are not flat they have teeth so would that be a listed fitting under bonding over 250 volts ex 4

 

[Smart $]

I have been known to be wrong more then being right. We use Bridgeport box connecters the set screw type and compression type both state that for connecting and bonding EMT to box are enclosure the lock nuts come with it they are not flat they have teeth so would that be a listed fitting under bonding over 250 volts ex 4

I believe those qualify under the 250.97 Exception items #3 and #4.

 

[jaggedben]

A lot of the bonding bushing stuff has to do with GEC requirements and readings of 250.64. When you have a large grounded inverter there may be some sense to this, but I agree it's probably overkill a long as everything is well bonded. For transformerless inverters it's definitely overkill, and the 2014 code says so. (Well, sort of.)

how much more does a bonding bushing cost over a standard lock nut?

I don't know much about solar installs but maybe there are some locals that think it is necessary and it is cheaper to add 50 cents to the cost of a job in hardware rather than fight it and spend thousands of dollars in time.

It's more a labor issue. I've spent as much as half an hour on a single bonding bushing, and I have a special small ratchet in my tool belt for the tight corners. When you have a job that's got 10 of the things and they each take a 5 minutes to install and land the wire on them that becomes a significant percentage of the time spent on a job that may be scheduled for one 8 hour day. It's the sort of thing that if you can avoid it might mean not having to rearrange schedules and piss off customers. And how much is that worth?

 

[Zee]

It's more a labor issue. I've spent as much as half an hour on a single bonding bushing,

aahhh.... the little grounding bushing. The bane of my working existence.:rant::rant:

To SHAWN:
DC side: You need those when 2 things are both simultaneously true: on eccentric or concentric KO's ( as shawn said: "ringed" ko's) AND when circuit is over 250 vdc (99% of DC PV).

AC side: only use if you have a GEC, aka big fat green wire, in conduit.

Usually, I see "underkill" on dc and overkill on ac.

As jaggedben said it is the labor: I have spent serious time on getting them conscientiously applied. I am embarrassed to even give a number.

I hate these so much...... i buy boxes for the DC side that DO NOT have stamped, ringed KO's so i can drill a hole and just use a lock ring.
Remember: even if dc V is over 250 V you do not need a bonding bushing if you have no "rings" on KO.

ALso: Use one if your conduit just ends in the air,( quite typical on a roof under array),
or in a plastic enclosure. (solaredge inverter for example)

 

[Zee]

I have a special small ratchet

The Husky, double ended, 1/4" hex drive, fine ratchet every 7 degrees?:thumbsup:

I call it the Magic Tool.

 

[djd]

djd

djd

I'm a electrician transition to solar about 2 yrs ago .fyi solar pays really good I just don't understand why. my first solar company I worked for used bond bushing everywere even the 240 volt AC side I ask my boss about it he said that's what the sub contracter wanted fair enough. So now I work for a company that sells there own solar I don't use bond bushing only on ringed knock outs and the box connecters we use have a lock rings with teeth I have worked all over ca but obviously not in every jurisdiction I try to tell the other guys you are over doing it with the ground bushing wast of money if we don't need it I have guys bond bushing the AC side there excuse is in the city Fontana are whatever city,they make you put bond bushing. I've never not passed a inspection because not having a bond bushing were it was not needed so is there excuse valid can the AHJ make you put bond bushing were you have a a means of bonding already that is listed in nec 250.92 thanks

We are doing and I have done what your talking about in the past. The engineers make us do it its in the specs of the job. I to think it a little overkill, but theres a whole lot of potential on these roofs for problems,, we used them on every connector AC and DC. I got really good at putting them and fixing the ones guys strip out. were grounded:happysad:

 

[electro7]

AHJ's in the bay area go hard on this ground bushing thing. I think the confusion is whether or not the grounding conductor from the roof array racking, etc. is a GEC or EGC. Didn't that get changed between a code cycle? Could somebody help me out with a reference for that?

After running into so many AHJ's in the bay area requiring ground bushings I am confused on where it is really required anymore. I thought the general rule was any circuits over 250 volts, use a ground bushing. Or wherever a GEC is run, use a ground bushing? How about at an LB where there is no place for a locknut or ground bushing?

 

[jaggedben]

AHJ's in the bay area go hard on this ground bushing thing. I think the confusion is whether or not the grounding conductor from the roof array racking, etc. is a GEC or EGC. Didn't that get changed between a code cycle? Could somebody help me out with a reference for that?

It's pretty vague. If you're on the 2013 CEC then there's no 690.47(D) so I would argue that nothing coming from the array is a GEC. If you're on other codes, then maybe you have to have this GEC somewhere. Exactly where is not clear.

Thankfully the AHJs I've dealt with in the bay area all seem to ignore 690.47(D). But then it's not part of the code right now, either.

Any in any case, you still have more stringent bonding for circuits over 250 volts, and you need some kind of bonding for chases between arrays.

Or wherever a GEC is run, use a ground bushing?

Pretty much, but see 250.92. It's not the only method allowed, just the easier one in many situations.
The key point is that you have to do it around concentric or eccentric knockouts.

How about at an LB where there is no place for a locknut or ground bushing?

Threaded hubs of any sort do not require bushings, as they are an acceptable means of bonding by themselves. 250.92(B)(2).

 

[Shawn pavich]

I just had a failed a inspection in tulare ca because I did not have a bond bushing on a concentric KO from the main service to the solar disconnect 240 volts, I ask for a code reference he said 250.92 services he said that solar is a service,I told him he is wrong talked to his superviser he told me the samething and if I want to come in he can show me a picture lol he did not even want to here about 250v are more. I was very polite I told him I would give him 1000 $ if he can actually prove me wrong with some type of code reference

 

[jaggedben]

I just had a failed a inspection in tulare ca because I did not have a bond bushing on a concentric KO from the main service to the solar disconnect 240 volts, I ask for a code reference he said 250.92 services he said that solar is a service,I told him he is wrong talked to his superviser he told me the samething and if I want to come in he can show me a picture lol he did not even want to here about 250v are more. I was very polite I told him I would give him 1000 $ if he can actually prove me wrong with some type of code reference

Yes, well some inspectors simply don't know the code as well as most electricians. :rant: And some are willing to read sections you point to, and some aren't.

Also, if you do have a grounded system, that AC side grounding conductor is probably also a GEC so you do need the bonding bushing. So they could have been right for the wrong reason, and you could owe them $1000. If it's a ungrounded system, it's much more debatable.

FWIW, I still install bonding bushings pretty much everywhere so that inspectors can't debate if I have enough bonding. And after all, most of this stuff is outdoors and subject to corrosion and other potential damage, so redundancy doesn't hurt.

 

[ggunn]

I just had a failed a inspection in tulare ca because I did not have a bond bushing on a concentric KO from the main service to the solar disconnect 240 volts, I ask for a code reference he said 250.92 services he said that solar is a service,I told him he is wrong talked to his superviser he told me the samething and if I want to come in he can show me a picture lol he did not even want to here about 250v are more. I was very polite I told him I would give him 1000 $ if he can actually prove me wrong with some type of code reference

Shaming an inspector into agreeing with you. Yeah, that always works.

 

[Shawn pavich]

It's a solar edge inverter ungrounded, but good point on the GEC for a grounded system,but wouldent the ground be a GES there for being a bonding jumper,I know that a bonding jumper does not have to be continuous and can have splices what I don't know is do I need to bond both sides of conduit for a bonding jumper thanks

 

[Smart $]

It's a solar edge inverter ungrounded, but good point on the GEC for a grounded system,but wouldent the ground be a GES there for being a bonding jumper,I know that a bonding jumper does not have to be continuous and can have splices what I don't know is do I need to bond both sides of conduit for a bonding jumper thanks

For a GEC, you must bond entries and exits. However, I think many misinterpret the requirement to think that means all raceway entries and exits. It is [in fact] conductive envelopment entries and exits. You only have to bond directly where the GEC transitions from conductive envelopment to non-conductive envelopment or completely exposed.

Let's say we have a combined EGC/GEC of PV system connected in MDP. Being the enclosure is metallic, the GES GEC(s) are bonded to the enclosure. The metallic raceway must be bonded... but it can be bonded to the enclosure using a bonding locknut. On the other end, the inverter enclosure is metallic, so the EGC/GEC is bonded to the enclosure. The raceway is bonded to the enclosure with a bonding locknut. No bonding bushings. No bonding jumpers.

 

[Smart $]

It's a solar edge inverter ungrounded, but good point on the GEC for a grounded system,but wouldent the ground be a GES there for being a bonding jumper,I know that a bonding jumper does not have to be continuous and can have splices what I don't know is do I need to bond both sides of conduit for a bonding jumper thanks

PS: A combination EGC/GEC is still treated as a GEC. Only difference is that it is permitted to terminate to the poco-side grounding bus, rather than using an irreversible connection. One gets to be creative if there are multiple inverters connected to the other end. :angel:

 

[Carultch]

For a GEC, you must bond entries and exits. However, I think many misinterpret the requirement to think that means all raceway entries and exits. It is [in fact] conductive envelopment entries and exits. You only have to bond directly where the GEC transitions from conductive envelopment to non-conductive envelopment or completely exposed.

Let's say we have a combined EGC/GEC of PV system connected in MDP. Being the enclosure is metallic, the GES GEC(s) are bonded to the enclosure. The metallic raceway must be bonded... but it can be bonded to the enclosure using a bonding locknut. On the other end, the inverter enclosure is metallic, so the EGC/GEC is bonded to the enclosure. The raceway is bonded to the enclosure with a bonding locknut. No bonding bushings. No bonding jumpers.

Thanks for the clarification. I'd like to put it in my own words to make sure I'm understanding this.

When you have a GEC routed through a continuous system of metal raceways and metal enclosures, you only need to connect the GEC via a bonding bushing to the raceways at the origin and destination of the GEC. All intermediate connections can have electrical continuity established by ordinary grounding practices (Myers hubs, standard locknuts, sealing locknuts, etc).

It is only when the raceway/enclosure system breaks electrical continuity (by a plastic enclosure, or similar reason), that you need to re-establish the connection to the GEC.

Additional question:
If your inverter has a GEC terminal inside it, that is also continuous with its metal enclosure, can this suffice? Or do you need an additional bonding bushing inside the inverter specifically because of the GEC?

The reason I ask, is that the space is limited inside a string inverter's cabinet. And it is difficult to get a bonding bushing in there, with its lug accessible. If the standard locknuts alone establish electrical continuity, and the GEC is internally bonded to the inverter enclosure, then I wouldn't see the need for the bonding bushing.

I do see the need for the bonding bushing inside the inverter, given conduit stubs in a bottomless enclosure, or given a non-metal enclosure for the inverter.