Overcurrent (Overload) Protection for Service Condutors and Equipment

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Clark Mason @MTC said:
There was an earlier post about panelboards that you responded to saying that the buss is a feeder. Did I read that correctly?
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Yes, that is correct.

There was also a post about tapping two feeders to the load side of the service OCPD.

Feeder doesn't mean wire, exclusively. In both of those cases, the load side of the OCPD is a feeder and 215.3 applies.
 
Okay thanks I reread them as well. (thanks for pointing out that a feeder isn't necessarily a conductor - I had to reread the definition to convince myself of that because I was about to argue that it had to be. :slaphead: not germane to the point I'm working on but still.....thanks)

So we are to consider the panelboard buss as a feeder. If that's the case, that feeder has to be sized according to Article 215, correct?
 
Clark Mason @MTC said:
So we are to consider the panelboard buss as a feeder. If that's the case, that feeder has to be sized according to Article 215, correct?
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Yes. Unless you have the situation of a main lug service panel with 6 or less breakers (meeting the 6 disconnect rule.). Then the panelboard bus would be service entrance conductors.
 
david luchini said:
Yes. Unless you have the situation of a main lug service panel with 6 or less breakers (meeting the 6 disconnect rule.). Then the panelboard bus would be service entrance conductors.
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Agreed on the MLO version.

So if that's the case (MCB version), according to 215.2, the "feeder" (buss) should have an allowable ampacity not less than 125% of continuous and 100% of non-continuous load. Correct?
 
Clark Mason @MTC said:
(thanks for pointing out that a feeder isn't necessarily a conductor - I had to reread the definition to convince myself of that because I was about to argue that it had to be. :slaphead: not germane to the point I'm working on but still.....thanks)
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Same goes for metering for that matter.

Group metering or Meter Packs without an OCPD in the Main Terminal box and the buss bars from the point of the incoming connection all the way to the line side of the individual tenant mains are considered Service Conductors.

Put a Main OCPD in the tap box, and now, the conductors to the line side of the Main OCPD are the service conductors, but, the same buss bar from the load side of the main to the line side of the tenant mains have now become a feeder.

JAP>
 
david luchini said:
Correct.
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Great, FWIW, IMHO, that would have been a much better way to argue your point from the beginning. :)

I see a small problem here which is semi-analogous to the 230.42/230.90 issue we've been discussing all along.

According to 408.30 "All panelboards shall have a rating not less than the minimum feeder capacity required for the load calculated in accordance with Part III, IV, or V of Article 220, as applicable."

None of those 220 sections require the 125%/100% calculation; as a matter of fact they allow for reduction of the allowable ampacity under some fairly common circumstances. Therefore, it seems to me that I could legally size the panelboard much smaller than 215.3 requires thereby violating the requirements for allowable ampacity if it is considered a "feeder".

Furthermore; "408.36 Overcurrent Protection. In addition to the requirement of 408.30, a panelboard shall be protected by an overcurrent protective device having a rating not greater than that of the panelboard." would require me to size the OCPD at not more than the buss size which would violate the 125%100% requirement for a feeder OCPD.

Does this seem about right?
 
jap said:
Same goes for metering for that matter.

Group metering or Meter Packs without an OCPD in the Main Terminal box and the buss bars from the point of the incoming connection all the way to the line side of the individual tenant mains are considered Service Conductors.

Put a Main OCPD in the tap box, and now, the conductors to the line side of the Main OCPD are the service conductors, but, the same buss bar from the load side of the main to the line side of the tenant mains have now become a feeder.

JAP>
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true enough - just goes to show you learn something every day if you pay attention. :D
 
Clark Mason @MTC said:
Great, FWIW, IMHO, that would have been a much better way to argue your point from the beginning. :)
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I did...about 75 posts ago.

Clark Mason @MTC said:
I see a small problem here which is semi-analogous to the 230.42/230.90 issue we've been discussing all along.

According to 408.30 "All panelboards shall have a rating not less than the minimum feeder capacity required for the load calculated in accordance with Part III, IV, or V of Article 220, as applicable."

None of those 220 sections require the 125%/100% calculation; as a matter of fact they allow for reduction of the allowable ampacity under some fairly common circumstances. Therefore, it seems to me that I could legally size the panelboard much smaller than 215.3 requires thereby violating the requirements for allowable ampacity if it is considered a "feeder".

Furthermore; "408.36 Overcurrent Protection. In addition to the requirement of 408.30, a panelboard shall be protected by an overcurrent protective device having a rating not greater than that of the panelboard." would require me to size the OCPD at not more than the buss size which would violate the 125%100% requirement for a feeder OCPD.

Does this seem about right?
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That doesn't seem about right. You are falling into the same trap, expecting a reference to something that has already been spelled out in the Code.

None of the Art. 220 sections require the 125%/100% calculation, because Art. 220 is for calculating loads, not sizing feeders.

"All panelboards shall have a rating not less than the minimum feeder capacity required for the load calculated..." Not less than the minimum feeder capacity are the key words here. This brings you back to 215.2. You still have to meet the 215.2 requirements for the 125%/100%, and you still have to meet the 215.3 requirements for the OPCD.
 
jaggedben said:
I don't know if it 'gives us a method.' It just says we have to do it somehow. Gotta look elsewhere for exact methods. There are several different code sections that could come into play. I think I agree with David as to the general principle he's arguing, although I would point out that the OCPD(s) may be protecting various things besides a 'feeder' on the load side. There might be a panelboard, a branch circuit, a inverter output circuit, or various combinations thereof. Each of those items is going to have a code section that is applicable to the load side. As far as I can tell, that's going to trump any calculation based on the service conductors every time.
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panelboard bus is a part of the feeder.

branch circuit? You are not in art 215 or 230 anymore if that is what is on load side of the breaker.

inverter output? If connected directly to feeder conductors - those conductors are still feeders. If there is another overcurrent device in there, then it may be a feeder or it may be a branch circuit.



david luchini said:


I'm not sure how many ways I can same the same thing...There isn't anything in Art. 230 about a minimum size for the OCPD because it has already been covered by Art. 215.



Did you take my simple exercise from post #61? Sorry, not trying to be silly, but I've given you the answer to your question and tried to explain it, but it obviously hasn't sunken in. A picture will be worth a thousand words in this case.
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Why is there a section on branch circuits, a section on feeders and a section on services? Why should an aspect of services be covered by the section on feeders if we have those three separately mentioned sections, or at least without wording that says "for this situation see 215.xxx".

david luchini said:
Like I said, a picture is worth a thousand words.

View attachment 21209
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Sorry if I missed something posted after this, kind of skimmed through those posts, but you didn't bring up anything I haven't already considered here.

it is possible to provide protection for the feeder and for the service conductors with one device. I still don't see how that means that 215 sets any requirements for the service conductors. You just happen to have one device that fulfills two requirements.

If you had an installation of a single load, you still likely have one overcurrent device that provides overcurrent protection to the service conductors as well as providing overcurrent protection for the branch circuit. You don't have a feeder at all in this installation and 215 shouldn't apply to anything in that installation.
 
kwired said:
Why is there a section on branch circuits, a section on feeders and a section on services? Why should an aspect of services be covered by the section on feeders if we have those three separately mentioned sections, or at least without wording that says "for this situation see 215.xxx".
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An aspect of services is not covered by the sections on feeders.

kwired said:
it is possible to provide protection for the feeder and for the service conductors with one device. I still don't see how that means that 215 sets any requirements for the service conductors. You just happen to have one device that fulfills two requirements.
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215 doesn't set any requirements for the service conductors. One device fulfills two requirements, why would the Code have minimum rating requirements for ONE device twice? Once you have established the minimum rating for that device, there is no reason to establish the minimum rating again.

kwired said:
If you had an installation of a single load, you still likely have one overcurrent device that provides overcurrent protection to the service conductors as well as providing overcurrent protection for the branch circuit. You don't have a feeder at all in this installation and 215 shouldn't apply to anything in that installation.
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215 doesn't apply to that installation...210 does. See post #77.
 
david luchini said:
215 doesn't set any requirements for the service conductors. One device fulfills two requirements, why would the Code have minimum rating requirements for ONE device twice? Once you have established the minimum rating for that device, there is no reason to establish the minimum rating again.
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I see this as no different than overload protection and short circuit/ground fault protection provided by same device for motors. Not something that normally is provided by one device, but not impossible on some small motors to accomplish that way either. Two different requirements from two different code sections. If one device can fulfill both requirements, there is no need for two of the same device. Both requirements still come from two different sections of code.
 
kwired said:
panelboard bus is a part of the feeder.
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Debatable perhaps, but also irrelevant given that Article 408 would still come into play if it weren't.

branch circuit? You are not in art 215 or 230 anymore if that is what is on load side of the breaker.
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I believe that was exactly my point. Any number of code sections might come into play for the OCPD of a permissible additional service disconnect for a single branch circuit.

inverter output? If connected directly to feeder conductors - those conductors are still feeders. If there is another overcurrent device in there, then it may be a feeder or it may be a branch circuit.
...
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An inverter output can be connected directly to a service with a single OCPD. Very debatable if there are any 'feeders' necessarily involved, but again that's also irrelevant because Article 705 governs the size of the OCPD.
 
jaggedben said:
Debatable perhaps, but also irrelevant given that Article 408 would still come into play if it weren't.



I believe that was exactly my point. Any number of code sections might come into play for the OCPD of a permissible additional service disconnect for a single branch circuit.



An inverter output can be connected directly to a service with a single OCPD. Very debatable if there are any 'feeders' necessarily involved, but again that's also irrelevant because Article 705 governs the size of the OCPD.
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Panel bus on load side of service disconnect is part of the feeder supplied by the main breaker, don't think there is much to debate there. If you have 125 amp bus you can't protect it with 200 amp breaker. Bus bars are "conductors" they just aren't art 310 conductors.

I'm not up to speed on all things associated with PV, but anything connected directly to service conductors is still service conductors. If there is a breaker between service conductors and the PV system, then utility side of that breaker is service conductors and conductors on non utility side is either a feeder or a branch circuit.
 
kwired said:
Panel bus on load side of service disconnect is part of the feeder supplied by the main breaker, don't think there is much to debate there. If you have 125 amp bus you can't protect it with 200 amp breaker. Bus bars are "conductors" they just aren't art 310 conductors.
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I think there's an unresolved point about whether panelboards are sized per 215 or 220-per-408. But that's still irrelevant to the original question concerning why 230 doesn't say anything. It's one of those above, not 230.

I'm not up to speed on all things associated with PV, but anything connected directly to service conductors is still service conductors. If there is a breaker between service conductors and the PV system, then utility side of that breaker is service conductors and conductors on non utility side is either a feeder or a branch circuit.
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No failing of yours that you aren't up to speed on all things PV, but there's a long standing debate over whther the conductors for a supply side inverter connection are service conductors. The CMP seems to be coming down on the side that they are not, in 2020. But anyway, 705 still supersedes anything in Chapter 2 regarding the OCPD for such a connection. It might as well not be a branch circuit or a feeder if none of the rules for those apply.
 
kwired said:
I see this as no different than overload protection and short circuit/ground fault protection provided by same device for motors. Not something that normally is provided by one device, but not impossible on some small motors to accomplish that way either. Two different requirements from two different code sections. If one device can fulfill both requirements, there is no need for two of the same device. Both requirements still come from two different sections of code.
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I guess your can compare it to motor overload/ scgf protection....other than the obvious differences.

For a motor, the overload protection and scgf protection are usually different devices. For the service OCPD, it's always the same device providing the overload protection to the service conductors on the line side and the overcurrent protection to the feeder conductors on the the load side. Not much of a comparison there.

And for the motor, there are separate rules for the scgf protection and overload protection...one device can provide both functions if it fullfils both requirements. While for the service OCPD, there is only one rule relating to the minimum size of the device based on the continuous/ non-continuous load. The device can't meet "both" rules if there is only one.
 
david luchini said:
I guess your can compare it to motor overload/ scgf protection....other than the obvious differences.

For a motor, the overload protection and scgf protection are usually different devices. For the service OCPD, it's always the same device providing the overload protection to the service conductors on the line side and the overcurrent protection to the feeder conductors on the the load side. Not much of a comparison there.

And for the motor, there are separate rules for the scgf protection and overload protection...one device can provide both functions if it fullfils both requirements. While for the service OCPD, there is only one rule relating to the minimum size of the device based on the continuous/ non-continuous load. The device can't meet "both" rules if there is only one.
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OP even mentioned three rules for minimum ampacity of conductor, one in 210, one in 215 one in 230.
 
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