Feeder "taps" not actually "tapped"?

[jap]

Simply stating "before" its point of supply would be a lot less ambiguous, but ambiguous is what the NEC does best. Thanks for clearing it up all the same, it makes more sense now. I assume also in GoldDigger's example with the MLO panel, which would supply NO OC protection at all to any feeders tapped off it's bus, then NO OCPD certainly "exceeds" the value permitted for similar conductors in 240.4. Although I guess if you continue upstream beyond the MLO panel you will eventually hit an OCPD that would most likely exceed the ampacity of the feeders, giving them the definition of a tapped conductor.

Your wording of this makes it confusing to interpret.

The Breakers (Or overcurrent protection devices) stabbed on to a MLO panel's buss bars creates the protection for a feeder or branch circuit.

Not all MLO panels have upstream protection.

The old 6 movement rule allowed 6 movement of the hands to kill a service, or, shutting off 6 breaker throws.

Yes the breakers in the MLO panels protect overloading the panel if sized correctly, but, if you put feed through lugs on the bussbars of a 6 movemne rule setup like this you are actually tapping service conductors not feeder conductors seeing as how the bussbars are not protected by an OCPD other than the fuse at the utility transformer.

Now, if the MLO panel does have an upstream overcurrent protection device such as an enclosed circuit breaker or fused disconnect ahead of it, and, you install lugs on the buss bars of that panel, then yes, you are then tapping the buss or feeder to the MLO panel.

But,

If your tap conductors are sized large enough for the OCPD serving the panel then you have not created a tap per se,, you have simply extended the feeder. If I connect a conductor of a lesser amperage to one of a larger amperage then I've made a tap and the tap rules start to apply to protect those smaller conductors from the larger amperage.

For something to be called a feeder it must have protection ahead of it to begin with.

JAP>

 

[ggunn]

240.21(B), aka "The Tap Rule" is explicitly written to govern feeder taps. Supply side connections (connections to service conductors) are not covered by this section of the code.

 

[electrofelon]

240.21(B), aka "The Tap Rule" is explicitly written to govern feeder taps. Supply side connections (connections to service conductors) are not covered by this section of the code.

Yeah there is often confusion on "service taps". The NEC doesn't call them "service taps" and the requirements are kind of spread over a bunch of sections, 230.40, 230.46, 230.70 thru 230.72. Then there is PV supply side connections which are sort of their own animal but really pretty much 230.40 exception number two in disguise

 

[hitehm]

Your wording of this makes it confusing to interpret.

The Breakers (Or overcurrent protection devices) stabbed on to a MLO panel's buss bars creates the protection for a feeder or branch circuit.

Not all MLO panels have upstream protection.

The old 6 movement rule allowed 6 movement of the hands to kill a service, or, shutting off 6 breaker throws.

Yes the breakers in the MLO panels protect overloading the panel if sized correctly, but, if you put feed through lugs on the bussbars of a 6 movemne rule setup like this you are actually tapping service conductors not feeder conductors seeing as how the bussbars are not protected by an OCPD other than the fuse at the utility transformer.

Now, if the MLO panel does have an upstream overcurrent protection device such as an enclosed circuit breaker or fused disconnect ahead of it, and, you install lugs on the buss bars of that panel, then yes, you are then tapping the buss or feeder to the MLO panel.

But,

If your tap conductors are sized large enough for the OCPD serving the panel then you have not created a tap per se,, you have simply extended the feeder. If I connect a conductor of a lesser amperage to one of a larger amperage then I've made a tap and the tap rules start to apply to protect those smaller conductors from the larger amperage.

For something to be called a feeder it must have protection ahead of it to begin with.

JAP>

Hey Jap - Thanks for the detailed explanation. Please see the attached pic that started my whole question about feeder tap. Notice the route in orange leaves MSP "A" on bus lugs, which the bus itself has 200A Main Breaker protection, then passes through the Backup Interface "B" with all of it's internal wiring (raises another question) and finally terminates at the subpanel "C" onto the 100A breaker. Also notice they sized the wiring for the 100A breaker in the subpanel (2awg) NOT the 200A breaker in the Main. So if I understand all of your guidance, this entire route is a feeder "Tap" because the protection "ahead of" it's supply (the 200A MSP bus) exceeds the ampacity of the conductors. So my 2 follow-up questions are:
1 - Am I correct in my assumption above that this entire route is a feeder "tap"
2- Does the 240.21B distance rules for feeder taps (10', 25' etc) apply to the entire route from "A" to "C" THROUGH device "B" with it's internal wiring, or since the wiring has 2 segments separated by Device "B" does that change which rule to follow (1/10th, 1/3rd etc).
Thanks for all your help!

 

[wwhitney]

Given the 200A main breaker in the Service Panel, the wiring from the Service Panel to the Backup Interface needs to satisfy one of these:

1) Be rated at 200A (not a tap)
2) Be supplied by a 100A breaker in the Service Panel and rated for 100A (not a tap)
3) Be rated at 100A and land on a 100A breaker in the Backup Interface (if that's an option), and comply with the tap rules.

And in case (1) above, the wiring from the Backup Interface to the 100A MCB Backup Loads Panel needs to either

4) Be rated at 200A (not a tap)
5) Be rated at 100A and comply with the tap rules.

Cheers, Wayne

 

[jap]

Hey Jap - Thanks for the detailed explanation. Please see the attached pic that started my whole question about feeder tap. Notice the route in orange leaves MSP "A" on bus lugs, which the bus itself has 200A Main Breaker protection, then passes through the Backup Interface "B" with all of it's internal wiring (raises another question) and finally terminates at the subpanel "C" onto the 100A breaker. Also notice they sized the wiring for the 100A breaker in the subpanel (2awg) NOT the 200A breaker in the Main. So if I understand all of your guidance, this entire route is a feeder "Tap" because the protection "ahead of" it's supply (the 200A MSP bus) exceeds the ampacity of the conductors. So my 2 follow-up questions are:
1 - Am I correct in my assumption above that this entire route is a feeder "tap"
2- Does the 240.21B distance rules for feeder taps (10', 25' etc) apply to the entire route from "A" to "C" THROUGH device "B" with it's internal wiring, or since the wiring has 2 segments separated by Device "B" does that change which rule to follow (1/10th, 1/3rd etc).
Thanks for all your help!
View attachment 2560767

Yes.
They've tapped a 200 amp feed with a smaller #2 conductor so yes from point "A" to point "C" is a feeder tap.
I would also venture to say that they've violated the tap rule by the tap conductors not landing on single OCPD or set of fuses first, seeing as how the Backup Interface seems to have no overload protection in it at all.

Some may not see it that way but I do.

JAP>

 

[jaggedben]

...
1 - Am I correct in my assumption above that this entire route is a feeder "tap"

Yes, but it's not allowed to be...

2- Does the 240.21B distance rules for feeder taps (10', 25' etc) apply to the entire route from "A" to "C" THROUGH device "B" with it's internal wiring, or since the wiring has 2 segments separated by Device "B" does that change which rule to follow (1/10th, 1/3rd etc).
Thanks for all your help!
View attachment 2560767

Okay well, you cannot really treat A to C as a single tap because the tap rules require the tap conductors from A to b1 to land at equipment with overcurrent protection, or a single overcurrent device if more than 10ft.
Where it says 'straight through connection from grid' at b1, can you not install a 125A breaker? That ends your tap conductors, and makes a lot of other questions go away.
I think you also need a breaker where the backup loads feeder connects to the Solaredge interface. But that's more of an article 705 requirement than a 240.21 requirement.

Also I second what Wayne said above as well, he was all correct, I'm just adding on.

 

[wwhitney]

Okay well, you cannot really treat A to C as a single tap because the tap rules require the tap conductors from A to b1 to land at equipment with overcurrent protection, or a single overcurrent device if more than 10ft.

Yes, this rule was the basis of my response, which I neglected to explain.

Cheers, Wayne

 

[hitehm]

Given the 200A main breaker in the Service Panel, the wiring from the Service Panel to the Backup Interface needs to satisfy one of these:

1) Be rated at 200A (not a tap)
2) Be supplied by a 100A breaker in the Service Panel and rated for 100A (not a tap)
3) Be rated at 100A and land on a 100A breaker in the Backup Interface (if that's an option), and comply with the tap rules.

And in case (1) above, the wiring from the Backup Interface to the 100A MCB Backup Loads Panel needs to either

4) Be rated at 200A (not a tap)
5) Be rated at 100A and comply with the tap rules.

Cheers, Wayne

So your choice #3 is definitely an option as SE makes the BU interface both straight through and with a breaker slot at point "b1". To be clear though, your choice #2 would not need a breaker at b1" correct? I know that may seem obvious but so often you see feeders with OCP on both ends sometimes the exact same OCP! Maybe to satisfy a disconnect rule and not OC rule. I also think the diagram actually showing the internal wiring of the BUI kinda throws me off because it seems like it's just extending conductors like splices but I assume internal wiring is considered "circuitry" and regardless, the equipment has separate input and output wiring and that is what is subject to the NEC rules - as separate conductors. Does that seem correct?

 

[Strathead]

So your choice #3 is definitely an option as SE makes the BU interface both straight through and with a breaker slot at point "b1". To be clear though, your choice #2 would not need a breaker at b1" correct? I know that may seem obvious but so often you see feeders with OCP on both ends sometimes the exact same OCP! Maybe to satisfy a disconnect rule and not OC rule. I also think the diagram actually showing the internal wiring of the BUI kinda throws me off because it seems like it's just extending conductors like splices but I assume internal wiring is considered "circuitry" and regardless, the equipment has separate input and output wiring and that is what is subject to the NEC rules - as separate conductors. Does that seem correct?

Don't discount option #1. If the BU interface and panel C aren't very far away, just run 3/0 wire rated for 200A and be done with it.

 

[jap]

I'd stab in a 2p 100 amp breaker at the meter/main and leave it as it is.

Your not gaining anything by tapping the 200 anyway.

I'd save the 200 amp feed through lugs for a special occasion.

JAP>

 

[jaggedben]

I'd stab in a 2p 100 amp breaker at the meter/main and leave it as it is.

Your not gaining anything by tapping the 200 anyway.

I'd save the 200 amp feed through lugs for a special occasion.

JAP>

Seems to me your making a lot of unwarranted assumptions about the meter main. I question what the drawing is showing. Is there busbar between the 200A breaker and the 30A welder, and if so what kind? Also why does it say 'two main breakers' and then there's a third one drawn next to them? (Just noticed that.) Without a picture or two I'd say we just don't know what can be done there.

 

[jap]

Seems to me your making a lot of unwarranted assumptions about the meter main. I question what the drawing is showing. Is there busbar between the 200A breaker and the 30A welder, and if so what kind? Also why does it say 'two main breakers' and then there's a third one drawn next to them? (Just noticed that.) Without a picture or two I'd say we just don't know what can be done there.

You're funny,,,

But I will agree with you that the drawing is unlike any meter/main I've ever witnessed.

JAP>

 

[jap]

I will however "assume" a 400 amp Single Phase House panel with a 200 Main feeding a distribution section and feed through lugs with a 125 amp Subfeed breaker installed in the provisional space like all the others I've installed, and, I'd bet I wouldn't be too far off base.

JAP>

 

[hitehm]

I will however "assume" a 400 amp Single Phase House panel with a 200 Main feeding a distribution section and feed through lugs with a 125 amp Subfeed breaker installed in the provisional space like all the others I've installed, and, I'd bet I wouldn't be too far off base.

JAP>

That's pretty much exactly what this is, see a attached pic. It's a 400A split-bus panel with a 200A protected main section that has feeder lugs feeding a 200A subpanel in the main house, so the bus is "tapped" physically but it is not a "feeder tap" bc both sides have the same 200A protection. On the other part of the split bus is a 125A smaller main feeding a subpanel in the apartment, which by the way lands on a 200A sub. And to answer Jaggedben's question about the welder, you can see it is the only branch circuit off the main 200A bus stabbed just under the feeders. And the unlabeled breaker in the drawing on the right side of the meter main is a mistake that should've been deleted. Note the BU interface will only be backing up the 200A feeder, NOT the apartment. So the straight feeders lugged off the main will be pulled out of that panel and landed in panel "C" on the 2p breaker that has a note saying "Existing Feeder....."

 

[jaggedben]

(Funny, I think I saw the same model panel the other day.)

Since the plans say the backup panel is a new 125A panel, and not the existing 200A sub being rewired...
Why wouldn't the 2awg feeder to the BU interface just land on a 125A breaker?

 

[hitehm]

(Funny, I think I saw the same model panel the other day.)

Since the plans say the backup panel is a new 125A panel, and not the existing 200A sub being rewired...
Why wouldn't the 2awg feeder to the BU interface just land on a 125A breaker?

It can. It can land on a 125A breaker in the BUI as "tap" or originate on a 125A breaker in the MSP, which Wayne was suggesting with his options 2 and 3 above (on Thursday). The other issue however is since this is a PV source, the 705.12.B.2.3 busbars rules throw a wrench in the plans. This is something else I'm not sure of: The panel is a 400A split-bus type panel. The lower main section is protected by a factory installed 200A breaker. Does that mean the BUS section it's attached to is rated 200A or is it still a 400A bus? I don't see anything on the label that suggests either (attached). If 200A lower bus then I'm gonna need to replace the whole thing. If 400A bus I'm OK.

 

[jaggedben]

The lower bus is 200A. (See where it says '200A lower section'.)

How much PV output? I only see the one inverter. If it's a 7.6kW or less you don't have a problem. If it's more, I know Solaredge is listed for Power Control Systems so you should look into that. I.e prevent the inverter from outputting more than 32A continuous to the MSP; it can still output more if the backup panel has the load to consume the excess.

 

[wwhitney]

With just a 125A feeder breaker and a 30A welder breaker on the 200A busbar, the configuration complies with (2017) 705.12(B)(2)(3)(c).

Cheers, Wayne

 

[jaggedben]

With just a 125A feeder breaker and a 30A welder breaker on the 200A busbar, the configuration complies with (2017) 705.12(B)(2)(3)(c).

Cheers, Wayne

But it violates 705.12(B)(2)(2) with the 200A feeder there as well. Let's not have that discussion again.