Tap rules for service conductors

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ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Where can I find the code governing taps to service conductors, i.e., on the supply side of the service OCPD? Is it 240.21(C)?
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
There are no tap rules for service conductors. The taps would just be service conductors.
OK, so riddle me this. Say you have a 400A 480V service and you tap a 100kW (~120A) PV system to the supply side of the service OCPD. The conductors between the tap and the PV fused disco are service conductors sized appropriately for ~120A, right? My understanding is that the disco needs to be less than 10' from the tap as the conductor flies; is that correct? If there is no spot available to mount the disco to satisfy that requirement, are there rules similar to the feeder tap rules which allow longer conductors (i.e., between 10' and 25' long) if they are sized up? Or is it 10 feet from the tap, period? Or can we put the disco anywhere we want irrespective of the distance from the tap?
 
There are no tap rules for service conductors. The taps would just be service conductors.

Article 230 does say that "service conductors can be spliced and tapped." I dont like their use of the word tap in this context because it clashes with other uses of the word in the code, and like you say there are not any "tap rules" for service conductors other than complying with the rules for the number of sets of service conductors.
 

Carultch

Senior Member
Location
Massachusetts
OK, so riddle me this. Say you have a 400A 480V service and you tap a 100kW (~120A) PV system to the supply side of the service OCPD. The conductors between the tap and the PV fused disco are service conductors sized appropriately for ~120A, right? My understanding is that the disco needs to be less than 10' from the tap as the conductor flies; is that correct? If there is no spot available to mount the disco to satisfy that requirement, are there rules similar to the feeder tap rules which allow longer conductors (i.e., between 10' and 25' long) if they are sized up? Or is it 10 feet from the tap, period? Or can we put the disco anywhere we want irrespective of the distance from the tap?

This is an application which is a blindspot in the NEC, for proper vocabulary. I consider these to be taps, others might consider them service conductors.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Oh G-d.

Seriously?

You are "reviving this issue"?
:lol:


The only indisputably applicable rules are in 705. The 10' rule, I believe, was added to the 2014 code. (I don't have the book handy at the moment.) If you are on a previous code there is no such rule, AFAIK.

As far as the tap rules in 240.21(B), they apply only to the load side of the service disconnecting means. The definition of a Tap Conductor in 240.2 applies only to Article 240. The use of the word 'tap' in any other article should not be construed as applying the rules in 240.21(B) unless that section is explicitly invoked.

So now...
Are they service conductors or merely inverter output conductors? :slaphead:
I will try to abstain from the discussion this time...
 
Last edited:

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Oh G-d.

Seriously?

You are "reviving this issue"?
:lol:


The only indisputably applicable rules are in 705. The 10' rule, I believe, was added to the 2014 code. (I don't have the book handy at the moment.) If you are on a previous code there is no such rule, AFAIK.

As far as the tap rules in 240.21(B), they apply only to the load side of the service disconnecting means. The definition of a Tap Conductor in 240.2 applies only to Article 240. The use of the word 'tap' in any other article should not be construed as applying the rules in 240.21(B) unless that section is explicitly invoked.

So now...
Are they service conductors or merely inverter output conductors? :slaphead:
I will try to abstain from the discussion this time...
Sorry, but I wasn't trying to revive anything. I have a client who is having trouble locating the disco within 10' of the tap. But thanks; 705.31 is the rule I was looking for. Everyone please stand down. :D
 

iwire

Moderator
Staff member
Location
Massachusetts
Oh G-d.

Seriously?

You are "reviving this issue"?
:lol:


The only indisputably applicable rules are in 705. The 10' rule, I believe, was added to the 2014 code. (I don't have the book handy at the moment.) If you are on a previous code there is no such rule, AFAIK.

As far as the tap rules in 240.21(B), they apply only to the load side of the service disconnecting means. The definition of a Tap Conductor in 240.2 applies only to Article 240. The use of the word 'tap' in any other article should not be construed as applying the rules in 240.21(B) unless that section is explicitly invoked.

So now...
Are they service conductors or merely inverter output conductors? :slaphead:
I will try to abstain from the discussion this time...

705 does not apply to service conductors. :p

705.1 Scope. This article covers installation of one or more
electric power production sources operating in parallel with
a primary source(s) of electricity.

You want to find the rules for service conductors you need to look in 230.

230.1 Scope. This article covers service conductors and
equipment for control and protection of services and their
installation requirements.


:D
 

Smart $

Esteemed Member
Location
Ohio
Sorry, but I wasn't trying to revive anything. I have a client who is having trouble locating the disco within 10' of the tap. But thanks; 705.31 is the rule I was looking for. Everyone please stand down. :D

705 does not apply to service conductors. :p



You want to find the rules for service conductors you need to look in 230.




:D
I agree.

Service conductors on POCO side of POCO/PV systems disconnecting means, feeders on PV side.

All 705.31 is saying is that the OCPD for the interconnection must be within 10' of the interconnection (which occurs at the disconnect). There is no restriction on the distance a service conductor tap can be run. If the disconnect were a standard service disconnecting means, the OCPD is required to be integral with the disconnect or immediately adjacent thereto. For the PV/POCO interconnect the disconnect and OCPD can be up to 10' apart.
 

mwm1752

Senior Member
Location
Aspen, Colo
Tapping service conductors would require the OCPD/dicsonnect be part of the max six switch rule & located in the vicinity ( nutshell) - but - , if you have an exterior feeder tap though there is an unlimited lenght involved & the OCPD can be located at any readily accessible location,.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Tapping service conductors would require the OCPD/dicsonnect be part of the max six switch rule & located in the vicinity ( nutshell) - but - , if you have an exterior feeder tap though there is an unlimited lenght involved & the OCPD can be located at any readily accessible location,.
Without going into the (endless) argument, I will point out that since the PV disconnect is "not a service disconnect", it could be in addition to the six permitted disconnects rather than included in that count. Same for location.
As a matter of design, putting it next to the other service disconnects and keeping the handle throw total to six would be good ideas. Just not necessarily required by code, depending on how the AHJ interprets the relevant Code sections.
 

Carultch

Senior Member
Location
Massachusetts
The only indisputably applicable rules are in 705. The 10' rule, I believe, was added to the 2014 code. (I don't have the book handy at the moment)

If you put the disconnect/OCPD on the opposite side of a wall from the point of interconnection equipment (where the tap is made), and it is more than 10 ft to walk around the wall, is that acceptable?
After all, it still is less than 10 ft of absolute distance.

I find this situation often, because the utilities commonly require an outside-mounted disconnect. Given an indoor main panel, and the master disconnect of the PV system being the utility required outside-mounted one (fused), it puts you in this situation.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Without going into the (endless) argument, I will point out that since the PV disconnect is "not a service disconnect", it could be in addition to the six permitted disconnects rather than included in that count. Same for location.
As a matter of design, putting it next to the other service disconnects and keeping the handle throw total to six would be good ideas. Just not necessarily required by code, depending on how the AHJ interprets the relevant Code sections.
I actually won that one with my AHJ. If an MLO MDP has six breakers they will allow PV to interconnect but not with a 7th breaker. It must be a fused disco.

They also cite 705.31 as requiring the fused disco for a supply side "tap" interconnected PV system to be within 10' (as the conductor flies) of the tap.
 

Smart $

Esteemed Member
Location
Ohio
Absolute distance?
As the crow flies?
Human walking distance?
Wire length?

How is the 10 ft measured?

If you put the disconnect/OCPD on the opposite side of a wall from the point of interconnection equipment (where the tap is made), and it is more than 10 ft to walk around the wall, is that acceptable?
After all, it still is less than 10 ft of absolute distance.

I find this situation often, because the utilities commonly require an outside-mounted disconnect. Given an indoor main panel, and the master disconnect of the PV system being the utility required outside-mounted one (fused), it puts you in this situation.
As I said earlier, 10 ft is the max distance allowed between disconnect and OCPD. Think about it. Is the disconnect THE point of connection if conductors on one side are service, the other side feeders.

And Code stipulates no means of measurement... so I'll say whichever yields the shortest measurement. AHJ may interpret otherwise. :lol:

And ultimately, 705.31 has nothing to do with where the disconnect is located with respect to any service disconnecting means.
 

kwired

Electron manager
Location
NE Nebraska
This is an application which is a blindspot in the NEC, for proper vocabulary. I consider these to be taps, others might consider them service conductors.
240.21(B) is titled "Feeder taps". The use of the word tap within that section is limited to feeder taps.

The use of the word tap anywhere else reverts back to the standard dictionary definition of the word tap.

We often just say "tap rules" when referring to what it covered by 240.21(B), but technically it is only talking about "feeder taps".


As has already been mentioned, a tap to a service conductor leaves you with additional service conductor(s) there is no overcurrent protection for service conductors. Once you have an overcurrent protection device (will be associated with a service disconnecting means) everything downstream is now feeders or branch circuits.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
705 does not apply to service conductors. :p

I don't see how you construe the scope you quoted as excluding them. It's always been my opinion that the conductors on a supply side tap are both. That is, both service conductors and inverter output conductors/ parallel power production source conductors. It's true 705 doesn't have much to say about them compared to 230. But then, whoever you're talking to has to agree that 230 applies. (That would include me, but not everyone.)

Well that was unexpected, just about fell off my chair. :D

Yeah, me too. :blink: Can't figure out now what we argued about for 80 posts.

If you put the disconnect/OCPD on the opposite side of a wall from the point of interconnection equipment (where the tap is made), and it is more than 10 ft to walk around the wall, is that acceptable?
After all, it still is less than 10 ft of absolute distance.

I find this situation often, because the utilities commonly require an outside-mounted disconnect. Given an indoor main panel, and the master disconnect of the PV system being the utility required outside-mounted one (fused), it puts you in this situation.

I think the point is not to have an extended stretch of conductors in or on a building with no overcurrent protection. (BTW, I thought there was a similar requirement for service conductors, but I can't find it?) Note that it applies to overcurrent protection but not disconnecting means.

To me the sticky situation is if the OCPD is less than 10ft in a straight line, but the wiring takes some circuitous route that is significantly more. Imagine a situation where it went up and over a room that was less than 10ft wide but more than 10ft tall. I think that violates the spirit if not the word. In the end, it's up to the AHJ. :roll:
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
There is no 10' limit for service conductors. Instead we have "nearest the point of entry" into the building. The interpretation of that as a hard limit will vary from one AHJ to another.
 

Smart $

Esteemed Member
Location
Ohio
Well that was unexpected, just about fell off my chair. :D
...
Yeah, me too. :blink: Can't figure out now what we argued about for 80 posts.
...
I've never contested conductors on the POCO side of THE disconnect being anything other than service entrance conductors. What I have contested is calling the disconnect a service disconnecting means and grounding requirements.
 
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