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)?
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.
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?
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.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...
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...
705.1 Scope. This article covers installation of one or more
electric power production sources operating in parallel with
a primary source(s) of electricity.
230.1 Scope. This article covers service conductors and
equipment for control and protection of services and their
installation requirements.
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.
I agree.705 does not apply to service conductors.
You want to find the rules for service conductors you need to look in 230.
I agree.
All 705.31 is saying is that the OCPD for the interconnection must be within 10' of the interconnection (which occurs at the disconnect).
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.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,.
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)
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.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.
Absolute distance?
As the crow flies?
Human walking distance?
Wire length?
How is the 10 ft measured?
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.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.
240.21(B) is titled "Feeder taps". The use of the word tap within that section is limited to feeder taps.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.
705 does not apply to service conductors.
Well that was unexpected, just about fell off my chair.
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.
Well that was unexpected, just about fell off my chair.
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....
Yeah, me too. :blink: Can't figure out now what we argued about for 80 posts.
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