I'm new to cable limiters. Looking to do a supply side connection and our conductor length is going to be over 10' (2014 NEC). Might be a stupid question, but do I need to add a cable limiter on the neutral or just the hot conductors? My assumption is no because it would be the same as fusing the neutral but hoping to double-check.
Cable Limiters On Neutral?
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electrofelon
Senior Member
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- Cherry Valley NY, Seattle, WA
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- Electrician
I am not that familiar with cable limiters either, but I would say NOT in the grounded conductor because the exception only talks about ungrounded conductors, and the basic rule about no OCPD's in the grounded conductor (unless they all open at once).
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- Illinois
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- retired electrician
Cable limiters do not provide overcurrent protection. If you are applying the rules of 240.21(B) or (C), you need to provide an overcurrent protective device.
Cable limiters are typically used at both ends of high available fault current parallel systems to take a shorted conductor out of the circuit. The only provide short circuit and ground fault protection, they do not provide overload protection. They are only used on the ungrounded conductors.
Cable limiters are typically used at both ends of high available fault current parallel systems to take a shorted conductor out of the circuit. The only provide short circuit and ground fault protection, they do not provide overload protection. They are only used on the ungrounded conductors.
Good catch Electrofelon, I overlooked that the exception specifically mentions it should be on the ungrounded conductors.
Thanks don_resqcapt19. We will definitely have OCPDs along with the cable limiters. And since we are not installing parallel conductors I'm 99% sure we will only need the limiters on one end (where we make our solar supply side connection) as there would be no way for fault currents from the utility to feed around to the back side of the fault like it would if we had paralleled conductors, necessitating limiters on both ends. Also our inverter outputs are a limited current source so there is no way the inverters could ever put out enough current to ever cause a limiter to trip.
You got that one correct don_resqcapt19, both ends of parallel circuits. The way the NEC calls for the use of cable limiters on parallel circuit supply side interconnections is not correct. I have yet to see a parallel supply-side interconnection that uses cable limiters that has them on both ends since the 705.31 exception says to install them on the service end.
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- Illinois
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- retired electrician
I guess I don't understand the need for cable limiters if there is not parallel conductors. Where would the cable limiters be installed in relation to the OCDP?
Ok, I went back and looked at 705.31 Exception and I think I understand what they are doing. They are letting you provided short circuit only protection by the use of cable limiters at the point of connection to the service conductors, where the OCDP is more than 10' from that connection point.
Ok, I went back and looked at 705.31 Exception and I think I understand what they are doing. They are letting you provided short circuit only protection by the use of cable limiters at the point of connection to the service conductors, where the OCDP is more than 10' from that connection point.
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- Location
- Illinois
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- retired electrician
I will look at a PI for the 2023 to say that where the connectors are connected in parallel, the current limiters must be installed at both ends. Having them only at one end of parallel conductors serves no real purpose.
The rule is in 705.11(C)(2) in the 2020 code and is "positive" text, not an exception.
McMac
Member
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- St. Louis, MO USA
I apologize if I've missed this elsewhere but my search did not come up with anything.
Is the 10ft in 705.31 meant to be in wire feet or 10 feet from the interconnection enclosure? I am assuming wire feet.
But also, does 240.21 not allow me 25ft if conductors are rated for 30% of the service? I've always used these feeder tap rules when considering the distance in wire feet to my fused disco on a supply-side tap.
Is the 10ft in 705.31 meant to be in wire feet or 10 feet from the interconnection enclosure? I am assuming wire feet.
But also, does 240.21 not allow me 25ft if conductors are rated for 30% of the service? I've always used these feeder tap rules when considering the distance in wire feet to my fused disco on a supply-side tap.
McMac
Member
- Location
- St. Louis, MO USA
ATM I am trying to decide how to approach a tap where I have 1000A worth of wire connected to a 2000A service on the supply side. Seems I shouldn't need anything additional if I have approx. 20ft of wire, and 18x 600V 400kcmil cable-limiters were not originally budgeted in. We can get a breaker disco in the MEP room within 10ft of the MSP, but it's still over 10 wire feet to get up and over, and only save a couple of those wire feet from the utility accessible fused disco on the other side of the wall.
Am I hijacking this thread now? sorry not a forum guru
jaggedben
Senior Member
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- Northern California
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- Solar and Energy Storage Installer
A new thread would probably be better but you're pretty on topic here.
The 240.21 rules are not very sensible to apply because there is no upstream overcurrent device to use in calculating percentages. I believe the 705 10ft rule was put in to address that gap.
The 240.21 rules are not very sensible to apply because there is no upstream overcurrent device to use in calculating percentages. I believe the 705 10ft rule was put in to address that gap.
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