310.10 parallel conductors

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Electrical PE

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I have a large battery bank with a main disconnect at its output rated for 1400A. At the output of the disconnect, there are (3) 500A fuses paralleled between (2) buses, one on each side of the fuses (done by the manufacturer).
On the other side I have a recombiner of an inverter that has individual fused inputs. Max fuse size that can be connected to it is 400A.

The intended connection is to run 5 sets on conductors in parallel from the bus at the output of the battery unit and terminating them on 5 individual 350A fused inputs in the recombiner. These 5 fuses are connected to the main bus of the recombiner.

Conductors are same length, same material, same size, same insulation, and terminated in the same manner.

Is this connection violating any of the requirements in this article? Including the requirement for parallel conductors to be "electrically joined at both ends" mentioned in 310.10(H)(1)? or it is considered code-compliant?

Thank you
 
What you can do is set a jb or wireway and combine the parallel conductors together and then tap off from there
 
Dennis Alwon said:
What you can do is set a jb or wireway and combine the parallel conductors together and then tap off from there
Click to expand...

Thank you. Yes that would be an option.

But my initial interpretation was that this connection is electrically joined through the fuses at the bus of the recombiner, since the NEC says electrically joined not mechanically/physically joined at both ends.

Any thoughts?
 
Everything is electrically joined if you go back enough but what happens when one pair is on a breaker and the breaker is off? You can only go so far.. Hopefully someone else will join in but IMO they are not electrically joined at both ends.

Add this to the statement-- electrically joined at both ends of the wire and I believe you will have the intent.
 
Disclaimer: the following is based on what I gleaned from the OP.

I believe Dennis is saying that the fuses that protect each conductor technically render the conductors not in parallel according to definition, and I agree. Also, that means the fuses are technically not in parallel.

Added: If one fuse were to blow due to overload, the rest would follow in a cascading event.
 
It sounds like you have fuses in parallel on the parallel conductors. If that's accurate, then I don't believe it is NEC compliant.

If one 400-amp fuse blows, all the load then is spread across the other fuses/conductors?
 
After reading the OP for the 3rd time, if you had a bus connecting the 350-amp fuses on the line side (where the 5 sets of conductors would land), then maybe you could consider the conductors in parallel since they are connecting to a bus on each end of the circuit.
 
Even if it was parallel would you not have an issue with this section

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. This overcurrent protective device shall be
located within or at any point on the supply side of the panelboard.
Exception No. 1: Individual protection shall not be required for a
panelboard used as service equipment with multiple disconnecting
means in accordance with 230.71. In panelboards protected by three or
more main circuit breakers or sets of fuses, the circuit breakers or sets of
fuses shall not supply a second bus structure within the same panelboard
assembly.
Exception No. 2: Individual protection shall not be required for a
panelboard protected on its supply side by two main circuit breakers or
two sets of fuses having a combined rating not greater than that of the
panelboard. A panelboard constructed or wired under this exception
shall not contain more than 42 overcurrent devices. For the purposes of
determining the maximum of 42 overcurrent devices, a 2-pole or a
3-pole circuit breaker shall be considered as two or three overcurrent
devices, respectively.
Exception No. 3: For existing panelboards, individual protection shall
not be required for a panelboard used as service equipment for an individual
residential occupancy.
Click to expand...
 
This is a hit and run - appologies.

I don't have a clear picture on the cable connections. Each cable has it's own fuse?
If so, this is similar to cable limiters - which would be considered paralleled cables. If fuses are an issue, could cable limiters be substituted?

What am I missing?
 
Electrical PE said:
I have a large battery bank with a main disconnect at its output rated for 1400A. At the output of the disconnect, there are (3) 500A fuses paralleled between (2) buses, one on each side of the fuses (done by the manufacturer).
On the other side I have a recombiner of an inverter that has individual fused inputs. Max fuse size that can be connected to it is 400A.

The intended connection is to run 5 sets on conductors in parallel from the bus at the output of the battery unit and terminating them on 5 individual 350A fused inputs in the recombiner. These 5 fuses are connected to the main bus of the recombiner.

Conductors are same length, same material, same size, same insulation, and terminated in the same manner.

Is this connection violating any of the requirements in this article? Including the requirement for parallel conductors to be "electrically joined at both ends" mentioned in 310.10(H)(1)? or it is considered code-compliant?

Thank you
Click to expand...

Why not combine them first and fuse them at 1600A?
 
Dennis Alwon said:
What you can do is set a jb or wireway and combine the parallel conductors together and then tap off from there
Click to expand...

Just confirming what exactly you mean by tapping off from there? Do you mean after combining the parallel conductors together, all of the 5 conductors would be tapping off the main breaker/fuse and then (each one) connected to its 350A fuse at the recombiner? Like what ggunn suggested in his post?

Thanks
 
Last edited:
If this is the case, wouldn't that be violating the NEC as well because the 5 conductors would be mechanically connected on one side (at main breaker of where the conductors are combined) and landing on 5 separate fuses on the other side at the recombiner?
Unless you mean having 5 separate taps at the bus where the parallel conductors are combined, each protected by an ocpd, and then landing each one on its 350A fuse at the recombiner?
 
iceworm said:
This is a hit and run - appologies.

I don't have a clear picture on the cable connections. Each cable has it's own fuse?
If so, this is similar to cable limiters - which would be considered paralleled cables. If fuses are an issue, could cable limiters be substituted?

What am I missing?
Click to expand...

Yes, in the proposed connection, the 5 conductors are connected to 1 bus at the output of the battery bank, and each one of the 5 is landing to a 350A fuse at the recombiner.
 
Electrical PE said:
Just confirming what exactly you mean by tapping off from there? Do you mean after combining the parallel conductors together, all of the 5 conductors would be tapping off the main breaker/fuse and then (each one) connected to its 350A fuse at the recombiner? Like what ggunn suggested in his post?

Thanks
Click to expand...

No, what I was saying is run all 5 sets and connect to the battery as you stated then at the other end splice them all together and use a properly sized conductor to connect to the recombiner. Thus at the junction you would have five sets tied together with the 5 sets going to the combiner. The 5 sets going to the combiner can probably be sized for just the 350 amp fuses. Look at 240.21 for taps
 
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