EV chargers have you seen this type?

[hhsting]

I am really stuck on this would really appreciate all your help. Previous post dealt with issues of 625.43. However this post its about protecting DC conductor between dispensers and power cabinet. The designer tells me the power cabinets have no internal breaker. Only software that detects 350A above and stops the system. Also designer says power cabinet each module has 20A 24 fuses in parallel which would protect DC cable 2 sets of 350kcmil. I have never heard if this but not sure

Attached sketches I have 480/277V 1600A switchboard. The switchboard 300A AC feeder breaker feeds 175kw(150kw) power cabinet. The power cabinet feeds the dispensers.

Power cabinet is Signet High Power Charging Model HpC175K.

From the power cabinet to the dispensers there are 2 sets if 2#350kcmil AL +#2 Gnd DC conductors

The power cabinet has 8 modules. Each module has 24 20A fuses in parallel. Their are no breaker or fuses other than those.

Questions:

1. Would not the 2 sets of 350kcmil AL DC conductors need to be protected? If so then would not one require overcurrent protection or would 24 20A fuses in parallel in each module be ok and would be acceptable to protect the cable?

2. Has anyone encounter the EV chargers below and has anyone placed overcurrent protection between the dispensers and the power cabinet? If yes then where is it in NEC 2017 section 625?

 

[augie47]

Assuming the "dispensers" are the "plug" that connects the charger to the vehicle I would look at the entire unit (charging station + dispensers) as one MET listed device and not concern myself with anything beyond supplying the 480v to the unit itself.(90.7)

 

[hhsting]

Assuming the "dispensers" are the "plug" that connects the charger to the vehicle I would look at the entire unit (charging station + dispensers) as one MET listed device and not concern myself with anything beyond supplying the 480v to the unit itself.(90.7)

I am not sure if I follow or not.

Dispenser is charging station + plug see picture below:

Power cabinet is cabinet that converts AC to DC and is separate from dispenser

Power cabinet:

The dispenser and power cabinet are 80 feet apart.


The question is about protection of DC conductors between dispenser and power cabinet 80 feet apart. See post #1

MET listed dispensers only and power cabinet only not entire system. How can you considered one system its 80 feet apart cables provided by customer DC?

 

[augie47]

Wasn't clear on the separation..... I have no input

 

[hhsting]

No one knows or has any opinions? I really appreciate anyone help

 

[brantmacga]

It seems to me like it is protected with the fuses?

I’ve never installed a DC fast charger but I’m guessing there are 24 rectifiers per module that combine for the 150kw. Probably a modular system that can be scaled to whatever the customer wants.


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[hhsting]

It seems to me like it is protected with the fuses?

I’ve never installed a DC fast charger but I’m guessing there are 24 rectifiers per module that combine for the 150kw. Probably a modular system that can be scaled to whatever the customer wants.


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Yes it does have 24- 20A parallel fuses each module but how does that protect 2 sets of 350 kcmil Al cable that is between the dispenser and power cabinet 80 feet apart?

 

[GoldDigger]

NEC has specific rules for use of parallel wires. The described situation meets the minimum size requirement. If the identical conductor requirement is also met, the only question is whether there is upstream OCPD to match the combined ampacity of the two cables.

 

[hhsting]

NEC has specific rules for use of parallel wires. The described situation meets the minimum size requirement. If the identical conductor requirement is also met, the only question is whether there is upstream OCPD to match the combined ampacity of the two cables.

The 24-20A fuses DC parallel are factory installed in the power cabinet. Only thing not factory install is the 2 sets of 350kcmil AL DC cable, the AC switchboard and AC cables between switchboard and power cabinet.

Only thing upstream of 24-20A DC fuses in power cabinet is the AC 300A breaker in AC switchboard shown single line post #1 but I dont see how 300A AC breaker in AC swbd can protect the DC 2 sets of 350 AL cables. Power cabinet is in the middle.

 

[GoldDigger]

The 24-20A fuses DC parallel are factory installed in the power cabinet. Only thing not factory install is the 2 sets of 350kcmil AL DC cable, the AC switchboard and AC cables between switchboard and power cabinet.

Only thing upstream of 24-20A DC fuses in power cabinet is the AC 300A breaker in AC switchboard shown single line post #1 but I dont see how 300A AC breaker in AC swbd can protect the DC 2 sets of 350 AL cables. Power cabinet is in the middle.

As long as it is part of the manufactured assembly it should be possible to count the 24 parallel 20A fuses as one 480A OCPD. If the combined cable ampacity is less than 480A I would say you have a problem.
I do not think that the specification of 2 x 350AL by the manufacturer relieves you of the NEC rules for field wiring.

 

[brantmacga]

240.8?

Not seeing anything in 625 that covers this.

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[hhsting]

As long as it is part of the manufactured assembly it should be possible to count the 24 parallel 20A fuses as one 480A OCPD. If the combined cable ampacity is less than 480A I would say you have a problem.
I do not think that the specification of 2 x 350AL by the manufacturer relieves you of the NEC rules for field wiring.

I dont get last paragraph?

“I do not think that the specification of 2 x 350AL by the manufacturer relieves you of the NEC rules for field wiring.”

 

[Charged]

I’ve worked on or reviewed designs for these type of installs all the time, including this manuf. The over current protection in the cabinet will satisfy the protection for the dc conductors. Occasionally a reviewer will ask for the cut sheet of the equipment, early on they they didn’t detail it great and it was tough. No additional disconnects, ocp is needed unless you are in a parking garage situation where the cabinet is on a different level then the dispenser, then we’ve added disconnects. I don’t have a NEC reference for you. I agree with your thought process and it took my company a long time to accept it was ok.

 

[hhsting]

I’ve worked on or reviewed designs for these type of installs all the time, including this manuf. The over current protection in the cabinet will satisfy the protection for the dc conductors. Occasionally a reviewer will ask for the cut sheet of the equipment, early on they they didn’t detail it great and it was tough. No additional disconnects, ocp is needed unless you are in a parking garage situation where the cabinet is on a different level then the dispenser, then we’ve added disconnects. I don’t have a NEC reference for you. I agree with your thought process and it took my company a long time to accept it was ok.

The cabinets and EV chargers are outside parking lot just 80 feet apart. The scenario is strip shopping mall with open parking lot. The cabinets are on the side of open parking lot

 

[tom baker]

No.

 

[ramsy]

I dont get last paragraph?

“I do not think that the specification of 2 x 350AL by the manufacturer relieves you of the NEC rules for field wiring.”

Perhaps: 215.12(C)(2)

For #350 DC feeder OCP
1) OEM can specify size of DC feeder per 110.3B, however, 80ft length may need OEM verification, or
2) Plans can specify feeder under Engineering Supervision, or
3) Request permission from AHJ to approve primary side OCP per 240.4(F)
The Power-Cabinet rectifiers are similar to "transformers having a 2-wire (single-voltage)"

 

[ramsy]

240.8?

Not seeing anything in 625 that covers this.

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Nice find with 240.8. Always wondered if such massively paralleled small conductors could be practicable.

 

[ramsy]

As long as it is part of the manufactured assembly it should be possible to count the 24 parallel 20A fuses as one 480A OCPD. If the combined cable ampacity is less than 480A I would say you have a problem..

You want DC feeder up-sized to #1000 to match 480 Amps?
The selected #350 AL has ampacity table limits of 250 Amps, inadequetly sized for Max load of each 350A rectifier.

Table shows #600 AL feeder works for 350 Amps.

 

[hhsting]

You want DC feeder up-sized to #1000 to match 480 Amps?
The selected #350 AL has ampacity table limits of 250 Amps, inadequetly sized for Max load of each 350A rectifier.

Table shows #600 AL feeder works for 350 Amps.

Its 2 sets of #350 AL so 500A ampacity

 

[GoldDigger]

I dont get last paragraph?

“I do not think that the specification of 2 x 350AL by the manufacturer relieves you of the NEC rules for field wiring.”

I did not take the time to determine the ampacity of the 2 x 350AL, so I made the general statement that if that ended up less than 480A, then you could not rely on the manufacturer's direction to use 2 x 350AL on the basis that it is part of the listed equipment. It is field wiring rather than part of the listed equipment.