Tap conductors metric wire

[MD84]

I have tap conductors entering a machine on a terminal block going to a 225A breaker. The wire from the Tb to the Ocpd is 60mm^2.

The primary is 175A ocpd to 480:120/208 xfmr.

I am thinking I need 4/0 but the 60mm wire looks smaller. What do I need here? OK to match the metric wire?

 

[petersonra]

I have tap conductors entering a machine on a terminal block going to a 225A breaker. The wire from the Tb to the Ocpd is 60mm^2.

The primary is 175A ocpd to 480:120/208 xfmr.

I am thinking I need 4/0 but the 60mm wire looks smaller. What do I need here? OK to match the metric wire?

I don't think these conductors qualify as tap conductors since they don't terminate at an OCPD but rather terminate at a terminal block. therefore I don't see how you can take advantage of the tap rules so I think these conductors need to be sized to the upstream OCPD rating.

 

[Carultch]

I have tap conductors entering a machine on a terminal block going to a 225A breaker. The wire from the Tb to the Ocpd is 60mm^2.

The primary is 175A ocpd to 480:120/208 xfmr.

I am thinking I need 4/0 but the 60mm wire looks smaller. What do I need here? OK to match the metric wire?

60 mm^2 is between 1/0 and 2/0.


With AHJ approval, you might be able to take ampacities published on the wire's datasheet. But if that isn't available, the default is that it has the ampacity of 1/0 wire.

 

[Smart $]

60 mm^2 is between 1/0 and 2/0.


With AHJ approval, you might be able to take ampacities published on the wire's datasheet. But if that isn't available, the default is that it has the ampacity of 1/0 wire.

That is likely an inaccurate statement. Metric-sized wire is a good indication of non-compliance with Article 310 Part III.

 

[Smart $]

Please describe what you have from the power source in the direction of the load, at least up to the point of connection. Your OP leaves me wondering which goes what way...

 

[petersonra]

That is likely an inaccurate statement. Metric-sized wire is a good indication of non-compliance with Article 310 Part III.

Quite possibly. Although I have been seeing some stuff coming from Europe with metric sized wire and UL markings on the wire.

 

[MD84]

Please describe what you have from the power source in the direction of the load, at least up to the point of connection. Your OP leaves me wondering which goes what way...

From the 480v main disconnect panel I have a 175A circuit breaker feeding a 200A non fused disconnect. The disconnect feeds a 112.5 kVA 480v:208/120v transformer. The secondary conductors will leave the transformer and connect to a terminal block in the utilization equipment. No nuetral is brought to the equipment it is 3 wire with Egc. The secondary conductors feeding the equipment will be about 12' long. From the terminal block in the utilization equipment there are the metric conductors which terminate in the 225A circuit breaker. The metric conductors are about 6' long. The transformer is only serving this one piece of equipment.

 

[Smart $]

Quite possibly. Although I have been seeing some stuff coming from Europe with metric sized wire and UL markings on the wire.

That's a step in the right direction.

The next IMO is compliance with 310.20(A)(4), which is marking shall indicate "The AWG size or circular mil area."

 

[Smart $]

From the 480v main disconnect panel I have a 175A circuit breaker feeding a 200A non fused disconnect. The disconnect feeds a 112.5 kVA 480v:208/120v transformer. The secondary conductors will leave the transformer and connect to a terminal block in the utilization equipment. No nuetral is brought to the equipment it is 3 wire with Egc. The secondary conductors feeding the equipment will be about 12' long. From the terminal block in the utilization equipment there are the metric conductors which terminate in the 225A circuit breaker. The metric conductors are about 6' long. The transformer is only serving this one piece of equipment.

See the rules of 240.21(C) for secondary conductors. Essentially to tap off the feed, you'd be tapping a "tap", in this case secondary conductors, if you went smaller than 4/0. And 240.21(C) pretty much requires secondary conductors land on a single OCPD, so running 4/0 may be out of the picture also. Perhaps the easiest solution is to run an entire new set of secondary conductors from the transformer for your application.

 

[petersonra]

That's a step in the right direction.

The next IMO is compliance with 310.20(A)(4), which is marking shall indicate "The AWG size or circular mil area."

I will have to look closer next time. It might have the size as well. I just never looked that close.

 

[Besoeker]

I have tap conductors entering a machine on a terminal block going to a 225A breaker. The wire from the Tb to the Ocpd is 60mm^2.

Are you sure about the 60mm^2?
Standard sizes are 50mm^2 and 70mm^2.

 

[MD84]

Are you sure about the 60mm^2?
Standard sizes are 50mm^2 and 70mm^2.

 

[Besoeker]

OK. Just not something we'd see here. BS7671 doesn't list it.

 

[petersonra]

LMFC appears to be a Japanese std and not a Euro std.

 

[MD84]

It is a Toshiba...

 

[MD84]

See the rules of 240.21(C) for secondary conductors. Essentially to tap off the feed, you'd be tapping a "tap", in this case secondary conductors, if you went smaller than 4/0. And 240.21(C) pretty much requires secondary conductors land on a single OCPD, so running 4/0 may be out of the picture also. Perhaps the easiest solution is to run an entire new set of secondary conductors from the transformer for your application.

I think bypassing the terminal block and running directly to the Ocpd will be the best solution.

 

[Smart $]

I think bypassing the terminal block and running directly to the Ocpd will be the best solution.

Perhaps I misunderstood earlier...

Are you wanting to power the equipment attached to the 225A breaker? If so, I agree.

 

[MD84]

Perhaps I misunderstood earlier...

Are you wanting to power the equipment attached to the 225A breaker? If so, I agree.

I think we are in agreement. I want to power the equipment attached to the 225A breaker.

The manufacturer brought the metric conductors from the 225A breaker to a single terminal block. It is all contained within the equipment enclosure.

 

[Jraef]

Quite possibly. Although I have been seeing some stuff coming from Europe with metric sized wire and UL markings on the wire.

Huh, I would think the wire itself would need to be UL listed, if for no other reason than the fact that the insulation qualities are something UL is very persnickety about. Maybe it is UL listed, just at an ampacity of the lower of the AWGs it falls between??

 

[Smart $]

I think we are in agreement. I want to power the equipment attached to the 225A breaker.

The manufacturer brought the metric conductors from the 225A breaker to a single terminal block. It is all contained within the equipment enclosure.

I believe so too.

Originally I thought the 4/0 was already run to the terminal block and you wanted to install [another] tap to the terminal block. Now I see you just want compliant transformer secondary conductors to 225A breaker.