Feeder/Tap Rules

[Goldseedlbg]

Hello,

I have a question about the feeder rule. Please see the attached document. Are the attached circuits legal usages of the feeder/tap rules? These circuits are for use in industrial control panels.

Thank for your help.

 

[don_resqcapt19]

How long are the tap conductors? What wiring method was used for the tap conductors?

 

[Goldseedlbg]

The tap conductor length is less than 3 feet. I would guest the length is 1 foot on the second circuit and 6 inches on the first circuit.

I'm not sure which wiring method was used.

 

[petersonra]

If they are "in" (meaning inside) of an industrial control panel, UL508a would tell you how this is handled for US use.

The 400V 50 Hz diagram would appear to be for something outside of the US and would need to follow whatever rules apply there.

For UL508a applications the 480V diagram appears to be acceptable given the very sparse information you have provided.

incidentally, as shown these are not feeders but branch circuits.

 

[iceworm]

... I have a question about the feeder rule. Please see the attached document. Are the attached circuits legal usages of the feeder/tap rules? These circuits are for use in industrial control panels. ...

Give us a bit more about the context of your question:
These schematics are normal for every motor starter bucket in the US. Are you modifying the buckets to add the control xfm? Are you modifying Listed combination starters? Did they show up from the factory this way? Are these built to UL-508a, or maybe NFPA 79.

The only thing that the NEC would say is 240.B.1.

There are additional restrictions in NFPA 79 - and that 13A CB in the first schematic has the look of an NFPA79 industrial control panel.

So, what exactly is your concern?

ice

 

[iceworm]

Give us a bit more about the context of your question:
These schematics are normal for every motor starter bucket in the US. Are you modifying the buckets to add the control xfm? Are you modifying Listed combination starters? Did they show up from the factory this way? Are these built to UL-508a, or maybe NFPA 79.

The only thing that the NEC would say is 240.21.B.1.

There are additional restrictions in NFPA 79 - and that 13A CB in the first schematic has the look of an NFPA79 industrial control panel.

So, what exactly is your concern?

ice

Whoops

 

[Goldseedlbg]

Give us a bit more about the context of your question:
These schematics are normal for every motor starter bucket in the US. Are you modifying the buckets to add the control xfm? Are you modifying Listed combination starters? Did they show up from the factory this way? Are these built to UL-508a, or maybe NFPA 79.

The only thing that the NEC would say is 240.B.1.

There are additional restrictions in NFPA 79 - and that 13A CB in the first schematic has the look of an NFPA79 industrial control panel.

So, what exactly is your concern?

ice

Thanks for your responses. The top box is going to over seas. We are a UL panel shop. We would like all of our control panels to meet NEC and UL requirements.

My concern is the conductor size to the transformers and are we correctly following the tap rules for reducing conductor sizes in both schematics.

 

[david luchini]

The only thing that the NEC would say is 240.21.B.1.

I don't think 240.21.B.1 would be the right NEC reference for two reasons. First, the conductors are tapped from a branch circuit rather than a feeder (at least for the one showing the motor.)

Second, they are a motor control circuit. 430.72(A) would be the place to look.

 

[iceworm]

I don't think 240.21.B.1 would be the right NEC reference for two reasons. First, the conductors are tapped from a branch circuit rather than a feeder (at least for the one showing the motor.)

Second, they are a motor control circuit. 430.72(A) would be the place to look.

Absolutely, good catch

ice

 

[iceworm]

Thanks for your responses. The top box is going to over seas. We are a UL panel shop. We would like all of our control panels to meet NEC and UL requirements.

My concern is the conductor size to the transformers and are we correctly following the tap rules for reducing conductor sizes in both schematics.

You are a UL panel shop - so you already know the UL requirements. What UL standard are you trying to meet?
The box is going overseas - so it is likely being built to an IEC standard. What IEC standard are you trying to meet.
The NEC does not apply to the insides of a NRTL listed box.

So, forget my responses. I'm not knowledgable on UL or IEC specific construction/design practices. I do not have an informed opinion. If I was looking for an informed opinion, I'd be asking you.

Sorry I can't help.

ice