NEC 2005 art 240.21(C)(1)

[Zane Bailey]

do the requirements of 240.21(C)(4)(outside secondary conductors) Nullify the requirements of 240.21(C)(1)(multi conductor 3 wire or multi conductor 4 wire not condidered protected by the primary overcurrent device)?

can a 3 wire single phase or a 4 wire three phase outdoor transformer secondary conductors be protected by the primary overcurrent device only, and run unlimited length before terminating on a single or single set of overcurrent devices?

Zane.

 

[chris kennedy]

Yes that is possible if your not talking service. See T450.3(B).

 

[raider1]

do the requirements of 240.21(C)(4)(outside secondary conductors) Nullify the requirements of 240.21(C)(1)(multi conductor 3 wire or multi conductor 4 wire not condidered protected by the primary overcurrent device)?

No, 240.21(C)(1) only applies to 2 wire single phase systems or 3 wire 3 phase systems.

can a 3 wire single phase or a 4 wire three phase outdoor transformer secondary conductors be protected by the primary overcurrent device only, and run unlimited length before terminating on a single or single set of overcurrent devices?

Zane.

No, 3 wire single phase or 4 wire 3 phase transformer secondary conductors run outside must terminate in an overcurrent protective device in accordance with 240.21(C)(4).

That section permits secondary conductors to be run unlimited in length without an OCPD at the transformer provided that when the secondary conductors terminate in a single circuit breaker located in accordance with 240.21(C)(4)(4).

Chris

 

[Zane Bailey]

ok then. would this mean that (refering to 240.21(C)(1)and 240.21(C)(4)) whether 2 wire single phase or 3 wire three phase or 3 wire sinlge phase or 4 wire three phase, and the transformer is outdoors, that the secondary conductors can be protected by the primary OCPD and be run unlimited length as long as it terminates on an overcurrent device that limits the load to the ampacity rating of the conductor?

Does this also mean that an indoor 4 wire transformer, when applying the requirements of 240.21(C)(1), must have OCPD with in 10ft or 25ft of where the secondary conductors receive their power?

 

[yired29]

ok then. would this mean that (refering to 240.21(C)(1)and 240.21(C)(4)) whether 2 wire single phase or 3 wire three phase or 3 wire sinlge phase or 4 wire three phase, and the transformer is outdoors, that the secondary conductors can be protected by the primary OCPD and be run unlimited length as long as it terminates on an overcurrent device that limits the load to the ampacity rating of the conductor?

Does this also mean that an indoor 4 wire transformer, when applying the requirements of 240.21(C)(1), must have OCPD with in 10ft or 25ft of where the secondary conductors receive their power?

240.4 (F) on a multi voltage secondary the primary OCPD is not considered to provide protection of the secondary conductors.
240.21 (C) allows secondary conductors not to have protection at the secondary when following the rules of 240.21 (C) (1-6).
240.21 (C) (4) allows an unlimitied length of unprotected secondary conductors up to the point where they enter the building.

 

[Zane Bailey]

Ok

then is it permissible for out door multi voltage secondary conductors as discribed in 240.21(C)(1) to run unprotected and for unlimited length up to the point where the enter the building?

 

[Zane Bailey]

Outdoor transformer secondaries as opposed to indoor.

Outdoor transformer secondaries as opposed to indoor.

Ok

then is it permissible for outdoor (only) multi voltage (3W single phase or 4W three phase) secondary conductors (as opposed to indoor) as discribed in 240.21(C)(1) to run unprotected and for unlimited length up to the point where the enter the building?

 

[raider1]

Ok

then is it permissible for out door multi voltage secondary conductors as discribed in 240.21(C)(1) to run unprotected and for unlimited length up to the point where the enter the building?

You are confusing 2 code sections.

240.21(C)(4) permits 3 wire single phase or 4 wire 3 phase secondary conductors to be run without overcurrent protection on the secondary side for an unlimited length provided that where the conductors enter the building they terminate in a single overcurrent protection device.

240.21(C)(1) does not apply to any 3 wire single phase or 4 wire 3 phase transformer secondaries.

Chris

 

[Zane Bailey]

Chris

the 2005 NEC 240.21(C)(1), specifies that 3 wire single phase and 4 wire three phase are not considered protected by the primary OCPD.

My question is
that 240.21(C)(4) appears to allow the secondary conductors of a 3W sng ph or 4W three ph transformer to run unprotected outdoor for unlimited length.
What is the purpose of the language on 240.21(C)(1) stating that these conductors are not protected by the primary OCPD, if the code allows the installer to run it an unlimited length anyway as long as it terminates on an OCPD nearest where it enters the building?

If you know the answer, please just say it straight, I know the rules in 408 concerning OCPDs for a lighting and appliance panel vrs a power panel.

thank you
Zane.

 

[don_resqcapt19]

Zane,
There are six rules in 240.21(C). These are six different rules. They do not interact with each other. You use whatever one of them that fits you installation. The rule in (1) permits the primary OCPD to protect the secondary conductors under specific conditions. If your installation does not meet these conditions, then you will need to apply one of the other rules.

 

[raider1]

Chris

the 2005 NEC 240.21(C)(1), specifies that 3 wire single phase and 4 wire three phase are not considered protected by the primary OCPD.

Correct, so then we find one of the other rules in 240.21(C) that applies to the installation.

My question is
that 240.21(C)(4) appears to allow the secondary conductors of a 3W sng ph or 4W three ph transformer to run unprotected outdoor for unlimited length.

That is correct, the secondary conductors of a transformer installed outdoors are permitted to be run unlimited in length provided that at the point that the conductors enter the building they terminate in an OCPD.

What is the purpose of the language on 240.21(C)(1) stating that these conductors are not protected by the primary OCPD, if the code allows the installer to run it an unlimited length anyway as long as it terminates on an OCPD nearest where it enters the building?

The secondary conductors allowed in 240.21(C)(4) are not considered to be protected by the primary overcurrent device and 240.21(C)(1) does not apply to these conductors.

The NEC permits the secondaries of outdoor transformers to be run as unprotected conductors for an unlimited length provided that an OCPD is installed at the point where the secondaries enter a building. That is the point at which the conductors receive their overcurrent protection.

If you know the answer, please just say it straight, I know the rules in 408 concerning OCPDs for a lighting and appliance panel vrs a power panel.

thank you
Zane.

I apologize if you feel that I am not being straight with my answers.

Chris

 

[Zane Bailey]

Ok then Don.

If you have an outdoor four wire three phase or a 3 wire sngle phase multi voltage secondary, which is not considered protected by the primary(240.21(C)(1)), does the code allow you in this situation to run unprotected from the transformer to nearest the point of entrance of the conductors as permitted in 240.21(C)(4)

Zane.?

 

[Zane Bailey]

Good explanation Chris.

Sorry I guess I was venting a little, this is appears to be a difficult article to interpret. I have read a lot of commentary that states this.

It just seems to me that 240.21(C)(1) and (C)(4) contradict each other.
Also conductors run unlimited length without overcurrent protection would only be protected from overload at the OCPD nearest where they enter the building. Ground fault short circuit would be dependent on the primary. A fault on the secondary conductors could cause unnecessary outages up stream.

thank you Zane

 

[raider1]

Good explanation Chris.

Sorry I guess I was venting a little, this is appears to be a difficult article to interpret. I have read a lot of commentary that states this.

Yes, the rules in 240.21(C) can be difficult to interpret and understand.

It just seems to me that 240.21(C)(1) and (C)(4) contradict each other.

They don't contradict each other, they just apply to 2 separate situations.

240.21(C)(1) basically states that a 2 wire single voltage single phase or 3 wire single voltage 3 phase secondary conductors that meet the requirements of that section are considered to be protected from overcurrent by the primary overcurrent device and no additional overcurrent device is required on the secondary side of the transformer.

Also conductors run unlimited length without overcurrent protection would only be protected from overload at the OCPD nearest where they enter the building. Ground fault short circuit would be dependent on the primary. A fault on the secondary conductors could cause unnecessary outages up stream.

thank you Zane

That is correct.

Chris