Transformer secoundary

[jado85]

Actual scenario, Xf (480/277V Y, solid grounded) on roof top, run the secondary unlimited length outside the building elevated from the surfaces(~3"), the feed enter into the building to an OCPD (SWG main CB) that is not over 25 ft horizontally and not over 100 ft in total length(measured to the entry point). is this compliant?

 

[templdl]

Actual scenario, Xf (480/277V Y, solid grounded) on roof top, run the secondary unlimited length outside the building elevated from the surfaces(~3"), the feed enter into the building to an OCPD (SWG main CB) that is not over 25 ft horizontally and not over 100 ft in total length(measured to the entry point). is this compliant?

How far did you say it was from the transformer secondary to the secondary OCPD? And what is the distance from the pri OCPD to the transformer primary?

 

[augie47]

I would say non-compliant as the overcurrent device is not "nearest the point of entry of the conductors"

 

[don_resqcapt19]

Actual scenario, Xf (480/277V Y, solid grounded) on roof top, run the secondary unlimited length outside the building elevated from the surfaces(~3"), the feed enter into the building to an OCPD (SWG main CB) that is not over 25 ft horizontally and not over 100 ft in total length(measured to the entry point). is this compliant?

Don't forget the temperature correction adder for derating purposes that is required by 310.15(B)(3)(c) for the roof top application.

I agree with augie that the installation is not compliant with the requirements of 240.21(C)(5)(4).

 

[jado85]

How far did you say it was from the transformer secondary to the secondary OCPD? And what is the distance from the pri OCPD to the transformer primary?

transformer secondary to the secondary OCPD: 340 ft on roof top
pri OCPD to the transformer primary: not 100% sure what you mean, but from Primary OCPD to XF is 35 ft

I would say non-compliant as the overcurrent device is not "nearest the point of entry of the conductors"

entry point is on the roof, so we'd have to go down to the floor level to a Switch gear, wouldn't the feeder tap rules (240.21 (C) (4) apply at for the portion between the entry point and the OCPD?

 

[david luchini]

entry point is on the roof, so we'd have to go down to the floor level to a Switch gear, wouldn't the feeder tap rules (240.21 (C) (4) apply at for the portion between the entry point and the OCPD?

240.21(C)(4)(4) says the disconnecting means must either be outside the building, or inside the building nearest the point of entrance of the conductors. You can't enter the building an then run 100' to the disconnecting means.

 

[jado85]

240.21(C)(4)(4) says the disconnecting means must either be outside the building, or inside the building nearest the point of entrance of the conductors. You can't enter the building an then run 100' to the disconnecting means.

I had a typo, is should read : B not C

basically defining the Xf secondary as a feed that is tapped at the point of entry
I dont mean to be an ASKhole, I'm asking the questions I was faced with from my manager.

 

[david luchini]

I had a typo, is should read : B not C


basically defining the Xf secondary as a feed that is tapped at the point of entry
I dont mean to be an ASKhole, I'm asking the questions I was faced with from my manager.

You have transformer secondary conductors which must comply with 240.21(C). You cannot provide a 240.21(B) tap to these conductors.

 

[jado85]

You have transformer secondary conductors which must comply with 240.21(C). You cannot provide a 240.21(B) tap to these conductors.

by definition a feeder would have OCPD on both ends, is that correct?

In order to be compliant, we'd have to provide an OCPD and the point of entry. what rules would I fall under for the portion from that point to the Switchgear?

 

[david luchini]

by definition a feeder would have OCPD on both ends, is that correct?

By definition, the transformer secondary conductors are a feeder.

In order to be compliant, we'd have to provide an OCPD and the point of entry. what rules would I fall under for the portion from that point to the Switchgear?

Yes, you would need an OCPD/disconnecting means at the point of entry. From there, there is no length limits to the switchgear.

 

[don_resqcapt19]

by definition a feeder would have OCPD on both ends, is that correct?

In order to be compliant, we'd have to provide an OCPD and the point of entry. what rules would I fall under for the portion from that point to the Switchgear?

Feeder. All circuit conductors betweenthe service equipment, the source of a separately derived system, or otherpower supply source and the final branch-circuit overcurrent device.

Transformer secondary conductors are a subset of the general term "feeder", but they must be protected by the rules in 240.21(C), not the rules in 240.21(B).

If you put an OCPD on the roof or inside the building nearest the point of entry, the conductors between than OCPD are feeder conductors and they would be protected at or below their ampacity. The transformer secondary conductors would end at the line side of the OCPD.

 

[jado85]

By definition, the transformer secondary conductors are a feeder.




Yes, you would need an OCPD/disconnecting means at the point of entry. From there, there is no length limits to the switchgear.

[FONT=arial, sans-serif]Feeders: are all circuit conductors between the service equipment, the source of a [/FONT]separately derived system,[FONT=arial, sans-serif] or other power supply source, and the final branch-circuit overcurrent device.
[/FONT]we agree to this point.
[FONT=arial, sans-serif] [/FONT]
[FONT=arial, sans-serif]How do I determine which definition I use, some one might argue since its a feeder we can apply feeder tap rule. on the other side If we argu it's a XF secondary, why didn't the feeder definition apply?

[/FONT]

 

[david luchini]

Feeders: are all circuit conductors between the service equipment, the source of a separately derived system, or other power supply source, and the final branch-circuit overcurrent device.
we agree to this point.

By definition, the transformer secondary conductors are a feeder.

How do I determine which definition I use, some one might argue since its a feeder we can apply feeder tap rule. on the other side If we argu it's a XF secondary, why didn't the feeder definition apply?

Even though they are a feeder, you cannot tap the transformer secondary conductors. See 240.21.

 

[jado85]

Even though they are a feeder, you cannot tap the transformer secondary conductors. See 240.21.

Are you referring to " conductor supplied under the provisions of 240.21 (A) -(H) shall not be supplied from another conductor except through an OCPD meeting the req..."

 

[david luchini]

Are you referring to " conductor supplied under the provisions of 240.21 (A) -(H) shall not be supplied from another conductor except through an OCPD meeting the req..."

Yes. That would prevent you from tapping the transformer secondary conductors.

But, as pointed out earlier, if you're connecting conductors to a transformer secondary per 240.21(C)(4), you need to have a disconnecting means either outside, or inside nearest the point of entrance.

 

[jado85]

Yes. That would prevent you from tapping the transformer secondary conductors.

But, as pointed out earlier, if you're connecting conductors to a transformer secondary per 240.21(C)(4), you need to have a disconnecting means either outside, or inside nearest the point of entrance.

The reasoning for this would be, to avoid having unprotected conductor inside the building to minimize the hazards. correct?

 

[don_resqcapt19]

The reasoning for this would be, to avoid having unprotected conductor inside the building to minimize the hazards. correct?

The addition of the outside secondary conductor rule in 240.21(C) was intended to put the secondary conductors from a privately owned transformer feeding a building on the same footing as the service conductors from an utility feeding that same building. The service conductors do not have overcurrent protection until they get to the building. The service OCPD is installed outside or inside nearest the point of entrance...just like what is required by the relatively new outside secondary conductor rule.

 

[jado85]

The addition of the outside secondary conductor rule in 240.21(C) was intended to put the secondary conductors from a privately owned transformer feeding a building on the same footing as the service conductors from an utility feeding that same building. The service conductors do not have overcurrent protection until they get to the building. The service OCPD is installed outside or inside nearest the point of entrance...just like what is required by the relatively new outside secondary conductor rule.

ok this makes sense to me. Thanks

 

[RB1]

Let's talk about that "inside, nearest point of entrance" interpretation: The disconnecting means must be in a readily accessible location nearest the point of entrance of the conductors. The roof may or may not be readily accessible. The switchboard location in the original post could be considered to be a readily accessible location nearest the point of entrance of the conductors, being that anything above the switchboard is not readily accessible. Just sayin.

When you install a breaker enclosure as a service disconnecting means inside a building, do you mount the switch on the slab, or do you extend the service lateral raceway up to the switch location?

 

[don_resqcapt19]

Let's talk about that "inside, nearest point of entrance" interpretation: The disconnecting means must be in a readily accessible location nearest the point of entrance of the conductors. The roof may or may not be readily accessible. The switchboard location in the original post could be considered to be a readily accessible location nearest the point of entrance of the conductors, being that anything above the switchboard is not readily accessible. Just sayin.

When you install a breaker enclosure as a service disconnecting means inside a building, do you mount the switch on the slab, or do you extend the service lateral raceway up to the switch location?

The OP was talking about 100' inside the building....that would get a red tag from me.