Tap Rule Confusion

[Smart $]

In that case, if I ran secondary conductors to an enclosed circuit breaker, and then extended a feeder from the enclosed circuit breaker to another device or panel, I'd be violating 240.21(C)(2)(2). The conductors "extend beyond" the device.

If the feeder connected to the load side of the enclosed breaker, yes, you would be extending beyond the device.

Yes, I am connecting them to the secondary without OCPD, because the code says I can. 240.21(C) says conductors can be connected to the secondary of a transformer, WITHOUT overcurrent protection [at] the secondary, as specified in 240.21(C)(1) through (C)(6). The conductors connected to the secondary run from the transformer to the device, but don't extend beyond it. Another set of conductors extending from the device would be required to have OCP in meeting the requirements of 240.4, but the requirements of 240.4 don't apply to flexible cords and cables.

As you pointed out previously, flexible cables/cords are covered by 240.5... and as I said previously, when you follow the permitted protection variations, they all say there must be branch-circuit ocpd ahead of where the cables/cords obtain their supply. So when you have a transformer NOT protected by primary OCPD, and the secondary supplies a receptacle to which a flex' cable/cord plugs in, where is the branch-circuit OCPD? You're good as long as nothing plugs into the receptacle :roll:

 

[Smart $]

Sorry, typing from memory, used the wrong word.




No, 240.21(C) permits conductors to be connected to the transformer secondary without overcurrent protection at the secondary, AS SPECIFIED in 240.21(C)(1) through (C)(6).

Some of the provisions of (C)(1) through (C)(6) require an OCPD to be located within 10', or 25' of conductor length, or unlimited conductor length for outside transformers, but the secondary conductors must terminate on an OCPD.

But 240.21(C)(2) PERMITS connection to either an OCPD or a DEVICE. It permits terminating secondary conductors (not more than 10' long) on a DEVICE without overcurrent protection. It doesn't say you are permitted to terminate on a device, as long as there is a secondary OCPD located somewhere else.

Please reread 240.21(C)(2). Its general statement says "the length of the secondary conductor does not exceed 3 m (10 ft) and complies with all of the following:".

Note the "device or ocpd" statement is in 240.21(C)(2)(1)(b).

Proceeding, 240.21(C)(2)(2) states "The secondary conductors do not extend beyond the switchboard, panelboard, disconnecting means, or control devices they supply." A receptacle can be used as a disconnecting means, so it complies with item (C)(2)(2).

But now we get to 240.21(C)(2)(3) where the list drops to "enclosure of an enclosed switchboard, panelboard, or control devices or to the back of an open switchboard." Receptacle used as a disconnecting means under (C)(2)(2) is no longer among the possible scenarios... therefore terminating an unprotected secondary conductor to a receptacle is not permitted under 240.21(C)(2) because it cannot comply with 240.21(C)(2)(3).

 

[david luchini]

If the feeder connected to the load side of the enclosed breaker, yes, you would be extending beyond the device.

So it is a code violation to run conductors from a xfmr secondary to an enclosed circuit breaker, and then to run a feeder from the c/b to a panel or other device, etc.?

I don't believe that is a violation of either the letter or the INTENT of the code. I wonder what others think.

 

[Volta]

Sorry, typing from memory, used the wrong word.




No, 240.21(C) permits conductors to be connected to the transformer secondary without overcurrent protection at the secondary, AS SPECIFIED in 240.21(C)(1) through (C)(6).

Some of the provisions of (C)(1) through (C)(6) require an OCPD to be located within 10', or 25' of conductor length, or unlimited conductor length for outside transformers, but the secondary conductors must terminate on an OCPD.

But 240.21(C)(2) PERMITS connection to either an OCPD or a DEVICE. It permits terminating secondary conductors (not more than 10' long) on a DEVICE without overcurrent protection. It doesn't say you are permitted to terminate on a device, as long as there is a secondary OCPD located somewhere else.

With the possible use of a fused receptacle as a disconnecting means notwithstanding, the receptacle cannot reasonably be considered a control device. That is partially why I offered a device such as a contactor for consideration as a permissible device, it must be able to control something under this sub-section.

 

[RUWired]

Section 240.21(C)(2)(2) implies that an unprotected secondary conductor may be allowed to feed control devices. A contactor qualifies as a control device, in my opinion.

Yes it is a device but as soon as the contacts close it will be feeding another conductor. If the contactor is inline with an OCPD and the whole assembly is all within the 10' rule, i see no problem.

Rick

 

[RUWired]

So it is a code violation to run conductors from a xfmr secondary to an enclosed circuit breaker, and then to run a feeder from the c/b to a panel or other device, etc.?

I don't believe that is a violation of either the letter or the INTENT of the code. I wonder what others think.

If the feeder is tapped on the line side of the enclosed circuit breaker it would be a violation. If on the load side no.

Rick

 

[Smart $]

Yes it is a device but as soon as the contacts close it will be feeding another conductor. If the contactor is inline with an OCPD and the whole assembly is all within the 10' rule, i see no problem.

Rick

That's assuming the contacts are what the secondary conductor(s) are connected to. What if only connected to switching and coil, such as in a large motor starter (even though the secondary is usually fused in these).

 

[Volta]

Yes it is a device but as soon as the contacts close it will be feeding another conductor. If the contactor is inline with an OCPD and the whole assembly is all within the 10' rule, i see no problem.

Rick

I don't agree with what you are saying. If the secondary current passes through a contact (say a pressure switch, or photocontrol), then through the coil of a contactor, that is seemingly within the phrase of 'control devices they supply'.

Devices = plural.

 

[RUWired]

What if only connected to switching and coil, such as in a large motor starter (even though the secondary is usually fused in these).

I don't agree with what you are saying. If the secondary current passes through a contact (say a pressure switch, or photocontrol), then through the coil of a contactor, that is seemingly within the phrase of 'control devices they supply'

Assuming all these control devices are 10' or less, i don't think it matters what they control as long as there is OCP on the load side of these devices. I refer to 240.21(C) and 240.21(C)1 for the logic. I am willing to give on this logic if one can show other better what if's.

Rick

Conductors supplied under the provisions of 240.21(A) through (H) shall not supply another conductor except through an overcurrent protective device meeting the requirements of 240.4.

Single-phase (other than 2-wire) and multiphase (other than delta-delta, 3-wire) transformer secondary conductors are not considered to be protected by the primary overcurrent protective device.

 

[Volta]

Assuming all these control devices are 10' or less, i don't think it matters what they control as long as there is OCP on the load side of these devices. I refer to 240.21(C) and 240.21(C)1 for the logic. I am willing to give on this logic if one can show other better what if's.

Rick

Conductors supplied under the provisions of 240.21(A) through (H) shall not supply another conductor except through an overcurrent protective device meeting the requirements of 240.4.

Single-phase (other than 2-wire) and multiphase (other than delta-delta, 3-wire) transformer secondary conductors are not considered to be protected by the primary overcurrent protective device.

Maybe my confusion lies in the use of 'supply another'. I think that these conductors are permited to have splices, and those are not considered other conductors. They are the same size of wire and order of riser, though the copper has been broken and repaired.

I think these conductors are permitted to provide a path through one or more actuating control devices, and then necessarily to and through the monitoring control device 240.21(C)(2)(2).

If a contactor coil, there would be no OCPD needed, in my opinion, in this thread . Whatever circuit exists on the coil's contacts has nothing to do with this sub-section.

 

[Smart $]

... I am willing to give on this logic if one can show other better what if's.

...

I'm not even going to try. My position regarding this matter, this thread thus far, has been one of a minimal requirements interpretation. That said, in any actual installation where I have any say, the secondary conductors will have an OCPD... period!

 

[david luchini]

As you pointed out previously, flexible cables/cords are covered by 240.5... and as I said previously, when you follow the permitted protection variations, they all say there must be branch-circuit ocpd ahead of where the cables/cords obtain their supply.

Where does the permitted protection variation say that? The permitted protection variation, in this case is is 240.21(C)(2), which permits conductors to be connected to a transformer, without an OCPD at the secondary, and to a device, where the secondary conductors are not over 10' long.

240.21 says the conductors supplied under the provisions of 240.21(C) shall not supply another conductor except through an OCDP meeting the requirements of 240.4.

240.4 says conductors, OTHER THAN flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent protection....

My example follow the permitted protection variation the the letter.

 

[david luchini]

Please reread 240.21(C)(2). Its general statement says "the length of the secondary conductor does not exceed 3 m (10 ft) and complies with all of the following:".

Note the "device or ocpd" statement is in 240.21(C)(2)(1)(b).

Proceeding, 240.21(C)(2)(2) states "The secondary conductors do not extend beyond the switchboard, panelboard, disconnecting means, or control devices they supply." A receptacle can be used as a disconnecting means, so it complies with item (C)(2)(2).

But now we get to 240.21(C)(2)(3) where the list drops to "enclosure of an enclosed switchboard, panelboard, or control devices or to the back of an open switchboard." Receptacle used as a disconnecting means under (C)(2)(2) is no longer among the possible scenarios... therefore terminating an unprotected secondary conductor to a receptacle is not permitted under 240.21(C)(2) because it cannot comply with 240.21(C)(2)(3).

By your logic here, you are not allowed to connect to the "disconnecting means" in (C)(2)(2) because it is not listed in (C)(2)(3). I don't believe that is what the code intends.

In any event, I would consider the receptacle in my example as a "control device" as it is controlling how electric power is delivered to the load. A manual disconnect switch could certainly be considered a control device, so why not a manual receptacle disconnect?

And by the way, thanks for the great discussion. It's been very illuminating.

 

[Smart $]

Where does the permitted protection variation say that? The permitted protection variation, in this case is is 240.21(C)(2), which permits conductors to be connected to a transformer, without an OCPD at the secondary, and to a device, where the secondary conductors are not over 10' long.

240.21 says the conductors supplied under the provisions of 240.21(C) shall not supply another conductor except through an OCDP meeting the requirements of 240.4.

240.4 says conductors, OTHER THAN flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent protection....

My example follow the permitted protection variation the the letter.

For the sake of my reply, let's say your transformer-secondary-supplied receptacle is not questionable ()...

As such, that is great, you've met the Code requirements... until you plug something into the receptacle. You then would be supplying another conductor without an OCPD.

Yes the requirements say the OCPD for another conductor must meet the requirements of 240.4. Since 240.4 does not cover flexible cables, cords and fixture wire, you must somehow meet the OCPD requirements of 240.4 before you can supply a 240.5 item. You cannot bypass 240.4 simply because it does not cover what you want to plug in.

 

[Smart $]

By your logic here, you are not allowed to connect to the "disconnecting means" in (C)(2)(2) because it is not listed in (C)(2)(3). I don't believe that is what the code intends.

In any event, I would consider the receptacle in my example as a "control device" as it is controlling how electric power is delivered to the load. A manual disconnect switch could certainly be considered a control device, so why not a manual receptacle disconnect?

You could if it were the disconnecting means for an enclosure of a switchboard, panelboard, or control device(s), or an open switchboard. But I foresee you using some unconventional fabrication to accommodate a receptacle as a disconnecting means for and IN the types of enclosures given. An open switchboard shouldn't be too hard... but still unconventional

And by the way, thanks for the great discussion. It's been very illuminating.

Glad to hear you enjoyed it

 

[inspector141]

You would be fine using the 90A primary OCPD to protect the secondary conductors on your 3Ph, delta-delta transformer with a one-to-one voltage ratio, using section 240.21(C)(1). However, the #4's have an ampacity of only 85, at 75 deg C. I don't believe you can use the 90 deg ampacity per 110.14, unless the equipment is listed and identified for such use.

So you may be violating 240.21(C)(1) by using a conductor which is too small on the secondary.

Yes, but even if the equipment is rated for 90 deg, the OCPD is not. Most likely 75 deg if more than 100 amps. 110.14 (c)

 

[Smart $]

Yes, but even if the equipment is rated for 90 deg, the OCPD is not. Most likely 75 deg if more than 100 amps. 110.14 (c)

If by equipment, you mean a factory assembly within one enclosure that contains the OCPD referred to, you are not correct. If the "equipment" is listed or is rated by the manufacturer for 90?C operation, it overides any rating of factory installed subassembly parts.

That said, I doubt anyone will run across equipment rated as such