Supplemental Disconnects???

[AndyK]

What is the correct usage for this section of the NEC; my co-workers are labeling everyhing outside of a MCC Enclosure as a supplemental disconnecting means and I think this is an incorrect use of this section. According to our in-house code expert, he has determined that because it says it does not need to be readily accessible that there is no height limit nor is there a clearance requirement, is this true, I have never heard of such an interpertation. Please give me your views, I personally think it is in regards to equipment such as HVAC Units with breakers enclosed as part of the system and items similar, I do not feel it was intended that all devices such as disconnects located at motors be labeled as supplemental and not subject to clearance issues.​

 

[petersonra]

What is the correct usage for this section of the NEC; my co-workers are labeling everyhing outside of a MCC Enclosure as a supplemental disconnecting means and I think this is an incorrect use of this section. According to our in-house code expert, he has determined that because it says it does not need to be readily accessible that there is no height limit nor is there a clearance requirement, is this true, I have never heard of such an interpertation. Please give me your views, I personally think it is in regards to equipment such as HVAC Units with breakers enclosed as part of the system and items similar, I do not feel it was intended that all devices such as disconnects located at motors be labeled as supplemental and not subject to clearance issues.​

I did a search of the code in acrobat reader and was unable to find the term "supplemental disconnect".

But, I think he is essentially correct. i don't know what you mean by "clearance limit".

 

[Smart $]

I did a search of the code in acrobat reader and was unable to find the term "supplemental disconnect".

I believe he is referring to...

240.10 Supplementary Overcurrent Protection. Where
supplementary overcurrent protection is used for luminaires,
appliances, and other equipment or for internal circuits and
components of equipment, it shall not be used as a substitute
for required branch-circuit overcurrent devices or in place of
the required branch-circuit protection. Supplementary overcurrent
devices shall not be required to be readily accessible.

...and...

240.24 Location in or on Premises.

(A) Accessibility. Overcurrent devices shall be readily ac-
cessible and shall be installed so that the center of the grip
of the operating handle of the switch or circuit breaker,
when in its highest position, is not more than 2.0 m (6 ft
7 in.) above the floor or working platform, unless one of the
following applies:
(1) For busways, as provided in 368.17(C).
(2) For supplementary overcurrent protection, as described

in 240.10.​

(3) For overcurrent devices, as described in 225.40 and

230.92.​

(4) For overcurrent devices adjacent to utilization equip-

ment that they supply, access shall be permitted to be
by portable means.​

...(B) through (F) not relevant to discussion and omitted for brevity...

But, I think he is essentially correct.

Not if they are required disconnecting means (i.e. switching with ocp), and definitely not if they are just disconnects (i.e. contain no ocp).

Also note 'not be required to be readily accessible' does not remove any 'accessible' requirement.

i don't know what you mean by "clearance limit".

Clear space about electrical equipment.

 

[Cavie]

What is the correct usage for this section of the NEC; my co-workers are labeling everyhing outside of a MCC Enclosure as a supplemental disconnecting means and I think this is an incorrect use of this section. According to our in-house code expert, he has determined that because it says it does not need to be readily accessible that there is no height limit nor is there a clearance requirement, is this true, I have never heard of such an interpertation. Please give me your views, I personally think it is in regards to equipment such as HVAC Units with breakers enclosed as part of the system and items similar, I do not feel it was intended that all devices such as disconnects located at motors be labeled as supplemental and not subject to clearance issues.​

Your inhouse guru is all wet. Sounds like he's writting his on code book.

 

[charlie b]

What is the correct usage for this section of the NEC

What section are you talking about?

 

[AndyK]

The reference is to 240.10, here is the issue, I have several motors all daisy chained off one main breaker, each disconnect is located adjacent to the motor it serves, the clearance in front of this blower motor to the disconnect is less than 10 inches, and in some cases is well over 10' above the ground. Can they be legally called supplemental disconnects? And if so, are they not still subject to have a minimum of 36" clearance at 277V to ground?

 

[AndyK]

Oops. its 240.24 not 240.10 (fingers faster than brain or visa versa)

 

[Smart $]

The reference is to 240.10, here is the issue, I have several motors all daisy chained off one main breaker, each disconnect is located adjacent to the motor it serves, the clearance in front of this blower motor to the disconnect is less than 10 inches, and in some cases is well over 10' above the ground. Can they be legally called supplemental disconnects? And if so, are they not still subject to have a minimum of 36" clearance at 277V to ground?

Oops. its 240.24 not 240.10 (fingers faster than brain or visa versa)

If multiple blower motors (not one machine) are fed by one breaker, the local disconnects are disconnecting means (i.e. switch and ocp)... not supplementary OCP.

 

[petersonra]

I believe he is referring to...



...and...





Not if they are required disconnecting means (i.e. switching with ocp), and definitely not if they are just disconnects (i.e. contain no ocp).

Also note 'not be required to be readily accessible' does not remove any 'accessible' requirement.


Clear space about electrical equipment.

you are mixing up the term "disconnect" with "overcurrent protection".

 

[Smart $]

you are mixing up the term "disconnect" with "overcurrent protection".

I don't believe I am. My replies are worded as such because I believe the OP'er is mixing them up. AFAIK, there is no such thing as a supplemental or supplementary disconnect.

If the ocp is part of a required disconnecting means, then 240.10/240.24(A)(2) does not apply. The same is true of a disconnect (i.e. switch without ocp).

 

[kwired]

The reference is to 240.10, here is the issue, I have several motors all daisy chained off one main breaker, each disconnect is located adjacent to the motor it serves, the clearance in front of this blower motor to the disconnect is less than 10 inches, and in some cases is well over 10' above the ground. Can they be legally called supplemental disconnects? And if so, are they not still subject to have a minimum of 36" clearance at 277V to ground?

If there is lower overcurrent protection on these multiple disconnects than on the "main" you do not have "supplemental" disconnects or "supplemental" overcurrent devices you have a feeder and a branch circuit that originates at each one of those disconnects.

Supplemental overcurrent protection would be a situation where you have a branch circuit and you put in additional (but not otherwise required) overcurrent protection. Example - you have a 20 amp branch circuit supplying a motor and you put 17.5 amp fuses in the motor disconnecting means for design purposes and not because of code minimum/maximum reasons. Same fuseholder could really have any size fuse in it and still be called supplemental as the 20 amp device at the source of the circuit is all that is required by code.

 

[Smart $]

....

Supplemental overcurrent protection would be a situation where you have a branch circuit and you put in additional (but not otherwise required) overcurrent protection. Example - you have a 20 amp branch circuit supplying a motor and you put 17.5 amp fuses in the motor disconnecting means for design purposes and not because of code minimum/maximum reasons. Same fuseholder could really have any size fuse in it and still be called supplemental as the 20 amp device at the source of the circuit is all that is required by code.

It can be a local [fused] disconnect to meet the 'within sight' requirement, but it cannot be the disconnecting means.

 

[kwired]

It can be a local [fused] disconnect to meet the 'within sight' requirement, but it cannot be the disconnecting means.

430.102 requires a disconnect within sight of the controller (the controller disconnect), and it requires a disconnect within sight of the motor (the motor disconnect). If a single disconnect is within sight of both the motor and controller then it can serve both purposes, and in some cases the controller disconnect, if lockable, can serve both purposes.

 

[Smart $]

430.102 requires a disconnect within sight of the controller (the controller disconnect), and it requires a disconnect within sight of the motor (the motor disconnect). If a single disconnect is within sight of both the motor and controller then it can serve both purposes, and in some cases the controller disconnect, if lockable, can serve both purposes.

I know all that. What I'm saying is if it is a required disconnecting means, i.e. switch and ocp, it cannot qualify as supplementary overcurrent protection. Required disconnects are not required disconnecting means, i.e. they are not required to have integral or immediately adjacent ocp. If they don't have ocp, then they definitely do not qualify as supplementary overcurrent protection. If they do have ocp, only the ocp qualifies, not the disconnect.

 

[kwired]

I know all that. What I'm saying is if it is a required disconnecting means, i.e. switch and ocp, it cannot qualify as supplementary overcurrent protection. Required disconnects are not required disconnecting means, i.e. they are not required to have integral or immediately adjacent ocp. If they don't have ocp, then they definitely do not qualify as supplementary overcurrent protection. If they do have ocp, only the ocp qualifies, not the disconnect.

Disconnecting means and overcurrent protection are two different things but often are contained within same device or enclosure. Often a disconnecting means is required but overcurrent protection is already taken care of farther upstream. This is a case where supplemental overcurrent protection may be provided. If overcurrent protection is not already provided somewhere upstream then it can not be supplemental, it has to be mandatory overcurrent protection.

I think we may be saying mostly same thing but not in same way, that never happens

 

[Smart $]

Disconnecting means and overcurrent protection are two different things but often are contained within same device or enclosure. Often a disconnecting means is required but overcurrent protection is already taken care of farther upstream. This is a case where supplemental overcurrent protection may be provided. If overcurrent protection is not already provided somewhere upstream then it can not be supplemental, it has to be mandatory overcurrent protection.

I think we may be saying mostly same thing but not in same way, that never happens

My bad... mostly. I finally realized I've been using slang wording. But to save at least a little face, I did explain in my posts.


Let me clarify using entirely correct NEC terminology...


If a required disconnecting means has integral ocp—which is not required—the ocp qualifies under 240.10 as supplementary overcurrent protection... but the disconnecting means must still meet the requirements of 404.8(A), which is worded very similar to the accessibility requirements of 240.24(A), but gives no blanketed leniency as 240.24(A)(2) does for supplementary overcurrent protection.

 

[ASG]

My bad... mostly. I finally realized I've been using slang wording. But to save at least a little face, I did explain in my posts.


Let me clarify using entirely correct NEC terminology...


If a required disconnecting means has integral ocp?which is not required?the ocp qualifies under 240.10 as supplementary overcurrent protection... but the disconnecting means must still meet the requirements of 404.8(A), which is worded very similar to the accessibility requirements of 240.24(A), but gives no blanketed leniency as 240.24(A)(2) does for supplementary overcurrent protection.

Except 404.8(A) has exceptions allowing it to be adjacent to the motor it serves and has no clearance requirements.

 

[Smart $]

Except 404.8(A) has exceptions allowing it to be adjacent to the motor it serves and has no clearance requirements.

Where does it say clearances do not apply? Clear space requirements is in Article 110, and I see no reference or exception to such.

404.8 Accessibility and Grouping.

(A) Location. All switches and circuit breakers used as
switches shall be located so that they may be operated from
a readily accessible place. They shall be installed such that
the center of the grip of the operating handle of the switch
or circuit breaker, when in its highest position, is not more
than 2.0 m (6 ft 7 in.) above the floor or working platform.


Exception No. 1: On busway installations, fused switches
and circuit breakers shall be permitted to be located at the
same level as the busway. Suitable means shall be provided
to operate the handle of the device from the floor.

Exception No. 2: Switches and circuit breakers installed
adjacent to motors, appliances, or other equipment that
they supply shall be permitted to be located higher than 2.0
m (6 ft 7 in.) and to be accessible by portable means.

Exception No. 3: Hookstick operable isolating switches
shall be permitted at greater heights.

 

[ASG]

Where does it say clearances do not apply? Clear space requirements is in Article 110, and I see no reference or exception to such.

It's a standing argument in our office but some of us don't think a switch is going to require servicing or maintenance while energized.

 

[Smart $]

It's a standing argument in our office but some of us don't think a switch is going to require servicing or maintenance while energized.

Doesn't matter. It must still remain at the very least accessible (as opposed to readily accessible). Additionally, switches and circuit breakers must always be operable from a readily accessible location, even if the equipment itself is only accessible. This is stipulated in the first sentence of 404.8(A) and the Exceptions thereto do not rescind that requirement.