Circuit pass through

[mslowley]

Can somebody tell me where in the NEC it speaks to not passing circuits from a lighting panel (240/120VAC 1Ph)through a control cabinet and out to the device. Or electrician tells me it is illegal to use the cabinet as a pull box. I can't seem to find the article and I'm not sure I understand what the issue is. The conductors are identified as being sourced from an alternate location and the just need to end up at the same area as many of the other control wires from the cabinet.

 

[iwire]

Re: Circuit pass through

It is OK to pass through the cabinet, make sure read the whole article.

The control cabinet is most likely an enclosures for switches.

312.8 Enclosures for Switches or Overcurrent Devices.
Enclosures for switches or overcurrent devices shall not be used as junction boxes, auxiliary gutters, or raceways for conductors feeding through or tapping off to other switches or overcurrent devices, unless adequate space for this purpose is provided. The conductors shall not fill the wiring space at any cross section to more than 40 percent of the cross-sectional area of the space, and the conductors, splices, and taps shall not fill the wiring space at any cross section to more than 75 percent of the cross-sectional area of that space.

 

[tshephard]

Re: Circuit pass through

I think we need to know a little more about the control cabinet. What exactly does it do and what is in it?

Also, your electrician may be using the code reference as a method to get you to consent to a better practice than the (minimum)code allows.

I've worked for/with folks who were too cheap/lazy to buy/carry another 2 sticks of pipe if there was another route nearby.

 

[mslowley]

Re: Circuit pass through

The control cabinet house CB's, contactors, a plc, temperature controllers, misc. gauges and readouts for the machine. It is a six foot wide double door 24" deep industrial cabinet provided by the machine manufacturer. We are retrofitting some of the control system and the 120/240 VAC originates in the LP mounted along side of the cabinet. My reasoning for passing through was actually because the area is already conjested with pipe. This is not the first time the electrician has used the term "illegal according to NEC" with me. If it is, I want to do it right. If it isn't, I want it done the way I requested. No issue about cheap, lazy or other....

 

[rickcham]

Re: Circuit pass through

MS
Couple of the reasons a Electrician would not want to enter the control cabinets, one is the influnence of the AC wire on the instrument signals and the other is the lack of barriers in most control cabinets to seperate the 120/240 from the 24VDC instruments. This can cause major headaches at times. Plus most control cabinets that contain transmitters,PLC's and such are designed for a certain free heat flow.
I feel this should be avoided

 

[tom baker]

Re: Circuit pass through

If its a control cabinet, then different rules apply. For example a motor controller installed under Art 430 can not be used as a junction box, as this is not an article 312 application. See section 430.10(A).
A "control cabinet" may be listed under UL508 as industrial motor control, and if so the rules of 312 don't apply. Look inside the door and see if there is an UL or ETL listing and what it is.

 

[dana1028]

Re: Circuit pass through

Tom - doesn't 430.10(A) say pretty much the same as 312.8?

..."unless designs are employed that provide adequate space for this purpose."

I.e. - if there is adequate space for running other conductors, splicing then you are allowed to do it, if not - you aren't allowed to do it.

The difference here is 430 doesn't spell out specific % of fill requirements.

However, I do agree with rickcham - I have encountered problems with line voltage causing havoc with the lower voltage PCs.

[ December 09, 2003, 11:25 AM: Message edited by: dana1028 ]

 

[tom baker]

Re: Circuit pass through

Yes you are correct, but it is specifically allowed in 318, but only in 430 if the equipment is designed for it. I feel its a bad practice to run conductors thru a control panel if they are not terminated in the control panel

 

[hurk27]

Re: Circuit pass through

Tom what about if you bring all your limit switchs and orher control wires back to a terminal strip to alow for faster trouble shooting? these wires are not needed for the system to work but are very helpful in trouble shooting and alow for faster repairs by alowing a single point to trouble shoot from.

 

[iwire]

Re: Circuit pass through

The opening post asked if it was an NEC violation, it is not.

Any electric equipment can be used as a junction box or raceway unless restricted by a particular article.

mslowley did not ask if it was a bad practice or not.

The code is the minimum and we can always go beyond it.

He said his electrician said it was a code violation and that was untrue.

 

[mslowley]

Re: Circuit pass through

Thanks iwire.

I'm glad you pointed out my original issue. It is true that "best practice" in many cases is to seperate wiring as we normally do for signal vs. 120ac vs. 480ac vs. dc. But, in our facility and most that I am aware of, mixing of these items may become required in control panels on occassion.