Pneumatics and Control Wiring

[jbergman]

I have always had the understanding that pneumatics and control wiring are not to be located in the same conduit run. Is this just a rule of thumb or is it actually in the NEC? If it is code, where is it referenced?

 

[roger]

See 300.8

Roger

 

[kwired]

I have always had the understanding that pneumatics and control wiring are not to be located in the same conduit run. Is this just a rule of thumb or is it actually in the NEC? If it is code, where is it referenced?

300.8 - keep in mind that that is for conductors that must be installed in a raceway. There is nothing wrong with installing pneumatic lines and listed cables that are not required to be in a raceway in some type of tubing, tray, or whatever that is there for support or physical protection.

 

[roger]

300.8 - keep in mind that that is for conductors that must be installed in a raceway. There is nothing wrong with installing pneumatic lines and listed cables that are not required to be in a raceway in some type of tubing, tray, or whatever that is there for support or physical protection.

Can you point us to where we can find this permission?

Roger

 

[kwired]

Can you point us to where we can find this permission?

Roger

How about telling me where it is not permitted.

This is just like running communications and power in same tubing, channel, bored holes - whatever. If the power cables are a type that do not need to be in a raceway such as NM cable, AC cable, MC cable nothing prohibits them from occupying the same spaces.

They would need to enter enclosures in separate openings in places where cables are required to be secured to a box, cabinet, etc.

Conductors that are covered in 313.13 would have to be installed in separate raceway from other systems - the raceway however could be installed within a trough, channel or other support with other items like water, air, gas - usually they will need to be associated with same equipment to do so - like a unistrut with electric, air, and gas attached to it running to same piece of machinery.

 

[roger]

How about telling me where it is not permitted.

Raceways or cable trays containing electrical conductors shall not contain any pipe, tube, or equal for steam, water, air, gas, drainage, or any service other than electrical.

I don't see where it spells out any particular conductors do you?

Roger

 

[iwire]

I see conductors as wires that need to be in a raceway, IMO if 300.8 meant to include cables it would say cables.

 

[roger]

I see conductors as wires that need to be in a raceway, IMO if 300.8 meant to include cables it would say cables.

And where can we find supporting code words for this?

Looking at the definition of NM for example,

Nonmetallic-Sheathed Cable. A factory assembly of two or more insulated conductors enclosed within an overall nonmetallic jacket.

that doesn't tell me these conductors enclosed within an overall nonmetallic jacket are exempt from article 300.8.

FWIW, I know of a lot of cable tray with numerous systems in them but, I don't see where it is allowed per the wording of 300.8


Roger

 

[roger]

Here is the way I see it, when a cable assembly is installed as a cable it lives by the rules of it's own article, when it is installed in a conduit or raceway it must comply with conduit and raceway installation rules such as derating and adjustment rules, conductor fill rules, the notes of chapter 9, 300.18, and 300.8.

I don't see where we get to change any of these rules because we are using a cable or conductor that does not have to be installed in a raceway on it own.

Let me ask this, does a cable assembly disperse heat inside of a conduit as well as it does installed outside of a conduit?


Roger

 

[bluesmoke...oops]

If you put a divider in a cable tray, is it now considered two separate trays for the purpose of running conductors/wires/hoses?

 

[roger]

If you put a divider in a cable tray, is it now considered two separate trays for the purpose of running conductors/wires/hoses?

But this is not the case in the trays I'm speaking of.

Roger

 

[ronaldrc]

I agree with Roger


NEC Article 300.8. Raceways or cable trays containing electrical conductors cannot contain elements of other systems?no water pipes, gas pipes, or any other non-electrical system elements can run in those electrical wireways.

Air line is non Electrical isn't it?

 

[iwire]

I agree with Roger


NEC Article 300.8. Raceways or cable trays containing electrical conductors cannot contain elements of other systems?no water pipes, gas pipes, or any other non-electrical system elements can run in those electrical wireways.

Air line is non Electrical isn't it?

I have never said an air line is 'electric'.

What I said is that IMO 300.8 does not apply to cables.

 

[iwire]

And where can we find supporting code words for this?

The large number of code sections that use the term 'cable' or 'cables and conductors' when that is what they mean.

We just see this differently.

 

[ronaldrc]

Bob

I was not addressing any certain individual, but I think that is one of the plainess statements I have read in the NEC. Non electrical is non electrical, sorry you took it personnel.

Ronald

 

[iwire]

Bob

I was not addressing any certain individual, but I think that is one of the plainess statements I have read in the NEC. Non electrical is non electrical, sorry you took it personnel.

Ronald

No big deal.

So we can mix electrical cables and say plumbing in a stud bay but it suddenly becomes a safety issue if it is a cable tray .........

Sorry I don't find that logical.

 

[ronaldrc]

Bob

I can see the logic with conduit but not necessarily with tray.

If you had a pneumatic Thermostat line run in a conduit with a fault in it,it could melt a hole in the air line and you would loose temperture control of those units or unit.

Why take that chance?

 

[roger]

Bob

I can see the logic with conduit but not necessarily with tray.

Hello Ronald, that is the way I see it too.



Roger

 

[iwire]

I looked at the ROPs for 2002, 2005, 2008 & 2011 and you know what the problem with 300.8 is?

Apparently no one wants to change it, I found almost nothing.:grin:


However, in a proposal about manholes I found a CMP comment that referenced 300.8 and without a doubt that CMP member felt like Roger and Ronald.

 

[kwired]

Bob

I can see the logic with conduit but not necessarily with tray.

If you had a pneumatic Thermostat line run in a conduit with a fault in it,it could melt a hole in the air line and you would loose temperture control of those units or unit.

Why take that chance?

What is it going to fault to? If poly air tubing they are insulators.

If the pipe they are run in is metallic it is either grounded and the overcurrent device trips or it is not grounded and the pipe becomes energized. The latter can be a dangerous situation but is of little threat to the air lines.

My suggestion of running an electric cable in same tubing, tray, or whatever does not mean run an EMT or RMC from a junction box at the ceiling that is part of electrical system down to a control panel with air soleniods in it and run both power and pneumatic lines down that raceway.

An example of what I am referring to would be a machine with several air actuated devices on it as well as proximity sensors, limit switches, etc. to sense presence of material before an air actuator makes its move. There would be nothing wrong with routing cables for sensors as well as air lines through a leg of the machine that happens to be hollow inside - as long as the cables are not required to be installed in raceways otherwise.

Single conductors of type MTW would not be allowed to be installed this way, they would have to be installed in a Ch 3 wiring method and the raceway would need to be complete from junction/device/pull box to the next junction/device/pull box.