Exposed Romex or MC

[HackWork]

I know things are different in different areas. From what I know, in NJ they don't like exposed romex in many situations and consider it subjected to physical damage. However, in many installations I have seen MC used and it passed. Since MC provides no more protection than romex, why is this allowed?

An example of a recent situation, a house was built last year and in the back of the garage they forgot to run the circuits for the heater and well pump, so they surface mounted the boxes and cables after the drywall was up. The homeowner told me that the inspector wouldn't allow romex exposed on the wall so they used MC.

Why is this allowed?

 

[brett711]

I know things are different in different areas. From what I know, in NJ they don't like exposed romex in many situations and consider it subjected to physical damage. However, in many installations I have seen MC used and it passed. Since MC provides no more protection than romex, why is this allowed?

An example of a recent situation, a house was built last year and in the back of the garage they forgot to run the circuits for the heater and well pump, so they surface mounted the boxes and cables after the drywall was up. The homeowner told me that the inspector wouldn't allow romex exposed on the wall so they used MC.

Why is this allowed?

mc is differently rated

 

[HackWork]

mc is differently rated

In what way would apply here? Don't they follow the same basic rules of not being permitted where exposed to physical damage?

 

[Dennis Alwon]

IMO, MC is much less subject to damage than NM cable would be.

 

[HackWork]

IMO, MC is much less subject to damage than NM cable would be.

Sure, logically speaking. But from the code, I don't see it.

 

[Dennis Alwon]

Be it known that NM is suitable to be exposed also however it will be an AHJ call on what subject to damage entails.

 

[Dennis Alwon]

Sure, logically speaking. But from the code, I don't see it.

It is all in the interpretation of "subject to physical damage"

 

[suemarkp]

To me, it takes less force to damage NM than AC/MC. But none of the thresholds of what is considered physical damage is defined in the code. So it is going to vary from inspector to inspector. In general, I'd say plastic sheathed cables, AC/MC, and flex conduits all need similar protection.

 

[Gold]

IMO, MC is much less subject to damage than NM cable would be.

Mine too but I think he is eluding to the fact that the NEC doesn't clearly distinguish the two it just relies on the generic phrase "where exposed to physical damage" in the situation he describes and many others MC is no less exposed then nm would be.

 

[Dennis Alwon]

Also remember that there are more restrictions on the use of NM in terms of use. In a dwelling NM is one thing but in different structures NM must be concealed behind a 15 min finished rating. Also it cannot be installed in suspended ceilings in non residence. These restrictions are there for some reason but to be honest I am not sure why other than the toxicity of the cable.

 

[ActionDave]

Exposed MC looks cool, exposed NM looks tacky, especially since they started sheathing it in different colours. That is the only difference I can think of.

 

[iwire]

Since MC provides no more protection than romex, why is this allowed?

I think that is the issue, as long as you hold that view the rules will not make sense to you. I think most folks would say metal provides more protection than plastic in most installations.

 

[iwire]

Be it known that NM is suitable to be exposed also however it will be an AHJ call on what subject to damage entails.

Exactly, and what conditions that can damage NM, MC, PVC, EMT, or RMC are all different and the inspectors call on psychical damage will be based on the specifics of the job.

It sure is not the clearest thing in the NEC but no one has found a better way yet.

 

[don_resqcapt19]

Since the code refuses to give any clue as to the meaning of "subject to physical" damage there will always be a wide range of how this section is read.

"Everything that you can see and some things that you can't see are subject to physical damage."

 

[kwired]

What is deemed likely to damage it is another way to look at it?

Even RMC can be subject to damage, but it takes a lot more abuse than NM cable does before actual damage results.