MC Cable Vs Pipe & Wire

[Jpflex]

When you derate a feeder conductor supplying several motors, the feeder conductor cannot use the next size up OCPD for non standard ampacity as you could for feeders supplying non motor loads as modified for motor circuits such as feeders for sub panels in houses. Is this correct?

And when you size a feeder to a house sub panel you adjust its ampacity by either the larger of two ways

1) calculating the feeder ampacity to 125% of continuous loads and 100% of non continuous loads or

2 ) calculating the feeder ampacity to ambient temperature derating plus conductor bundling derating to meet the load requirement

Is this correct?

And you can go up to the next size breaker for sub pannel feeders but not motor feeders?

 

[herding_cats]

From the Kansas City rea here....

MC runs direct out of panels is the norm, if inside walls. Local code here prohibits MC ran below 8' if exposed, outside of a wall. So above 8', you can attach MC cable anywhere you want. Looks terrible, but for cheapskate landlords it works.

 

[Jpflex]

From the Kansas City rea here....

MC runs direct out of panels is the norm, if inside walls. Local code here prohibits MC ran below 8' if exposed, outside of a wall. So above 8', you can attach MC cable anywhere you want. Looks terrible, but for cheapskate landlords it works.

What other code number for this?

Mc cables can be run in walls for fabricated walls in hospitals but I think that is a rule modification?

 

[herding_cats]

Not sure on code article. This is just local standard practice. I have seen firsthand MC cable above drop ceilings in Hospitals. So, in walls I'm sure is fine.

One thing is weird, is the use of smurf tubing. The provisions for that are all over the place, so I don't ever use it. I'm sure i could save some $$ here or there if I checked, but taking it all out at an inspection could be more expensive than just using MC cable to begin with. The last time I was in Guatemala City, I went by a huge high rise new construction project. The entire building had Romex pulled through it.

 

[letgomywago]

Not sure on code article. This is just local standard practice. I have seen firsthand MC cable above drop ceilings in Hospitals. So, in walls I'm sure is fine.

One thing is weird, is the use of smurf tubing. The provisions for that are all over the place, so I don't ever use it. I'm sure i could save some $$ here or there if I checked, but taking it all out at an inspection could be more expensive than just using MC cable to begin with. The last time I was in Guatemala City, I went by a huge high rise new construction project. The entire building had Romex pulled through it.

They make hospital grade MC which is a type of MCap with an extra ground.

Even though it's not as tough of a wiring method I'd take properly installed romex vs improperly installed mc with the wrong fittings and such any day. We've all seen the barn with plastic octagons and mc into it.

 

[herding_cats]

Right on. I agree with you on the Romex. Hospital isolated ground makes sense on hospital grade MC. My wholesaler has MC with 0-10 vdc shielded control wire in it, and another set pair for misc. controls 24vac-vdc supply for controllers. Living in a networked world...