MOCPD

[John Fimbianti]

When I increase the wire size due to correction factor and ambient temperature do I then have to increase the OCPD to the new wire amperage rating?

 

[broadgage]

No, you dont have too, and in many cases you should not.
Think about wire that at normal temperatures could carry 40 amps, but that is only suitable for 30 amps in a particular situation due to grouping and/or high ambient temperatures.
It would be most unwise to fit a 40 amp breaker since any future change in the load could then pass 40 amps through wire only suited for 30, under the relevant conditions.

 

[Lectricbota]

When I increase the wire size due to correction factor and ambient temperature do I then have to increase the OCPD to the new wire amperage rating?

No. That is the reason for enlarging the wire size.If you also increase the OCPD then you would have gained nothing as the calculations for correction and/or ambient stipulate your OCPD rating.

 

[John Fimbianti]

When I increase the wire size due to correction factor and ambient temperature do I then have to increase the OCPD to the new wire amperage rating?

What if I had a 30amp load and the next available wire after the correction factor and
adjustment factor that wire was rated for 40amps? what size overcurrent protection device
should I install?? 30 or 40?

 

[ActionDave]

Thirty.

 

[jeremysterling]

The title of this thread is MOCPD. In most instances, the M stands for a maximum size of OCP and then type of OCP (breaker or fuse) may be specified. Therefore, if the MOCPD = 30A, then the largest breaker or fuse you can use is 30A, regardless of the wire size.