Breaker sizing for MOCP

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brantmacga

Señor Member
Location
Georgia
Occupation
Former Child
Equipment MCA is 22A
MOCP is 35A


We installed L6-30R to match equipment L6-30P cord and fused with 30A breaker.

Inspector failed final, said must have a 35A breaker, and must go to next size recep which would be 50A; will also have to change cord.

Conductors are #8 as equipment schedule showed 40A unit going in, but details noted to verify nameplate. It did show a receptacle connection, but no details on recep type other than "250v".

Is this accurate?

I always thought you only needed to clear MCA.


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iwire

Moderator
Staff member
Location
Massachusetts
The inspector is asking for more than the NEC.

You can use up to the MOCP but you do not have to.

Also if this unit has a factory 30 amp plug on it I would tell the inspector no way am I changing it.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
The MOCPD rating is just that the maximum you can use with 22 amp conductors. The unit requires a circuit with a minimum ampacity of 22 amps so you could use a 25 amp circuit breaker which is more than 22 amps. I agree with Bob I would change nothing. Why would anyone recommend changing the factory cord cap?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Putting the unit on anything larger than a 35A breaker would be a flat out NEC violation, and unsafe too!
And, depending on the details, putting a 50A receptacle on a 35A breaker could also be a violation.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Putting the unit on anything larger than a 35A breaker would be a flat out NEC violation, and unsafe too!
And, depending on the details, putting a 50A receptacle on a 35A breaker could also be a violation.

How so?
 

Smart $

Esteemed Member
Location
Ohio
210.21(B)

(1) Single Receptacle on an Individual Branch Circuit.
A single receptacle installed on an individual branch circuit
shall have an ampere rating not less than that of the branch
circuit.

Exception No. 1: A receptacle installed in accordance
with 430.81(B).

Exception No. 2: A receptacle installed exclusively for the

use of a cord-and-plug-connected arc welder shall be permitted
to have an ampere rating not less than the minimum
branch-circuit conductor ampacity determined by 630.11(A)
for arc welders.
 

brantmacga

Señor Member
Location
Georgia
Occupation
Former Child
Thanks ...... I mean, this is exactly what I've always thought was the case. Unfortunately I'm out of time to argue against this one, but we're about to build the same thing across town so I'll bring it up then.


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Smart $

Esteemed Member
Location
Ohio
Maybe. You can always use a 50A recpt because there are no 40A recpts. Then there is something about welders if I remember correctly.
Well we're not dealing with welders in this thread.... and if we get back on topic, the MOCP is 35A, which is not provided for in Table 210.21(B)(3).
 
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