Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
If a panel has a particular size MCB and the total connected load is obviously lower do you still need to have wiring rated for MCB size regardless of connected load?
Feeding MCB Panel
- Thread starter Alwayslearningelec
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- Location
- New Jersey
- Occupation
- Journeyman Electrician
No. It would need to be sized according to the OCPD ahead of the feeder.
- Location
- Illinois
- Occupation
- retired electrician
The size of the conductor will be no less than the rating of the upstream OCPD. The OCPD at the panel just becomes a switch if it is smaller then the feeder overcurrent protector. Note this assumes we are not talking about a service panel.
If you don't size the wiring to the capability of the MCB's OCPD, what's going to protect the wiring?
JAP>
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
- Location
- Illinois
- Occupation
- retired electrician
Is this panel the service equipment? If not, how does it get its power?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I don't think that this is a service, so if the panel is 225 amps with a 225 amp main but the calculated load is 100 amps then a 100 amp feeder can supply the panel.
I still don't understand where you all are coming up with a "Feeder" based on the OP"s opening statement.
What if this is a service panel directly behind a meter where the Main is the one and only OCPD?
How could you size the wire feeding the 225amp main breaker from the meter at only 100 amps ?
JAP>
- Location
- New Jersey
- Occupation
- Journeyman Electrician
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
Source OCPD feeding MCB panel. I referring to the MCB in the panel in this scenario . So your saying wire needs to be sized to the OCPD at this source in this scenario? This is not a service .
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Yes, feed a 225 amp panel with a 60 amp ocpd and #6 conductors if the calculated load is 60 amps.
Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
So to be clear, except for service , when feeding from source OCPD to another panel OCPD the feeder/wire size needs to be sized to the source OCPD and the calculated load your feeding obviously can’t be higher than the source OCPD?
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Short answer yes.
Usually it's not looked at as "I'm going to use this size breaker and need this size wire", it's usually looked at as "I'm going to use this size wire and need this size OCPD to protect it".
JAP>
"Feeding" is simply a much simpler way to say "I'm going to extend wiring from one source to another..
"Feeding" should never be confused with our definition of "Feeders", Taps, Branch Circuits and Service Conductors.
JAP>
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
Thanks professor!"Feeding" is simply a much simpler way to say "I'm going to extend wiring from one source to another..
"Feeding" should never be confused with our definition of "Feeders", Taps, Branch Circuits and Service Conductors.
JAP>
I never hear anyone saying "I'm feeding my 200A service"
I hear "I'm feeding my xxxA subpanel" or "I'm feeding my stove circuit with ..."
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