Hvac vavs

hhsting

Senior Member
So I have 7 vavs fed from on branch circuit #1.

Vav-1: MCA: 0.28A, MOCP: 15A
Vav-2: MCA: 0.28A, MOCP: 15A
Vav-3: MCA: 0.28A, MOCP: 15A
Vav-4: MCA: 0.28A, MOCP: 15A
Vav-5: MCA: 0.28A, MOCP: 15A
Vav-6: MCA: 0.28A, MOCP: 15A
Vav-7: MCA: 0.28A, MOCP: 15A

My #1 branch circuit breaker size provided is 20A that feeds all 7 vavs above. Cable size provided is #14 awg.

Would the branch circuit #1 breaker size be 15A or 20A?
 

david luchini

Moderator
Staff member
Location
Connecticut
Occupation
Engineer
So I have 7 vavs fed from on branch circuit #1.

Vav-1: MCA: 0.28A, MOCP: 15A
Vav-2: MCA: 0.28A, MOCP: 15A
Vav-3: MCA: 0.28A, MOCP: 15A
Vav-4: MCA: 0.28A, MOCP: 15A
Vav-5: MCA: 0.28A, MOCP: 15A
Vav-6: MCA: 0.28A, MOCP: 15A
Vav-7: MCA: 0.28A, MOCP: 15A

My #1 branch circuit breaker size provided is 20A that feeds all 7 vavs above. Cable size provided is #14 awg.

Would the branch circuit #1 breaker size be 15A or 20A?
15A
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
So I have 7 vavs fed from on branch circuit #1.

Vav-1: MCA: 0.28A, MOCP: 15A
Vav-2: MCA: 0.28A, MOCP: 15A
Vav-3: MCA: 0.28A, MOCP: 15A
Vav-4: MCA: 0.28A, MOCP: 15A
Vav-5: MCA: 0.28A, MOCP: 15A
Vav-6: MCA: 0.28A, MOCP: 15A
Vav-7: MCA: 0.28A, MOCP: 15A

My #1 branch circuit breaker size provided is 20A that feeds all 7 vavs above. Cable size provided is #14 awg.

Would the branch circuit #1 breaker size be 15A or 20A?
Are you familiar with the term MAXIMUM overcurrent protective device?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
My #1 branch circuit breaker size provided is 20A that feeds all 7 vavs above. Cable size provided is #14 awg.

Would the branch circuit #1 breaker size be 15A or 20A?
There are two issues here, one the #14 conductors on a 20 amp OCPD and two the use of a 20 amp OCPD when the maximum permitted OCPD for any of the VAV's is 15 amps.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
This is hvac VAV. Cable size would depend on MCA correct? So #14 awg is good for 15A and total MCA is less than 15A all 7 no?
Yes, I think that you've got it. It needs to be on a 15 amp circuit with a conductor sized for a minimum of 15 amps.
 
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