HVAC sizing

Etanuye

Member
Location
Los Angeles
Occupation
Junior Engineer
Can anyone please verify if I sized Air Condition correctly. Thank you in advance.

The system is 480V, 3p,60Hz
MCA is given 22.6A​
MOP is given 25A​
FLA is given 24​
LRA is given 130
  1. Branch circuit per NEC 310.15—> (3) #12AWG at 75 degree.
  2. OCPD is given maximum 25A HACR type circuit breaker by the manufacture
  3. Disconnect per 440.12A1—>1.15x 18.08 = 20.47—> next standard 30A, 3 pole Non-disconnect switch
  4. EGC per 250.122–> (1) #10AWG
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
1) OK if not using NM cable and the equipment is rated for 75 degree (likely)
2) 25 amp is correct and a standard value
3) Good
4) EGC never has to be larger than the phase conductors.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
The FLA being higher than the MCA does not comply with either the listing standard or the NEC rules. The manufacture needs to send out the correct tag.
 

david luchini

Moderator
Staff member
Location
Connecticut
Occupation
Engineer
the FLA is listed under the min disconnect. Please check the attached data sheet. Maybe it is listed to size the disconnect?
I think you are correct. It's not actually the full load amps of the unit, but 115% of the sum of all currents for Disconnect Ampere Rating per 430.110(C)(2).
 

Etanuye

Member
Location
Los Angeles
Occupation
Junior Engineer
What do the notes say?
The notes say:
  1. Minimum circuit Ampacity
  2. Dual element. Time delay type
  3. HACR Type per NEC
  4. Non-fused Disconnect, verify on the unit nameplate that the disconnect is properly sized for the application. Units with field installed electric heat kits may exceed the factory installed disconnect amperage rating
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
The notes say:
  1. Minimum circuit Ampacity
  2. Dual element. Time delay type
  3. HACR Type per NEC
  4. Non-fused Disconnect, verify on the unit nameplate that the disconnect is properly sized for the application. Units with field installed electric heat kits may exceed the factory installed disconnect amperage rating
3) Just as an FYI all breakers today are rated HACR as part of their listing. Years ago you had to specify the HACR rating.
 
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