Mike Dolt Enterprises
Mike Dolt Enterprises
User: GlennG, Location: Hicksville, NY
Asked on: Thursday, April 21, 2011 at 8:35 am EDT
Answered on: Tuesday, May 14, 2024 at 4:28 am EDT
Question: I dont have too much experience with air conditioning and I have a few questions about properly designing the installation of 2 new 5 ton AC compressors going in place of one 10 ton. The new units are 3 phase, minimun circuit ampacity is 24Amps and the max breaker size is 40Amps. Any info or code references would be helpful. .Do i need to have a 40 amp breaker to handle any inrush current or do i size the breaker based on the wire size needed to handle the min. amps (24) for my application?Also I have an existing 1" run of EMT feeding the old unit that i would like to pull my new circuits through, would i still only need one ground sized to the largest conductor in that pipe?This is something i was never really sure about and i am starting to do more AC units and want to make sure I am doing whats best. thanks
Breaker Sizing
According to the National Electrical Code (NEC), the breaker size must be determined based on the minimum circuit ampacity, which is 24 amps in your case. Therefore, you do not need a 40 amp breaker to handle inrush current.
Grounding
Yes, you still only need one ground conductor sized to the largest conductor in the conduit. In your case, the ground conductor should be sized according to the minimum circuit ampacity, which is 24 amps.
Pulling New Circuits Through Existing EMT
It is possible to pull new circuits through an existing 1-inch EMT conduit, as long as there is enough space. The NEC requires that the conduit be filled to no more than 40% of its cross-sectional area. For a 1-inch EMT conduit, this means you can have up to four 12 AWG conductors or three 10 AWG conductors.
Code References NEC 430.22(B)(3): Breaker sizing based on minimum circuit ampacity NEC 250.122(C): Size of grounding electrode conductor NEC 358.40: Fill in conduitsAdditional Considerations Verify the voltage and phase configuration of your existing electrical system to ensure it is compatible with the new AC compressors. Ensure that the wire size and type used for the new circuits is appropriate for the voltage and current requirements. Use proper connectors to terminate the wires and securely mount the AC compressors.* Have a qualified electrician inspect and approve the installation to ensure it meets all applicable codes and standards. Flag for review