Hello Everyone,
I am working with hermetic compressors. I know the NEC handles these differently than straight motor loads, but overall I think most of the calculations are the same. The main differences being the FLC table is not used for compressors, instead we use the name plate RLA for conductor sizing, ocpd, and overload protection.
I have attached a picture that will help illustrate what I am trying to ask, hopefully.
Conductors are sized at 156% of the compressor RLA (that is where the overload is sized at on hermetic compressors,). I can size my breaker at 250% of the compressor RLA. I know my branch circuit is everything after the final OCPD leading to the motor. So, my question is this. Can I size the conductors before and after the branch fuse at 156% of the RLA, or can I only size the conductors after the fuse at 156%.
Are the conductors on the line side of the fuse (1L1 and 1L2) considered feeder conductors? Would they need to be sized according to the branch breaker which is 250% RLA?
Are the conductors on the load side of the fuse (4L1 and 4L2) considered to be in the branch and can therefore be sized at 156% of the RLA, and be protected by the compressor overload?
If this were a straight up motor application, would anything be different? Could all of the conductors before and after the fuse be sized at 125% FLA, or only the conductors on the load size of the fuse?
I am working with hermetic compressors. I know the NEC handles these differently than straight motor loads, but overall I think most of the calculations are the same. The main differences being the FLC table is not used for compressors, instead we use the name plate RLA for conductor sizing, ocpd, and overload protection.
I have attached a picture that will help illustrate what I am trying to ask, hopefully.
Conductors are sized at 156% of the compressor RLA (that is where the overload is sized at on hermetic compressors,). I can size my breaker at 250% of the compressor RLA. I know my branch circuit is everything after the final OCPD leading to the motor. So, my question is this. Can I size the conductors before and after the branch fuse at 156% of the RLA, or can I only size the conductors after the fuse at 156%.
Are the conductors on the line side of the fuse (1L1 and 1L2) considered feeder conductors? Would they need to be sized according to the branch breaker which is 250% RLA?
Are the conductors on the load side of the fuse (4L1 and 4L2) considered to be in the branch and can therefore be sized at 156% of the RLA, and be protected by the compressor overload?
If this were a straight up motor application, would anything be different? Could all of the conductors before and after the fuse be sized at 125% FLA, or only the conductors on the load size of the fuse?
