LHarrington
Senior Member
- Location
- Saginaw Bay area Michigan
Good morning all,
I have a burning question that I seem to encounter a lot lately. My responcibilities in this facilty is to manage and coordinate installation of new equipment as well as the maintenance electrician. One thing I encounter often is machine builders will specify, for example they need a 100 amp service to their MCC. As it is with our next new piece of equipment. I have a EE get P.O.ed at me because I had requested information on how many motors would be on the feeder circuit I provided so I can size the Conductors correctly and protect them with a breaker. He has stated just provide me with a 100amp service and protect it with 125amp breaker and it will be fine. If this is the case I'm multipling the 100amp by 1.25 percent and call it good. What is the correct way to do this. Am I sizing this correctly form the MCC to my Buss? I have list a few parameters and will provide more to those that chose to reply. Thank you in advance for your time.
480V 3 phase
100amp service to MCC
GE series molded case circuit breaker 125amp plug
50ft. to MCC from buss
120 ambiant temp.
2 motor on circuit 50hp and a 5hp
considering #3 copper thhn with 8ga. ground
As always thank you for your time and patients
LHarrington
I have a burning question that I seem to encounter a lot lately. My responcibilities in this facilty is to manage and coordinate installation of new equipment as well as the maintenance electrician. One thing I encounter often is machine builders will specify, for example they need a 100 amp service to their MCC. As it is with our next new piece of equipment. I have a EE get P.O.ed at me because I had requested information on how many motors would be on the feeder circuit I provided so I can size the Conductors correctly and protect them with a breaker. He has stated just provide me with a 100amp service and protect it with 125amp breaker and it will be fine. If this is the case I'm multipling the 100amp by 1.25 percent and call it good. What is the correct way to do this. Am I sizing this correctly form the MCC to my Buss? I have list a few parameters and will provide more to those that chose to reply. Thank you in advance for your time.
480V 3 phase
100amp service to MCC
GE series molded case circuit breaker 125amp plug
50ft. to MCC from buss
120 ambiant temp.
2 motor on circuit 50hp and a 5hp
considering #3 copper thhn with 8ga. ground
As always thank you for your time and patients
LHarrington