# sizing service for water well



## aquaman (Mar 21, 2013)

I have a 125hp 277/480 submersible pump i need to build service for.I am confused on sizing fuse size and conductors from service to vfd that will be controlling pump; 156 fla x 175 % = 273 for fuse size? what would the wire size be from service to vfd would it be rated for 300 amp 350 mcm?


----------



## frenchelectrican (Mar 15, 2007)

aquaman said:


> I have a 125hp 277/480 submersible pump i need to build service for.I am confused on sizing fuse size and conductors from service to vfd that will be controlling pump; 156 fla x 175 % = 273 for fuse size? what would the wire size be from service to vfd would it be rated for 300 amp 350 mcm?


 
First of all.,

I know you mention VSD ( VFD ) the sizing of max OCPD will be differnt useally about 150% but check with the VSD manufacter for latest details on the max size of OCPD it will be needed.

Second thing I will hold back the conductor size just a bit but the key issue is the service to the VSD controller what is the distance is? ( plus the depth of well unit ) it may need two differnt conductor size. ( that part I am pretty sure it will happend anyway ) 

125 CV motour @480 volts if I used the NEC listing which it will say 156 amps and do you any chance you have main breaker or fuse in there ? due this figure will change a bit.

The other thing this item you may want to keep in your mind is the numbers of start/ stop per hour some POCO providers may have some restriction of numbers of start and stop operation so if you start and stop pretty often you may end up useing larger service.

Merci,
Marc


----------

