¿ªÔÆÌåÓý

ctrl + shift + ? for shortcuts
© 2025 Groups.io
  1. Felderownersgroup
  2. Messages
Single Messages Topics Expanded Polls

Re: Wire and breaker size for 7.5HP 3 Phase Felder Shaper - NEC Code compliant

 

¿ªÔÆÌåÓý

wow, the cost of tru 3 phase continues beyond load center. i should have clarified that mine are all single phase breakers. i did not go to the tables referenced in the link but it seems breaker even for single phase should be larger than the conductor capacity. i have not heard of this until now but then again i gave not looked this up before.

being expensive would you put more than one machine on the same circuit as you would not be using both at the same time? however reading the link it says to upsize for multiple motors which makes me think that CB would really need very high current from one machine to trip.

knowing that you will only run one motor at a time, would the code allow you to size for one motor even though you have more than one on the circuit? likely not.

imran

On Aug 14, 2020, at 3:47 PM, Joe Jensen <joe.jensen@...> wrote:

? I¡¯ve always done what you are for single phase but at over $100 for the 3 phase breaker so I¡¯d like to not have to upsize later?


On Aug 14, 2020, at 12:11 PM, imranindiana via groups.io <imranindiana@...> wrote:

?
Joe,

according to this link you are in correct neighborhood


i have breakers that match cable size so apparently my breakers need to be higher amperage but i have not had one trip on me in 20 yrs and not a single one has failed.

imran?

On Aug 14, 2020, at 2:57 PM, Joe Jensen <joe.jensen@...> wrote:

?

I have been reading the NEC for wiring a motor.? The photo of the tag on the side of the machine says 19A at 230V.? NEC makes a distinction between FLC and FLA.? When I googled FLA for a 7.5HP 3 Ph motor I get 22A.? So lets use 22 as FLA.? Now NEC wire size is 125% of FLA or 27.5A and you size up so I need wire size for 30A.? This all makes sense.? Then onto the breaker.? NEC says to size for 250% of FLA so the breaker would be 22*2.5=55A so I need a 55A breaker.? In reading they point out that this is counter intuitive as the breakers job is to protect the wire and you are over-sizing the breaker.? They say the motor must have protection for overload at 115% -125% of FLA and apparently that is what protects the wire.? ?Does a felder F700Z have heaters or other protection in the starter?

Am I reading this correctly??
Join [email protected] to automatically receive all group messages.