开云体育

ctrl + shift + ? for shortcuts
© 2025 Groups.io
  1. Felderownersgroup
  2. Topics

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

 

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??
 

开云体育

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??
 

开云体育

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??
 

开云体育

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??
 

On Fri, Aug 14, 2020 at 11:57 AM, Joe Jensen wrote:
I have been reading the NEC for wiring a motor.?
It looks like you're reading Article 430 Motor Circuits.? ?That applies to directly wired motors, not to equipment (that contains motors.) 430 is no more applicable to a F700Z than it is to a washing machine.

Size your breakers to your conductors.? It is no more complicated than that.
 

开云体育

Hmm, nearly 100% of the load for the shaper is the motor.? That distinction is interesting

?

Joe Jensen ?| VP Internet of Things Group?| GM Retail Banking Hospitality and Education

480-554-8207–翱蹿蹿颈肠别 | 480-231-0669–颁别濒濒 ?

?

?
 

开云体育

it may have more to do with motor protected by an enclosure/cabinet vs out in the open. just a guess.

imran

On Aug 14, 2020, at 5:44 PM, Joe Jensen <joe.jensen@...> wrote:

?

Hmm, nearly 100% of the load for the shaper is the motor.? That distinction is interesting

?

Joe Jensen ?| VP Internet of Things Group?| GM Retail Banking Hospitality and Education

480-554-8207–翱蹿蹿颈肠别 | 480-231-0669–颁别濒濒 ?

<image001.jpg>

?

?
 

Hello Joe

My Electrician pulled #10/4 wire from the 3ph load center. He installed a 3 pole 30A breaker In the circuit for my 10hp Dual 51. Runs fine. No trips.?

im not conversant in NEC but I would not want a 55A breaker on a 10 AWG circuit. The breaker serves as over current protection for the wiring.?


david shores?
 

开云体育

Size the breaker to the wire. ?Size the wire to the motor. ?For your F700z w 7.5 HP, #10 wire with 30 Amp breaker is plenty. ?

David Best - via mobile phone?

On Aug 14, 2020, at 2:44 PM, Joe Jensen <joe.jensen@...> wrote:

?

Hmm, nearly 100% of the load for the shaper is the motor.? That distinction is interesting

?

Joe Jensen ?| VP Internet of Things Group?| GM Retail Banking Hospitality and Education

480-554-8207–翱蹿蹿颈肠别 | 480-231-0669–颁别濒濒 ?

<image001.jpg>

?

?
 

Joe, I believe you previously said you installed #6 or #8 wire, so while a 30A breaker is fine for you machine, you can also install a larger one for future-proofing.
 

开云体育

Those prewires are on the other side of the shop. I will have to run conduit and wire to the new shaper?


On Aug 14, 2020, at 5:48 PM, mark thomas <murkyd@...> wrote:

?Joe, I believe you previously said you installed #6 or #8 wire, so while a 30A breaker is fine for you machine, you can also install a larger one for future-proofing.

 

btw, what kind of panel do you have?? ?$100 for a breaker seems like a lot.? ? If you have SquareD, a 30amp 3P is $50 new on amazon:



There's also a zillion breakers new and used on eBay and you can get this breaker for $20 there.
 
Edited

I am also wiring three-phase equipment off of a Phase Perfect with my biggest motor being a 7.5 HP. Although I didn't need to, I pulled #8 wire and will be using a 40 amp breaker. I was torn between a 30 and 40 amp as I saw various different charts that show one or the other. I also spoke with the electrician who ran the 400 amp service to my building and installed the Phase Perfect. He said he would install a 40 amp breaker whereas another electrician buddy of mine said throw a 30 amp in and be done with it. I opted for the 40 amp. As a side note, I have discovered over the years that if you ask 3 electricians the same question you get a minimum of 5 answers and all claiming it came right out of the code.

BTW...all those that say that the breaker is to protect the installed wiring and not the machine are correct. If I overdrive my table saw, either the safeties installed In the table saw will shut it down or, failing that, the circuit breaker will trip. If you undersize your wiring, you run the risk of IT becoming your tripping device with the potential added excitement of a fire. But, admittedly, I am not an electrician in real life; I just play one on internet forums! ;)
 

Over-sizing is common with some residential electricians and DIYers, where the incremental cost of doing so is not great.? At commercial scale, an electrician who routinely over-sizes is also known as an unemployed electrician.

The NEC is extremely conservative.? Over-sizing for any reason other than future-proofing is completely pointless.
 
Edited


?mark thomas
11:05am??
Over-sizing is common with some residential electricians and DIYers, where the incremental cost of doing so is not great.? At commercial scale, an electrician who routinely over-sizes is also known as an unemployed electrician.

The NEC is extremely conservative.? Over-sizing for any reason other than future-proofing is completely pointless.


You are correct but, as you pointed out with "incremental costs", I was able to get 8 ga for pennies more than 10 ga so I didn't hesitate to over-size. In this scenario, I wouldn't be as harsh as to say it is "completely pointless."
11:05am???
 

On Sat, Aug 15, 2020 at 09:12 AM, Larry wrote:
In this scenario, I wouldn't be as harsh as to say it is "completely pointless."
99.99% pointless?

I'm just saying it confers no benefit to the intended application.? Doesn't increase safety, doesn't make your saw work better, etc.

Future-proofing is a totally different issue, and certainly makes sense if free.??
 
Edited

99.99% pointless?

I'm just saying it confers no benefit to the intended application.? Doesn't increase safety, doesn't make your saw work better, etc.

Future-proofing is a totally different issue, and certainly makes sense if free.?
My bad...I should have been clearer. In my case, it is a 1500 sq. ft. steel building for a small wood shop. Pulling larger gauge wire now for some unknown future use was worth it in my mind.

To the OP, ?my angst wasn't over wire gauge, like you, it was what was the proper size breaker to use for my 7.5 HP table saw and bandsaw and for my 5 HP DC and jointer-planer.
 

开云体育

I had “prime” selected and the same breaker on Prime is $105.?? On Zoro it’s $115, and one Automation Direct $90.? I can wait an extra week to save $50.

?

From: [email protected] <[email protected]> On Behalf Of mark thomas
Sent: Saturday, August 15, 2020 8:30 AM
To: [email protected]
Subject: Re: [FOG] Wire and breaker size for 7.5HP 3 Phase Felder Shaper - NEC Code compliant

?

btw, what kind of panel do you have?? ?$100 for a breaker seems like a lot.? ? If you have SquareD, a 30amp 3P is $50 new on amazon:



There's also a zillion breakers new and used on eBay and you can get this breaker for $20 there.

 

The "Prime" search returns a different model, the Q0330CP:



The "CP" suffix is the Canadian-certified version.? The QO330 is the true, all-American version.?
 

Hi all, Just reading through on this chat, does anyone have a go to chart for sizing cables and breakers for 3 phase equipment. I am being told by Felder c16 breakers are fine in my shop, with an kf700s saw/spindle, ad 741 planer, fb610 bandsaw and rl160 extractor, each on c16, and All this rolls up to c40 main breaker. Heating/AC, small power separate.

seems ok?
?
thanks
?
colum

1 - 20 of 23