machines

[couzer1023]

I have a machine that shows it uses 56 amps. Do i go 125 percent over that for overcurrent protection?

 

[infinity]

What kind of machine?

 

[couzer1023]

What kind of machine?

It is a parts washer. It has a couple of motors and heating elements.

 

[Jraef]

First you have to size the conductors at a minimum of 125% of the load, then you size the circuit protection to protect the conductors. So in essence, yes, the OCPD usually ends up sized for 125% of the load. I just think it's important to remember to do things in the proper order, it helps avoid mistakes. For example if you size the circuit protective device first, then you find out you have to increase the conductor size because of voltage drop, you may end up with conductors that are too big for the terminals on the breaker. Things like that can be avoided by taking it step by step rather than jumping.

 

[infinity]

First you have to size the conductors at a minimum of 125% of the load, then you size the circuit protection to protect the conductors. So in essence, yes, the OCPD usually ends up sized for 125% of the load. I just think it's important to remember to do things in the proper order, it helps avoid mistakes. For example if you size the circuit protective device first, then you find out you have to increase the conductor size because of voltage drop, you may end up with conductors that are too big for the terminals on the breaker. Things like that can be avoided by taking it step by step rather than jumping.

If it runs for less than 3 hours at full ampacity is the 125% required?

 

[kwired]

If it has motors it may need more than 125% to start motors without operating overcurrent devices.

 

[infinity]

I was asking if it's required to be sized as 125% as Jraef suggested.

 

[augie47]

IMHO, if the nameplate says 56 amps there is not need to factor in 125% unless you know it's a continuous load.

 

[infinity]

IMHO, if the nameplate says 56 amps there is not need to factor in 125% unless you know it's a continuous load.

My feeling as well that's why I asked what type of machine it was. Even if it runs for more than 3 hours to be a continuous load it would have to operate at it's maximum ampacity for more than 3 hours. Any cycling within that 3 hour period would make it a non-continuous load.

 

[couzer1023]

First you have to size the conductors at a minimum of 125% of the load, then you size the circuit protection to protect the conductors. So in essence, yes, the OCPD usually ends up sized for 125% of the load. I just think it's important to remember to do things in the proper order, it helps avoid mistakes. For example if you size the circuit protective device first, then you find out you have to increase the conductor size because of voltage drop, you may end up with conductors that are too big for the terminals on the breaker. Things like that can be avoided by taking it step by step rather than jumping.

So for this machine ....#4 copper on 70 amp fuses with #8 ground.

 

[infinity]

So for this machine ....#4 copper on 70 amp fuses with #8 ground.

Code wise you could use #6 THHN copper conductors with a 60 amp OCPD and #10 EGC.

 

[couzer1023]

Code wise you could use #6 THHN copper conductors with a 60 amp OCPD and #10 EGC.

?? I guess I am missing something. If I am supposed to take 125% of 56 I get 70 amps. It is my understanding that one is to use 75 degree column when landing on terminals. So I come up with #4? Seems like 60 amp fuses might be too small and cause nuisance tripping.

 

[infinity]

?? I guess I am missing something. If I am supposed to take 125% of 56 I get 70 amps. It is my understanding that one is to use 75 degree column when landing on terminals. So I come up with #4? Seems like 60 amp fuses might be too small and cause nuisance tripping.

Would this appliance be by definition a continuous load? If it's non-continuous then you do not need to use the 125%.