Is this ever OK #1 TW on 200a breaker

[rookie4now]

I ran across something interesting. This is a building built in 1965 with 2 elevators (20 stories). I was doing some work in the panel and noticed that there was a 200a breaker servicing the elevator which has #1TW wire. I'm trying to think of a scenario where that is OK. Clearly the elevator doesn't require the 200a, but it seems like something way too obvious to be a mistake. Any thoughts? FYI the gear all appears to be original.

 

[hurk27]

I ran across something interesting. This is a building built in 1965 with 2 elevators (20 stories). I was doing some work in the panel and noticed that there was a 200a breaker servicing the elevator which has #1TW wire. I'm trying to think of a scenario where that is OK. Clearly the elevator doesn't require the 200a, but it seems like something way too obvious to be a mistake. Any thoughts? FYI the gear all appears to be original.

Could be ok depending upon the tap length or if the conductors could be considered outside of the building? and what size OCPD is at the end of these conductors?

 

[infinity]

If the only load is the elevator motors or MG sets, the oversized OCPD could have something to do with starting current.

 

[rookie4now]

If the only load is the elevator motors or MG sets, the oversized OCPD could have something to do with starting current.

Can you point me to an NEC reference that permits a 200a breaker on #1TW in a situation like this?

Thanks.

 

[templdl]

I ran across something interesting. This is a building built in 1965 with 2 elevators (20 stories). I was doing some work in the panel and noticed that there was a 200a breaker servicing the elevator which has #1TW wire. I'm trying to think of a scenario where that is OK. Clearly the elevator doesn't require the 200a, but it seems like something way too obvious to be a mistake. Any thoughts? FYI the gear all appears to be original.

Whats the ampacity of #1? Is it the old TW 60deg of is it 75degC rated wire?
No matter, even #1 75degC rated wire is rated at 130a. And you have a 200A breaker? And a breaker's job is to protect the wire? Unless that breaker has aninterchangable trip unit of 150a a breaker with a 200a trip unit is an issue.

 

[ActionDave]

Can you point me to an NEC reference that permits a 200a breaker on #1TW in a situation like this?
Thanks.

IV. Motor Branch-Circuit Short-
Circuit and Ground-Fault Protection
430.51 General
Part IV specifies devices intended to protect the motor
branch-circuit conductors, the motor control apparatus, and
the motors against overcurrent due to short circuits or
ground faults. These rules add to or amend the provisions of
Article 240. The devices specified in Part IV do not include
the types of devices required by 210.8, 230.95, and 590.6.
The provisions of Part IV shall not apply to motor cir-
cuits rated over 600 volts, nominal.

 

[kwired]

Can you point me to an NEC reference that permits a 200a breaker on #1TW in a situation like this?

Thanks.

IV. Motor Branch-Circuit Short-
Circuit and Ground-Fault Protection
430.51 General
Part IV specifies devices intended to protect the motor
branch-circuit conductors, the motor control apparatus, and
the motors against overcurrent due to short circuits or
ground faults. These rules add to or amend the provisions of
Article 240. The devices specified in Part IV do not include
the types of devices required by 210.8, 230.95, and 590.6.
The provisions of Part IV shall not apply to motor cir-
cuits rated over 600 volts, nominal.

Now lets go one more step and apply this to an actual install.

Lets say we have a 60HP 460 volt 3 phase motor.

T 430.250 says full load current is 77 amps. 430.22(A) tells us the conductor ampacity must be an ampacity of not less than 125 percent of the motor?s full-load current rating. So 77 x 1.25 = 96.25. If we are using 60 deg conductors then 1 AWG is minimum size allowed.

Next comes branch circuit short circuit and ground fault protection. T430.52 allows 250% of motor full load current for inverse time circuit breakers. 77 x 2.5 = 192.5 Exception 1 allows the next higher standard size which is 200 amps.

This is your example of a 1 AWG allowed to be connected to a 200 amp circuit breaker.

If the breaker were an instantaneous trip type T430.52 allows 800% of motor FLC for the breaker setting. You could easily have a 600 amp instantaneous trip breaker on this 1 AWG conductor.

 

[rookie4now]

Now lets go one more step and apply this to an actual install.

Lets say we have a 60HP 460 volt 3 phase motor.

T 430.250 says full load current is 77 amps. 430.22(A) tells us the conductor ampacity must be an ampacity of not less than 125 percent of the motor?s full-load current rating. So 77 x 1.25 = 96.25. If we are using 60 deg conductors then 1 AWG is minimum size allowed.

Next comes branch circuit short circuit and ground fault protection. T430.52 allows 250% of motor full load current for inverse time circuit breakers. 77 x 2.5 = 192.5 Exception 1 allows the next higher standard size which is 200 amps.

This is your example of a 1 AWG allowed to be connected to a 200 amp circuit breaker.

If the breaker were an instantaneous trip type T430.52 allows 800% of motor FLC for the breaker setting. You could easily have a 600 amp instantaneous trip breaker on this 1 AWG conductor.

GREAT INFO. Thanks for that example, it was extremely helpful. I feel like this Forum is my own personal On-Line college course sometimes!

 

[Cow]

Perfect example Kwired!