Article 440

[OK Sparky 93]

On occasion wording in the code will trip a guy up, however you get it worked out.

Looking at 440
Part II
Disconnecting means
440.12 A 1

115% of nameplate

Part III
BCSC & GF protection
440.22 A

Not exceeding 175% of rated load, no more than 225%

I understand each by themselves, however they don’t make sense to me together.

Why would the one be less than the other?

What am I missing/ not understanding?

Anyone?

Mike

 

[Dennis Alwon]

The 225% is only allowed if the motor won't start with 175% overcurrent protective device.

 

[OK Sparky 93]

The 225% is only allowed if the motor won't start with 175% overcurrent protective device.

I understand that part. My question is why is disconnecting rated at least 115% vs bc protection at 175%?

 

[Dennis Alwon]

I understand that part. My question is why is disconnecting rated at least 115% vs bc protection at 175%?

I can only assume is that the disconnect can handle that current for split seconds while the breaker obviously will or can trip. I don't know the specifics of that data.

 

[OK Sparky 93]

I can only assume is that the disconnect can handle that current for split seconds while the breaker obviously will or can trip. I don't know the specifics of that data.

If one was to look in article 430, it is basically the same except that your BCSCGF Device can be much larger.

The disconnect may or may not be fused. I would think that if it were fused. If it were fused would the rating be per table 430.52 or 430.110 A?

Either way would still be less than the former.

Just trying to understand the difference

 

[Dennis Alwon]

If one was to look in article 430, it is basically the same except that your BCSCGF Device can be much larger.

The disconnect may or may not be fused. I would think that if it were fused. If it were fused would the rating be per table 430.52 or 430.110 A?

Either way would still be less than the former.

Just trying to understand the difference

Sure if it were a fused disconnect then your fuse would be limited to the disconnect size so if you wanted 175% or 225% then your fused disconnect would have to accommodate those fuses. I don't do commercial work but I have never seen a residential motor then had a problem at 175%.