Minimum current ampacity

[jim dungar]

Other than the requirement for carrying LRA on fire pumps, I can't readily recall any place in the NEC that controls the minimum size of OCPD.

For sure, I regularly used smaller than 125% primary side protection of 75kVA transformers so I could stay in a 100A disconnect.

 

[LarryFine]

Well I thought all those thumps up were for me guess I lost one..

Well I guess I am wrong. Or misunderstood lol

Me too!

 

[AC\DC]

Me too!

Well you carry the value of 10 individuals lol

 

[LarryFine]

Well you carry the value of 10 individuals lol

 

[ggunn]

I agree with the inspector. 20 is below the minimum circuit ampacity.

Although if it were to pull 23A through a 20A breaker and never ran continuously for several hours at a time, the breaker might never trip.

 

[jim dungar]

Although if it were to pull 23A through a 20A breaker and never ran continuously for several hours at a time, the breaker might never trip.

Actually it could pull 115% forever, per UL listing of minature nolded case breakers. OCPD trip curves are based at a specific ambient temperature.

 

[Dennis Alwon]

now this equipment is in 440- I don’t have my book I am at an event.. it this by default consider continuous use?? For the over current protection device. if it doesn’t state it in 440 this overrides 220.
General rules are chapter 1 through three apply and 400 can modify

90.3 Code Arrangement

This code is divided into the introduction and nine chapters, as shown in Figure 90.3. Chapters 1 through 4 apply generally. Chapters 5 through 8may supplement or modify the requirements in Chapters 1 through 8.
Chapter 9 consists of tables that are applicable as referenced.
Informative annexes are not part of the requirements of this code but are included for informational purposes only.