Latching contactor used for EPO

[hillbilly1]

We have a customer that uses those prefab gas stations, and the factory uses a 200 amp latching contactor for the pump EPO. (Turns the whole panel off) First, this does not seem to be a good design due to it not being “Fail safe”, second, since it is not fail safe, does it meet code? I haven’t found anything so far that says it isn’t, but engineers from time to time have been wrong before! LOL!

 

[ptonsparky]

Who requires 'Fail Safe"? Where do you find the definition?

Is the use of a latching relay approved by your AHJ? Ref last sentence 514.11(A).

 

[hillbilly1]

Who requires 'Fail Safe"? Where do you find the definition?

Is the use of a latching relay approved by your AHJ? Ref last sentence 514.11(A).

Most emergency stops are designed “Fail safe”. If the control power is turned off, the EPO does not work, the contactor does not open, and since the control power is not supervised, it would not be known until it’s too late. May just be a poor design issue and totally legal.

514.11(a) is all I’ve seen too, and it does not specify other than all conductors must be disconnected, which this does because they route the neutral through the contactor. Leaving it up to the AHJ is a crap shoot, some AHJ’s are very knowledgeable, while others are carpenters by trade! LOL!

 

[rbalex]

Philosophically, the danger is automatic restarting/resetting, similar in concept to Section 430.43 or 430.225(B)(4).

NOTE: Chapter 5 in general and Articles 511-517 in particular must still comply with Chapters 1 through 4.

 

[hillbilly1]

Philosophically, the danger is automatic restarting/resetting, similar in concept to Section 430.43 or 430.225(B)(4).

NOTE: Chapter 5 in general and Articles 511-517 in particular must still comply with Chapters 1 through 4.

They use maintained e-stops, so there would be no automatically restart or reset if electrically held was used. With the latching contactor, they have a momentary switch at the cash wrap to re-energize the panel. They have an issue with the grease drying out and jamming because the contactor is not exercised but once a year during inspections. Some of the stations do use electrically held, but a shunt trip breaker requiring a manual reset.