Fuel Pump Estops

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Well it looks like the OSFM is going to require an Estop near the pumps - within 20'. And when they say you can't fight City Hall, it applies 10 times over to the State of Illinois.

I kept thinking activation of an Estop also had to remove power from the Estop button, since its near the pumps. I finally came up with a schematic that would actually disconnect both the hot and neutral wires from the Estop button after the button was pressed.

Actually, it was harder to find a way to reset the entire shutoff, since I ran into this Catch 22 situation: The contactor would not energize without the Estop button energized, and the Estop button wouldn't be energized until contactor was energized.

Anyhow, It looks like that was all wasted effort, because even though the Estop button may be fairly close to the pumps, as long as its 18" above ground, and 18" away from the pumps, its not actually in the hazardous area. Therefore power to the Estop button can remain connected.
ahhh well post the schematic you came up with anyways. Might be handy for reference.
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
I'm not going to post the whole schematic, but its pretty easy to describe:

All power is supplied through a contactor that also opens the neutral. Estop power is taken from the load side of the contactor, and ran through 2 normally closed switches in series to supply the contactor coil.

The necessary trick to avoid the Catch 22 situation was to add a Double Pole Momentary Pushbutton Switch to temporarily bypass the Estop circuit and energize the contactor.
 
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