Emergency Shut Off wiring

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451F

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Work in Maryland, Virginia, West Virginia, DC.
The site is a fleet diesel dispensing system. The owner wants maximum redundancy to avoid shut down of the entire system.

The installation is two suction pump dispensers with internal 2' fluorescent lights. The pumps are controlled by a Ward controller that is monitored remotely by a computer. The Ward is outside of the classified area.

The dispenser manufacturer wants the lights on separate circuits from the pumps.

Two questions:
1. Is there an industry standard method of wiring?

2. My thoughts are these, what do you think?
a. Three switched-neutral shunt-trip breakers
i. one for each dispenser
ii. one for the lights in both dispensers
b. Momentary contact emergency shut off (ESO) mushroom switch with plastic shield (STI stopper station)
c. Feed 120v to ESO from dedicated breaker equipped with a toggle-lock
d. daisy chain shunt-trips to ESO using wire nuts to permit quick replacement of breakers
e. separate neutrals to shunt-trips

TG
 
I don't care for shunt-trip breakers because if anything happens to the control circuit (and there is always something that could happen) then the E-Stop is non-functional (system fails in the on position).

My preference would be to feed a sub-panel for all the fuel equipment through a contactor (that drops the neutral as well as the ungrounded conductors) and let the E-Stop (normally closed contacts) allow the contactor to be closed. Wire in as many E-Stops as you like (in series) and any failure, the system fails in the off condition.

If your in Canada though, I don't think you drop the neutral.

If you are wiring an unattended site, pay close attention to the last sentence of 514.11(C).
 
clairification

clairification

buckofdurham said:
Would"nt (d) minimize the maximum reduntancy?
Click to expand...

What the owner wants is a reliable system that will provide fuel when something breaks. In this case the intention was to be able to change a breaker without having to rewire a second breaker as would be required if the switched side was doubled up on each screw.
The coil terminals are designed such that one could insert a solid conductor under each side of the screw like a load connection on a breaker.

I suppose it could work both ways. If the wires spring apart when the wirenut is removed, the other breakers also are going to be off of the ESO.

Thanks for the comment!

Tom
 
That is what was there without the contactor

That is what was there without the contactor

hardworkingstiff said:
I don't care for shunt-trip breakers because if anything happens to the control circuit (and there is always something that could happen) then the E-Stop is non-functional (system fails in the on position).

My preference would be to feed a sub-panel for all the fuel equipment through a contactor (that drops the neutral as well as the ungrounded conductors) and let the E-Stop (normally closed contacts) allow the contactor to be closed. Wire in as many E-Stops as you like (in series) and any failure, the system fails in the off condition.

If your in Canada though, I don't think you drop the neutral.

If you are wiring an unattended site, pay close attention to the last sentence of 514.11(C).
Click to expand...
(514.11(C) is a State requirement here for all dispensing systems.)

That is what was there without the contactor, instead, they had several DPDT relays that energized when fuel was requested. The relays were not doing well as the contacts were quite burned.

Further, it was pointed out that the system could energize the neutral with voltage from another running pump when the control system called for fuel on both pumps. This reportedly has shocked many a service tech when working on pumps without switched neutrals.

When the owner has 50 vehicle tanks to fill in a short time they frown on shutting everything down for repairs on one pump.

So, for the techs and NFPA we disconnect the neutral with the breaker.

514.13 Provisions for Maintenance and Service of Dispensing Equipment.
Each dispensing device shall be provided with a means to remove all external voltage sources, including feedback, during periods of maintenance and service of the dispensing equipment. The location of this means shall be permitted to be other than inside or adjacent to the dispensing device. The means shall be capable of being locked in the open position.​

I really like your ESO system as the Contactor is always on which will eliminate burning of the contacts and will fail-safe. (Unless the contacts weld shut. Alas, there is almost always a failure mode.)

Thanks so much for your response.

Tom
 
Can you even get a shunt trip switched neutral?
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What about normally closed contacts. E stop opens them, pumps shutdown
 
451F said:
Further, it was pointed out that the system could energize the neutral with voltage from another running pump when the control system called for fuel on both pumps. This reportedly has shocked many a service tech when working on pumps without switched neutrals.
Click to expand...

Sounds like you need one of these:

http://www.franklinfueling.com/products/sps/DHI.asp

or these:

http://www.redjacket.com/doc/RJP-8001.pdf

I'm assuming you have submerged pumps and dispensers, not individual pumps at each fueling point.
 
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The first post says Suction pumps

I like the FE PEtro isolation boxes, the red jacket ones are a pain to wire up, too small a space to get alot of wires into
 
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