Fuel Pump Estops

steve66

Senior Member
Location
Illinois
Occupation
Engineer
I was going to post in the hazardous location group, but this seems more like a control design question.

So I have a design with a fuel pump. My initial design included a remote Estop button as required by the NEC. The Estop has to disconnect any hot wires, and also any neutral wires (per the 2020 NEC), so my initial design included contactors.

It was pretty simple - the normally closed Estop button would drop out the contactors when pressed, and the contactors would open both the hot and neutral wires.

But now I see another requirement - the pumps are unattended, so I also need an Estop button at the pumps. The problem is, this button must also have any hot wires and neutral wires disconnected when pressed.

First I though no problem, I'll just show the estops wired through the same contactors they shut off. Then I realized there isn't any way to reset this. The estop buttons wouldn't be energized until relay is energized, and the relay won't be energized until the estop buttons are.

So I started thinking about using a shunt trip circuit breaker. But that won't shunt trip a neutral wire.

So now I'm thinking a shunt trip for the hot wires and a contactor for the neutral. But I hate having a relay that only opens the netural wire - it seems kind of dangerous since having the relay open could allow the neutral wire to be energized with 120 volts all the way from the pumps back to the contactor.

I feel like this is becoming really over complex, and i must be re-inventing the wheel somehow.

But I can't seem to find a simpler solution.
 

Barbqranch

Senior Member
Location
Arcata, CA
Occupation
Plant maintenance electrician Semi-retired
I am in California, so rules may be different. But I have never seen an Estop button actually at the pumps, here they are normally on the side of the building closest to the pumps. I don't know what the rules say here, that is just my observation.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Since this is required by 514.11, and has been for some time, I would expect there are products available for that purpose.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
...

But now I see another requirement - the pumps are unattended, so I also need an Estop button at the pumps. The problem is, this button must also have any hot wires and neutral wires disconnected when pressed.

...
Where are you seeing that requirement? It is not in the NEC, nor is it in NFPA 30A, which has purview over the installation.
NFPA 30A requires the emergency shutoff to be at least 20' from the pumps.
6.7.2
Emergency shutoff devices or electrical disconnects shall be installed in approved locations, but not less than 6 m (20 ft) or more than 30 m (100 ft) from the fuel dispensing devices that they serve.
For a large facility the requirement that an emergency shut off device be readily accessible from each group of dispensing devices many require additional shutoff devices to comply with the 100' distance limit.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Since this is required by 514.11, and has been for some time, I would expect there are products available for that purpose.
I am not aware of any, there are ones for the low intercom/voltage cat 5 circuits, but I have yet to see one for the pumps.
also 514.11 got changed in 2020
Where are you seeing that requirement? It is not in the NEC
He is referring to 514.11(C) unattended self-service, one per island
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
You would need individual shunt trip breakers, but they do make them that switch the neutral also. Been a long time since I seen them used, so they are probably very pricey.
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
I am not aware of any, there are ones for the low intercom/voltage cat 5 circuits, but I have yet to see one for the pumps.
also 514.11 got changed in 2020

He is referring to 514.11(C) unattended self-service, one per island
Yes, 514.11C. It says an additional device or disconnect shall be readily accessible to each group of dispensing devices on an individual island.

The way I read that, I think the device or disconnect must be at the island or pump. Or at any rate, its going to have to be within the 20' classified area around the pumps.

You would need individual shunt trip breakers, but they do make them that switch the neutral also. Been a long time since I seen them used, so they are probably very pricey.
I shall search for those.

Also just saw the exception for intrinsically safe electrical equipment. I wonder if I could just put an intrinsically safe isolator on the estop circuit?
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I was going to post in the hazardous location group, but this seems more like a control design question.

So I have a design with a fuel pump. My initial design included a remote Estop button as required by the NEC. The Estop has to disconnect any hot wires, and also any neutral wires (per the 2020 NEC), so my initial design included contactors.

It was pretty simple - the normally closed Estop button would drop out the contactors when pressed, and the contactors would open both the hot and neutral wires.

But now I see another requirement - the pumps are unattended, so I also need an Estop button at the pumps. The problem is, this button must also have any hot wires and neutral wires disconnected when pressed.

First I though no problem, I'll just show the estops wired through the same contactors they shut off. Then I realized there isn't any way to reset this. The estop buttons wouldn't be energized until relay is energized, and the relay won't be energized until the estop buttons are.

So I started thinking about using a shunt trip circuit breaker. But that won't shunt trip a neutral wire.

So now I'm thinking a shunt trip for the hot wires and a contactor for the neutral. But I hate having a relay that only opens the netural wire - it seems kind of dangerous since having the relay open could allow the neutral wire to be energized with 120 volts all the way from the pumps back to the contactor.

I feel like this is becoming really over complex, and i must be re-inventing the wheel somehow.

But I can't seem to find a simpler solution.
you can get breakers with an extra pole to disconnect the neutral.

The estops we used for NG dispensers had a remote reset PB.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
I am not aware of any, there are ones for the low intercom/voltage cat 5 circuits, but I have yet to see one for the pumps.
also 514.11 got changed in 2020

He is referring to 514.11(C) unattended self-service, one per island
514.11(C) does not really say that. There is no requirement for an emergency shutoff to be at the island and the rule on NFPA 30A prohibits it from being within 20' of a pump.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Yes, 514.11C. It says an additional device or disconnect shall be readily accessible to each group of dispensing devices on an individual island.

The way I read that, I think the device or disconnect must be at the island or pump. Or at any rate, its going to have to be within the 20' classified area around the pumps.


I shall search for those.

Also just saw the exception for intrinsically safe electrical equipment. I wonder if I could just put an intrinsically safe isolator on the estop circuit?
The governing document is NFPA 30A and that prohibits the emergency shutoff from being within 20' of a dispenser. The numbers in brackets, [30A:6.7.2], following 514.11(C) tell you that the language is extracted from NFPA 30A.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
514.11(C) does not really say that. There is no requirement for an emergency shutoff to be at the island and the rule on NFPA 30A prohibits it from being within 20' of a pump.
Don I know you know the code better than me so I trust your correct, funny how we read the same thing and get two different impressions here is 514.11(C)
(C) Unattended Self-Service Motor Fuel Dispensing Facilities.
At unattended motor fuel dispensing facilities, the devices
or disconnects shall be readily accessible to patrons and at least
one additional device or disconnect shall be readily accessible
to each group of dispensing devices on an individual island.
[30A:6.7.2]
Same wording in 2017 and 2020 NEC
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Right but 20' away from the pump in every direction puts it in a lane of traffic or in a parking lot.
Then is joe public capable of reaching it quickly for operation if he has to cross over lanes?
Accessible, Readily (Readily Accessible). Capable of being
reached quickly for operation, renewal, or inspections without
requiring those to whom ready access is requisite to take actions such
as to use tools (other than keys), to climb over or under, to remove
obstacles, or to resort to portable ladders, and so forth. (CMP-1)
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Right but 20' away from the pump in every direction puts it in a lane of traffic or in a parking lot.
Then is joe public capable of reaching it quickly for operation if he has to cross over lanes?
The code does not say it cannot be 20 feet away. It also does not say anything about traffic. It seems like sometimes people create code requirements in their heads that don't actually exist. Keep in mind that readily accessible includes (at least generally) being in a locked closet.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
The code does not say it cannot be 20 feet away.
Right but the next closest E-stop location at some stations could be well over 200' of parking lot and other islands. I dont see anything in the NEC that prohibits the emergency shutoff from being within 20' at the end of the island.
It also does not say anything about traffic.
Having to cross a lane of traffic might not be considered Readily Accessible
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
514.11(C) does not really say that. There is no requirement for an emergency shutoff to be at the island and the rule on NFPA 30A prohibits it from being within 20' of a pump.
Don;

I think it says one emergency shutoff must be more than 20' away, so someone can reach it if there is a fire at the pumps.

But I don't think the same requirement applies to the second Estop button. In fact, I think it has to be close to the pumps. Why else would they say "readily accessible to each group of dispensing devices on an individual island."

But the more I read 514.11, the more it looks like it just contradicts itself.

I know this will be inspected by a Fire Marshall and I don't want to get caught having to have things rewired to get their approval.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Right but the next closest E-stop location at some stations could be well over 200' of parking lot and other islands. I dont see anything in the NEC that prohibits the emergency shutoff from being within 20' at the end of the island.

Having to cross a lane of traffic might not be considered Readily Accessible
I think if readily accessible includes being in a locked closet, it certainly includes having to cross a lane of traffic.

As a design choice maybe not so good but very hard to argue it is not readily accessible.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
True I just verified in the 2021 NFPA 30A don is correct. The e-stop cannot be with in 20', the 2014 NEC used to say just that also.
The thing that confused me is they actualy took that wording out of the 2014 NEC, so I thought the intent was to get them closer.
 

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