Control circuit

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hhsting

Senior Member
Location
Glen bunie, md, us
Occupation
Junior plan reviewer
I have existing relay contactor cabinet from which I have 2#14 AWG cable going to gas station Emergency stop switch.

My questions are following:
1. Is EGC required per code? If yes then what code section.
2. How one sizes wire for such an application? It is currently sized #14 AWG.

Thank you for your input

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Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
I have existing relay contactor cabinet from which I have 2#14 AWG cable going to gas station Emergency stop switch.

My questions are following:
1. Is EGC required per code? If yes then what code section.
2. How one sizes wire for such an application? It is currently sized #14 AWG.

Thank you for your input

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Have you researched this at all?

What do you think is the answer?

We do not know all the details you have left out.
 

hhsting

Senior Member
Location
Glen bunie, md, us
Occupation
Junior plan reviewer
Have you researched this at all?

What do you think is the answer?

We do not know all the details you have left out.
I am not sure what the answer is nor which article to look in. I looked in NEC 2014 Article 514 but does not say anything about control circuit itself except distance E stop to dispenser and neutral is required to be opened . Its gas station emergency stop switch. Contactor is placed on feeder cables feeding fuel panel which is 120/208V single phase 60A.

Thank you for your input.
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tom baker

First Chief Moderator
Staff member
For the EGC, start with section 250.122, I don't have a code book handy so thats as close as I can get.
The wire is sized based on section 240.4 and article 310

These are pretty basic questions, are you getting a permit and inspection?
My concern is the work is at a gas station, work in classified locations and the risk involved.
 

hhsting

Senior Member
Location
Glen bunie, md, us
Occupation
Junior plan reviewer
For the EGC, start with section 250.122, I don't have a code book handy so thats as close as I can get.
The wire is sized based on section 240.4 and article 310

These are pretty basic questions, are you getting a permit and inspection?
My concern is the work is at a gas station, work in classified locations and the risk involved.
Yes there would be permit and inspection. Just have not dealt with contol circuit that much sizing and EGC.

240.4 has power hazards, overcurrent devices rated 800A or less, overcurrent devices rated over 800A, small conductors, tap conductors, transformer secondary conductors, overcurrent protection for specfic conductor application.

250.122 has general, increased in size, muliple circuits, motor circuits, flexible cord and fixture wire, conductors in parallel, feeder taps.

None of them have control circuit except close is 240.4 overcurrent protection for specific conductor application but none for 250.122.
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
Yes there would be permit and inspection. Just have not dealt with contol circuit that much sizing and EGC.

240.4 has power hazards, overcurrent devices rated 800A or less, overcurrent devices rated over 800A, small conductors, tap conductors, transformer secondary conductors, overcurrent protection for specfic conductor application.

250.122 has general, increased in size, muliple circuits, motor circuits, flexible cord and fixture wire, conductors in parallel, feeder taps.

None of them have control circuit except close is 240.4 overcurrent protection for specific conductor application but none for 250.122.

What is the size of the fuse that is in your control circuit?

400 Amp fuse would require a #1 Cu EG. That doesn't sound like your install. You have to tell us. Typically a #14 would be protected at no more than 15 amps and even if its more, the EG is not required to be larger than the circuit conductors. 250.122(A). Continue reading on down to (F)(2). Is this circuit entirely in a nonmetallic raceway and boxes?

Is your control 24vac? 120? IDK.
 

hhsting

Senior Member
Location
Glen bunie, md, us
Occupation
Junior plan reviewer
What is the size of the fuse that is in your control circuit?

400 Amp fuse would require a #1 Cu EG. That doesn't sound like your install. You have to tell us. Typically a #14 would be protected at no more than 15 amps and even if its more, the EG is not required to be larger than the circuit conductors. 250.122(A). Continue reading on down to (F)(2). Is this circuit entirely in a nonmetallic raceway and boxes?

Is your control 24vac? 120? IDK.
Ok all I was given by the engineer is attached in sketch and in post #1. Voltage is low 24V and their is no overccurent protection from contactor to E stop. I understand this still may not be much.
4dccfb293b831a651bb39cf3ca04d83a.jpg


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Last edited:

hhsting

Senior Member
Location
Glen bunie, md, us
Occupation
Junior plan reviewer
Ok all I was given by the engineer is attached in sketch and in post #1. Voltage is low 24V and their is no overccurent protection from contactor to E stop. I understand this still may not be much.
4dccfb293b831a651bb39cf3ca04d83a.jpg


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Also contactor and E stop are not located in classified hazardous location. E stop is on outside wall of convience store facing dispensers and contactor is inside the convience store along with Panel A and fuel Panel F

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jap

Senior Member
Occupation
Electrician
Is that contactor switching the neutral to the fuel panel also?

If there are any neutral requiring circuits out at the pump, and, your contactor is not switching the neutral conductor feeding the panel, then, all of the rules for fueling island shutdown are not being followed.

JAP>
 

hhsting

Senior Member
Location
Glen bunie, md, us
Occupation
Junior plan reviewer
Is that contactor switching the neutral to the fuel panel also?

If there are any neutral requiring circuits out at the pump, and, your contactor is not switching the neutral conductor feeding the panel, then, all of the rules for fueling island shutdown are not being followed.

JAP>
Yes neutral is switched although question is about EGC required and sizing since no overcurrent protection and control circuit cable to E stop sizing.

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hhsting

Senior Member
Location
Glen bunie, md, us
Occupation
Junior plan reviewer
Come to think of it I might have placed this thread in wrong section. Should it not go to Controls and PLC forum?

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kwired

Electron manager
Location
NE Nebraska
No one can help or provide input?

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Sounds like a portion of a circuit that falls under art 725 to me.

If it is 24 volts pretty good chance it is a class 2 circuit - likely could have used 18-2 thermostat cable for this circuit and no need for
EGC.
 

hhsting

Senior Member
Location
Glen bunie, md, us
Occupation
Junior plan reviewer
Sounds like a portion of a circuit that falls under art 725 to me.

If it is 24 volts pretty good chance it is a class 2 circuit - likely could have used 18-2 thermostat cable for this circuit and no need for
EGC.
What if you still provide EGC but not require is it extra safe or not recommended?

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paulengr

Senior Member
Class 2 circuits are power limited.

Among multiple reasons for an EGC, one is to provide a low impedance path back to the transformer so that in the event of a fault to ground, the breaker/fuse will trip. In class 2 circuits which are power limited the need to clear a fault doesn’t exist because of the current limitation but it does exist in non-power limited circuits even at 24 VAC (chapters 1-4). In that case you can tell minimum wire size by overcurrent protection but Code also specifies a minimum gauge.

Another purpose is to keep the voltage low on metallic enclosures to prevent shocks from killing someone. This is not necessary under 50 V and Code makes that clear.

Another reason is to maintain the voltage to Earth in a separately derived system. But many small control power transformer installations just connect the neutral of the primary and secondary coils. This makes it no longer a separately derived system so the EGC already exists on the high side of the transformer. Code at this voltage requires grounding except if you fall under one of the exceptions to the grounding requirement. Under chapter 1-4 rules it is easier to look at the exceptions than to look where grounding is required. Chapter 7 rules ignore 1-4 except where the appropriate section specifically calls out 1-4. This is explained in chapter 1. Does this ring a bell or are you qualified to do the work?

Either way the engineer is responsible for doing the design work which includes grounding. You should be asking or submitting requests for clarification followed by change order requests for things not included on the bid request. Obviously the engineer has no idea what they are doing or is used to qualified electrical contractors. This means if this thing blows up chances are you will be the one liable. Better talk to your insurance agent. I’m not going to get into licensing but hazardous location installations are simply not a place for someone inexperienced, whether they are licensed or not. Most commercial/residential electricians know to no bid these automatically. The oil and gas industry is full of specialists that work with this stuff all the time. There is a lot to the design and installation that is not in the Code like understanding how conduit seals work and how and where to properly install them, and which NEMA ratings to use, never mind intrinsically sage designs. The fact that you even have to ask about wire gauge on a control circuit tells me you don’t know the basics in the Code. Even if you by some miracle pass inspection there is a good chance of something going seriously wrong in the future. Someone can get seriously hurt or die. If that happens quite often it’s not just a money issue. They will put people in prison for gross negligence. Get a contractor that does fuel islands. This is not DIY.



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augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
The lack of response by some of the more senior members here might be due to the fact that you have asked almost the same question more than once on the Forum (search gas pumps and your name )
The term "troll" comes to mind for some of us :)
 

hhsting

Senior Member
Location
Glen bunie, md, us
Occupation
Junior plan reviewer
Class 2 circuits are power limited.

Among multiple reasons for an EGC, one is to provide a low impedance path back to the transformer so that in the event of a fault to ground, the breaker/fuse will trip. In class 2 circuits which are power limited the need to clear a fault doesn’t exist because of the current limitation but it does exist in non-power limited circuits even at 24 VAC (chapters 1-4). In that case you can tell minimum wire size by overcurrent protection but Code also specifies a minimum gauge. In case you have not notice control circuit is not in hazardous location at all.

Another purpose is to keep the voltage low on metallic enclosures to prevent shocks from killing someone. This is not necessary under 50 V and Code makes that clear.

Another reason is to maintain the voltage to Earth in a separately derived system. But many small control power transformer installations just connect the neutral of the primary and secondary coils. This makes it no longer a separately derived system so the EGC already exists on the high side of the transformer. Code at this voltage requires grounding except if you fall under one of the exceptions to the grounding requirement. Under chapter 1-4 rules it is easier to look at the exceptions than to look where grounding is required. Chapter 7 rules ignore 1-4 except where the appropriate section specifically calls out 1-4. This is explained in chapter 1. Does this ring a bell or are you qualified to do the work?

Either way the engineer is responsible for doing the design work which includes grounding. You should be asking or submitting requests for clarification followed by change order requests for things not included on the bid request. Obviously the engineer has no idea what they are doing or is used to qualified electrical contractors. This means if this thing blows up chances are you will be the one liable. Better talk to your insurance agent. I’m not going to get into licensing but hazardous location installations are simply not a place for someone inexperienced, whether they are licensed or not. Most commercial/residential electricians know to no bid these automatically. The oil and gas industry is full of specialists that work with this stuff all the time. There is a lot to the design and installation that is not in the Code like understanding how conduit seals work and how and where to properly install them, and which NEMA ratings to use, never mind intrinsically sage designs. The fact that you even have to ask about wire gauge on a control circuit tells me you don’t know the basics in the Code. Even if you by some miracle pass inspection there is a good chance of something going seriously wrong in the future. Someone can get seriously hurt or die. If that happens quite often it’s not just a money issue. They will put people in prison for gross negligence. Get a contractor that does fuel islands. This is not DIY.



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I am not wiring this thing. I am just a reviewer and not by choice they gave this to review. Now I do know why EGC are provided. However controls are different then power circuits. The control circuits that I have does not have overcurrent protrection and so question was how to size wire gauage.

I placed this question multiple thread because no one gave answer nor no one helped answer question. I was thinking if not this forum then another forum might have people who know something. Looks like the thread are seen by same people no matter where you placed it.

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