outdoor street lighting Ground fault protection and OL protection? Question

[Huntxtrm1]

I have a cod question on out door street lighting. We have 2 lighting control panels. They both feed outdoor street lights and out door area pole lights. It is set up like this. 100A breaker to a #10 wire, #10 wire feeds the Lighting control Panel. There are fuses at the pole lights. I am think it is set up at 250% for GF protection(100A Breaker), and overload is handled at each individual pole light by the fuses local to the pole light? I cannot find this in the code? It is and engineered design. I would just like to know the code that says this is correct. My big boss says its not right. I think it is. I trust the EE did his job correctly. Thanks in advance to any replies.

 

[Cow]

Wiring must be different in Texas.

Off the top of my head, I can't think of any code approved situation that would allow #10 on a 100 amp breaker for lighting. How does the EE have you terminating the #10 on the 100 amp breaker lugs?

 

[James L]

#10 or 1/0 ??

 

[Huntxtrm1]

Wiring must be different in Texas.

Off the top of my head, I can't think of any code approved situation that would allow #10 on a 100 amp breaker for lighting. How does the EE have you terminating the #10 on the 100 amp breaker lugs?

No pins, just under the lugs. We are not the installers. We are the end users, a vendor installed it.

 

[Huntxtrm1]

#10 or 1/0 ??

#10 Thwn-2

 

[James L]

#10 Thwn-2

I would suggest going back to your installer, engineer, or general contractor if you think you have an issue.

 

[zbang]

My big boss says its not right. I think it is. I trust the EE did his job correctly.

Absent other info, I agree with your boss. Why do you think the EE is right? They do make mistakes (or there may be important info we don't know).

 

[Jerramundi]

The 250% primary protection is a somewhat decent guess as #10 @ 90 deg. (i.e. 40A) x 250% = 100A... but this would have to be on the primary side of a transformer at 1000V or less... and also the 250% is NOT 250% of the conductor ampacity, it's 250% of the transformer rated current (see Table 450.3(B)).

Is there a transformer between the lighting control panels and the poles?

 

[Huntxtrm1]

Absent other info, I agree with your boss. Why do you think the EE is right? They do make mistakes (or there may be important info we don't know).

Not necessarily saying the EE is right. I have corrected a few myself. But, ground fault protection at the source, and OL protection at each individual light sort of makes sense to me. I have just never dealt with this on an outdoor lighting circuit. So, I was wondering if it was acceptable per NEC.

 

[Huntxtrm1]

The 250% primary protection is a somewhat decent guess as #10 @ 90 deg. (i.e. 40A) x 250% = 100A... but this would have to be on the primary side of a transformer at 1000V or less... and also the 250% is NOT 250% of the conductor ampacity, it's 250% of the transformer rated current (see Table 450.3(B)).

Is there a transformer between the lighting control panels and the poles?

I understand what you are saying. Just wondering if there was a code that allowed this? For inrush? each light does have a transformer. They step the voltage up, instead of down. These are Merc Vapor lights.

 

[Jerramundi]

I understand what you are saying. Just wondering if there was a code that allowed this? For inrush?

Table 450.3(B) allows for various combinations of (1) primary only and (2) primary and secondary protection... under the required circumstances, which I am by no means saying your situation meets. There's simply not enough information to confirm or deny. But general speaking, 450 addresses this.

There's guys on here a lot smarter than me that have taught me about this and can better answer your questions as to why... I'm just pointing you in the same direction they pointed me.

My general understanding, based on what they told me, is that yes, it allows for inrush current and that transformers can generally handle more than their nameplate rating.

 

[zbang]

But, ground fault protection at the source, and OL protection at each individual light sort of makes sense to me.

OL at each pole does make some sense, but the leads to the poles still need to be protected as do all of the related components. By my understanding of the code, even if the total lighting load (what is it?) was within the rating of that single #10, it's still not protected at the source, which is needed. Also, the entire system's impedance might be too high to overcurrent-trip a 100a breaker on a fault.

If the 100a breaker was a GFI/GFP breaker, that would be different.

Missing from the discussion are info about the loads and the feed lines to them.

 

[Huntxtrm1]

OL at each pole does make some sense, but the leads to the poles still need to be protected as do all of the related components. By my understanding of the code, even if the total lighting load (what is it?) was within the rating of that single #10, it's still not protected at the source, which is needed. Also, the entire system's impedance might be too high to overcurrent-trip a 100a breaker on a fault.

If the 100a breaker was a GFI/GFP breaker, that would be different.

Missing from the discussion are info about the loads and the feed lines to them.

Unfortunately, I do not know the loads. But, from what I am hearing, this is not a legit way. Sounds like boss is right. I am merely equating it to my knowledge of motors and short circuit protection, and OL protection. OCPD at 250% for Short Circuit, and OL's at the starter for over current. Or, in a xfmr instance, the 250% on the primary for Short Circuit, and the percentage on the secondary for over current. Not saying it works the same way. Just sort of made sense. Was just wondering if in fact it was allowed.

 

[Huntxtrm1]

Table 450.3(B) allows for various combinations of (1) primary only and (2) primary and secondary protection... under the required circumstances, which I am by no means saying your situation meets. There's simply not enough information to confirm or deny. But general speaking, 450 addresses this.

There's guys on here a lot smarter than me that have taught me about this and can better answer your questions as to why... I'm just pointing you in the same direction they pointed me.

My general understanding, based on what they told me, is that yes, it allows for inrush current and that transformers can generally handle more than their nameplate rating.

Guys on here a lot smarter that me too! That's why I ask the questions. Lol Any Electrician that is too proud to use the resources available to him, is not an electrician. In my opinion.

 

[jim dungar]

...each light does have a transformer. They step the voltage up, instead of down. These are Merc Vapor lights.

Actually as far as the NEC goes, those are magnetic ballasts not transformers, they would be subject to article 410, such as 410.138, not 450.

Your # 10 conductors must be protected at 30A per 240.4(D)(7). The protective device must be located per 240.21(A) or (B).

 

[winnie]

I suspect that the engineer specified 1/0 AWG conductors and they were installed as 10 AWG conductors... However is there any chance that these are 'outside taps of unlimited length'?

If the #10 is protected at the load end at 30A, and the #10 is outdoors, then this might be compliant.

-Jon

 

[romex jockey]

overload is handled at each individual pole light by the fuses local to the pole light? I cannot find this in the code?

That's been the 'unspoken fix' for longer than i've been around

~RJ~

 

[jim dungar]

That's been the 'unspoken fix' for longer than i've been around

~RJ~

that doesn't make it right.

Many lighting poles are provided with supplementary protection and use the tap rules of 240.21(B).
However the OP said they were protection #10 conductors with a 100A breaker. There is no general provision to provide only ground fault protection for conductors, like these.

 

[James L]

I suspect that the engineer specified 1/0 AWG conductors and they were installed as 10 AWG conductors....

-Jon

That's what I say, too

 

[romex jockey]

that doesn't make it right.

Many lighting poles are provided with supplementary protection and use the tap rules of 240.21(B).
However the OP said they were protection #10 conductors with a 100A breaker. There is no general provision to provide only ground fault protection for conductors, like these.

True Jim
but what does one really get for GF say, 1 1/4 mile away ? ~RJ~