Traffic Signalization, is it considered safety control equip related to life hazard?

[Traffic Control]

Good morning forum,
I work in the traffic signalization industry. My main question today is regarding running low voltage and high voltage through the same conduit for rewire situations (traffic signal intersection rewiring). 725.31 says to classify safety control equipment as class 1 if the failure of the remote-control circuit or equipment introduces a direct fire or Life hazard. I would consider the failure of a traffic light as a life hazard. Am I correct?

Next, after I classify the traffic signal cabinet and other traffic signal parts as class 1, on traffic signal rewire situations, can I run a 24 volts DC low voltage wire in the same conduit as the 120VAC high voltage wire? We actually already do this with special composite cables (that contain many types of cables in one sheath/wrapper). 725.48 (B)(1) indicates that I can.

Thanks so much and I look forward to any replies and/or advice!

 

[petersonra]

are traffic signals even covered by the NEC?

 

[Traffic Control]

are traffic signals even covered by the NEC?

yes, we try to adhere to the NEC. Often times the PE on the job can provide special condition changes but we always stick to the NEC.

 

[petersonra]

yes, we try to adhere to the NEC. Often times the PE on the job can provide special condition changes but we always stick to the NEC.

where does it say in the NEC that traffic signals are covered?

if they are covered, what special requirements does the code stipulate?

 

[tom baker]

where does it say in the NEC that traffic signals are covered?

if they are covered, what special requirements does the code stipulate?

If signals are not covered, why did the 2104 NEC add an exemption for traffic signal cable in 250.119 exemption 3?
I wrote an article some years ago for the IMSA on NEC or NESC, as there are often those who say the NEC does not apply. Out here, our standards reference the NEC and we get permits and inspections
Tom B, IMSA Level II TS Tech.

 

[tom baker]

The issue with TS is none of the equipment in the signal cabinet is UL listed, so its difficult to say this is a class 1 or class 2 circuit.

I don't see TS as life safety equipment. The conflict monitor will trip the signal to flash in a mis wire, and if the signal is dark, the MUTCD says treat it as a 4 way stop.

In Washington we have state rule that allows mixing limited energy and power circuits (low voltage and high voltage are not definable terms)

Most signal folks don't worry about mixing circuits.....

 

[petersonra]

If signals are not covered, why did the 2104 NEC add an exemption for traffic signal cable in 250.119 exemption 3?
I wrote an article some years ago for the IMSA on NEC or NESC, as there are often those who say the NEC does not apply. Out here, our standards reference the NEC and we get permits and inspections
Tom B, IMSA Level II TS Tech.

Which one of these 4 locations would include traffic signals?

90.2 Scope.
(A) Covered. This Code covers the installation of electrical
conductors, equipment, and raceways; signaling and communications
conductors, equipment, and raceways; and optical
fiber cables and raceways for the following:
(1) Public and private premises, including buildings, structures,
mobile homes, recreational vehicles, and floating
buildings
(2) Yards, lots, parking lots, carnivals, and industrial substations
(3) Installations of conductors and equipment that connect
to the supply of electricity
(4) Installations used by the electric utility, such as office
buildings, warehouses, garages, machine shops, and
recreational buildings, that are not an integral part of a
generating plant, substation, or control center.

ETA: I think there are places covered in the 4 locations above that might have traffic signals that would be covered, but normal traffic signals on public roads, no.

 

[Traffic Control]

The issue with TS is none of the equipment in the signal cabinet is UL listed, so its difficult to say this is a class 1 or class 2 circuit.

I don't see TS as life safety equipment. The conflict monitor will trip the signal to flash in a mis wire, and if the signal is dark, the MUTCD says treat it as a 4 way stop.

In Washington we have state rule that allows mixing limited energy and power circuits (low voltage and high voltage are not definable terms)

Most signal folks don't worry about mixing circuits.....

Thanks for the reply Tom,
My boss and I sat down and read your response. We agree you. Just a few months ago, for Pedestrian buttons and the pedestrian signals, we were allowed to mix 24VDC and 120VAC in the cable using one conduit. This is now changing to where 2 separate conduit will have to be used to run the 24VDC and the 120VAC separate (with separate pull boxes also). Also, there are many times on traffic signal rewires etc, that mixing LV and HV are allowed by the EOR or the CEI in charge of the job. In my case, the CEI, P.E. Engineer decided to make it a point that no mixing was allowed. No mixing allowed on a traffic signal rewire could mean huge costs. So, I think the CEI P.E. is rethinking his position. Thanks again!

 

[Cavie]

Traffic control cabinets are not covered by the NEC in Fl. The services feeding the signals are inspected by the local AHJ but that's where it stops. Control cabinets are inspected by Certified Traffic Control Inspectors. Most roadway lighting and signal work is governed and designed by engineers that go well overboard as related to the NEC. There is are Unified Traffic Control Standards adopted by each state

 

[tom baker]

Traffic control cabinets are not covered by the NEC in Fl. The services feeding the signals are inspected by the local AHJ but that's where it stops. Control cabinets are inspected by Certified Traffic Control Inspectors. Most roadway lighting and signal work is governed and designed by engineers that go well overboard as related to the NEC. There is are Unified Traffic Control Standards adopted by each state

In Washington its similar, the AHJ inspects the service, but not the cabinet. They look at any conduits and wiring. Street lighting is almost always under the NEC. Our state code rules have the local jurisdiction accept responsibility for the traffic signal cabinet and load wiring as none of the equipment is listed.

Before we had the state code rule, a private developer would pay $100,000 for a traffic signal, the AHJ would inspect, whoops, none of this is UL listed, the job stops, the mayor gets a call, and the signal gets turned on.

 

[mopowr steve]

Thanks for the reply Tom,
My boss and I sat down and read your response. We agree you. Just a few months ago, for Pedestrian buttons and the pedestrian signals, we were allowed to mix 24VDC and 120VAC in the cable using one conduit. This is now changing to where 2 separate conduit will have to be used to run the 24VDC and the 120VAC separate (with separate pull boxes also). Also, there are many times on traffic signal rewires etc, that mixing LV and HV are allowed by the EOR or the CEI in charge of the job. In my case, the CEI, P.E. Engineer decided to make it a point that no mixing was allowed. No mixing allowed on a traffic signal rewire could mean huge costs. So, I think the CEI P.E. is rethinking his position. Thanks again!

Just wondering, so are you running a flexible conduit method from ground level inside the pole up to pushbutton all the while there are 120 volt wires just floating inside the pole until they get to the signal? I would have to think that as long as the LV wires are in fact made with insulation with a voltage rating => that of the high voltage wires you should be ok. Naturally using a color code that would help identify the different voltages.

 

[tom baker]

where does it say in the NEC that traffic signals are covered?

if they are covered, what special requirements does the code stipulate?

I can only answer for Washington. Job specs and documents for state and local agencies reference the NEC.

And again, why was the exception added in the 2014 NEC for traffic signal 250.119 Ex 3 if signals are not covered?

 

[gnuuser]

generally you do not mix signal cables with power conductors in the same conduit or raceway without a shield partition

if you use shielded cabling that is properly bonded (one end only) this can work
but this is dependant upon what the load current draw is.

generally the (load traffic signals) will not be that high as to induce a noticeable error voltage in the shielded cabling.

working with motor loads (split phase, single, and 3 phase) requires careful planning with signal and load conductors, particularly with emergency power systems being factored into the picture.

 

[tom baker]

are traffic signals even covered by the NEC?

Just a comment for many years I wrote NEC related articles for the IMSA Journal - I was awarded three Journalistic Excellence awards. I also got a lot of emails with TS and NEC questions, so I can safely state the most agencies follow the NEC for TS installations.

I guess if you disagree, then write some articles and send to the IMSA for publication.

 

[RichB]

I can only answer for Washington. Job specs and documents for state and local agencies reference the NEC.

And again, why was the exception added in the 2014 NEC for traffic signal 250.119 Ex 3 if signals are not covered?

Tom, Just my 2 cents worth here on how we do this,,
Our signals folks and Inspectors, at WSDOT, believe that ex 3 was added because we use the green wire in the cable for the ungrounded conductor for the green indication. There were people asking about this especially ones who had not done TS work and were trying to use the green as an EGC.

We do try to follow NEC as much as possible however there are no NEC sections covering TS.

We also only run a conduit into the bottom of the pole--be it street lighting, ped button/displays or signal standards--then run the cable up the pole--in the case of EVP which is 24V it is run right with the 120V--

Some easy advice that I learned years ago from an old timer--Don't over think it

 

[tom baker]

Tom, Just my 2 cents worth here on how we do this,,
Our signals folks and Inspectors, at WSDOT, believe that ex 3 was added because we use the green wire in the cable for the ungrounded conductor for the green indication. There were people asking about this especially ones who had not done TS work and were trying to use the green as an EGC.

I have instructed many code classes for WSDOT...
There is a WAC rule that exempts your signal equipment, look in WAC 296-46B-010 ((16) under traffic management systems. It basically says traffic signals don't comply with the NEC, and the local jurisdiction takes responsibility. This rule was put in by Don Anders, Olympic Region, who retired a few years ago.
There are many sections in the NEC that apply to traffic signals:
Art 100, 110, 200, 210, 220 etc
For example I now see arc flash warning labels on your service cabinets, this is per 110.16.

 

[tom baker]

Tom, Just my 2 cents worth here on how we do this,,
Our signals folks and Inspectors, at WSDOT, believe that ex 3 was added because we use the green wire in the cable for the ungrounded conductor for the green indication.

Yes that is correct. I had almost the same proposal to allow the use of IMSA 19-1 cable back in the 2005 cycle, the CMP rejected it. They said the NEC does not apply to traffic signals...Actually there is a UL listed traffic signal cable that the listing states the green is used for other than an EGC. But no mfg makes it as there is no demand. In Canada, they use a cable with a blue conductor that has GREEN printed on the insulation.
But again, in Washington we have the traffic management rule in our state electrical code that says if what ever you are doing is approved by NEMA, IMSA, etc, then its allowed.
You just need to install the engraved label on the inside of the signal cabinet to state you are accepting responsibility for the non code compliant installation.

 

[kwired]

I fail to see NEC exempting itself from traffic control signals from what is mentioned in 90.2, and therefore if those signals are exempt from NEC it is because of other local regulations - not because of 90.2.

 

[RichB]

You are all correct-Tom and kwired- I was just trying to convey how we do it here in the DOT and other municipalities.--As I stated we try to follow NEC as much as possible, and all the articles do apply, but since all the municipalities that own their own signals including WSDOT, we are able to do things expressly forbidden by NEC, i.e., like the green wire as the ungrounded conductor for the green display, which is now under the exemption Tom referenced..

However, if, say for instance, Farmer John puts up a signal on his property to direct his cows out in the south forty--then that is a privately owned installation and must comply with all wiring/installation methods in NEC and State rules, WACS here in Wa., some of which we are exempt from as Tom stated, and it must then be inspected by L&I


For example I now see arc flash warning labels on your service cabinets, this is per 110.16. Yesterday, 01:03 PM--

Yes we are trying to comply with all the requirements for labeling--but have been having a difficult time getting it thru all the regulatory agencies--However we are starting to make progress and people are getting more interested in establishing a policy for us.
.
I think that says what I meant--As to the OP--It is easy to start over thinking things and getting carried away--as I remember doing waaay back when I started out--I would look something up in the code and spent the next 2 hours tracking down each and every thing that said for this see that then oh go to this section and by the way this article may also apply!!:?
Got to running around in circles in the book!!!

Thanks folks for the conversation and education--For the OP--This is a great place to be--LOTS of experience and always great advice!!

 

[RichB]

I fail to see NEC exempting itself from traffic control signals from what is mentioned in 90.2, and therefore if those signals are exempt from NEC it is because of other local regulations - not because of 90.2.

Forgot to add---I agree--sort of--I think you could make an argument that 90.2(B)(5)c & d could apply

c. Are located in legally established easements or
rights-of-way, or
d. Are located by other written agreements either des­ignated by or recognized by public service
commis­sions, utility commissions, or other regulatory agen­cies having jurisdiction for such Installations. These written agreements shall be limited to installations for the purpose of communications, metering, gen­eration, control, transformation, transmission, or distribution of
electric energy where legally estab­lished easements or rights-of-way cannot be ob­tained. These
installations shall be limited to federal lands, Native American reservations through the
U.S. Department of the Interior Bureau of Indian Affairs, military bases, lands controlled by port
au­thorities and state agencies and departments, and lands owned by railroads.

Informational Note to (4) and (5): Examples of utilities may include those entities that are
typically designated or recognized by governmental law or regulation by public service/utility com­missions and that install, operate, and maintain electric supply (such as generation,
transmission, or distribution systems) or communications systems (such as telephone, CATV,
Internet, sat­ellite, or data services). Utilities may be subject to compliance with codes and
standards covering their regulated activities as adopted under governmental law or regulation.
Additional infor­mation can be found through consultation with the appropriate governmental
bodies, such as state regulatory commissions, the Federal Energy Regulatory Commission, and the
Federal Com­munications Commission.