Grounding and Bonding

Maintaining good bonding on traffic signal installations is an important part of the maintenance of these systems. Most traffic signal standards, controller cabinets, and etc are metallic and therefore are good conductors. When these systems are properly installed, they are bonded together and grounded to provide protection from shorts of the wiring to the conduits, standards and cabinets. If there is a wiring fault, the circuit breaker will then trip.

If the bonding is not installed, is broken, or has a high resistance then, not only might the circuit breaker not trip if there is a short but the conduit, standard or cabinet my become hot and present a shock hazard.Visual inspection may not be enough. A high resistance connection may occur while the mechanical connection still exists. This is especially true in older installations. A Ground Resistance Tester should be used to identify problems. Of course, you could also just measure for voltage across connections and between conduits and standards or to the neutral conductor.

I remember two occasions in particular where this problem exhibited itself.

A bicyclist called and said he felt a tingle when he pushed the bike push button. When I checked the location, I didn’t feel the tingle, but again, that doesn’t mean there isn’t a problem. I measured 35 volts AC from the standard to the conduit. My electrician shoes do work!

Since I measured the voltage, it means there were at least two problems with the installation. Of course, the bonding had a problem. But, also rather important was why was there voltage present at all. Was it just inductive or was there a wiring fault. Of course there was a fault. Induced voltage in typical systems with typical wiring distances is usually below 5 volts. I inspected each traffic signal head and found a pinched wire from one of the lamp sockets to the reflector frame. I corrected the fault then corrected the conduit bonding. Then checked the voltage on the standard and all was well. I then checked all the other standards.

On another occasion, I was troubleshooting a traffic signal wiring problem looking for why a conflict monitor was randomly tripping. The induced voltages at the cabinet field terminals were higher than normal. When I measured in one pull-box I found more than a 12 volt differential between some conduits. When the bonding was corrected, even though the bonding wires were in place, the conflict monitor tripping problem disappeared.

You might think that a standard with its reinforcing steel and anchor bolts would provide a good ground, likewise for a metal conduit. It might, but even if it did, there can be a considerable voltage drop across the ground path through the earth. That’s why the bonding is important.

Now that most newer installations utilize non-metallic conduit, bonding is still at least as important.

I don’t want to ramble on too much about this, just bring the thought to your attention for consideration.

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The New TSA Forum

It’s been a while since our forum was active. It’s back! For it to be useful, it needs to have readers and just as importantly, contributors. If you have something to share or if you need an answer, try making a post. If you read a post and can provide relevant information, make a reply. The forum can be helpful for all of us if we all use it. Join in!

Links to the forum are available on the sidebar. Try the TSA Forum

You must register to be able to post to the forum. It’s painless. Just click on the register link at the top of the page. Enter your name, a password, and your email adress. Enter the characters that you see in the image. Then modify your profile if you like. You’ll receive a confirmation email.

After the administrator receives notice of your registration and approves it (Usually within a day), your account will be activated. You’ll then receive another email indicating your account has been activated. Sorry for the need for registration approval but spammers were already hitting the forum within an hour after it was activated.

Register now so you can participate immediately when you have a thought to share.

Meeting Minutes for July 18, 2007 – Malibu Grand Prix in Redwood City

TSA-SVC quarterly meeting was held at the Malibu Grand Prix in Redwood City.  Meeting was called to order at approximately 10:30 am by President Roy Dexter.  With a quick treasurer’s report by Vice Dave Mooso and minutes recap by Secretary Robert Asuncion, TSA-SVC quickly introduced Fortel Traffic President Emory Dyer and Fortel’s newest member, Luke Faubion, NorCal Regional Sales Manager.

Fortel Traffic provided an excellent presentation and demonstration of their latest V-CALM speed feedback product lines.  Fortel Traffic talked about V-CALM’s newest developments included it’s new SD (Smart Drive) technology, Bluetooth, and Wi-Fi technologies allowing one of the most user-friendly and deployment easy setups.  Fortel President Emory Dyer also unveiled Fortel’s newest line of speed feedback signs— the mini V-Calm sign.  More information Fortel’s V-Calm signs as well as their other product lines, please contact Emory Dyer or Luke Faubion at 714-701-9800.

The TSA-SVC then had a round table on improving member attendance.  Ideas such as involving vendors in any TSA announcements or publizing events via email was discussed.  Meeting was concluded at around 11:45 which was then followed up by a pizza lunch, then with fun activities such as go-kart racing and mini-golf. Next Meeting is scheduled for October 15-18 at the Santa Clara Biltmore.