ECN Forum Forums General Topics of the Trade General Discussion Area Bad neutral

We see a lot of posts here related to a bad neutral.

Here's another example.

Any of you work on traffic signal equipment?

Uhh, I fixed the turn signal light on my car once.


Glenn, (its been a long day ,sorry:> )

pauluk, i was employed by a city as an electrician. we had to install/repair traffic signals i seen many code violations with the service equipment. i have been shocked by several un-grounded improperly bonded control panel cabinets. i learned to check the cabinets for stray voltage before preforming maintenance. these things can be deadly....

Glenn, same thing happens with turn signals/brake lights/tail lights on a car with a bad ground on the light circuit....

Strange that they don't use neutral fault devices. No, I've never seen such a beast, but it would be rather easy to design, I think.

If this is a 120-0-120V setup you'd need two voltmeters and a control circuit:

Voltages:
Hot1 - Neutral
Hot2 - Neutral

Hot1-Neutral should be in the 110-125V range
Hot2-Neutral -"-

Should any of the voltages fall outside the interval, the device cuts power to prevent damage from over/under voltage. (It would work on three phase too.) If the neutral comes loose and the load is unbalanced, the voltage will drift out of the allowed range causing the device to cut power.

BTW: What's wrong with the lights? Aren't they always red-yellow when switching from red to green? (Or is it just here?)

We have a traffic light indoors. (Ermmm, it had fallen down, you see... ) Logically the green wire is for the green light. (But for some reason, the red light has a brown wire)

[This message has been edited by C-H (edited 11-24-2002).]

C-H,
British traffic lights have a red-&-amber phase before green, so I assume from your comment that Swedish lights do likewise.

In the U.S. however (and also in France & Ireland), they just go straight from red to green. The only place you should see red and amber at the same time is on a multiple-head signal with separate turn arrows.

Possibly because of your old system in which red was used for ground?

I see that all the time. I've also been asked about this problem often, and people seem so amazed when I just tell them to look for a bad ground at the light cluster. They seem to think that the interaction between lights is something much more complex and are amazed (and happy!) that the fault is easily cured.