I have a customer that we have performed electrical work for many years. They have 30' poles with 1000w metal halide large,old "cobra head" fixtures to illuminate the parking lots. We are having a problem with the fixtures failing within 2-3 months of repair. The last repair date was early April 2010, 6 fixtures had complete lamp and ballast kits replace, now five of the six are no longer working. The source power feeding the lights is 480v. This problem has been continual for at least 18 months to 2 years. I am at a loss to find the cause. Voltage at the pole base/head is 475-485v, wire size is # 8 from the breaker to the base of the poles, # 10 up the poles. The only thing I can think of is the poles are not grounded properly and that is causing capacitor/ballast failure. Customer is becoming rightfully frustrated, as well as I am at the end of my patience for warranty issue. Any suggestrions are appreciated. What am I missing?
Pole lighting mystery
- Thread starter mez1st
- Start date
- Status
Cavie
Senior Member
- Location
- SW Florida
Florida street lighting requires a MIM #6 ground wire run with all conductors to the pole base. Also 20' copper ground rods at each light pole. Also a surge arrester and fuse at each pole. Do 200 of these on a project and the price goes up up and away but premiture failures are not a problem.
broadgage
Senior Member
- Location
- London, England
Inadequate grounding could well present an electric shock hazard, but is unlikely to reduce the life of the ballasts.
I would suspect
Fake or inferior ballasts or lamps.
European spec 400/440 volt ballasts on 480 volt supply
Lights regularly lit in sunlight and ballasts or lamps overheating due to solar gain and electrical heating combined.
I would suspect
Fake or inferior ballasts or lamps.
European spec 400/440 volt ballasts on 480 volt supply
Lights regularly lit in sunlight and ballasts or lamps overheating due to solar gain and electrical heating combined.
charlietuna
Senior Member
I would suspect low voltage causing these ballasts to fail --under ground raceways stay full of water and a damaged feeder will sit in this water and cook--but also cause extream voltage drop. You need to monitor the fixture farthest from the power source for a few nights, then you'll know whats going on !
dbuckley
Senior Member
- Location
- Canterbury, New Zealand
You're not clear on exactly what is failing - the lamps and ballasts were replaced April 2010 (not long ago!), and now the fixtures are not working; is it a lamp failure or a ballast failure?
Cold Fusion
Senior Member
- Location
- way north
And what were the failure modes? It is difficult to figure out what to fix when you don't know what failed. "No longer working" covers a multitude of evils.
cf
There has been one ballast short circuit and burn completely up. The others are all capasitor failures. The caps are found swollen; when replaced the lights work again.
In response to the VD, the pole light closest to the source, about 100', has the most problems. It has never stayed working for longer than 3 months.
I have checked the voltage at the farthest pole, 350' away from source, and have a reading of 470v with 6 1000w lamps burning.
In response to the VD, the pole light closest to the source, about 100', has the most problems. It has never stayed working for longer than 3 months.
I have checked the voltage at the farthest pole, 350' away from source, and have a reading of 470v with 6 1000w lamps burning.
Hmmm, swollen caps and a voltage of 470 at the furthest pole under max load...methinks the voltage from the source may be a bit high. It is possible too that the high voltage combined with surges are killing the caps. (Did the ballast burn-up also have a blown cap?)
Get a no-load measurement at the nearest pole and one with all lights burning.
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brantmacga
Señor Member
- Location
- Georgia
- Occupation
- Former Child
are your guys using the right taps on the ballasts?
i've seen it happen . . . .
i've seen it happen . . . .
sparks2274
Member
I would recommend installing inline fuses for each light down and the base of the light. Make sure it is grounded properly!
mivey
Senior Member
480 volts on a 277 tap? How would that last 2-3 months?
ptonsparky
Tom
- Occupation
- EC - retired
I had problems with caps a few years back. Finally tested them before putting them in. If I rember correctly 3 out 5 did not come within 10%.
Do everyone a favor and name that brand please. It could possibly be the solution to the OP's problem.
mcclary's electrical
Senior Member
- Location
- VA
I agree,,,,,,and if not,,,send PM's to me and slick so we'll drop the dime:grin:
I wanna know. I replace alot of caps
cadpoint
Senior Member
- Location
- Durham, NC
Did U megger the circuits ? If you said I missed it, I'd make everything sing to U'ya once...
If it wasn't right then your just wearing out the equipment, now.
Ask the owner if he recalls work on the property before two years ago and where and if it matches your circuit runs. I would even look at any site drawings if avaiable, see where other stuff is...
Interesting reading on the lamps and the various thoughts, on the cobra's...
If it wasn't right then your just wearing out the equipment, now.
Ask the owner if he recalls work on the property before two years ago and where and if it matches your circuit runs. I would even look at any site drawings if avaiable, see where other stuff is...
Interesting reading on the lamps and the various thoughts, on the cobra's...
charlietuna
Senior Member
Without a method to monitor the operating voltage and current for a period of time---everything is "guesswork". One of the best contractor tools for service work is a good data logger. Customers don't like "quesswork" - they want the problem solved. Your in the business, be professional, invest in a good data logger and rent it out to your customers and charge them to install it and to pick it back up to download the data. The logger will not identify the problem every time -- but it will point you in the right direction. Night lighting see's service voltages that can be both high and low due to other customer loads. Buy a good data logger that can be used on power quality and provide a downloaded chart for your customer to see. All of the posts here are good suggestions--but they are educated guesses and over half could be thrown out if we knew what was happening to the source voltage to the problem..
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