troubleshooting hid lights

[alfiesauce]

I have a outside lighting circuit that is tripping to troubleshoot tomorrow night. I would appriciate any offers of advice before I dive in.
The circuit has a time clock and a photocell and the lights themselves. I believe the lights are MH - I would guess 250W.
Once I go through the photocell and timeclock which are both easy to access and have to find a fault in the light system I was wondering what the best way to isolate the problem is. I was thinking about going half way down the light line, splitting the circuit in half and taking ohm readings to each side. The only problem with this is that I do not know if readings through the ballast transformers negate any help through this means.

 

[480sparky]

Breaking the circuit in half is the absolute best way to narrow down where a fault is. However, an ohms reading won't help you much.

My guess is there's a short somewhere. What voltage are they operating on?

 

[Cow]

If they're wallpacks, I usually take a stroll around the building looking at each one just to see if I can spot the ballast juice blown all over the lense. Sometimes you get lucky.

Otherwise, I divide and conquer.

I wish outside lighting was always individually fused. Better for the customer and easier to troubleshoot.

 

[electricalperson]

you probably have a either a bad ballast, or burned insulation on conductors that were too close to the lamp. bring some MC, lamp and a ballast kit.

 

[mdshunk]

Breaking the circuit in half is the absolute best way to narrow down where a fault is. However, an ohms reading won't help you much.

My guess is there's a short somewhere. What voltage are they operating on?

I agree and your tool is not an ohm meter. Your tool should be a megger.

 

[ceb58]

How many lights? You may need to go to each pole, unwire the line going to lights to find out which pole is causing the problem. You very well could have a ballast shorted out in the fixture.

 

[220/221]

I wish outside lighting was always individually fused

Ugh....I hate individual fuses especially when they are in the fixture.


If it's a dead short it will be easy to isolate. If it is a ballast that takes a while to heat up, you will need some patience.

 

[ZZZ]

We had over 800 outside fixtures on our lots and the problem of one bad ballast shutting down the whole circuit (10-30 fixtures)was unacceptable to the safety and security dept. We installed 600 vac weatherproof inline fuseholders in the handhole in the base over a period of 2 years and now we know exactly which fixture has the shorted ballast. I can't even guess how much labor it saves us every year. The electricians like it because they can easily disconnect power to the pole while servicing it. They always used an ohmmeter from each line to ground after dividing the lights in half. After finding which half was grounded they divided that circuit in half again, etc until you find it. A megger might work better, but they don't like to use them.

 

[alfiesauce]

Not quite cool enough to have a megger yet
If I had a megger how would I hook it up?
On the hot and neutral? If so would I worry about damaging the components inside the lights at all?
The divide and conquer method is gonna be the way.
I think I might try the hot to ground resistance check. I hate resetting breakers on potential faults over and over again- that's not the kosher way and seems unprofessional.
Most of the lights are on the main building, and then it boots out 150' across the yard to a shed. My hope is that it is not the underground portion of the circuit...
it's a 120V 20A cct.

 

[480sparky]

.......it's a 120V 20A cct.

If it's a short, take a temporary light pigtail and put a bulb in it. Put one lead into the breaker terminal, and the other lead wire-nut to the circuit feed. That will put the bulb in series with the short, and keep the CB from tripping

If it shines at full brighness, you still have a direct short. When it dims, it's in series with the fixtures and you've cleared the fault.

 

[Greg Swartz]

... They always used an ohmmeter from each line to ground after dividing the lights in half. After finding which half was grounded they divided that circuit in half again, etc until you find it. A megger might work better, but they don't like to use them.

I hear that a lot. I do not understand why electricians do not like meggers. They are a very good tool to use! And fluke has a neat one that is combined with a multimeter too...

 

[480sparky]

..........And fluke has a neat one that is combined with a multimeter too...

1587.

 

[alfiesauce]

If it's a short, take a temporary light pigtail and put a bulb in it. Put one lead into the breaker terminal, and the other lead wire-nut to the circuit feed. That will put the bulb in series with the short, and keep the CB from tripping

If it shines at full brighness, you still have a direct short. When it dims, it's in series with the fixtures and you've cleared the fault.

I've heard of this method.
Sounds like fun
But.. If it is a direct short, then am I creating a potentially dangerous situation by placing current into the bonding system?

 

[480sparky]

I've heard of this method.
Sounds like fun
But.. If it is a direct short, then am I creating a potentially dangerous situation by placing current into the bonding system?

If the system is properly grounded, the the current will flow properly back to the source along the ground path. Turning the breaker on and 'seeing if it holds' does the same thing if there's still a short.

 

[alfiesauce]

As i said earlier.

I hate resetting breakers on potential faults over and over again- that's not the kosher way and seems unprofessional.

 

[quogueelectric]

If the system is properly grounded, the the current will flow properly back to the source along the ground path. Turning the breaker on and 'seeing if it holds' does the same thing if there's still a short.

It is now against osha rules to flash a breaker until you find out why it tripped and fix it. No more flashing the breaker until the short clears.

 

[quogueelectric]

Ugh....I hate individual fuses especially when they are in the fixture.


If it's a dead short it will be easy to isolate. If it is a ballast that takes a while to heat up, you will need some patience.

Are you kidding me ?? The bad balast is the one that is out.

 

[ZZZ]

I hear that a lot. I do not understand why electricians do not like meggers. They are a very good tool to use! And fluke has a neat one that is combined with a multimeter too...

I use meggers a lot but our outside lighting guys don't feel they need them, they also don't like having 1000 volts run through their fingers when they forget and touch the leads. Meggers are great for finding insulation faults that only show up with a higher applied voltage, but are overkill if you just need an ohmmeter. We use them extensively on a/c compressors.

 

[ZZZ]

It is now against osha rules to flash a breaker until you find out why it tripped and fix it. No more flashing the breaker until the short clears.

A good rule, but I don't think it will catch on. Of course, I always follow it if any inspectors are reading this

 

[220/221]

Are you kidding me ?? The bad balast is the one that is out.

If it is a ballast that takes a while to heat up, you will need some patience.

Sometimes a bad ballast will not short until it gets hot.....is what I was trying to say.