What could cause 30 MH bulbs to blow at once?

Status
Not open for further replies.
hockeyoligist2

hockeyoligist2

Senior Member
Location
close to greenville sc
In the bottom section of a sewer filtrate building, 30 MH bulbs less than a year old, went out at the same time. Most of them had broken parts inside the bulb. They are all on one lighting contactor, 8 circuits. The other 60 or so are on different contactors but from same panel and none of them blew, so I don't think it could have been a power problem.

120v and 40' from the floor, so I checked for loose grounded conductors first, all good. Then I went up and opened them up. All ballasts match bulbs, all ballasts correct voltage at the socket. Replaced all of the bulbs and they are working fine now.

There was no lightning, clear weather. Cold outside but about 50 degrees inside.
 
Y

yekcoh15

New member
Neutral

Neutral

I had a similar event occur once, in a gym all the MH lamps went. It was a 3 phase panel with all the lighting on a shared neutral; properly phased. Had one bad neutral connection and with no path for the unbalanced current it used the lamps and caused them to all fail prematurely. Sewer gas is very corrosive and causes high resistance paths on copper, check all the neutral connections both in splice boxes and panels. Also meter any transformers, including the utility's. (I experienced a leaking primary on a utility transformer once that melted the water pipe bond!) I would suggest to thoroughly test everything, there is certainly an underlying reason, besides playing detective may be less expensive (and more enjoyable) than replacing all the lamps again.
 
J

jeremysterling

Senior Member
Location
Austin, TX
If you find out, let us know...

Typically, a customer says, The lights all went out out at "the same time"!

I usually find that "the same time" means "during the 12 months since the last person changed out lamps..."
 
kwired

kwired

Electron manager
Location
NE Nebraska
yekcoh15 said:
I had a similar event occur once, in a gym all the MH lamps went. It was a 3 phase panel with all the lighting on a shared neutral; properly phased. Had one bad neutral connection and with no path for the unbalanced current it used the lamps and caused them to all fail prematurely. Sewer gas is very corrosive and causes high resistance paths on copper, check all the neutral connections both in splice boxes and panels. Also meter any transformers, including the utility's. (I experienced a leaking primary on a utility transformer once that melted the water pipe bond!) I would suggest to thoroughly test everything, there is certainly an underlying reason, besides playing detective may be less expensive (and more enjoyable) than replacing all the lamps again.
Click to expand...

This could very well be the case.

Remember that if the loads on MWBC's are balanced the neutral carries zero current, and there will be no problem as long as the loads are balanced. Once the first lamp that fails puts an imbalance in current voltages will start to change, eventually more lamps may fail causing more changes. I could see a chain reaction of lamp failures happening.

You could have a bad neutral for some time with a balanced load but the first time the load changes - like when a lamp fails - you will have problems.

If you are lucky all you have is bad lamps - I bet ballasts may have had some overheating and even if they still work may have shorter life.
 
hockeyoligist2

hockeyoligist2

Senior Member
Location
close to greenville sc
kwired said:
This could very well be the case.

Remember that if the loads on MWBC's are balanced the neutral carries zero current, and there will be no problem as long as the loads are balanced. Once the first lamp that fails puts an imbalance in current voltages will start to change, eventually more lamps may fail causing more changes. I could see a chain reaction of lamp failures happening.

You could have a bad neutral for some time with a balanced load but the first time the load changes - like when a lamp fails - you will have problems.

If you are lucky all you have is bad lamps - I bet ballasts may have had some overheating and even if they still work may have shorter life.
Click to expand...

They are all on different circuits (8) no shared grounded conductors, zero current on the GC. All had close to the same amp readings except one circuit that had fewer lights on it. The only thing they have in common is the lighting contactor. No splices, I opened every LB and JB. No corrosion on any connections. Nothing loose.

I had been in the building working on a Asco valve 2 days before and all of them were working, so it wasn't the operators claiming that they were all working. I actually was coming back to replace the valve and tried to turn on the lights, no blink, no sound just darkness!
 
Status
Not open for further replies.
Top