trouble shooting MH

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ceb58

ceb58

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Raeford, NC
Went to trouble shoot some lights under a covered walk way. Here is what I found 19 Metal halide recessed cans, 8 were on one 20 amp circ. 11 were on a separate 20 amp circ. both circ. were controlled by a DP timer. The breaker was tripped on the circ. with the 11 cans, reset breaker, lights came on no problem, let them burn for a while shut them down to check connection's all good, turned breakers on waited for lights to come on in about 5 min. the breaker running the 11 tripped, put amp meter on circ. and reset breaker it was pulling 26.8 amps held for about 5 more min. tripped again. I waited about 15 min. turned it on again pulled the 26 amps for about a minute then the lamps started coming on and amp draw fell to 10. My conclusion is when the lamps are hot the transformer will not fire the lamps off until they cool down, during this time the breaker will not hold that long for the lamps to come on and let the amp draw come down. The circ. that has 8 will pull 17 amps. until they finally come on and drop to 7 amps. The store mang. said the 11 had been out for about 8 months I think they may have had a short power outage, lamps tryed to come on but breaker could not hold that long. Only fix I know of is to pull new circ. and split the 11 up so when they have power trouble again they wont be going through this again. Have I missed any thing?
 
Hmmmm....It's been my experience that the ballasts generally draw more amperage as they heat up. I haven't done the lighting maintenance thing in a while so maybe I'm wrong.

I have seen several cases where a bad ballast would slowly trip a breaker. It's obviously more time consuming to isolate than a dead short.

Start by getting the amp draw off the fixtures so you know your target. Then isolate/disconnect a section and see what happens.
 
ceb58 said:
Went to trouble shoot some lights under a covered walk way. Here is what I found 19 Metal halide recessed cans, 8 were on one 20 amp circ. 11 were on a separate 20 amp circ. both circ. were controlled by a DP timer. The breaker was tripped on the circ. with the 11 cans, reset breaker, lights came on no problem, let them burn for a while shut them down to check connection's all good, turned breakers on waited for lights to come on in about 5 min. the breaker running the 11 tripped, put amp meter on circ. and reset breaker it was pulling 26.8 amps held for about 5 more min. tripped again. I waited about 15 min. turned it on again pulled the 26 amps for about a minute then the lamps started coming on and amp draw fell to 10. My conclusion is when the lamps are hot the transformer will not fire the lamps off until they cool down, during this time the breaker will not hold that long for the lamps to come on and let the amp draw come down. The circ. that has 8 will pull 17 amps. until they finally come on and drop to 7 amps. The store mang. said the 11 had been out for about 8 months I think they may have had a short power outage, lamps tryed to come on but breaker could not hold that long. Only fix I know of is to pull new circ. and split the 11 up so when they have power trouble again they wont be going through this again. Have I missed any thing?
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What was the lamp wattage and did they match up tothe fixture wattage. You should individually fuse them with pigtail fuses and you will find a bad ballast quickly. It is a better job. I think you just have a bad ballast but which one??????????
 
quogueelectric said:
You should individually fuse them with pigtail fuses and you will find a bad ballast quickly. It is a better job. I think you just have a bad ballast but which one??????????
Click to expand...
I agree. Pretty classic, in my experience, for a ballast on its way out. They fail this way sometimes. The only good way I've found is to fuse them separately and see what crops up.
 
Keep in your mind some of the MH in the recessed cans luminarie some are High Power factor units and with the capaitor go bad they will draw almost double of the normal current rating sorta like Normal Power factor ballast set up.

That genrally true for under 175 w Pulse start and Probe starters for over 250 or larger genrally they are useally are at CWA set up so if you blow the cap the lamp will be very dim or not come on at all.

Merci,Marc
 
I understand what every one is saying however, the 8 lights that are on a circuit by them selves will do the same thing accept it only pulls 17 amps until the lamps re-fire and then the amp draw drops to 7 amps. The lamps are 100 watt. When the lamps do come back on they go to full illumination in a very short time. This only occurs if the lamps have been on for a while and are hot. When the lamps are cold they come on and go to full illumination in about a minute.
 
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