metal halide lighting

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  #1  
Old 02-12-03, 08:40 PM
tom sawyer
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Exclamation metal halide lighting

hello
i purchased a GE high bay 400 watt fixture.....for growing indoors
my problem, is the fixture is fuse protected,4 amp slow blow, and the fixture has blown two fuses so far.it is sharing a breaker in the panel with all the other lights in the downstairs ...4 lights total...and also a freezer 22 cu inch size,, is on there also.
the breaker has yet too trip...but my fuses keeping dieing.......the fuse on the fixture is on the black wire feeding in too fixture.
should i step up too 5 amp???
my voltage is 120/110 in the house
help please!!!!
thanks
Tom
oops i forgot too state one thing....
the fixture calls for 90c degree wire i have put 60 degree celsius wire on it is this the problem?????
 
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  #2  
Old 02-12-03, 11:10 PM
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I could be wrong here so we will get more opinions I am sure. I would say 4 is marginal and a 5 would probably do it. It might be blowing when the freezer starts. Are you on number 12 wire (20A circuit?) and how far is it from the panel? Depending on your service you could have a couple things come together at the same time to drop the voltage just low enough for a sec or 2 to increase current draw to pop that fuse. If I was doing it I think if at all possible I would have ran a 14 wire right from the panel to a recept just for it.
 
  #3  
Old 02-13-03, 05:37 AM
tom sawyer
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hello
from the breaker panel too outlets ..is 12 guage i am sure.
the power cord from out let too fixture is 14 gauge.
what about the 90 degree celcius wire requirment?????
the guy at electric store was wondering why my fixture has a fuse on it anyways.he says all of the ones he sells dont have fuses.maybe GE did this for a reason on this model number
thanks so far
T>
 
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Old 02-13-03, 06:34 AM
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I would advise against replacing the fuse with a larger one. Something is wrong, and changing the fuse is not the correct response. For some reason, the fixture is drawing too many amps. This could be because the voltage is too high (you can check it with a voltmeter), or the fixture could be malfunctioning, or the bulbs could be higher wattage or different kind than called for, or could it be that you connected some kind of downstream load.

The 60 degree wire is a problem that you should correct. All you need to do is add an extra accessible junction box a few feet from the fixture, and run new 90 degree wire for the last few feet.
 
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Old 02-13-03, 07:27 AM
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John, how close would you fuse a fixture like that? It has a 400W lamp and how much heat is given off in the ballast? It seems awfully close but I supose the manufacturer made it that way. How long was it running before it blew the fuse? It sounds like it might be operating right along and then the fuse blows. I would be tempted to try it with a cord from another source without the freezer on it. I know those types of fixtures draw the most power as they are fully heated, the current draw increases as it warms up. I agree with voltage check and this is another good case for a guy buying an amprobe.
 
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Old 02-13-03, 09:00 AM
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Wouldn't it draw more amps if the voltage is too low?
In this case if the voltage would be less then or close to 100V you'd probably cause the fuse to open. (100V x 4A = 400 VA =~ 400W)
 
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Old 02-13-03, 11:27 AM
Brewbeer
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I'd return the fixture to where you got it and get another one. It sounds defective.
 
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Old 02-13-03, 02:55 PM
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trinitro,

That's a common misconception. It seems to come from the idea that a 100-watt light bulb somehow "knows" that it is supposed to consume 100 watts and adjusts its amp draw accordingly. But a light bulb is nowhere near that smart (even the brightest bulb in the box). When a light bulb says 100-watts and 120 volts, it means that it will use 100 watts if presented with 120 volts. If presented with less volts, it will use less amps and therefore less than 100 watts. If presented with more volts, it will use more amps and therefore more than 100 watts.

Mathematically, V=IR. Since R (resistance in ohms) doesn't change, then I (current in amps) must go down as V (voltage in volts) does. And since P=VI, when both V and I go down, so does P (power in watts).

Note that the above analysis only works with linear loads such as light bulbs. Once you get into motors, Ohm's Law (V=IR) no longer applies. And if you are picky, you will point out that "R" does indeed change, even in a light bulb, as it warms up.
 
  #9  
Old 02-13-03, 04:17 PM
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Re: metal halide lighting

Originally posted by tom sawyer
hello

oops i forgot too state one thing....
the fixture calls for 90c degree wire i have put 60 degree celsius wire on it is this the problem?????
Yes it is a problem. The fixture will/could create more heat than the wire can withstand. It is also against code to install a fixture against the manufacture's directions.
 
  #10  
Old 02-13-03, 07:51 PM
tom sawyer
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hello again
i am currently running a 5 amp fuse with good luck
i feel the freezer is the culprit because while in the same room ...listening too the ballast humm slightly...when the freezer cuts on the humming sound dips quickly then back up.
also no breakers have been tripped yet.
thanks for the help.
T>
 
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Old 02-14-03, 07:45 AM
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I'm used to designing/working on circuits which will consume their rated wattage regardless of the input voltage, and will increase their current draw if the voltage drops. I guess sometimes you have to think simpler.
Regarding the actual post, I would really put a clamp-on ammeter and measure the actual current. There is a reason why a 4A fuse was used... and there is a reason why a higher value fuse should not be used instead.
 
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Old 02-14-03, 08:48 AM
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Yes, I agree with John and didnt mean to imply that the current went up with V drop, I was thinking more along the lines of the way the ballast reacts to the sudden drop and increase. That circuit could be nearly loaded when the freezer comes on and on the condition of the motor. Normally I would be suspicious of increasing the fuse, but that seems so close to the demand that there isnt much room for error. If you have a 4 a fuse, 400 watts of lamp and how many watts of heat does that ballast give off? I have some fixtures and they dont even have fusing on them.
 
  #13  
Old 02-14-03, 07:43 PM
tom sawyer
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i am leaning towards sberry's thought.....the local electric supply shop wondered why it was fused also????they didnt even sell a fused halide fixture......the shop owner thought maybe that GE made this series of fixtures for a special install in which my use would not call for a fuse.
the ballast is a multi volt ballast....and i did read the label closely today....i noticed it had all 4 voltages listed then right below the voltages it said maximum amps in the same order as voltages listed.....120 had a maximum amp of 4.2...the others were even less. what does this mean??????
thanks for the help too all of you
T>
 
  #14  
Old 02-14-03, 08:03 PM
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High-bay fixtures using Metal Halide and High Pressure Sodium lamps are often specified with optional fusing. It's not unusual at all. What is unusual is for such a fixture to be operated at 120 volts instead of 208, 240, 277 or 480 volts.

Most fixtures of this type have a multi-tap ballast which allows the fixture to be wired for 120, 208, 240 or 277 volts. (If the fixture is to be used for 480 volts the ballast is usually rated for just a single voltage.)

Kooter
 
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Old 02-14-03, 08:49 PM
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Is the "maximun" amp stated that way in the instructions or is that just amps on the label? I think that it is a multi volt fixture someone might have acked the wrong fuse, that would work fine on 208, but if it says 4.2 on the tag and you are using a 4 seems to make sense that you are having problems. I wouldnt think 20% over its actual draw would be fused too much. But, thats just if I was doing it, there are others here way more qualified than me though.
 
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Old 02-14-03, 08:52 PM
tom sawyer
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its the amps on label ...which says max amps 4.2 for 120 volt
it is a multi tap ballast which is made for 120 as one selection.
thanks???
T>??????
 
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Old 02-14-03, 09:31 PM
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Well obviously it needs more than 4 a fuse then. You are ok with the 5, I bet that was for higher voltage hookup. Like some florecent, I have some with fuses, some dont. 80 watts were fused at amp and a half, about twice the power they were using. I think if you can find some recomendation you will find 8A for that voltage. That 4 sounds about right for 208
 
  #18  
Old 02-15-03, 08:18 AM
tom sawyer
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hey thanks!!!
as you all talked about ....as the volts got higher on product sticker....the amps went down,, 120 was the highest amp with 4.2
you all have been a big help!!!!!!!!!!!!!!!!!!!!!!!!!
T>
 
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Old 02-15-03, 11:57 AM
whitey2
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Everyone that replied all had some of the issues. Her is my take, not in any order. The 90 deg wire is only required for the terminations at the fixture because of heat, not the the branch conductors. If this is a new cord supplied from the OEM, it probably meets this requirement. typically the cord should have a temp rating on it. Fusing is normally an option for fixtures of these types in multifixture installations so if one fixture goes bad it doesnt trip the branch circuit breaker ahead of it, and shut down the rest of the circuit. Multitap ballasts are common, make sure it is on the correct voltage. typically a 400 watt MH fixture is calcualted at 460 watts and draws ~ 4 amps at 115 volts. The name plate says 4.2 amps, that would be the greater of starting or running amps. Make sure you have at least 110 volts at all time to the fixture. as far as the fuse size, 5 amps should be OK for the 120 tap, unless the UL listing or the manufacturer states otherwise. remember that fuses come in different ratings...ie. slo-blow, quick-blow, time-delay. this would also have an impact on its function. As with all electrical equipment it must be installed per manufacturers instructions. Carefull, somewhere in the code (cannot remember) limited residental installations to 300 watt. better check this out.
 
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Old 02-15-03, 03:12 PM
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Ya learn somthin new every day. It just didnt occur to me why that fuse was in there and it certainly makes sense. Now I see why, besides a safety factor some of the multiple ballast florecent fixtures have fuses in them too. It sure would make trouble shooting on that fixture or circuit easier and wouldnt knock out several lights.
 
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Old 02-15-03, 03:59 PM
texsparky
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whitey2,
I believe you may be referring to 470.75 which refers to 300 volts,not 300 watts.
IMO the concern with the fixture would be the listing from UL.Is this fixture listed for a residential application or is it only for commercial,industrial?
 
  #22  
Old 02-15-03, 04:14 PM
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Does UL test and define the use of various electrically related items by "residential", "commercial" and/or "industrial"? What difference would it make from an electrical (or UL) standpoint if an item was used in any of the three different applications?

Kooter


Originally posted by texsparky
IMO the concern with the fixture would be the listing from UL.Is this fixture listed for a residential application or is it only for commercial,industrial?
 
  #23  
Old 02-15-03, 06:37 PM
texsparky
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Kooter ,
I didn't look up the UL listing, but GE Supply's website lists the fixture under commercial/industrial.
 
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Old 02-15-03, 06:56 PM
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I wasn't aware that UL recognized any item [that they give approval for] to be used "only" in certain applications; i.e. residential, commercial or industrial. In other words, I was unaware that a high-bay light fixture, which is normally used in commercial or industrial applications, might not be UL approved for use in a residential application...or an explosion-proof motor starter (which is usually used in an industrial application) couldn't be used to protect a residential swimming pool pump motor.

Kooter
 
  #25  
Old 02-23-03, 07:19 AM
tom sawyer
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just an update
the 5 amp fuse has apparently ,,so far ,,,fixed the problem.
everything is growing strong.
you all helped me out very much!!!!!!
T>
 
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