I am retrofitting a large warehouse full of 2x4 lay ins. The plan was to use the 4' LED lamps that don't require bypassing the ballast. come to find out, the lamps do not work with all ballast ( a little tidbit the supply house failed to mention when bidding). I am more than a little apprehensive about bypassing the ballast and putting 277 volts directly on the tombstone. would be interested in others perspective.
led retrofit
- Thread starter deec
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You’ll be fine, I just did a 6,000 sf office they work just fine on 277
“ shoot low boys their riding shetland ponies”
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
If I'm not mistaken, ballast open-circuit voltages can approach 600v, so you should be okay.
xformer
Senior Member
- Location
- Dallas, Tx
- Occupation
- Master Electrician
Last time I actually measured ballast OC Voltage it was @ 540 volts.
Setscrew
Member
- Location
- Las Vegas, NV. USA
I work at a university and am currently removing ballasts from 156 light fixtures and hooking 277V to the tombstones and installing T5 ballast bypass double ended LED lamps with no problems. I also did it with can lights that had 175 Watt Metal Halides in them. It's cheaper to use plug n play lamps, but at least you don't have to buy ballasts anymore if you use direct wire (ballast-bypass), plus the quality of the lamps are usually better.
Flicker Index
Senior Member
- Location
- Pac NW
- Occupation
- Lights
Ballast bypass don't necessarily increase efficiency. One is like a bridged tube PL-C that uses an external ballast while the other is like a corkscrew CFL with a built-in ballast somewhere in the lamp. TLEDs are quite reliable simply because LEDs are spaced out over such a large area and you have considerable cooling. TLEDs usually stay cool to the touch, but ballast bypass type will heat up considerably on one end where the internal ballast is located.
They don't always reveal this in the spec sheet, but when the cooling is inadequate to sustain full performance, they either fail prematurely or they self activate dimming to prevent premature burnouts. Get a product sample and put it in a fully enclosed fixture and rig it up in a closet. Set a light meter and read the FC. Without moving anything around, come back a few hours later and recheck. the reading. If the readings are dropping drastically with time, the lamps are throttling, thus you can expect similar performance drop on hot summer days in a warehouse.
They don't always reveal this in the spec sheet, but when the cooling is inadequate to sustain full performance, they either fail prematurely or they self activate dimming to prevent premature burnouts. Get a product sample and put it in a fully enclosed fixture and rig it up in a closet. Set a light meter and read the FC. Without moving anything around, come back a few hours later and recheck. the reading. If the readings are dropping drastically with time, the lamps are throttling, thus you can expect similar performance drop on hot summer days in a warehouse.
This voltage could approach 600 volts but at a very low current that usually only product a very small spark when shorted. A 277 volt circuit feed from an existing 15 or 20 amp circuit breaker could easily start a fire if it shorts out. Had old 277 volt breakers that could almost swear you could weld with. Had guys use a piece of #12 solid copper and shorted it to a 2" heavy wall conduit. Gave up trying to trip 277 volt breaker after 5 or 6 attempts.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
Had to be FPE! LOL!
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