277 light ballast running on 240

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I did not actually see this but a coworker of mine was called to a job to add 2 lights to a building, while cheking the ballast of the single light that was in the building, he noticed that the ballast was a 277 volt ballast running on 240 volt, my question is has anyone ever come across this?
 

broadgage

Senior Member
Location
London, England
A multi tap ballast is generaly understood to mean one that can work from a number of different supply voltages, but that this requires manuall selection of the correct wire or terminal by the installing electrician. Not automatic.

A smart ballast is generaly understood to be one that has only two input wires or terminals, that may be connected to any supply voltage within a range.
The internal circuitry adjusts automaticly to any voltage within the range. Nothing requires selecting by the installer.

The O/P however appears to be refering to neither of these, but to a fixed voltage 277 volt only ballast being worked from a 240 volt supply.
Although not correct, the difference is not that great especialy if the nominal 240 volts is in fact nearer 250.
It is probably running the lamp at less than the design power with the likelyhood of reduced output and problematic starting in cold conditions. In warm or hot conditions it is probably fine.

Arguably a violation to use equipment on the wrong voltage, but I doubt that there is in fact any danger.
 

jeremysterling

Senior Member
Location
Austin, TX
A multi tap ballast is generaly understood to mean one that can work from a number of different supply voltages, but that this requires manuall selection of the correct wire or terminal by the installing electrician. Not automatic.

A smart ballast is generaly understood to be one that has only two input wires or terminals, that may be connected to any supply voltage within a range.
The internal circuitry adjusts automaticly to any voltage within the range. Nothing requires selecting by the installer.

The O/P however appears to be refering to neither of these, but to a fixed voltage 277 volt only ballast being worked from a 240 volt supply.
Although not correct, the difference is not that great especialy if the nominal 240 volts is in fact nearer 250.
It is probably running the lamp at less than the design power with the likelyhood of reduced output and problematic starting in cold conditions. In warm or hot conditions it is probably fine.

Arguably a violation to use equipment on the wrong voltage, but I doubt that there is in fact any danger.

Well put. However there could be some danger in that the light switch is probably single pole.
 

kbsparky

Senior Member
Location
Delmarva, USA
We had a bunch of salvaged 277 volt fixtures that we installed in our old shop. Initially, I had connected them to 240 Volts, but they were a bit sluggish in getting lit first thing in the morning.

So, I installed a small buck/boost transformer and boosted the voltage up to 264. The lights worked just fine with that arrangement.
 

Electric-Light

Senior Member
A smart ballast is generaly understood to be one that has only two input wires or terminals, that may be connected to any supply voltage within a range.
The internal circuitry adjusts automaticly to any voltage within the range. Nothing requires selecting by the installer.

The case must be grounded and unless designed specifically, significant voltage between ground and neutral voids warranty or may cause early failure.

347-480 range ballasts are designed with one specific or either leg 347v(between ground and pole on 600Y/347v) above ground or 480v across poles on 480Y/277v with both leads 277v above ground.

120-277v ballasts are fine on 230v European system with power derived from 400Y/230V units but they're not meant to be used across poles on 208Y/120 or 230V Delta, or anything that places more than a few volts between case and white wire.

It will start up, but the internal surge suppression or starting circuit is not designed for such usage in mind, so it can lead to early failure or improper lamp starting(i.e excess glow current on PRS ballast) shortening system life.
 
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hurk27

Senior Member
there are two type of smart ballast being produced, but I'm inclined to think the OP was talking about a older single voltage 277 volt ballast.

Of the two types the earlier smart ballast that was being shipped out from manufactures had a 120/277 on its label, these were only design for a 120 volt or 277 volt supply and like was said some even opened a fuse that would not let you go back and use the other voltage latter, most newer one I get now have 120-277 on the label, these ballast will work on 120 thru 277 and anything between, but theres no switching anymore since the advent of voltage regulators have been introduced to these ballast they simply electronically adjust the voltage it supply's the circuits that power the load in the case the lamp.
 

charlietuna

Senior Member
I ran 8-straight 277 volt metal halide fixtures in my warehouse on a 208 volt circuit for 12 years without any problems. When i took them down a buddy needed some lighting in his shop and we installed four of them on a 240 volt circuit -- no problems...
 
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