Originally Posted by porschedude996T
Hello, I bought some 400watt Metal Halide Low Bay Fixtures and wonder what other wattage bulbs I can use. Can I place 250watt Bulbs in these fixtues. I asked the guy who I bought them from and I'm not sure he was educated on the subject.
Unforetally those type of lowbay luminaires they are very ballast specifed and bulb type.
you can NOT use the 250 W Metal Halide in 400 w Metal Halide ballast system the reason why is that because the ballast is designed to limited the current on the HID's.
and there are quite few diffrent type of 400 W MH's some are horzontal burning setting and some are base up only and some are open lamp rated
note : please check the lamp ordation [ postion ] which way the base is
Most lowbays useally are base up so it should not have some issue with it but i know 2 or 3 type of Lowbay they have the bulb cantered at 45° angle
if you want to change from 400 w to 250 W there is two choice change ballast / bulb or get diffrent luminaire.
The other thing is that they can load up the lighting circuit pretty good each one will draw about 4 amp [ at 120 v ] if you have more than 2 in the shop the max is 4 - 400 W MH on 20 amp circuit basied on contouis load but if you have other luminaires on that circuit you may have to reduce prorated depending on what it on it.
also when you turn them on expect the Luminaire take up to 5 min to fully warm up and when you turn off and turn it back on it will take about 5-20 min to come back on., so keep a flourscent luminaire on that circuit as well because most HID dont like " short " starting
at last but FINAL warning just about all the HID's they useally wire for multi voltage as well so i strongly advise check the voltage connection at the termatal block or junction box at the luminaire.
they will useally wired one of the 4 voltage depending on the type some are single voltage ballast type also
that why i advise check the voltage as well
the multi tap ballast will have 120,208,240 and 277 volts it will be pretty well marked on the ballast lead[s]
the single voltage ballast you will see it will mark for that voltage only
if this will be used in the resdental garage if so please hook up at 120 v only [ the code is pretty strict on this ]