Install a
twofer at the end of the run and
meter the
voltage and see if it drops. Also if you have an
Edison breakout
meter the amperage the
unit is pulling.
Your answer may be in the numbers regarding the breakers
tripping. First of all, lets look at what a 20 amp
breaker can hold for a long period of time:
20A X 80% = 16 amps
Now, how much does the
fixture draw? Well, 1500 watts for the lamp, maybe another 100 watts for the
ballast, and another 250 watts for all the electronics and motors. That's a total of 1850 watts.
(
http://www.martin.com/product/product.asp?product=mac2000washxb )
1850 / 125 volts = 14.8 amps, so the
breaker holds.
Now, what happens as the
voltage drops and the electronics compensate:
120 = 15.41
115 = 16.08
110 = 16.81
100 = 18.50
So, you want to get a
voltage reading
at the fixture while the rest of the show is running. As you can see, everything can be working fine and the
breaker could still trip if the
voltage dips enough.
I can't say I ever measured one in normal operation, nor do I have the plate handy to see what its listed draw at a given
voltage is, but the problem may be a simple matter of
voltage drop in cabling or
line voltage changes.
If the
nameplate rating is higher than 1850, then matters become even more critical. Also, electronic
ballast alignment can produce some big changes in draw. The lamp may be working fine, but the
ballast is out of alignment and running the lamp at 1800 watts (for example) and the
fixture be drawing 2100 watts.
Remember, even a properly running
ballast is +/- 10% and that's once the lamp is up to temperature. The "
strike/warm-up" time runs higher yet.
I think this is why the
stock Mac 2k is set up for 208-240 volts. It's just too close for 120, although I am sure in most cases they will work on a 20.
EDIT: The above info was based on the above link. Most of the other links for
Mac 2k link to the older 1200
watt unit. Although my first thought would be they draw less, I am seeing their draw listed as 18 amps at 120, 20.9 amps at 100 volts. (Electronic
ballast) Darn close for something with a 20 amp
fuse and a 20 amp
breaker. Even their
fuse rating for 240 volts is 15 amps. 20 may be the limit for the
fuse holder!