what the oringail luminaire wired on 120 v or 208 volt??
and i will suggest to megger the line to find out sometime you will get a bad spot of wire.
rule of thumb anytime you increase the voltage on parking lot luminaire system is megger it first if the wire are fine otherwise replace it.
that useally take care of bad curpits with connection and who know what happend in the pipe as well
what the wattage on the luminaires now ?? and the voltage it is on now 277 or 480 ??
if the megger pass the test then you should amprobe it to check the current drawage make sure it dont get too much loading escpally with the MWBC set up
Merci , Marc
