Ecnerwal wrote:
- you'll need
a lot of fixtures to warrant #12 and a 20 amp 240V circuit, .vs. #14 and
a 15 amp circuit.) At half an amp or so per 4-lamp F32T8 ballast at
240V, 24 ballasts (circuit derated to 80% for being on a long time) and
96 tubes (384 feet, if you like) on one circuit and 14 ga wire. For that
matter I'm danged if I know why folks are talking 12Ga wire on a
lighting-only circuit that might, at most, be 16 two-tube fixtures, and
probably won't even be that. Unless the ballasts are terrible (awful
power factor, inefficient) that should normally be well within the
capacity of a single 15 amp 120V circuit - and if being split in twain
so that they don't all go out at once (which, if it is really a lighting
only circuit, is far from likely in my experience, but I respect it as a
design goal) it's even more blatantly inside the reach of a 15 amp 120V
circuit to run half or 2/3's of that load on 14Ga wire.

I do overkill, but I try to avoid _stupid_ levels of overkill when it
costs me serious money. 20 amp breakers and/or 12ga wire to feed 2-lamp
4-foot fixtures in this quantity seems rather stupid, even for me - and
I have most of 1000 feet of 12-2NM I happened to buy back when it cost
$118.

Please see if my math makes sense:

Amps/fixture = (32w + 32w)/120v .6.

So a 15 Amp circuit(derated 80% to 12) with 14ga wire may support
at least 12/.6 = 20 fixtures.

Should I be considering a "ballast surge" or anything like that (like
they have when an electric motor is first started)?

Bill