I feel your pain here!
My maiden voyage into the fun and exciting Circus World, better known as: "Large Mall Developement Projects"
has left me wondering, just who the heck came up with this newer, improved version of Counter-Production and Anti-Coordination! [venting big time!]
Must find this individual and remove (Him, Her, It, Them, whatever) from this Planet.
Stamp a big-old "Return To Planet Of Origin - Defective Unit(s)" label on their head(s), and request operative replacements!
Ok, now that I have vented slightly, on to the Luminaire situation.
I would love to say "Of course the Ballasts will have a 480 VAC tap - after all, these are 1000 watt HIDs, obviously used for Parking Lot or Street/Highway applications, which tend to have large distances between poles and source", but for some reason, I totally see these fixtures being shipped with the most assinine Ballast possible!
You might even wind up receiving something with only a 120 VAC lead!
If so, then things are going to suck!
(see, I told you there is a "wee-bit" of frustration boiling away, from my funderful mall experience!)
Chances are the Ballast kit will be like the Advance Transformer's "Quadri-Volt" CWA and HX Family.
It would have taps for 120 VAC, 208 VAC, 240 VAC and 277 VAC.
If you are lucky, the Ballast kit might be one in the "F" code for input Voltages (per Advance Transformer).
These come with taps for 277/480 VAC, 277/347 VAC, 277/347/480 VAC and 347/480 VAC input ratings at the "Primary" side of the CWA (or the "actual" Primary winding of a Regulated Lag Ballast).
With Lamps of this size, you will most likely see a CWA Ballast driving the Lamp - typical for >750 Watt Metal Halides and HPS.
There is an optional Isolation version of the CW Ballast, and it has 480 VAC provisions at the Primary.
If the Ballast is CWA "Type T Input", then it should have a 480 VAC tap, along with 277 VAC and even 120 VAC "T" (just if you want job security, as to the endless resetting of the Breakers!... joking).
Here's some data regarding your pending scenario:
Per Appendix C, the maximum wire sizes, number of wires, and types - vs. duct size and types are as follows:
1" PVC Schedule 80:
THHN "non-compact" Conductors;
* #6 = 5 Conductors maximum,
* #8 = 7 Conductors maximum.
It would work out using #8 cu, and running two - 3 wire circuits.
Conductors would equal 7 - including a #8 cu EGC.
Current carrying Conductors would be 6.
Derated capacity would be 44 Amps max.
( 55 amps × 0.8 )
Voltage drop per segments:
- 277 VAC input to Ballasts,
- CWA type Ballasts,
- 1000 Watt Lamps - HPF Ballasts,
- 4.2 Amps per Ballast @ 277 VAC,
- 3 Ballasts per 2 wire Circuit between contactor panel and first pole, and between second and third poles,
- One 1Ø 3-Wire Multiwire Circuit
Volt loss for 1st segment (200 feet run to 1st pole) - each L-N 2 wire circuit: 3.65 Volts
This equates to around 1.3% Voltage drop on a 277 VAC circuit, carrying 12.6 Amps on 200 feet of #8 cu. in a non-magnetic raceway, with a 90% Power Factor.
For the 300 foot segment, a 2-wire circuit carrying the load current of 3 Ballasts (12.6 Amps) would be a loss of 5.47 Volts, so adding the previous loss of 3.65 Volts, the loss is now 9.12 Volts.
This is now a 3.29% drop in Voltage, and the nominal 277 VAC is something like 267.8 VAC.
Same 2-wire circuit carrying the load of only 2 Ballasts (8.4 Amps) would have a loss of 3.65 Volts - equal to the first segment's loss.
Collectively, the total Volt loss is now 7.3 Volts, and resulting as a 2.63% Voltage drop.
For the last segment (the 400 foot run), figuring 2 Ballasts (8.4 Amps) on a 2-wire circuit, results in a loss of 4.86 Volts.
Worst-Case scenario would result in 13.98 Volts lossed, and now the circuit is down to 263 Volts.
This value is 95% of the original 277 VAC, so the resultant loss is 5%.
Looks like you just made it! #8 cu just may work!
The CWA Ballast draws a pretty much uniform level of current throughout the operation of the Lamp.
It draws the same Amperage during Lamp Starting as it does during normal operation.
Also, the CWA can tolerate Voltage sags - to some degree. Not as well as the Isolated type counterparts, but overall the light output should not suffer drammatically from a 5% Voltage drop - I think the output will be between 90 and 95% of the possible wattage related output (Lumens), with a drop of 10% in Line Voltage.
As the Lamp ages, it will begin to act wierd, since it will require an ever increasing Voltage at the Arc Tube.
This will exibit the infamous "Cycling On-Off" effect, as seen with HPS Lamps.
The figures change drammatically as the above data is fine tweeked.
Also, if the raceway is PVC Schedule 40, you could use "Compact Conductors" with THHN insulation, and get the 7 #6 cu's in the first segment!
Refer to Appendix C of the NEC for further information.