This has been legal in Oregon, Washington and California for a wile now, and since we get so much rain here and have the low cost electricity farmers use these systems in green houses for all types of starts anyways. We have seen this allot. I wired a show room for a indoor agricultural lighting store. I used 2 200A panels and 1 150A, all 20A branch circuits and 40A rated contactors. Ballast units mount on unistrut above the hood.
Remote ballasts is a more and more common question I get. From pastry cases to ag lighting.
Article 410.30(C)(1) Condition (1) requires The luminaire (fixture) is located directly below the outlet or busway. That includes the ballast.
Here is 410.30(C)(1);
" Electric-Discharge Luminaires (Fixtures)
(1) Cord-Connected Installation A listed luminaire (fix-
ture) or a listed assembly shall be permitted to be cord
connected if the following conditions apply:
(1) The luminaire (fixture) is located directly below the
outlet or busway.
(2) The flexible cord meets all the following:
a. Is visible for its entire length outside the luminaire
(fixture)
b. Is not subject to strain or physical damage
c. Is terminated in a grounding-type attachment plug
cap or busway plug, or is a part of a listed assembly
incorporating a manufactured wiring system connec-
tor in accordance with 604.6(C), or has a luminaire
(fixture) assembly with a strain relief and canopy"
1000W or HPS / MH remote ballasts are really a 2 capacitors and a constant wattage autotransformer in an aluminum housing?
Could you request/propose an alternate installation method to the manufacturer allowing a 1/2" KO to be drilled in to the housing and flex in to the unit, remove the inlets and blank off the holes with panel blanks, or use RE washers and pipe into one of the rectangular panel inlet mounts?
You might have it drawn up and submit it to the manufacturer or find a listed product that provides a 1/2" K/o. I think I remember some custom baseball pole lights that had a ballast in a generic 3R box 1/2way up the pole that did 2 heads. I don't reacll if it was a listed product or UR components. Ask your inspector what he/she will require.
NOTE: There is a maximum distance that ballast can be from the screw shell.
With the agricultural hoods and remote ballasts however you will need the proprietary hood connector to mount on a four square raised cover? Can the manufacturer supply that as a listed product? I don't think you want to use a regular twistlock up there. Or you can hard wire the hood also.
The thing that always concerns me about any HID lighting is when the people designing and selling this stuff recommend using 30A or 50A branch circuits.
I remember working as an apprentice 15 years ago on highbay 400W MH lighting and installing 15A twistlocks on a 277V 30A branch circuit. I did not like it.
I still see this once in a wile on pole lights or parking lot lights.
210.21(B)(3) Exception 2 sends you to 410.30(C) Which paragraph (2) allows a 6-15 15A 240V receptacle to be on a 50A branch circuit as long as you meet 240.5. (1)
I seen these green house or hot house agricultural lighting installations have 30 and 50 amp branch circuits wired in to a typical intermatic timer and 6-15 receptacles taped off the load side on 12AWG wire.
I am of the opinion that the maximum size circuit can be 20A or in the case of a 240V branch circuit 3 1000W lamps.
20A branch circuits require a few contactors or latching lighting relays. For a large system like you are doing you should look into GE latching type lighting controls and a sequencer that pluses each 20A latching relay circuit a second or two apart. Then you don't have the inrush.
410.30(C)(2):
"(2) Provided with Mogul-Base, Screw-Shell Lampholders
Electric-discharge luminaires (lighting fixtures) provided
with mogul-base, screw-shell lampholders shall be permitted
to be connected to branch circuits of 50 amperes or less by
cords complying with 240.5. Receptacles and attachment
plugs shall be permitted to be of a lower ampere rating
than the branch circuit but not less than 125 percent of the
luminaire (fixture) full-load current."
240.5(1) basically states you have to go with manufacturer recommendations.
"240.5 (1) Supply Cord of Listed Appliance or Portable Lamps
Where flexible cord or tinsel cord is approved for and used
with a specific listed appliance or portable lamp, it shall be
considered to be protected when applied within the appliance
or portable lamp listing requirements."
So the manufacturer should state the max size branch circuit the remote cord and plug ballast/hood unit can be on (if more than 20A).
One other thing to remember is I think 410.48 requires a 2 pole contactor if you are using both hots of a 240V system. I was just asked about this by maintenance person whom got shocked by the screw shell relamping a 240V HID lamp. People think it is OK because you could turn off the breaker when relamping.
Hope that helps