30-50 amp HID lighting circuits

[kwired]

the few times I have measured this, I only got 2-3 amps on a fully loaded 20 amp MWBC, Probably less neutral current than you typical install of a bunch of dissimilar unbalancable stuff.

were you using a true RMS meter?

I do believe that the worst offenders are data centers but as I said OP's application still possibly has a majority of load as non linear and line to neutral, so it at least needs some consideration.

 

[thunder15j]

I am back to civilization. .. two long days of control wiring getting MCC online... anyway latest on my grow project

Customer is coming up with 1000 watts MH fixture ; said to have the capibility to be daisy chained plugins..they can be controlled (dimmed/on-off switching via wifi).. no need for lighting contactors, timers etc.. all we do is run 50 amp-240 volt circuit to j-box and then the first fixture will be tagged into it, then let the daisy bloom..I see only allowing 9 fixtures per circuit (1000x9/240=37.5amps) (lights on for probably long enough to call it continuous load) They are looking at 70 fixtures..thus 8 lighting circuits. Would be nice to get 10 lights/ circuit..have to see fixture specs..maybe I could tap transformer to get lower secondary voltage to push less amps..however that would be counterproductive.

I am shopping for a 75 kva 480 x 240 delta xformer. with x4 terminal to give me 120 and/or 208V (stinger) to ground.. I like that option better than corner grounded delta giving 240V to ground on two legs.. I am thinking that we need a ground reference for safety fault clearing..I have seen some installs with no grounding ref. do not think that met code.

Please note this existing facility that has a 400 amp, 480 volt, 3 phase 3 wire system-underground.

 

[electrofelon]

I am back to civilization. .. two long days of control wiring getting MCC online... anyway latest on my grow project

Customer is coming up with 1000 watts MH fixture ; said to have the capibility to be daisy chained plugins..they can be controlled (dimmed/on-off switching via wifi).. no need for lighting contactors, timers etc.. all we do is run 50 amp-240 volt circuit to j-box and then the first fixture will be tagged into it, then let the daisy bloom..I see only allowing 9 fixtures per circuit (1000x9/240=37.5amps) (lights on for probably long enough to call it continuous load) They are looking at 70 fixtures..thus 8 lighting circuits. Would be nice to get 10 lights/ circuit..have to see fixture specs..maybe I could tap transformer to get lower secondary voltage to push less amps..however that would be counterproductive.

I am shopping for a 75 kva 480 x 240 delta xformer. with x4 terminal to give me 120 and/or 208V (stinger) to ground.. I like that option better than corner grounded delta giving 240V to ground on two legs.. I am thinking that we need a ground reference for safety fault clearing..I have seen some installs with no grounding ref. do not think that met code.

Please note this existing facility that has a 400 amp, 480 volt, 3 phase 3 wire system-underground.

Yes the ballasts with the internal controllers are nice. The ones I installed had a central controller so I didnt have to deal with time clocks and contactors.

I am still skeptical that using 240 volts is the wisest option, but I certainly dont know all the details.

I agree the High leg delta is probably the way to go for this application - its by far the most standard of your three options. The other two would be code compliant if done properly, but many would consider these oddball bastard systems for this application. Further, every breaker would need to be straight rated (with a high leg, 1/3 could be slash rated - probably trivial cost difference in the scheme of things but worth mentioning). The ungrounded would require ground detectors. The corner grounded would likely require a factory gear order.

 

[thunder15j]

I propose using 240 volt circuits because you are able to run twice as many lights on a daisy chained setup (modular) than you could on 120 volts..

Availibility of fixtures that are out there is dictated by supply..Customer is getting fixtures..

Re. corner grounded delta.. that is field connected to ground.

 

[kwired]

I am back to civilization. .. two long days of control wiring getting MCC online... anyway latest on my grow project

Customer is coming up with 1000 watts MH fixture ; said to have the capibility to be daisy chained plugins..they can be controlled (dimmed/on-off switching via wifi).. no need for lighting contactors, timers etc.. all we do is run 50 amp-240 volt circuit to j-box and then the first fixture will be tagged into it, then let the daisy bloom..I see only allowing 9 fixtures per circuit (1000x9/240=37.5amps) (lights on for probably long enough to call it continuous load) They are looking at 70 fixtures..thus 8 lighting circuits. Would be nice to get 10 lights/ circuit..have to see fixture specs..maybe I could tap transformer to get lower secondary voltage to push less amps..however that would be counterproductive.

I am shopping for a 75 kva 480 x 240 delta xformer. with x4 terminal to give me 120 and/or 208V (stinger) to ground.. I like that option better than corner grounded delta giving 240V to ground on two legs.. I am thinking that we need a ground reference for safety fault clearing..I have seen some installs with no grounding ref. do not think that met code.

Please note this existing facility that has a 400 amp, 480 volt, 3 phase 3 wire system-underground.

Keep in mind 1000x9/240=37.5 amps is figuring 1.0 power factor and 100% efficiency, which your luminaires are probably somewhere below in both categories which increases total VA.

 

[thunder15j]

Grounding secondary of 3 phase transformer

Grounding secondary of 3 phase transformer

I am struggling with finding a definitive code requirement for grounding/bonding of the secondary of the 3 phase 480 to 240 volt delta 3 wire system that I will be installing. All loads on this system will will be 240 volt single phase. We already have another transformer installed that take care if our 120 volt loads. I looked at art. 250 and 450 but found nothing (at least something that I could comprehend) that led me to believe that I need a ground reference to phase conductors.

A transformer with a nuetral (x4) terminal would provide 120,120 and 208V references..not all mfgs make them..corner grounding one leg of the delta secondary would provide 240,240, 0 volts...a more hazardous voltage to ground than the first option.. option #3 would not bond any of the secondary wires, just grounding all metal parts and not have a ground reference..just not sure if #3 meets code. If one leg were to make accidental contact to ground, then we would have an accidental corner grounded system..I know there are ground detection sensors out there but you get into excessive costs, so the delta-stinger comes back into play..

Note: I realize that all option will require branch breakers rated at 240 volt to ground..But if a ground reference is not there, then what (120/240)?

 

[electrofelon]

I am struggling with finding a definitive code requirement for grounding/bonding of the secondary of the 3 phase 480 to 240 volt delta 3 wire system that I will be installing. All loads on this system will will be 240 volt single phase. We already have another transformer installed that take care if our 120 volt loads. I looked at art. 250 and 450 but found nothing (at least something that I could comprehend) that led me to believe that I need a ground reference to phase conductors.

A transformer with a nuetral (x4) terminal would provide 120,120 and 208V references..not all mfgs make them..corner grounding one leg of the delta secondary would provide 240,240, 0 volts...a more hazardous voltage to ground than the first option.. option #3 would not bond any of the secondary wires, just grounding all metal parts and not have a ground reference..just not sure if #3 meets code. If one leg were to make accidental contact to ground, then we would have an accidental corner grounded system..I know there are ground detection sensors out there but you get into excessive costs, so the delta-stinger comes back into play..

Note: I realize that all option will require branch breakers rated at 240 volt to ground..But if a ground reference is not there, then what (120/240)?

See 250.20. You will see that a 240 delta is allowed to remain ungrounded. An ungrounded system still needs straight rated breakers. Which one to go with? As I already said, I would likely go with the high leg. Some consider this system an oddball and never/hardly ever see it, but I see them all the time thus consider them totally standard. The problem with ungrounded systems is, most non electrical people would have no idea what the fault indicator light is and would likely just ignore it or put some tape over it With a grounded system if there is a problem, it takes care of itself automatically. Corner grounded is fun because it looks like single phase.