warehouse lighting 740' ? 218'

[ssgnort]

We have a job coming up where a customer is enclosing a warehouse and adding lights. The voltage drop for getting 277 volt up over and down to the end is almost a thousand feet away. The recommendation to use a buck boost transformer at the midway point was made. Is this a possibility to run a smaller cable then boost that voltage back up, and what down falls are there?

 

[Cow]

You DO NOT want to use a buck boost.

Is it possible to set a subpanel farther down the building closer to some of the lighting load?

If not, I'd bump up your conductor sizes and utilize MWBC's alternating circuits at each lighting outlet. MWBC's have less voltage drop than a standard 2 wire circuit.

 

[ssgnort]

I made the suggestion of it would be better to have a sub panel in the center for lighting and power. I personally think one voltage drop vs. Multiple for lighting and power is better cost wise. The powers that be buddy made the boost it comment. Part of me is wrapping my mind around how that works. So if you need 277 volt 18 amp a thousand feet away for a lighting circuit. Do you run run cable to accommodate voltage drop for 500' run it to a buck boost, and continue on to destination?

 

[winnie]

The idea is that if the voltage drops (say) 10%, then you can use a boost transformer to bring the voltage back up.

The problem is that voltage drop is not a constant; it changes with load. Unless the load is constant, the voltage drop will change. An ordinary boost setup can't compensate for these changes; so at light load your voltage will be too high.

If, rather than reducing the actual voltage drop, you want somehow compensate for it, then you would either need a transformer (or other converter) that adjusts to stabilize the output voltage, or you would need loads that tolerate and adjust for wide supply voltages. For example some lighting ballasts function perfectly well on anything from 120 to 277 volts.

However such compensation for voltage drop doesn't fix the fact that voltage drop is pure efficiency loss.

-Jon

 

[Electric-Light]

We have a job coming up where a customer is enclosing a warehouse and adding lights. The voltage drop for getting 277 volt up over and down to the end is almost a thousand feet away. The recommendation to use a buck boost transformer at the midway point was made. Is this a possibility to run a smaller cable then boost that voltage back up, and what down falls are there?

To cut corner to lower cost? Compensating for a level of voltage drop that wouldn't be allowed otherwise using a step-up is not a code complaint method.

You DO NOT want to use a buck boost.

Is it possible to set a subpanel farther down the building closer to some of the lighting load?

If not, I'd bump up your conductor sizes and utilize MWBC's alternating circuits at each lighting outlet. MWBC's have less voltage drop than a standard 2 wire circuit.

You might as well bring the pipe for 480Y/277v and alternate between all three phases in clusters and you would actually balance the load on all phases and reduce flicker because, you the flicker occurs at different time on each of the phase.

The flicker comment is not applicable if it's T5/T8 fluorescent and some Light Emitting Decoration.

MWBC saving using two poles is not as effective off of 3 phase circuit.

If you have a 10A on A+N and B+N, the neutral current is 10A.

neutral current is 0A if it is from a split phase single phase source.

 

[Electric-Light]

We have a job coming up where a customer is enclosing a warehouse and adding lights. The voltage drop for getting 277 volt up over and down to the end is almost a thousand feet away. The recommendation to use a buck boost transformer at the midway point was made. Is this a possibility to run a smaller cable then boost that voltage back up, and what down falls are there?

I would obtain a sample of one fixture. Run it off of a phase and neutral from a 480v air conditioner circuit. This will get 277v phase-to-neutral. Observe from distance how it behaves as you cycle the A/C unit. This will give you a feedback on dip tolerance, which is usually not part of specifications.

Light Emitting Decoration fixtures can have a slow transient response that they can produce a pathetic amounts of objectionable flicker. They may hold the output quite well if you were to hook them up to a variable power supply and slowly ramp up and down from 200 to 300v, but flicker when subject to a brief 20v dip from a motor start and the like.

Transient response is almost NEVER part of fixture specs and it can lead to extreme creature dissatisfaction if it flickered noticeably every time some motors started. This is why I highly recommend this "pot hole response" test whenever you consider Light Emitting Decoration installs.

 

[coop3339]

You could try to get 480v ballasts and run 3 phase circuits. Then you wont need a neutral, plus you will have less VD for the same watts because of the higher voltage.

 

[don_resqcapt19]

To cut corner to lower cost? Compensating for a level of voltage drop that wouldn't be allowed otherwise using a step-up is not a code complaint method. ...

Can you cite the code section that supports your statement?

 

[Electric-Light]

Can you cite the code section that supports your statement?

Not code recommended. I retract code the blanket statement"non-compliance" without further qualification. I add the qualification UNLESS equipment manufacturer says this practice is NOT recommended, in which case, I opine that it may in fact be a code violation on the ground of not installing per instructions.

However, Section 110-3(b) requires equipment to be installed in accordance with the equipment instructions. Therefore, electrical equipment must be installed so that it operates within its voltage rating as specified by the manufacturer. Figure 1.


"Branch Circuits ? This FPN recommends that branch circuit conductors be sized to prevent a maximum voltage drop of 3%. The maximum total voltage drop for a combination of both branch circuit and feeder should not exceed 5%. [210-19(a) FPN No. 4], Figure 2."

www.mikeholt.com/technnical-voltage-drop-calculations-part-one.php

 

[ActionDave]

You DO NOT want to use a buck boost.

Is it possible to set a subpanel farther down the building closer to some of the lighting load?

If not, I'd bump up your conductor sizes and utilize MWBC's alternating circuits at each lighting outlet. MWBC's have less voltage drop than a standard 2 wire circuit.

I agree 100%

I would want to add a sub panel half way down the building just to make life easier. I would still use MWBC's.

If that is not an option then I'd bump the wire size up to 10AWG, that should keep the VD under ten percent which won't bother the lights.