Changing from 277V to 208V supply for road way pole lights.

[wireguy8169]

Here is what we have.....We are retro fitting approx. 10 pole lights we are removing HPS heads and installing LED heads. While doing the work we found that the feed to the first pole is damaged and unusable, as well there was an issue previously that during some plan upgrades some conduits were hit while digging one being to the first pole. The previous maintenance person ran UF to the pole to fix the issue. Now we have an issue as I said with the UF.

Instead of digging up three sections of road to get to the vault and tie into the feeder another maintenance person wants to switch the lighing over to 208V, reason being we can get easily to another pole and feed it from a building with out any road work, problem is 277 is not available from this location, we only have 480V 4 wire or 120/208 in that building. I realize we can put in a delta/wye tranny but I am running into resistance due to the amount of money to install a panel and tranny. There is going to be some road work done next year and we can at that time install a new section of conduit to the orignally fed light.

Now, when I did the voltage drop calculation it was way over code requirements at 208V close to 11 percent and at 277 just around 4-5 percent. Our voltage does tend to run a bit high but even if we have 230 actual volts I still would much rather use the 277. If my boss decides to do this on the 208 volts and we are putting say 180V at the furthest part of the circuit due to drop what issues could we run into if any. The drivers for the led is rated from 120-277V and we would not be overloading the circuit at least not by my calculations (approx 17 amps at 208V).

It is going to get done how my boss decides as I am not on the job definitly but if we are going to have issues that cost more than the tranny and panel then it may get done the way I think it correct.

Hope this makes sense.

Thanks

 

[copper chopper]

you may be in luck,,I recently did this to a hospital parking structure and the fixtures were ordered 120 volt and when we began installing them only to find the old ones are feed from 208 volt.. After contacting the manufacurer (Cooper Lighting) they told me that there driver (ballast) is made to work of any supplied voltage from 120 to 277 volts.. He was right the job has been done for 1 month now and it looks great....

 

[wireguy8169]

you may be in luck,,I recently did this to a hospital parking structure and the fixtures were ordered 120 volt and when we began installing them only to find the old ones are feed from 208 volt.. After contacting the manufacurer (Cooper Lighting) they told me that there driver (ballast) is made to work of any supplied voltage from 120 to 277 volts.. He was right the job has been done for 1 month now and it looks great....

Yeah our lights will run on the 208 volts, but my concern is if the supply voltage is 208 and the run is at least 1000ft one way we are going to have a voltage drop of close to 11%, we do not have any way to split up poles to have more than one circuit at this point and it would probably cost more than the delta/wye tranny and panel. My issue is mainly a code issue if we just swap over to 208 and we have such a large voltage drop we are violating the NEC's 3-5% of Voltage Drop.

I guess my quandry is the supply is 208V at the furthest distance it would be in the range of 180V after the drop the drivers should still work fine but then you end up with other issues like now the amp draw at each fixture is a bit higher as the voltage drops and then you end up overloading the circuit. I suppose we could install a 30A 2pole breaker but with out looking into it I am not sure if that will cause us to be in any grey area or violate the NEC.

Thanks for your input....

 

[Volta]

Well the NEC doesn't really prohibit voltage drop (with a few exceptions), what we are usually thinking of is just a Fine Print Note.

If the equipment is rated for that range of voltages, rather than having multiple taps, it is likely to not just work, but comply with 110.3(B) too.

As far as the 2-pole 30 amp, at 17 amps continuous you are over a 20 amp circuit already. I assume that the conductors are already at least #10, so the 30 amp is ok. That has no effect on voltage drop, however.

 

[hillbilly1]

Why not just set a 208 volt to 277 SINGLE phase transformer, No need to go to the expense of a panel and three phase transformer.

 

[guschash]

Is there any way a step-up transformer would work? Mybe you can step it up close to 277. You should be able to step it up to 236v

gus

 

[hillbilly1]

Is there any way a step-up transformer would work? Mybe you can step it up close to 277. You should be able to step it up to 236v

gus

I have a 7.5 kva single phase transformer stepping up 240 single phase to 277 single phase for my shop lights (new)old magnetic 0 degree ballast fixtures, eventually going to upgrade to T-8 electronics and get rid of the transformer. It's been working for 20 years now. Real easy to do.

 

[kwired]

Why not just set a 208 volt to 277 SINGLE phase transformer, No need to go to the expense of a panel and three phase transformer.

Looks like best option to me, you only need a transformer large enough for the load served, which from the posts sounds like less than 20 amps @ 277 volts. If only serving a single two wire circuit the primary overcurrent device (which is needed anyway) can protect the secondary if sized according to primary to secondary voltage ratio.

Buck/boost transformer would likely work if you were stepping up from 240 and would not need to be a full load sized unit, but to attempt to do this with 208 volts will not quite get what you need with standard 12,16,24,32,48 volt models.

 

[Hv&Lv]

IMHO, you don't really have a problem. The drivers input voltages are listed at 90V-305V. As long as the voltage doesn't drop below 90 Volts, all is well.

 

[kwired]

IMHO, you don't really have a problem. The drivers input voltages are listed at 90V-305V. As long as the voltage doesn't drop below 90 Volts, all is well.

The driver may accept the lower voltage but is going to compensate by drawing more current which could be another problem.

 

[Hv&Lv]

The driver may accept the lower voltage but is going to compensate by drawing more current which could be another problem.

If the circuit is that close, then the discussion is useless. Has the incoming voltage been checked? Is it 208? I realize what 220.2 says, but the incoming voltage could actually be as high as 217V. This could get the VD down to around 7-9%, while the increase in current draw could be negligable. I am curious as to the calculations. are they calculated per 220.4(B)? Aren't devices amperages listed using their utilization voltages of 115,200,230, and 460?

 

[Volta]

If the circuit is that close, then the discussion is useless. Has the incoming voltage been checked? Is it 208? I realize what 220.2 says, but the incoming voltage could actually be as high as 217V. This could get the VD down to around 7-9%, while the increase in current draw could be negligable. I am curious as to the calculations. are they calculated per 220.4(B)? Aren't devices amperages listed using their utilization voltages of 115,200,230, and 460?

In the OP it says that the voltages run high, 230 or so.

 

[Hv&Lv]

In the OP it says that the voltages run high, 230 or so.

I had assumed that was an incorrect assumption as it is way above the 10%bandwidth for 208V. Service voltage is supposed to be between 197 &218.

 

[Volta]

I had assumed that was an incorrect assumption as it is way above the 10%bandwidth for 208V. Service voltage is supposed to be between 197 &218.

Yup, but it could be. I've seen it.

 

[tom baker]

There is one issue to be aware of when changing from HPS with a mogul base to a LED luminaire. NEC 210.23(B) and (C) allows non residential lighting to be supplied by 30-40 or 50 amp branch circuits. But LED Luminares don't have mogul (or heavy duty) lamp holders. One option is to change the BC protection to 15 of 20 amperes, or provide supplementary OC protection at each luminaire pole

 

[kwired]

There is one issue to be aware of when changing from HPS with a mogul base to a LED luminaire. NEC 210.23(B) and (C) allows non residential lighting to be supplied by 30-40 or 50 amp branch circuits. But LED Luminares don't have mogul (or heavy duty) lamp holders. One option is to change the BC protection to 15 of 20 amperes, or provide supplementary OC protection at each luminaire pole

What kind of lampholders does the LED's have? Not saying you are wrong but I don't think the current wording actually considers some evolving lighting methods. If supplying a luminaire that does not contain a 'lampholder' I would say it can not be on more than a 20 amp circuit as it is now worded, yet some equivelant retrofit into a mogul base lampholder could possibly be installed up to a 50 amp circuit.

 

[wireguy8169]

Well the NEC doesn't really prohibit voltage drop (with a few exceptions), what we are usually thinking of is just a Fine Print Note.

If the equipment is rated for that range of voltages, rather than having multiple taps, it is likely to not just work, but comply with 110.3(B) too.

As far as the 2-pole 30 amp, at 17 amps continuous you are over a 20 amp circuit already. I assume that the conductors are already at least #10, so the 30 amp is ok. That has no effect on voltage drop, however.

Yes, the conductors are #10 thanks for the reply....

 

[wireguy8169]

I had assumed that was an incorrect assumption as it is way above the 10%bandwidth for 208V. Service voltage is supposed to be between 197 &218.

Yeah at times we seem to have very high voltage readings, on some 277V readings I have had as high as 300V

 

[wireguy8169]

There is one issue to be aware of when changing from HPS with a mogul base to a LED luminaire. NEC 210.23(B) and (C) allows non residential lighting to be supplied by 30-40 or 50 amp branch circuits. But LED Luminares don't have mogul (or heavy duty) lamp holders. One option is to change the BC protection to 15 of 20 amperes, or provide supplementary OC protection at each luminaire pole

We are replacing the complete head unit on the pole light not just the guts so we should be good with the 30A but again that really does not affect the issue with voltage drop, I just hate to see us put in 10-13 $900 dollar retro fits and have them burn up in a a year or other issues. Its not my call as I am a lowly maintenance person :dunce: but occasionally I am listened to....

 

[Volta]

But Tom does have a good point, the 30 amp circuit is only allowed if the "lighting unit" has a "heavy-duty lampholder".

I think that is usually interpreted as "mogul", though it does not seem to be defined that way. Had to imagine that an LED module socket is "heavy-duty" though.