Pole Lights

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PEL11

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Particulars

240 volts
175 watt M137
.89 amps x 2 There are 2 lights per pole

I have 4 light poles. They are 125' from each other, so from the first pole to the last one is 375'
From the 1st pole to the panel it is 240', so from the panel to the last pole it is 617'.
The poles are 20' tall and have not been included in the measurement.

How would I go about calculating the voltage drop and wire size for this installation?

Thanks in advance!
 
PEL11 said:
Particulars

240 volts
175 watt M137
.89 amps x 2 There are 2 lights per pole

I have 4 light poles. They are 125' from each other, so from the first pole to the last one is 375'
From the 1st pole to the panel it is 240', so from the panel to the last pole it is 617'.
The poles are 20' tall and have not been included in the measurement.

How would I go about calculating the voltage drop and wire size for this installation?

Thanks in advance!
Click to expand...
Point to point, 4 times. You are dropping some load at each point so you have a different calculation for each segment of the circuit. You possibly even find you can reduce conductor size at some point simply because of less load further out you go, keeping in mind you still may have a minimum branch circuit size required though.
 
kwired said:
Point to point, 4 times. You are dropping some load at each point so you have a different calculation for each segment of the circuit. You possibly even find you can reduce conductor size at some point simply because of less load further out you go, keeping in mind you still may have a minimum branch circuit size required though.
Click to expand...

Thanks kwired. I guess I am going to go ahead and pull #6 to the pole bases and #12 inside the poles.

I was hoping there was a formula to calculate this installation.
 
PEL11 said:
Thanks kwired. I guess I am going to go ahead and pull #6 to the pole bases and #12 inside the poles.

I was hoping there was a formula to calculate this installation.
Click to expand...


I figured you would only have about 3% voltage drop at the first pole if you ran 12 AWG for the first run, I might get the bid if everything else is equal, unless I misunderstood what you have. I had eight .89 amp @ 240 volts luminaires being supplied by the first 240 foot run.

After that point we will lose the load of at least the first two luminaires, maybe more if we branched in more then one run from that point so VD would be less on next segment but need to run new calculation at 3% less voltage and new load to know exactly what is at the end of the next segment, which may possibly make me up the first run to 10 AWG.

Of course one needs to have a target VD they want to achieve for this to mean much as well.
 
kwired said:
I figured you would only have about 3% voltage drop at the first pole if you ran 12 AWG for the first run, I might get the bid if everything else is equal, unless I misunderstood what you have. I had eight .89 amp @ 240 volts luminaires being supplied by the first 240 foot run.

After that point we will lose the load of at least the first two luminaires, maybe more if we branched in more then one run from that point so VD would be less on next segment but need to run new calculation at 3% less voltage and new load to know exactly what is at the end of the next segment, which may possibly make me up the first run to 10 AWG.

Of course one needs to have a target VD they want to achieve for this to mean much as well.
Click to expand...

kwired - What you are saying is correct. From the panel to the first pole - 240' and they are in a straight line. Pole 1 to Pole 2; Pole 2 to Pole 3; Pole 3 to Pole 4 and a 125' between each pole. Just trying to find the right size wire because there are 14 of these poles and the one that I described is the longest run.
 
PEL11 said:
kwired - What you are saying is correct. From the panel to the first pole - 240' and they are in a straight line. Pole 1 to Pole 2; Pole 2 to Pole 3; Pole 3 to Pole 4 and a 125' between each pole. Just trying to find the right size wire because there are 14 of these poles and the one that I described is the longest run.
Click to expand...
four poles or fourteen?:huh:
 
kwired said:
four poles or fourteen?:huh:
Click to expand...

kwired - There is a total of 14 poles. But the 4 I asked about are the farthest ones from the panel and than there is another run of 4, a run of 3 and another run of 3, for a total of 14. I thought if I could get the information for the first 4 than I could use it to figure the next 3 runs.
 
PEL11 said:
kwired - There is a total of 14 poles. But the 4 I asked about are the farthest ones from the panel and than there is another run of 4, a run of 3 and another run of 3, for a total of 14. I thought if I could get the information for the first 4 than I could use it to figure the next 3 runs.
Click to expand...
That is where I got confused, if only 4 on a run the others don't matter when it comes to voltage drop on a particular run.

What you need to remember is your first segment of the run is pulling all the current for all loads on the run. Calculate the VD for that run based on total current, size of conductor, length of the run.
Then deduct the amount of drop from source voltage, subtract amount of load dropped off at the first pole and start over with remaining current, length, etc. to the second pole, subtract your drop for that run from voltage you had at first pole.

If a significant enough of load is dropped off at a pole or depending on length of subsequent runs will determine how severe drop of a particular segment may be and what change of conductor size is necessary for compensation. If your first run were relatively short, you may not need to increase conductor size for the first segment, but may need to for second segment if it is long.

On top of all that you need to determine what kind of voltage drop is acceptable for the load supplied - NEC only gives recommendations not requirements for general purposes. You may find specific requirements for some chapter 5-7 applications but in general there is no requirement.
 
kwired - Thank you for your help.

Phil - Sorry. More work than time lately, but I have not seen anything. I will PM you again with my email address.
 
PEL11 said:
Particulars

240 volts
175 watt M137
.89 amps x 2 There are 2 lights per pole

I have 4 light poles. They are 125' from each other, so from the first pole to the last one is 375'
From the 1st pole to the panel it is 240', so from the panel to the last pole it is 617'.
The poles are 20' tall and have not been included in the measurement.

How would I go about calculating the voltage drop and wire size for this installation?

Thanks in advance!
Click to expand...

I don't know if you figured this out or not. But attached is a quick calc. that I did. let me know if this helps.
 

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