I have 15 pole lights that are 240 volt,and wish to drop them down to 120 volt to use regular energy saving 120 volt bulbs... my problem is this... I only have 2 wires running to each light socket,with a ground wire attached to a steel rod driven into the ground,and when I cut one wire loose I lose about 5 lights and a 480 light post... also,all the pole lights are not on the same circuit,so how do I convert to 120 volt,without affecting the 480 light and without losing the other lights

1 hot wire needs to be identified as a neutral, connect to neutral bar, also identify all junctions and light pole with white tape for the new neutral. Connect the hot to a single pole 20 amp breaker if #12 or larger.

If you have 240 volt poles, where is the 480 volt coming from? That needs a separate pair of wires.

Changing a circuit from 240 volts to 120 volt should be easy. Change out a 2 pole breaker with a single pole, and change one live wire to a neutral, Done.

Why going to 120 volt? This will increase voltage drop.

And the 480 volt going out when you cut one leg of a 240 volt, hmmmm, something is not right, or your mistaken.

I would like to know what is the existing pole lighting source is. Before you consider going to " regular energy saving" lamp, you should consider what the light output is of the existing pole lights, and will the new lamp meet or exceed this light output.

How far are the poles out from the building? The reason for 240v is more lights on a circuit and to lessen voltage drop.
Are the lights HID? Such as metal halide or HPS?

This sounds like a commercial setting, and from the sound of your questions you do not seem like an electrician. Are you sure you should be working on this stuff??

I was hoping he meant the Light Post was a model 480?

Stanforty and TK make good points on the Voltage Drop.
If you are talking about "regular energy saving 120 volt flourescent bulbs" you shoud be OK.

Wolfie250,

If these pole lights are at your home they are already 120v, you could check this by

Removing a lamp and looking at the info on it. Unless this is a 'custom' install you have

Two 120vac circuits (240vac) feeding the 15 poles.

If this is at your work place and in fact are 240v fixtures, you will not be able to simply

Change voltage and install new lamps.

IMO, you need to get someone with a little more experince to check this out for you.