Phantom Voltage?

[starsandstripes]

Can someone explain why I could read 115V at the base of a HPS light pole; but when I disconnect the HPS fixture and directly connect a 100w incandescent lamp it would not light? I used a digital and analog meter and they both read 115v. I checked the lamp in another location and it lights. I eventually found a receptacle with a burned up neutral feeding the pole and that got the pole working but I can't explain the voltage reading unable to light the lamp. The pole is fed with 100 ft #10 uf at least 20 yrs old.

 

[Minuteman]

Stars, was the 115V read from Hot to ground. Hot to neutral, or Hot to the pole, or all the above? Or was it from ground to the pole?

I'm going out on limb here, but I think the directly connected a 100w incandescent lamp would not light because of voltage drop. Your meters have a small load compared to the lamp.

 

[TomChamp]

Can someone explain why I could read 115V at the base of a HPS light pole; but when I disconnect the HPS fixture and directly connect a 100w incandescent lamp it would not light? I used a digital and analog meter and they both read 115v. I checked the lamp in another location and it lights. I eventually found a receptacle with a burned up neutral feeding the pole and that got the pole working but I can't explain the voltage reading unable to light the lamp. The pole is fed with 100 ft #10 uf at least 20 yrs old.

You say the "burned up neutral" fixed it right? Because of the burned up neutral the system could not handle a load on it. In other words the connection was not good enough to allow current to flow. The meters unlike the light do not put a load on the system. The power was there, but the bad neutral was not allowing current to flow. BTW it is not uncommon troubleshooting to rig up a load source like a light bulb to see if the curcuit can handle a load.

 

[starsandstripes]

I was reading 115v h to n, and hot to g. I replaced the receptacle and got the pole working. The heavier load idea makes sense. I have seen this in the past but there was no problem involved. I could read proper voltage at a halogen lamp shell for an auditorium but no light with good lamp. Is anyone familiar with computer controlled auditoium lighting?