Originally posted by @Mark Forest:
Originally posted by @Nicholas DeLouisa Jr:
Where did the voltage drop? Where were you measuring that you saw the drop?
I tested several outlets on that circuit when the lights were plugged into their respective outlets. This measurement occurs throughout the garage.
In residential AC circuits, things are wired in what's called parallel. In this wiring method, the voltage remains the same from place to place. Every outlet and light fixture will get 120 volts (for single pole circuits), and turning off a light or unplugging a device won't effect any other light or outlet (unless specifically designed to do so). In series circuits, the voltage is split among the different items along the circuit, and whenever you turn off one item, or unplug a device, power will be lost to everything on that circuit. That's why we use parallel circuits.
But in this situation, you are describing something that sounds like a series circuit. When you have one or both of the halogens on, the voltage in other parts of the circuit is dropping. That is characteristic of a series circuit, which indicates a wiring issue, not a bulb issue. In parallel circuits, it doesn't matter what you plug into an outlet or how much current it draws, if wired correctly it will never effect the voltage of anything else on the circuit (of course there are exceptions, but those aren't present here).
As someone else said (and I'm on my phone so I can't check right now to give them credit), this sounds like a return wire issue (what is commonly, but mistakenly, referred to as the neutral). What can happen is, if a circuit "neutral" is loose under its lug in the panel (main or sub), it can come into contact with another loose "neutral" and they could create a new path for the current. So instead of current coming out of the breaker, going through the circuit, and then going back to the transformer on the utility pole, the current will go from one breaker, through the circuit, then backwards through another circuit (the one whose loose "neutral" was touching the first loose "neutral"), and into a second breaker, then finally back to the utility pole. This would create a 240 volt circuit. If this is the case in your situation, it would certainly explain why the bulbs were burning so brightly. They could be getting twice their normal voltage.
But for the above to be the case, the outlets on the walls would have to be on a different circuit breaker than the outlets in the ceiling. Turn on the halogens, then find the breaker that controls that circuit and turn it off. (You may want to mark this breaker in some way for future use.) Now test for voltage in the wall outlets. Now turn the halogen breaker back on and try the other breakers to see if any of the others will also turn off that circuit. If you find two breakers that control that circuit, you have confirmed the loose "neutral" theory.
However, even if that test doesn't pan out, that doesn't mean you have ruled out a loose "neutral" issue. Working in a panel can be a bit dangerous for people who don't know exactly what they're doing, but if you so chose, you could go into the subpanel and lift the "neutral" for the halogen circuit off the neutral bus bar. Then check the voltage in the wall outlets. While you are in there, make sure that all of the lugs in the "neutral" bus are tight, and are clamped down on copper and not on the insulation of any wires. Sometimes an electrician might put the wire too far under the lug and when they tighten it, the screw clamps down on insulation instead of copper. If this happens to two "neutral" wires in the same space, you can get that series circuit I mentioned above. So make sure you can see copper on both sides of every lug. By the way, you can mitigate you exposure to danger in this subpanel by turning off the power to the sub in the main panel.
I'd like to hear some results of those tests, and the hair dryer test that was mentioned before. Maybe we can figure this thing out.
But whatever you do, please be careful. Electricity is unforgiving. The consequences of mistakes happen at the speed of light. It's not like screwing up a plumbing job and getting leaks.
Also, I apologize for the haphazard way this post is organized. I'm on my phone and it's hard to edit.
Good luck.