Hopefully someone has an explanation that was not visible to me.
I had two light fixtures in a bathroom one a bank of four lights on the wall above the lavatory and a ceiling mounted above the lavatory. There were two standard switches that controlled both fixtures. In the on position of the right switch the bulbs burned as if the power was 120 volts on both fixtures, but when the left switch was turned to the on position both fixtures dimmed as if a dimmer switch was being activated. No dimmer switch is visible. I left this scratching my head and will turn it over to the electricans.
Without actually checking, this can lead to only guessing…
Was the house really big, and the lights big? Yes and Yes might suggest a voltage drop.
However, I’ve heard of where people did some crazy things and switched wires and manage to wire wire loads in series. Meaning that the neutral (“grounded conductor”) was the feed to anther set of lights.
Why the two switches, who knows, but the toggle dimmers were quite common for a while. Was there a vent/fan? Could they have replaced a fan/light combo with just a light fixture and combined the wires? The second switch could have been for the fan portion with the light operated by the first switch. A quandary for sure.
Others will chime in I am sure…this sounds weird because that switch that controls the ceiling lights should not DIM with the other light being switched. What I find hard to believe ( in the theory that is ) is that if voltage drop caused this…that a single light bulb would do this simply by turning it on.
I would venture to say inside that double gang box…they are doing something they are no supposed to be doing…but I wish I could say that for sure…I am the kinda electrician who has to get in their and get my hands dirty…every now and then guess could get me into trouble and as Stephen said…you just NEVER know what the home owner will do to get what they want…
If the BOTH dimmed…yet one switch contols each light I would write it up for evaluation…should not take an electrician on site long to see what could be going on…I mean you never know…they could have only (1) cable coming down…could be using the EGC for conductor in the manner it is not supposed to be…in the end…you did the right thing in refering it as anything that seems strange to you…should be checked out.
Others will chime in I am sure…this sounds weird because that switch that controls the ceiling lights should not DIM with the other light being switched. What I find hard to believe ( in the theory that is ) is that if voltage drop caused this…that a single light bulb would do this simply by turning it on.
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Paul; The one switch actually activates 5 bulbs four on one fixture and one in the second fixture. I did not really think a voltage drop but it did enter my thought process. Being and old HVAC mech I am the kind of person that needs hands on to understand and in this business that is not always possible as you well know.
Its out of my hands now anyway but I would still like to know what the He!! was going on.
There could be a 240 volt circuit present with two or three 120 volt bulbs in series on each. One switch is on a hot lead, the other on the neutral. When the neutral switch is off, the current has to go through all 5 bulbs in series, dimming them. Scary!