I was at my parents’ house today and their lights were dimming all over the house, randomly, for a split second at a time.
Nothing new was going on electrically at the house lately. The tree’s been up and lit for about 3 weeks now - same tree and lights as the last 5 years. No outdoor Christmas lights, no new appliances.
We think that when we were standing in the kitchen getting ready for the Christmas party the lights dimmed in response to the oven regulating it’s temperature. I had thought maybe it was the furnace coming on that triggered it, but that wasn’t the case.
It happened all throughout the evening, even when the oven was off. We didn’t have time to make note of every occurrence and what might have been happening to trigger the dim every time (someone turning on a bathroom light, the exterior flood turning on, the garage light being turned on, etc) but it kept happening.
My dad’s going to call the electric company Tuesday to see if they’ll come out and take a look - but in the meantime can anyone explain what this might be?
For the record the house was built in 1968 and it does have some shady wiring (hasn’t been a problem in the 30 years they’ve lived there.) They did get new wiring in part of the house they had an extension added (1991) and new wiring when the kitchen was remodeled about 8 years ago, and the track lighting in another room has new wiring but the rest of the house is original.
A very large load on the same transformer.
The well pump does that in my household. When it first turns on, due to it’s being a large motor, an inductive load sucks up current for a second. Once the motor is running, the lights return to normal.
It could be a sign of something going south in the wiring, but not necessarily.
To some degree, any heavy load switching on and off is going to cause the lights to dim. This could be your oven, a well pump (like carnivorousplant mentioned), the refridgerator, electric heat pump, anything that draws a decent amount of current. Lights, even powerful floodlights, usually don’t draw enough current to make a difference. If you can make the rest of the lights dim by turning on your bathroom light, then call an electrician ASAP!!! (and don’t take a bath until it’s fixed!)
In most areas, you and a couple of your neighbors will all be fed from the same transformer, so it could be a device in your neighbor’s house that is causing your lights to dim. Don’t worry, your electric meter only measures the power that you are using, so if the lights dim because someone else is loading down the circuit, you aren’t charged for the loss in energy.
The electric company also switches things on and off the lines every now and then. They do this so that they can keep the voltage level up to where it should be and so that they can make things more efficient (google watts, vars, and power factor correction if you want the gory details).
Because of all of that, a certain amount of dimming is normal. However, excessive dimming could be an indication of a potentially dangerous wiring fault. Just because it hasn’t been a problem in 30 years doesn’t mean there’s not a problem. I had a wiring fault show up in my house a few years ago, and my house was built in 1960. It’s the minor faults that don’t blow the breaker right away that tend to make your house burn down.
You probably don’t have a problem, but it’s not a bad idea to have someone come out and inspect everything. Make sure that whoever is inspecting the wiring checks for a degraded ground, in addition to looking for other typical wiring faults.
One thing that can cause lights to dim is a floating ground. Most houses are fed by two 110-volt lines in phase with each other, with a ground line. Each 110-volt outlet is connected to the ground and one of the “hot” lines, while 220-volt outlets are connected to the two hot lines. If the ground line has a high resistance it can cause an outlet that’s supposed to be at 110 volts to lose voltage if a load is placed on the same circuit. At the same time, the voltage for outlets connected to the other 110-volt source will increase.
This happened to me years ago - there was a high resistance in the ground line to my house. Every time there was a heavy load some of the lights in my house would dim while others would brighten. It was most obvious when I ran the microwave oven at less than full power - this would cause the oven to pulse power on and off, and I could watch as the two sides of the house would go alternately bright and dim.