TV Flickers when I flip a switch

[Saltybitterman]

My 55" Samsung LED TV is plugged into an outlet wired with 12/2 wire, in a 14/2 circuit and a surge protector. When I turn on the circuit to ignite the vented gas fireplace, and during lightning storms, the TV flickers. Can the dissimilar wire be causing a voltage drop?

 

[Ralston18]

Is it a 20 amp circuit or a 15 amp circuit? 12/2 wiring for 20 amps, 14/2 for 15 amps as I understand the codes. Look at the breaker.

It is not so much the voltage drop that matters as the potential to overload the circuit and cause a fire.

12/2 in a 15 amp circuit is one thing. 14/2 in a 20 amp circuit is another. You can find the NEC codes online....

What is the total load on the circuit?

If the wiring cannot handle the total load before the breaker trips then things may be getting dangerous.

Not uncommon to have lights, etc. flicker when an additional load is applied. Or to have storms cause the same.

However, the best thing to do is to have an electrician check things out. You never know what a previous home owner or some contractor may have done. Or perhaps there is some corrosion, worn insulation, or some other problem developing.

Therefore I strongly suggest that you get the circuit checked out by a professional!

 

[Saltybitterman]

It is a 15 amp circuit, but I don't know the total load.
Most of the circuit is 14/2, with only about 2 ft of 12/2 that I installed myself.
I had to move the outlet up about 18 inches to hide it behind the TV, but there was not enough slack in the wire to move it, so I put a junction box behind the center channel speaker and ran a pigtail up to the new location.
We are the first owners, so the only other people to touch the wiring was the builder's electrician.

 

[Ralston18]

Okay - thanks.

I would not expect that 2 feet of pigtailed 12/2 wiring would cause the flickering problem.

That said:

First, I would check the wiring to the extended ("18 inches") circuit again. And especially all of the connections, screws, wire nuts, etc. from the junction box to the new location. All tight and with good contact.

It appears that you would be and are able to check the various outlets and switches in the entire circuit. Make sure they all have clean tight connections. (Disclaimer: If you are not comfortable with working through and checking the entire circuit then an electrician should be brought in.)

Next, I would turn off the appropriate breaker and find everything that does not work. There could be some unexpected loads on the circuit via hidden junction boxes branching off somewhere to serve other areas. Code prohibits doing so (i.e., junction boxes not being visible) but it still happens. I trust you just put a blank plate over the original outlet box vs drywalling it in......

Then look at the power consumption for each load and then total up the load. Just ensure that there is no overload or near overload. Is there a fan on the vented gas fireplace than comes on at ignition? Could draw some initial startup current.

Tedious but you could also start adding loads back one by one to see when the flickering starts...

And try things without the surge protector. Maybe it has some problem.... Unplug the TV first to see if anything else flickers when starting the gas fireplace. TV may be more sensitive than anything else to any current drops. Or use an appropriate size (wattage) lamp/light bulb to simulate the TV's load - see if that load flickers. With and without the surge protector.

 

[Saltybitterman]

Okay - thanks.

I would not expect that 2 feet of pigtailed 12/2 wiring would cause the flickering problem.

That said:

First, I would check the wiring to the extended ("18 inches") circuit again. And especially all of the connections, screws, wire nuts, etc. from the junction box to the new location. All tight and with good contact.

It appears that you would be and are able to check the various outlets and switches in the entire circuit. Make sure they all have clean tight connections. (Disclaimer: If you are not comfortable with working through and checking the entire circuit then an electrician should be brought in.)

Next, I would turn off the appropriate breaker and find everything that does not work. There could be some unexpected loads on the circuit via hidden junction boxes branching off somewhere to serve other areas. Code prohibits doing so (i.e., junction boxes not being visible) but it still happens. I trust you just put a blank plate over the original outlet box vs drywalling it in......

Then look at the power consumption for each load and then total up the load. Just ensure that there is no overload or near overload. Is there a fan on the vented gas fireplace than comes on at ignition? Could draw some initial startup current.

Tedious but you could also start adding loads back one by one to see when the flickering starts...

And try things without the surge protector. Maybe it has some problem.... Unplug the TV first to see if anything else flickers when starting the gas fireplace. TV may be more sensitive than anything else to any current drops. Or use an appropriate size (wattage) lamp/light bulb to simulate the TV's load - see if that load flickers. With and without the surge protector.

 

[Saltybitterman]

Good stuff. I did not drywall the junction box in, I have seen enough of Mike Holmes to know better.
Your solution will take some time, but I will check it out. I have read about surge protectors with EMI filters. I don't know much about those, but I may check them out too.
Any idea why it happens for lightning strikes too?

 

[Ralston18]

I view flickers as being one of two ways: 1)A drop in voltage/current due to a suddenly applied load. 2) An increase in voltage/current due to some added source of electricity - i.e., a lightning strike.

Direct hits can destroy circuits and devices. More distant strikes can cause all sorts of current flows through any conductive paths available. Saw a strike come in via a telephone line once, threw a spark over a king size bed and across the room. Blackened the telephone jack.

As for EMI filters they are mostly to screen out unwanted frequencies that can can/could interfere with devices on the circuit. Probably more useful for high end audio devices etc. For the most part I am skeptical of the effectiveness of most such things - more marketing hype than substance. Especially for the lower end surge protectors sold by big box stores.

Some folks just tie a simple, loose overhand knot in power cables. Others purchase iron rings, baluns, etc, to clamp on the power cables.

As I understand it, the most effective way is to have a completely separate ciruit set up and wired/protected to be "clean" at the start of the circuit. Usually such circuits are designated with orange outlets in commericial settings. They can be installed in private residences as well provided they meet the codes. Becoming more popular because so many people have had devices destroyed due to power line and power circuit problems.

Black & Decker publish an excellent book - The Complete Guide to Home Wiring. You can also download the NEC Code Book for more information.

Black Box also has a very comprehensive set of tutorials via the Resources tab on their home page (www.blackbox.com). Also just reading some of the online user manuals can be very informative and helpful.

 

[westom]

Your solution will take some time, but I will check it out. I have read about surge protectors with EMI filters. I don't know much about those, but I may check them out too.
Any idea why it happens for lightning strikes too?

If any voltage change is causing that flcker, then incandescent bulbs are also dimming to 50% intensity. Dimming would be obvious. Voltage changes approaching 100 volts are completely irrelevant to noise that is less than 1 volt.

For some reason, noise is probably getting into signal wires. Is it an antenna or cable box? Long before anyone can provide a useful reply, first define every wire / connection on every incoming cable.

Digital signals can be interrupted by less than a volt noise causing flickering or other screen interruption. Every device and cable from that TV to all signal sources (including others such as DVR) must be defined to say anything useful.

If incandescent bulbs do not dim, then AC power is sufficient. Filters inside a protector are typically too tiny to do anything useful - exist for other reasons.