Mtn-Lover-58
Member
- Location
- Canada
- Occupation
- Retired Electrical Technician
Having an electrical problem I hope someone can help with.
We built a new garage/shop last summer, with a fairly straightforward electrical system. 100A. Power supply is fed underground #1/0 ACWU 120/240V. Main Panel is Siemens 100A.
I will mention this shop was fully permitted with multiple inspections and built to the latest edition of the CEC.
There are five receptacle circuits. Each circuit has 3-20A. plugs, fed with #12CU NMD, off a 20A. breaker.
Shop contains 6 lights, these lights are the screw in type LED 100W lights, details here.
https://www.amazon.ca/gp/product/B08DK57WMG/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1
Yes, these are unfortunately cheap china made lights, and they are simply screwed into a standard lampholder.
The lights are on their own circuit, no receptacles on this circuit. The lighting circuit is a 15A Breaker, feeding #14Cu NMD90 going thru the attic space directly to triple gang box by the door with three switches.
Switch #1 on the box controls 3 of the above mentioned LED lights. Switch #2 controls the other 3 LED lights. Switch #3 controls the exterior over the door light. Other than original testing we never use the outdoor light.
Now on to the problem
For the first 4 months - no issues.
Then a couple months ago something weird happened. Working in the shop, All 6 lights go dim for a few seconds, then get bright again, this repeats several times sometimes dim for a few seconds, sometimes longer maybe 30 seconds. I grab my Multimeter, check the voltage in a plug. What? 170 Volts or so Line to Neutral. Wow this is strange. When the lights get bright, Voltage goes back to the normal 120 Volts. When they're dim, 170 or so. Shut the light switches off, the voltage in the plug is normal.
I'm obviously a bit worried. Shut off the shop main breaker, hustle across the property to the main electrical building where the power supply is. Check the voltage there. Everything is good here and no dimming of the lights in this building.
Go back to the new shop, turn on the main breaker, check for the problem again, but it's now gone, can't get it to replicate. Check the voltages - all good. Lights are normal brightness with no issues. At this point I'm not sure if this problem was localized to our new shop or if it affected all of our buildings.
I call the service provider, and ask them if they have any records of problems at the time. Customer service advises they have no records of any outages, but admits at their level they would not have any record of voltage anomalies were they to exist. I check with a couple neighbors, they didn't notice anything but since I failed to note the time very well they weren't sure if maybe they were outside at the time or not.
My next thought is maybe I have an open neutral, or something wired wrong in the lighting circuit. I get my ladder and fully open up each lighting box. As mentioned, this is a very simple install, nothing complicated here to mess up. All the wires are securely fastened, no visible damage, no open neutrals. Reassemble and reinstall the lights. Take the covers off my receptacles and switches, have a good look, no problems evident. Use a receptacle checker in every receptacle, they're all good and wired correct.
Problem disappears for 2 months - hmmmm interesting.
Then yesterday the problem reappears, very similar to the first time but it lasted a bit longer so I was able to do more troubleshooting.
So obviously I'm concerned, and at this point I can only think of two potential sources for my problem.
We built a new garage/shop last summer, with a fairly straightforward electrical system. 100A. Power supply is fed underground #1/0 ACWU 120/240V. Main Panel is Siemens 100A.
I will mention this shop was fully permitted with multiple inspections and built to the latest edition of the CEC.
There are five receptacle circuits. Each circuit has 3-20A. plugs, fed with #12CU NMD, off a 20A. breaker.
Shop contains 6 lights, these lights are the screw in type LED 100W lights, details here.
https://www.amazon.ca/gp/product/B08DK57WMG/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1
Yes, these are unfortunately cheap china made lights, and they are simply screwed into a standard lampholder.
The lights are on their own circuit, no receptacles on this circuit. The lighting circuit is a 15A Breaker, feeding #14Cu NMD90 going thru the attic space directly to triple gang box by the door with three switches.
Switch #1 on the box controls 3 of the above mentioned LED lights. Switch #2 controls the other 3 LED lights. Switch #3 controls the exterior over the door light. Other than original testing we never use the outdoor light.
Now on to the problem
For the first 4 months - no issues.
Then a couple months ago something weird happened. Working in the shop, All 6 lights go dim for a few seconds, then get bright again, this repeats several times sometimes dim for a few seconds, sometimes longer maybe 30 seconds. I grab my Multimeter, check the voltage in a plug. What? 170 Volts or so Line to Neutral. Wow this is strange. When the lights get bright, Voltage goes back to the normal 120 Volts. When they're dim, 170 or so. Shut the light switches off, the voltage in the plug is normal.
I'm obviously a bit worried. Shut off the shop main breaker, hustle across the property to the main electrical building where the power supply is. Check the voltage there. Everything is good here and no dimming of the lights in this building.
Go back to the new shop, turn on the main breaker, check for the problem again, but it's now gone, can't get it to replicate. Check the voltages - all good. Lights are normal brightness with no issues. At this point I'm not sure if this problem was localized to our new shop or if it affected all of our buildings.
I call the service provider, and ask them if they have any records of problems at the time. Customer service advises they have no records of any outages, but admits at their level they would not have any record of voltage anomalies were they to exist. I check with a couple neighbors, they didn't notice anything but since I failed to note the time very well they weren't sure if maybe they were outside at the time or not.
My next thought is maybe I have an open neutral, or something wired wrong in the lighting circuit. I get my ladder and fully open up each lighting box. As mentioned, this is a very simple install, nothing complicated here to mess up. All the wires are securely fastened, no visible damage, no open neutrals. Reassemble and reinstall the lights. Take the covers off my receptacles and switches, have a good look, no problems evident. Use a receptacle checker in every receptacle, they're all good and wired correct.
Problem disappears for 2 months - hmmmm interesting.
Then yesterday the problem reappears, very similar to the first time but it lasted a bit longer so I was able to do more troubleshooting.
- When the lights dim, a Multimeter in a plug on one circuit was showing approx. 170 Volts L-N. A second Multimeter in a plug on a different circuit would show approx. 68 Volts
- The problem would appear whether switch 1, or switch 2, or both, were on.
- If both light switches were off, voltage readings on both Multimeters would revert to normal 120V
- If switch 2 was on but not switch 1, the meter reading 170 would flip to about 68, and the one reading 68 would flip to about 170
- The lights would alternate between normal and dim. Corresponding changes with the Multimeter readings would change at the exact same time.
- Operating the garage door seemed to aggravate the problem making them flicker a lot more.
- Unplugging the garage door opener and running it on battery also caused the problem, so maybe vibration related.
- Banging my fist on the wall, causing a bit of vibration, also seemed to aggravate the problem.
So obviously I'm concerned, and at this point I can only think of two potential sources for my problem.
- At some point when installing the exterior siding, or interior drywall, a screw or nail missed the stud and hit one of the lighting cables causing an intermittent problem that is not severe enough to trip the breaker. If this is the case then I believe the damage would have to have happened between the panel and the triple gang box. If it happened after the triple gang box, then the problem could be isolated to one bank of the lights or other. Does my logic make sense? Additionally, I will never say never, but the walls are 2x6 walls and the cables were carefully in the middle of the wall. I tried to be careful about where the screws were put in and the screws were only 1-1/4" long. However I did have a lot of help on the construction, so maybe someone else on the crew put a screw in the wrong spot.
- The cheap LED lights from China are the source of my problem and I should throw the lights away and buy something better. My inclination at this time is to lean towards this as the root cause, but for the life of me I can't explain how it would cause the weird voltage readings I am seeing.
