Overlooking the Obvious: Taking my own PQ advice

Published On
Jun 15, 2022

My February column was about looking for the obvious when troubleshooting power quality problems. At one of this week’s jobs, I should have followed my own advice. This job was one of those mentioned in that article: it began with a Sunday phone call, during which the resident was panicking about defective kitchen lights burning the house down. It turned out to be just burned-out light bulbs. This house has had several other electrical challenges, including an arc that fused the mounting screw to the ceiling fan plate when attempting to replace the ceiling fan in a bedroom, even though the switch was in the off position.

A doorbell problem and solution

The customer’s complaint this time was about their video doorbell. The new device was installed about three years ago and only worked for a month before it began to malfunction due to low battery voltage. That problem was traced to the old doorbell transformer, which didn’t put out enough voltage to reliably charge the unit’s internal battery. These new devices typically require 18–24V AC. The old transformer barely put out 12V.

The wires between the transformer and the old doorbell were shedding insulation, so a new power source for the video doorbell was provided. There was an external 120V receptacle near the doorbell location. The 120V:18V step-down doorbell transformer enclosed in a weatherproof plastic box terminating in a weatherproof plug was assembled and the plug went into the covered receptacle. The 18V AC supply wires ran up to the doorbell.

The problem, again

All was fine for three years until the customer complained that a similar problem occurred, with the doorbell showing low battery and intermittent operation. Figuring that the battery was still good, and not wanting to undo that tiny screw in the bottom of the unit to get to it, the first course of action was to open the transformer box to see if something was wrong.

No water, no spiders and no 18V out. Finding no 120V in, the next step in the chain was the external receptacle. No voltage was there, so the receptacle was removed, which led to no voltage under the wire nuts. The cable went out of the box and into the earth, leading to the uneasy thought that it may be a critter problem.

Going into the garage to check the breakers, I found the overhead in the light was not functioning. Though the wires didn’t seem to lead anywhere that would connect to the outside receptacle, a check of the breakers found none tripped or hinting of a partial trip. There also was no GFCI breaker in the panel, nor was the external receptacle a GFCI type.

An obvious solution

After I ran a temporary extension cord from the garage to the external transformer to restore the video doorbell’s operation, I informed the customer that this problem was becoming more than just a quick fix. I explained the options, including getting an electrician to run a new 120V circuit to the external box with the proper electrical and weather protection. That also could have involved moving the 18V transformer to a non-weather location and running the low voltage up to the doorbell.

Just before I dialed the electrician, the homeowner asked about the switch. What switch? I had tried all of them by the front door. She directed me to the switch in the middle of the house near the basement stairs. The switch was used to control an external light post until it failed and was subsequently removed from the top of the conduit hidden in the bushes.

A flip of that switch restored the voltage to the external receptacle. The next 15 minutes was spent restoring everything back to the state it was in when I arrived. The customer then asked if I could reprogram the video doorbell’s Wi-Fi and all their phones to work with a new wireless router. Already a bit frustrated for overlooking the obvious and not wanting to add more, I gracefully declined, indicating that I needed to get to another pressing matter (lunch).

By the way, the nonfunctioning overhead light in the garage that I initially thought was a clue to the zero voltage outside the house turned out to be another burned-out light bulb.

About the Author

Richard P. Bingham

Power Quality Columnist

Richard P. Bingham, a contributing editor for power quality, can be reached at 732.248.4393.

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