The Shoemaker’s Children…

….go barefoot. An old proverb that speaks to those with particular skills and aptitude often taking care of their own stuff last. And usually the case with me!

I had a couple of basement outlets / lights go intermittent, I tracked it down to a particular outlet, and so far as a bad neutral (because the voltage tester was chirping on a “dead” outlet.

This noontime, I pulled a shelf away from the wall, pulled the outlet, and heard the familiar (and unsettling) crackle-crackle of arcing as a nearby light on the circuit blinked.

The sparky-monkey who wired the basement (no doubt the former owner) used those stupid / dangerous outlet holes to make connections (called “back-stabbing”) One neutral connection was high resistance, getting warm, and thankfully broke connection before anything caught fire.

I cut out the outlet, replaced with properly screwed down and wrapped around the terminal connections, and all better.

Best of all, since the circuit in question also powered my desktop computer, I got to listen to my UPS chirp while I made the swap (NASCAR-like) and returned the circuit to service with 12 minutes to spare (my UPS is oversized for the load, so lots of battery time).

How to Annoy Your Friendly Neighborhood Electrical Engineer

Problem Statement: A power assist chair (that we purchased for my mother back in 2016 and no longer need, looking to sell used) had an intermittent – the up/down LED lamps would go out, and the chair would not operate, until one jiggled the power cord.

Annoyance #1: Called the manufacturer to get a replacement cord (I had troubleshot it down the cord itself). Turns out the cord is hard-wired into the motor, so the solution is to replace the motor. (bad answer, the motor itself is fine). Why is a simple power cord that will invariably get a bit of wear and tear not be easily replaceable?

Annoyance #2: Yes, it’s under warranty, but it requires both a service call (to replace the motor) and shipping charges. Um, no.

Annoyance #3: Additionally troubleshot the cable and discovered the intermittent was in a little inline molded box containing an LED, the sole purpose of which (as far as I can see) is as a redundant and unnecessary troubleshooting tool – since both the chair control pendant and the transformer also have LEDs to indicate power on.

Solution: Cut the molded box LED out, strip and splice the cable (nicely soldered and insulated), it’s a wee bit kludgy with electrical tape, but perfectly safe and solid). Took about 15 minutes including time to heat up the soldering iron and then test the crap out of it afterwards.

Ultracomfort America – not impressed.

The Grid: The Fraying Wires Between Americans and Our Energy Future

Heard yesterday on Fresh Air: Aging And Unstable, The Nation’s Electrical Grid Is ‘The Weakest Link’

In her new book, The Grid, Gretchen Bakke argues that the under-funded power grid is incapable of taking the U.S. into a new energy future. She explains the challenges to Fresh Air‘s Dave Davies.

Just ordered a copy online; was a great interview and sounds like a wonderful book, dealing with the realities of balancing nearly unlimited, yet inconsistent renewable power sources (solar, wind, etc.) with the reality of consumer and commercial demand.

I confess to being a little curmudgeonly about issues of power usage, renewable energy sources, attempts to encourage consumer energy savings, etc. and this book gets to the heart of a lot of that. Really looking forward to this read!

Losing the Neutral Conductor

This one came across my social media timeline this morning (edited a bit):

I came home on Friday, an hour before we had a birthday party planned. There was a cable company guy who came over and asked if I was the home owner. He did not explain the problem very clearly and became very frustrating but in short, he saved our house from burning down.

He shut down the Internet and told us to shut down the electricity. Apparently the neutralizing wire that runs under ground was not working causing brown outs and power shortages. The smell of electrical fire was heavy in the house.

We managed to have a great party despite the problems. The output caused a shortage in the hot tub and pool. We have no refrigeration or dishwasher along with a few other things that burned out. Last night, we found a power strip that had really burned out with burn marks on the floor. As he moved it, the same electric burn smell filled the room.

Through it all God spared us big. We are still without a refrigerator but at least the stove works.

What happened was that this home lost the neutral conductor from the utility to the service entrance. Without that neutral, there’s no return path except for the safety ground, which is often substandard or high impedance (~25 ohms). The result: Phase-Phase voltages (such as used for an electric stove, water heater, or electric dryer) are fine, but Phase-Neutral voltages can be anywhere from 0 VAC to 240 VAC.

So yes, things blow up, burn, etc. and often in a bad way (high current but not a dead short, so not enough to trip breakers). The “power strip with burn marks on the floor” is typical as internal surge suppressors / MOVs overheat, not because of short term transients, but because of prolonged, sustained AC overvoltage.

Oftentimes this sort of situation has some warning signs: lights dimming or brightening as appliances switch on and off, light bulbs failing prematurely. One online board reports:

When i turned the oven on, the fan went back to normal, the lights normal.  The 240v load
apparently balanced the system.

Sadly, a lot of electricians and utility workers are not that well versed in this sort of issue. From the same message board:

So i get on the horn with the power company.  They come out, and basically look at what i’m experiencing and the first thing the guy does is pull the meter.  Then he measures the voltages on the incoming legs.  All is equal.  Then he tells me the problem must be on the inside.  Puts the meter back in and the imbalance returns.  “yep , he says, problem is on your side”.


No Current? No Problem!

We recently looked at Fluke 1750 data from an ultrasound site. As is often the case with these 120 VAC, 1 Phase monitoring, it’s voltage only (due to the need to use a break-out cable to monitor current on a manufactured power cord; even if they are made up and sent with the monitoring equipment, they tend to disappear from the power analyzer kits over time.

A lack of current data can be a real handicap when analyzing data, but we go back a few years, to the days before current monitoring was ubiquitous. Here’s a few things we were able to determine, even without current data.

Ultrasound OutageFirst, an outage was captured, identified by the service engineer as “hospital power went out”. We’re not so sure; the rapid loss of voltage, with no significant decay, points to a local event (not facility wide), and the neutral-ground voltage swell and phase voltage collapse points to a high current event. Our best guess – equipment fault caused an overload and a subsequent breaker trip.

Ultrasound TransientsNext some voltage transients, captured a few times during monitoring, on both phase-neutral and neutral-ground. Without current data, it’s hard to make much of a guess regarding the source of these. But zooming out a bit provides additional evidence.

Ultrasound Switch-onRMS voltage logs show some small drops in voltage immediately after the transient – typical of a load switch-on (neutral-ground data, not shown, also supports this). We’re sure the transients are associated with load switch-on; probably switch bounce of a circuit breaker, relay, or contactor.

Power analysis without current data. Kicking it old school…..