Take care of electric BEFORE you insulate with cellular foam…

Regardless of what type of weatherization or home energy conservation improvements you do, filling cavities with some type of insulation will typically be a part of any treatment plan for older homes built before 1970 — the same cavities used by existing and, especially, new wiring for electrical receptacles and lights. So, it is important to take care of electric BEFORE you insulate with cellular foam… Read more on coordinating electrical wiring with thermal insulation of the building envelope

Miswired bathroom fan, light, heater needs 14/4+Gnd (not 14/3)

DANGER! White used for switched-phase, bare used for current-carrying grounded conductor!

I encountered this thoroughly miswired switch location while attempting a ‘simple’ faulty GFCI receptacle replacement. The 20A GFCI circuit served the GFCI as well as a 3-in-one fan/light/heat control for the bathroom overhead fixture. Unfortunately, the 14/3 plus ground (black, red, white, and bare) cabling for the fixture was too small (#14 conductors rated for 15A, not 20A) and included only two phase (hot) conductors, whereas the three switched loads integrated into the fixture require three hot conductors.

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Troubleshooting AFCI breaker tripping

INTRODUCTION

AFCI breakers are so sensitive that I often hear of electrician complaints that they may be giving false alarms. However, I have installed more than 100 of them and only ever encountered one – maybe – that may have been tripping improperly. I’m not sure I could report as good a record for standard breakers, whose failure rate I’ve not monitored as closely (they cost 1/5 as much, for one thing).

Recently, I had the new experience of inadvertently using an AFCI breaker as a fake-grounded receptacle tester. Initially, I was chagrined to have to extend my work to troubleshooting a ‘perfectly functional’ circuit, but it turns out this was a dangerous circuit and the AFCI ‘fake-ground detector’ is a good tool to keep in the proverbial chest, and one more reason to use these breakers as much as possible, even on existing circuits, in spite of their expense. Goto more on troubleshooting AFCI circuit breakers…

Consequences of over-lamping

Few lampholder sockets, except for outdoor fixtures or three-position floor lamps, are rated to accommodate the all-too-common 100W incandescent light bulb (lamp).

This photo shows what happens over time, if you use 100W incandescent lamps in the wrong fixtures (most of which are rated 60W or 75W maximum). Incandescent lamps are being replaced by CFL’s and LED’s because 90% of the energy they consume is invisible heat radiation. The heat destroys lamp holder screw-shell sockets and the wires leading to them.

In the photo, the insulation around the screw-shell has become brittle from baking by the 100W lamp. The screw-shell itself makes electrical contact via rivets at the base, which is cheap aluminum and has also baked its way loose of the rivets. The result is a familiar problem in old houses with old fixtures: a slowly-worsening problem of lamp flicker and intermittent lamp failure. The intermittent, poor contact at the loose rivets can generate heat from arcing at the connection, and could ignite wires and start a fire. Read more >>

Cable track lighting systems are elegant, only good for 300 Watts

12V LED lamps save an overloaded track lighting system

I recently encountered a fine mechanical installation of a cable track low voltage lighting system that was electrically overloaded. The cable track cable is good for 300W. That’s six (6) 50W lamps. Many installations will benefit from new high-efficiency LED lamps that provide similar light levels with improved optics at only 10W each. So if you have 40 linear feet of cable track zig-zagging over a public gathering area, you easily position 3 or even 6 lamps per 10′ section, whereas with 50W halogen lamps, each 10′ section would get only one or two lamps every 10′ section.

More on overload for low voltage lighting systems >>

Who needs ground wires? Modern cables don’t mean proper wiring

I recently extended an existing circuit that looked great on initial inspection, but turned out to consist of multiple basement junctions where the equipment grounding conductor in the modern type NM cable had been cut short and left hanging un-terminated.

In a lightning storm, the magnetic fields induced by nearby high-voltage lightning strikes will induce current in anything metal in the home, including wires. When grounding conductors are bonded properly to provide a low-impedance path to ground at the service equipment, they can help to quickly drain away transient voltage surge before it can find an unintentional path to ground that may cause damage. Similarly, the same low-impedance ground fault path ensures that short-circuit current through circuit breakers will be maximized, helping them to trip quickly and protect equipment, buildings, and people. 

More lazy ground wire twist photos and notes >>

Twisting wires does not bond them

Most common with equipment grounding wires, twist-only wire termination or splicing can result in dangerous problems, because the connections can and do fail. Failure in a grounding wire will likely be in the mode of ‘lightning surge damage throughout the home was considerably worse due to poor, twist-only connections, but would have been bad either way’ or ‘grandma died of a heart attack when the ground path didn’t allow sufficient current to flow to trip the circuit breaker and open a fault from the ungrounded (‘hot’) conductor to the exposed metal housing of the washing machine’.

Faults due to improper twist-only wire terminations in the actual circuit conductors may be even more dangerous — especially if a similarly slack approach was taken with the grounding wires.

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Learning to live with old wiring in Philadelphia homes

Much of Philadelphia’s housing stock is more than 100 years old. Whether it’s a tiny row-house, a trinity, a grand victorian twin or a free-standing home from before the Civil War, houses built before World War II will tend to have some frail circuits in them that may need special attention — or replacement.

Why does my space heater/vacuum cleaner keep tripping its breaker?

Why do lights in my bedroom go out when I turn on the vacuum on the first floor?

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Troubleshooting dusk-til-dawn flood lights

Dusk-til-dawn flood lights may have any of a variety of configurations and features that could be involved in a failure. The simplest involve a fixture with photo sensor that interrupts (switches) power to the floodlight lamp holders when daylight is present. Other ‘enhancements’ such as outdoor motion sensing flood lights and dual brightness level settings may come at the cost of increased susceptibility to weather, mechanical and electronic failures (usually due to temperature extremes or else voltage surges from nearby lightning strikes, damaging circuitry inside the sensor assembly). Where possible, consider use of an astronomically-self-calibrating timer (see Intermatic), rather than sensor-based controls for outdoor lights. If photo-sensing, and especially motion-sensing, are critical or cheaper due to the wiring configuration of your fixture(s), then consider a whole-house surge suppressor to protect their sensitive electronic components along with those of consumer electronics and newer appliances inside the home.

A timer may be the culprit if your outdoor lights don’t seem to operate correctly in Spring or Fall: daylight savings time, your own pattern of being outdoors vs. indoors, and changing daylight hours could individually or cumulatively amount to the timer being out of sync with your lighting needs. The most common timer for exterior lighting is a 9″ x 5″ mechanical clock with set-screw timing points that trip a mechanical switch on and off. The Intermatic T101R has been a go-to classic for decades, but may be effectively replaced today by the astronomically auto-adjusting digital version for location in utility areas, or a more elegant wall switch timer that you can locate for convenient manual override to turn your floodlights on/off when the timer would otherwise prevail.

Read on to understand photo sensor dusk-to-dawn failure modes

Daylighting is supposed to be interior sunlight, not exterior lighting

As I travel Philadelphia neighborhoods, I see a lot of exterior lighting turned on in the middle of the day. Regardless of the immediate cause, we can and should do better.

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Repairing outdoor outlets and wiring methods

Botched DIY electrical installations are common enough indoors; outdoors, the ways weekend installers can go wrong multiply, as do the number and frequency of fatal consequences. People tend to underestimate the forces of nature, which include driving rain, ice damming, freeze-and-thaw cycles, relentless UV radiation, temperature extremes, corrosion, and more. Outdoor/exterior installations also may be accessible to strangers, unattended children, and strangers’ unattended children, exposing the building owner to lawsuits if something does go wrong. Finally, people outdoors are more at risk to electric shock and electrocution because they are on the earth, in the earth, or likely to be touching earthed objects (grounded).

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Faulty receptacle grounding

Grounded receptacles require proper wiring methods and proper implementation of those methods, including compression wire nuts that chemically bond wires to each other, rather than wires just twisted together.

Electrical continuity for power wiring in buildings requires bonding conductors wherever continuity relies on more than one piece of conductor (wire). Bonding involves a chemical bond between separate pieces of conductor that will carry current.

Improper bonding of equipment grounding conductors in a receptacle wire box.

In this photo, the installer has used a common shortcut that may provide adequate grounding immediately upon completion of the job, but which will degrade over time, due to oxidation of the outer surface of the copper equipment grounding conductors. For copper EGC’s, oxidation only occurs on the outer surface of the copper. By creating a proper bond at the time of installation, oxidation cannot penetrate and interrupt the bond over time. More on properly bonding receptacle ground wires in a daisy-chained wiring topography >>

Why do rodents chew wires?

I have found that chewed cables tend to be the ones that were not properly strapped along solid supports. It’s widely reported that rodent’s teeth never stop growing, and therefore require constant grinding to keep them from growing long enough to ‘hamper the hamster’. But why do they chew wires that could kill them?

I recall a recently published article suggesting that rodents chew because evolution selected for ‘neurotic’ traits that helped ensure the rodents have no difficulty with the will to keep their teeth properly ground down to size. Perhaps for parallel reasons of natural selection for reproduction, many of us don’t have sex to make babies (necessarily): we obsess about it and we enjoy it. It seems likely that rodents don’t chew to grind their teeth. They may enjoy chewing, it may be a neurotic itch or symptom, and it may be both. Whatever may be in the rodent’s brain, the result is that their teeth stay short enough that they can function.

On any given length of chewed wires, the most heavily-chewed portions are always the ones hanging in mid air — right at mouth height for everyone’s favorite furry rodent. Picture a neurotic character, your rodent, pacing up and down the length of a dark, dusty attic on a cold, windy night. Which cable are they going to get involved with? The one they trip over, over and over again, or the one their distracted consciousness probably doesn’t even register, because it’s neatly strapped to the building’s structural members?

In new construction, the National Electrical Code (NEC) requires that all cables be fastened snugly along solid supports where possible. In retrofit wiring, cables fished behind finished surfaces cannot be secured, so older homes will tend to have wiring that is more vulnerable to rodent chew. More on how neat wire runs prevent rodent chewing damage >>

AFCI’s, cost, and fire-safety

An excellent video on YouTube details the function, costs, and fire-prevention advantages of Arc Fault Circuit Interrupters (AFCI’s). These advanced electronic devices monitor current fluctuations on both conductors of the 120V AC circuit (standard breakers provide only a simple current limit, and only on one conductor). In addition to the standard feature of absolute and time-dependent limits on current in the circuit, AFCI circuit breakers also ‘look’ for patterns of instantaneous spikes in current characteristic of intermittent arcing faults.

More on the most useful applications for AFCI breakers to improve old house wiring safety >>

Polarity matters in AC wiring

AC polarity isn’t right, just because ‘it works’

Polarity in AC circuits doesn’t matter; until it does.

A common mistake of amateurs (and some experienced but untrained installers) is to assume that because house AC wiring is ‘alternating current’ moving alternately in two directions, the polarity of the circuit conductors has no significance. Most loads will in fact operate when wired backward (or connected to reversed-polarity receptacles), and the ‘it works’ test often is as far as some installers go in their understanding of proper installation.

Read on to learn the safety concerns with reversed polarity in AC wiring