Browsing articles in "Electric 101 Blog"

Units of measure for electricity and energy (V, A, Ohm)

Mar 31, 2015   //   by Robert Monk   //   Electric 101 Blog  //  No Comments

The most important units for consumers to know about are:

  • Watts (W) measure the power flowing. Also known as work-per-time: 100 Watts will do a certain amount of work per second, such as generating heat, lighting a bulb filament, or turning a motor against internal and connected load / resistance.
  • Volts (V) measure the electromotive force of attraction for electrons at two points in an electrical system. All else being equal, the more volts you have the more potential for delivery of power (flowing electrons)(see watts). Also, higher volts are usually more dangerous and require more insulation and other measures to prevent accidental discharge or short-circuiting. When volts are high, there is more force of attraction impelling electrons to move. Sometimes you don’t want them to move. Insulation ratings in home wiring tend to be 600V, while the nominal voltage of a home electrical system is only 240V.
  • Amperes or ‘Amps’ or ‘current’ (A) measure a number of electrons moving through a point in an electrical circuit per second. All else being equal, more amps will result in more power. In fact, Volts x Amps = Watts (power). Breakers and fuses limit current to within the rating of the wiring system connected to them, so wire or switches rated to 15A will be protected by a breaker or fuse that trips/blows when current exceeds 15A for some time. If the overcurrent condition is extreme, the amount of time to trip/blow is small (miliseconds), while if the overcurrent is marginal, it could take hours to trip/blow a breaker or fuse.
  • Ohms or ‘Resistance’ affects voltage in different parts of the circuit. Volts, Amps and Ohms are related by the formula I = V/R, so that in a given electrical system, applying a higher-voltage supply line will result in more current, whereas inserting more series resistance into the system will result in less current. Inserting resistance into circuits reduces the amount of power that will flow through the circuit. Accidental resistance due to terminal failure may reduce current (and power) in the circuit, preventing breakers from tripping, while the terminal failure will typically heat up, presenting a possible fire hazard. Resistive (partially-conducting) short-circuits will create a parallel resistive path to the normal circuit path, such that the overall resistance to current flow is actually diminished. This may or may not cause enough extra current to flow to trip a breaker. Again, a resistive short-circuit could heat up and start a fire.

CSST flexible yellow gas pipe requires careful electrical bonding

Jul 16, 2014   //   by Robert Monk   //   Electric 101 Blog  //  No Comments

CSST (corrugated stainless steel tubing) flexible gas pipe with an outer yellow plastic protective coating has been involved in several explosions during the past 10 years, as builders use it increasingly for its flexibility and cost-competitiveness. The incidents have been attributed to voltage surge during lightning storms where nearby strikes can induce voltage across all metal systems in a building, and high voltage in the CSST pipe may arc through the thin corrugated wall, causing a gas leak and or igniting gas at the leak.

The following video shows how to reduce this risk by ensuring that if rigid gas pipe becomes energized with high voltage, there is a solid path to ground that circumvents the CSST pipe sections as much as possible, rather than allowing the CSST pipe sections to become a potential path.
Robert Monk Electric can do this work for you, for as little as $100 and usually for under $350. Contact us to schedule an appointment.


Light switch mysteries solved!

Oct 27, 2013   //   by Robert Monk   //   Electric 101 Blog, Trouble & Repairs blog  //  No Comments

Got a mystery switch? This can be a good thing, presenting an opportunity to add control of stair/hallway lighting from both ends of the hall or stairwell, or the ability to switch a receptacle outlet (or bypass a switch to eliminate mystery outages at the outlet).

A properly wired 3way or multi-way switch coordinates with other switches to control a light fixture or lighting zone (group of fixtures or recessed lights), or any other switched load.

In Philadelphia shotgun row houses, first floor 3way switches are often mis-wired to have no function (on the first floor) and only compromised function on a remote stair landing or other location closest to the lighting fixture. Using only the proper switch component and an understanding of multi-way switch wiring systems, we can often restore the original, coordinated multi-location switching configuration to control 2nd floor lighting (or other locations remote from your mystery switch) so that you can turn it on (or off before leaving the house) without climbing stairs or traversing rooms in darkness.

How can I tell if my switch is a coordinating type switch (part of a multi-way switch system)?

Simple single-location, standard ‘toggle’ style light switches have ‘on’ and ‘off’ embossed at the visible fulcrum of the lever, whereas switches designed to participate in a multi-way switching system may be ‘on’ or ‘off’ in either position, depending on the position of other switches in the system. Therefore, 3way and 4way switches have no ‘on’ or ‘off’ designation. So if your mystery switch is of the latter sort, you may have a miswired multi-way switching system. If your switch does have on/off embossing, it may be properly wired to control a lighting fixture or plug-in receptacle load (for floor lamps) from only one location, OR, it could be that an unskilled installer updated switch and receptacle devices in the home but ignored, lost track of, or abandoned a coordinating switch wiring system, turning a very useful switch location into a cloying mystery.

Multi-way switch systems often suffer from a mis-wired location that disables the other switches when that bad switch is thrown to the up or down position. 90% of the time, the original wiring is good but someone installed a wrong switch or installed the right switch incorrectly. Occasionally, the wiring system itself is deficient and the only fix is new cable runs between switch locations and/or the switched light fixture.

Can I use twin breakers in my breaker panel?

Feb 24, 2013   //   by Robert Monk   //   Electric 101 Blog  //  No Comments

Twin, or ‘two-for-one’, breakers allow the connection of two, separately-protected circuits in the space of one standard breaker. Two circuit overcurrent protective devices (COPDs) connect to a single leg of the phase bus bar in the breaker panel, effectively doubling the capacity of the breaker panel in terms of number of branch circuits connected. The total power capacity of the panel does not change with the addition of twin type breakers (and is largely unaffected by what breakers may be installed — a common misconception that can lead to the wrong conclusion that a panel is overloaded simply because the Ampere rating of all breakers adds to more than the main breaker Ampere rating).

How do I tell whether my breaker panel accepts twin breakers?

Most breaker panels are rated to accept at least a few twin breakers. Some accept twins throughout the panel, and some accept no twins at all. The diagram inside the panel cover should indicate which breaker positions accommodate twin breakers (see photos).

See also:

Advantages of LED lamps and high-efficiency lamps

Jan 27, 2013   //   by Robert Monk   //   Electric 101 Blog, Smart Energy Blog  //  3 Comments

It’s not just about energy savings: CFL’s, LED’s and other SSL types offer aesthetic, labor-saving, and special-application advantages

Kitchen renovation with crown molding and semi-recessed lights

Semi-recessed LED downlights ring the perimeter above cabinets, along with crown molding

Compact fluorescent,  and LED and other high-efficiency lamps in the emerging field of Solid State Lighting (SSL) promise dramatic advantages in energy use and control convenience in homes, businesses and industry. Although high-efficiency has been the primary focus in promotion of these lamps, all the new technologies also claim significantly longer lamp life, as well as a variety of other advantages not widely reported.

Read on about CFL and SSL advantages relating to lamp life, power factor, and reduced fading from UV

How to recess a switch box or receptacle box in plaster-and-lath walls

May 21, 2012   //   by Robert Monk   //   Electric 101 Blog, Field Reports Blog  //  No Comments

The book Wiring Simplified has an excellent print guide with illustrations, for how to install beveled wallcases into plaster-and-lath walls. Since I install receptacles outlets and switches in old walls at least once per week in West Philly (Philadelphia, PA), I figured I might as well make my own guide using photos. Here’s my guide on how to recess a switch box or receptacle box in plaster-and-lath walls


What is a receptacle?

Feb 5, 2012   //   by Robert Monk   //   Electric 101 Blog  //  1 Comment

Also referred to colloquially as “outlet” or “power outlet”, an electrical power receptacle is a female connector for portable electrical loads such as lamps, power tools, small appliances — anything moveable, which could be anything from a night-light (with no cord) to an industrial kiln via cord-and-plug connection.

What is an outlet (power outlet)?

In professional electrical terms, an outlet is any accessible point in a wiring system. This can be for the purpose of connecting loads (as for receptacles and lighting fixtures) or simply for safe installation and maintenance of wires (junction boxes and condulette bodies used to make splices or to pull wires in conduit/raceway around sharp angles).

Residential Receptacle Types

15 Amp-rated grounding duplex receptacles

Selecting recessed lighting housings, trim, LED options

Aug 9, 2011   //   by Robert Monk   //   Customer Resource Blog, Electric 101 Blog  //  5 Comments

First: What is recessed lighting?

Recessed lighting dates to the 1930’s, but appears most commonly in houses built or renovated after 1980. Like track lighting, it came in as a kind of construction fashion trend: the lighting method and different styles have their place, but can be over-used as a symbol of modernity or designerliness, where cheaper and time-tested lighting types can get the job done better.

A damp location recessed fixture lamped with new LED technology will not need a lamp change for up to 50,000 hours of lamp on-time.

To me, recess lighting at its worst screams: “Dallas“(TV show) or “cocaine”(a la Miami Vice) — in short, excesses of the ’80’s. Before choosing recess lights, consider a few gateway questions:

  1. Do you want them to solve a particular lighting design problem, or because they’re fashionable or your neighbor just got them?
    Recessed lighting can offer the advantages of direct light to specific areas from lamps with high-quality optics, reduced glare, and minimalist styling that eliminates business from a ceiling. However, lighting has existed long enough that it is an architectural feature in itself, and well-chosen surface-mount lighting fixtures — including track — can contribute to a room’s aesthetic just as well as they may sometimes detract.
  2. In retrofit installations (aka: ‘old work’ — renovations), you may have less choice about locating your recessed light housings than you might imagine. The finished look may be a magical disc that floats in the ceiling with no attachment business, but structural joists concealed by plaster/drywall may run dead-center to the location you want, and will in any case make layout and wiring of recessed lights time-consuming and/or messy. If you are installing more than a single recessed light without taking down the whole finished ceiling first, then be prepared to compromise on your ideal location.
  3. The housings inside (above) the finished ceiling surface can invite drafts. Insulation Compatible (IC) housings may be nearly air-tight, but even these will increase air-flow between finished and un-finished spaces in your house, reducing the energy efficiency of your home.
  4. Make sure you have a high-quality, flat surface on your ceiling (drywall level 4 or better), or else be prepared for gaps to show between trim edge and ceiling, where the trim sits across an uneven section of ceiling. Plaster ceilings typical of older homes will make a good trim fit difficult, as well as complicate any installation other than complete removal and re-installation of the ceiling. Recess lights look great in those drywall level 5-happy houses typified as the drug-lord mansion in Miami Vice. Read more >>

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 (aka ‘electronic eye’) 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, 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

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 >>

Frayed service cable / power quality

Frayed service cable / power quality


What type of electric service cable damage are you looking out for?

If you can see exposed aluminum strands on your service entrance cable, it has frayed to the point where you should replace it. Cost may vary from $750 – $2200, depending on your service capacity (usually between 100A – 200A for residential electric accounts) and the capacity of your replacement service (for those wanting central air conditioning, an upgrade from 100A to 150A or 200A will often be needed; subsequent solar PV or micro wind power installations over 5kW capacity may be cheaper to install if the existing service is larger than 100A).

More on causes and effects of worn electric service entrance cable >>

Fuse cabinet as distribution panel

Apr 22, 2011   //   by Robert Monk   //   Electric 101 Blog, Field Reports Blog, Trouble & Repairs blog  //  No Comments

Fuse cabinet as distribution panel

Many homes in West Philadelphia feature a distribution panel remote from the main service equipment. In older installations, this may be a wooden cabinet with a picture-framed wooden or glass-pane door, usually located in a stair- or hallway, and lined with a felt-like friable material that may be asbestos.

Several fuse-holder modules provide for branch circuit over-current protection. Unlike with modern wiring, the fuses may protect both the grounded (neutral) and ungrounded (‘hot’) conductors of 120V circuits, so a single circuit may have two fuses in it.


These fuse cabinets may not meet the demands of modern electrical usage

More on working with, or replacing old fuse cabinet type distribution panels >>


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