It’s that chilly, blown fuse and tripped breaker time of year again.
Based on my experience as an electrician serving residential customers, electric space heaters cause more electrical trouble tickets in Philadelphia than any other single connected appliance or event. With the cold weather comes the seasonal task of explaining to homeowners and tenants that they simply should not be using their space heaters — at least not unless their entire house has been rewired top to bottom, or until they have their breaker distribution panel mapped and make up a plan to balance loads with extreme care. The difficulty is that knob-and-tube circuits remain in any older (pre-WWII) home that hasn’t been rewired, and that these circuits tend to serve a dozen locations — much too much to be able to handle the additional load (overload) of a space heater.
The risk of fire from a circuit overloaded by a space-heater is like the risk of cancer from smoking: you may have done it for decades without obvious damage, but cancer/fire could strike any day. You need to find a way to pay for a better solution than putting everything you own and everyone you love at risk just to stay warm.
If your house lacks dedicated circuits appropriate for space heaters, then it may be worthwhile to just keep the central heating system’s thermostat dialed comfortably and/or invest in weatherization to avoid the risk of catastrophic circuit failure and fire, and convenience issues such as 90% of the lighting in the house being unsafe to use after a near-fire on the shared circuit where you plugged in a heater. Space heaters largely just shift heating costs from gas or oil to electric, rather than save money, anyway.
But I need to use my space heater, because…
Make that space-heater work
If you still need to use a space heater, there are ways to reduce risks from space heaters on older circuits — and you may be able to find or install a new circuit that can operate your space heater with no worries. Many older homes have a mix of old and new wiring, and the most common new receptacles were installed near bedroom windows to power window type air conditioners; these dedicated (single-location) circuits are perfect for space heaters, too.
Minimizing other loads sharing the circuit, avoiding extension cords and using proper cords when necessary, replacing receptacles whose contact spring-tension has become loose, and carefully managing the heaters’ controls can all improve your odds of avoiding a tripped breaker or house fire.
- Balance your loads. Map your home’s electrical system, and plug your high-power appliance into a lightly-loaded circuit (and then avoid adding other loads to that circuit, whether they be one-time (a corded tool) or semi-permanent (a floor lamp or entertainment system).
- Get connected. Don’t use an extension cord unless you have to. The most legitimate use of an extension cord for a space heater would be to place it beside your desk or reading chair, and extend its cord within the same room to reach a dedicated or lightly-loaded receptacle not otherwise within reach of the manufacturer’s cord. When using an extension cord, use one rated for 15A or better (not the smaller household type cord). Use the shortest cord available, that will reach. Go out and buy one that is the right size (15A or greater rating) and within 3′ of the right length. Use a 9′ cord for a 9′ job and a 6′ cord for a 6′ job. Never daisy-chain cords together, especially for something like an unattended, high-power appliance like a space heater: buy a cord that is long enough. The contacts at each coupling are a weak link in the chain of contacts in the circuit, and a frequent point of ignition in house fires — so much so that much of the National Electric Code (NEC) for residences amounts to rules that prevent you from ever needing extension cords in newly-built homes and compliant renovations.
- Keep snug. Check the spring-tension of contacts in any receptacle you will be using. If the cord-end doesn’t sit snugly in the receptacle, have the receptacle replaced with a new one (or replace the extension cord or multi-outlet strip with the loose socket). Loose contacts may result in open connections and result in arcing across tiny gaps between the receptacle and the prongs of the cord-end plug. An arcing contact gap may operate the heater, but it scorches the contacts, further degrading the connection, and heats the metal parts more than they would heat if connected firmly. This type of loose, arcing connection causes many fires each year, a problem for which AFCI breakers are a solution.
- Stay in control. Most plug-in electric space heaters feature a thermostat and a power setting. Many people never take time to consider how best to use either setting. They turn everything up full blast and then turn it all off 10 minutes later when their shins start to get scalded by the excessive heat.
You may be able to achieve a comfortable temperature without resorting to the highest power setting of the heater — it’ll just take a bit more time. The power setting of a heating appliance is related to time. Power = work per time. How many degrees will the appliance change the room temperature (work) in a given amount of time? More power (work/time) faster temperature change per time — but has no direct connection to the final/equilibrium temperature. Some heaters indicate right on the control, the wattage associated with each setting. A common control configuration is a 500W switch and a 940W switch. Individually, they do what they say: 500W or 940W of heating. Together, they draw the full 1440W for which the heater is rated (the entire capacity of a typical 15A residential circuit that shares several receptacle and lighting locations throughout the house. 500W is ‘low’; 900W is ‘medium’; and both together, 1440W, is ‘high’. Plan your heating. Turn on the heater on low or medium before you need the heat, and then use high only if you still need it when you settle down to use the room. If you know your circuit is overloaded by setting your heater to the ‘high’ setting, remember that ‘overloaded’ means ‘enough of a risk of fire that a respected national fire-prevention association studied more than 100 years of fire statistics and determined you should never do this.’ It’s not that you will start a fire. It’s that the small chance of starting one is unacceptable. Compare to cigarette-smoking and cancer. It’s a risk thing, involving a small chance of a big catastrophe.
- The thermostat actually works. You can turn on the heat ahead of time, and the thermostat will turn it off automatically when the room temperature reaches its target. Many thermostats on space heaters lack a degree scale, but you should be able to hear the thermostat click in and out as you adjust it with the heater on. Set the thermostat ‘too hot’ and leave it there just until the heater brings the temperature to ‘just right’. Then dial the thermostat slowly back down until you hear it click (off). It is now set for your comfort temperature.
Sometimes, even these precautions won’t mitigate circuit overload sufficiently. It doesn’t matter that a space heater ‘always worked in the past’. It doesn’t matter that ‘nothing else is turned on, on that floor’. Knob-and-tube wiring, especially, tends to serve multiple floors (there is no reason for any type of circuit wiring to be confined to one floor), and knob-and-tube wiring is very old. Overloading it for decades could work out fine, but eventually the years of excessive heat from overload can cause it to fail. Alternatively, a system normally capable of handling a slight overload might have another marginal failure (such as spring tension wearing out on an old receptacle, resulting in a poor contact to the inserted cord plug-end), such that the combination of two or more factors, though unlikely, eventually does occur, after decades of good fortune, and a receptacle or appliance cord catches fire (or a breaker trips that never tripped before).
Upgrade your electric, if necessary
If you can’t be sure that your receptacle (and the circuit serving it) has capacity for your plug-in electric space heater’s high or medium setting, then don’t use it. Have a new circuit installed, and stop worrying.
- Learning to live with multi-generational wiring in Philadelphia homes
- Philadelphia Top Injury Lawyer: Space heaters create fire risk in Philadelphia
- Philadelphia Fire Department: Fall (heating season) safety tips
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- Annapolis Home Inspection, LLC Aluminum branch circuits, homes 1965-1972
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- Electric Monk TV (YouTube) Video channel for PhillyLicensedElectrician.com Robert Monk
- EnergyConservation HowTo A tinkerer genius discusses energy conservation and his ladder system for accessing the attic (where a lot of energy-saving work happens).
- PennFuture Energy Center Energy and energy efficiency news for the Commonwealth of Pennsylvania
- Phila area rife with building efficiency upgrade opportunities Philadelphia Inquirer article discusses recent study showing Philadelphia’s inner-ring suburbs stand to save from energy conservation retrofits.
- Philadelphia Row-house Manual A design, maintenance, and modifications manual for our most widely-used form of housing.
- Robert Monk Robert Monk’s personal blog
- SolarCities (DOE) Solar PV Levelized Cost Interactive Comparator Simple graph compares ‘levelized cost’ of energy from solar PV to conventional grid rates, with a time-slider interactive feature.
- The Circuit Detective – Solve Home Electrical Problems Yourself! Electrical troubleshooting procedures pitched to homeowners.
- The Energy Co-op Blog from a leading alternative energy provider in PECO territory, includes fun conservation tips.
- Weatherization: the anti-Solyndra Salon.com article praising the continued success of the federal Weatherization Assistance Program (WAP), low-income energy-savings and job-creation.
- West Philly Tool Library Official site of WPTL, Philly’s own community tool lending library: like a book library, but tools!
- WestPhillyLocal .com Site name say sit all.
- Bartram's Gardens Founded in Philadelphia’s colonial era, today the gardens continue pioneering in horticulture and agriculture with a variety of herbs, trees and other vegetation in an arboretum/gardens on the Schulkill River banks, and a new farm abutting sadly neglected
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- Philly Household Hazardous Waste Drop-off Schedule City of Philadelphia dates and places for disposing of spent batteries, CFL lamps, unused paint and cleaning products, etc. LovePhilly: don’t pour these in the drain or send them out with the trash.
- Reading Terminal Market Purveyors of fine foods and foodie stuff, all under one roof downtown under the PA Convention Center
- Secret Garden on the Rails Jacques-Jean Tiziou shows some dramatic natural and urban and naturalized-urban scenes along abandoned rails of Philadelphia
- Sketch Burger, Fishtown A vegan-friendly burger joint with a #1 in Philly contender beef burger, best fries that somehow stay fresh for 1/2 hour while you tackle burger, and a vegan cafe vibe of friendly folks.
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