A recent circuit troubleshooting job at 44xx Locust St. probably started when a plug-in electric space heater overloaded a knob-and-tube circuit serving a dozen locations besides the one where the heater was connected. Space heaters typically consume 100% of permissible circuit load, although when connected to a knob-and-tube location, they may be sharing with a dozen or more lights and other receptacles.
The overload might have had no consequence if a wire-nutted splice in a basement ceiling junction had been better made-up. Unevenness in the wire twist combined with absence of any metal bonding sleeve inside an old ceramic wire-nut probably allowed oxidation to partially insulate the spliced wires from each other. When the heavy heater load subjected this poor connection to overload, the connection failed entirely — probably due to arcing and burning of the tiny contact-points that remained. A problem such as this could be identified before it manifested as a complete fault, by use of a loading receptacle tester to analyze voltage drop under a load of 12A or 15A (see FAQ-Voltage Drop by SureTest(TM)).
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…
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
Customer Resource Blog Categories
Off-site Links ->
- Annapolis Home Inspection, LLC Aluminum branch circuits, homes 1965-1972
- ComplianceAndSafety.com OSHA Electrical Safety Training
- 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
- HiddenCity Philadelphia Surprising places it takes an adventurer to discover; events, too.
- 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.
- WXPN: Philly sings in key of love Love songs by Philly artists