Poor connection between heater plug and receptacle sparks electrical fire



Reference number

Incident overview


A heater is suspected of causing a fire in the kitchen of a duplex under construction.

Regulated industry sector

Low voltage electrical system (30V to 750V)


Campbell River

Investigation conclusions

Site, system and components

The heater utilizes a heating element to create heat which is removed and distributed by a self-contained fan. The built in thermostat will automatically turn heater off when desired temperature set by the thermostat is reached.

Failure scenario(s)

A poor connection between the blackened prong heater cord end and a used receptacle caused overheating. The overheating destroyed the cord end, receptacle and the branch circuit.

Facts and evidence

A 4.8KW heater was plugged into a 30Amp 240V receptacle on a 40Amp breaker.
• First heater 4.8KW used was removed due to inoperability. (see statement)
• A heater in the same suite shows signs of damage. (see photo of black and pitted prong)
• A new 4.8KW heater was plugged into the same receptacle (see statement)
• Warning labels on heater cords state, “Check your heater cord and plug connections. A loose fitting outlet can cause the plug to overheat and or cause a fire.” (see photo of label)
• The breaker was in the tripped position.( see statements)
• The cord end, receptacle and branch circuit were destroyed. (see photo)
Witness Statement
• Electrical contractor stated the drywall heater first used stopped working and a second heater was purchased and plugged into the 240V 30Amp receptacle. He also stated the 2 pole 40 Amp breaker for this circuit was in the tripped position after the fire.
• The Building Contractor stated that the 2 pole 40 Amp breaker was in the tripped position after the fire. He also stated a heater was plugged into an extension cord that was plugged into the 30 Amp outlet.


  • Injury
    • Qty injuries: 0
    • Injury description: N/A
    • Injury rating: None
  • Damage
    • Damage description: Heater cord end, 30 Amp temporary receptacle in 4-11/16 box, wire in the concealed wall behind 4-11/16 box and insulated wall were damaged by fire.
    • Damage rating: Minor

Incident rating


Attachment Size
4629-636571 (07-05-2018).pdf 893.51 KB