Question. Recently, a major manufacturer initiated a voluntary recall of in-wall, or baseboard, electric heaters. The media reported that “under certain conditions these heaters could fail, causing the units to overheat, catch fire, and spew flames and molten particles. The heaters may also become energized, creating a potential electrical shock hazard.” Has CSA International ever examined these products and found them to cause a potential or real hazard?
— Bill McMullen, acting chief electrical inspector for the Province of Manitoba, and Canadian Section President for IAEI
Answer. CSA International recently investigated an incident involving in-wall electric heaters and the results of this probe are worth revisiting. An investigation initiated by the Ontario Fire Marshal (OFM) focused on determining whether the cause of a residential fire that resulted in a triple fatality was an in-wall electric heater. CSA International’s Corporate Audits and Investigations (CA&I) group was asked to assist the OFM with their investigation.
In this case, it was discovered the origin of the fire was a baseboard heater that was improperly installed —in fact, it was installed upside down. The investigation by CSA began by looking at the requirements for the appropriate standard that applies to baseboard heaters.
To obtain CSA certification for a permanently installed electric baseboard heater, manufacturers must comply with all of the applicable requirements outlined in CSA Standard C22.2 No. 46-M1988 Electric Air Heaters. It goes on to state that a CSA-certified electric baseboard heater will operate safely and pose no potential fire hazard when it is installed correctly. While a heater installed upside down will operate, it will not be protected by the highlimit device and could become a fire hazard if blockage of the air discharge occurs.
CSA’s investigators determined the heater was provided with a high-limit device composed of a capillary tube attached to a switch; the capillary tube was charged with a selected fluid or gas under partial vacuum. When the temperature increases, the fluid or gas expands, producing a pressure which acts against the diaphragm within the switch. The tube is strategically mounted in the upper area of the heating element to sense a restricted air flow over the heating element—which will cause an over-temperature condition. The diaphragm in the switch snaps at the calibrated temperature and opens the electrical contacts, cutting off the power to the heating element.
With the baseboard heater installed upside down, as it was found at the fire scene, the capillary tube of the high-limit device was located at the bottom (below the heating element). The safety device sensed the incoming cold air and not the exiting hot air. If a restriction is placed in front of the heater, and if combustible materials are draped over it, there will be no protection to limit abnormal temperature increases.
A heater installed properly and operating for several years was removed and used for testing by CSA. It was rated 240 volts AC, 2,500 watts, and was the same model and year of manufacture as the one involved in the fire.
The CSA team proceeded to conduct four tests from the standard. The two initial tests, the Rating and Temperature Normal Test and the Drape Test, were conducted under normal conditions and in both cases the heater performed within the requirements of the standard.
Results from the two subsequent tests were startlingly different. With the heater installed upside down and two layers of loosely folded cheesecloth (designed to simulate hanging drapes) placed directly on the aluminum fins of the heating element, air flow to the heater was partially restricted. This situation can occur because the enclosure of an improperly installed heater can no longer provide a protective clearance barrier for drapes. After just over five minutes of operation, the cheesecloth began to burn.
Next, bed sheets were substituted for cheesecloth and the same test was carried out. After one hour and 37 minutes, the bed sheets were ablaze.
CSA testing confirmed that a certified electric baseboard heater which is properly installed will not become an undue fire hazard when operated under the abnormal conditions specified in the CSA standard. However, when a baseboard heater is installed upside down, the response time for the safety device to operate will increase due to its location and proximity to the heating source.
Upon completion of the investigation, the OFM concluded that the improperly installed electric baseboard heater was the most likely cause of this fatal fire.