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10-17-2009, 01:59 PM #1
240 Volt Cord Connected Electric Construction Heaters
My experience in the insurance industry has shown that portable construction-type heaters have been the cause, or suspected cause of countless fire losses.
In December of 2008 CSA released the attached alert which recognizes the aforementioned fact.
Homeowners will often use these types of heaters to heat crawl spaces, basements, garages, etc. Sometimes they will even remove the cords so they can be hard-wired into the electrical system.
It is my opinion that any time one of these heaters is discovered in any building (residential dwelling or commercial building) the inspector should note the date of manufacture to verify if it is one of the 'affected' heaters, note the presence of the heater in the report and recommend that the heater be replaced.
The CSA Alert specifically refers to 240 volt / 3,000 watt (or greater) electric heaters; however all of the tips in the alert can be applied to any portable electric heater.
Also, I have spoken with several individuals (insurance industry, a firefighter, Manitoba Hydro engineers, and other electrical engineers) who have all been involved in a Task Force to identify the causes of failure. They've all essentially told me that CSA is stuck in some sort of 'political' battle regarding these heaters and although the alert is a step in the right direction, they strongly believe that these heaters should be recalled because of the high probability of failure - and that they fail even when used properly (i.e. not used in harsh environments, not placed too close to combustibles or where airflow is restricted).
Summary of info I've collected:
- The 'defective' heaters include only 240 volt / 3,000 watt (or greater) electric heaters (all brands)
- All of these heaters use a heating element housed inside of an aluminum coil that is insulated with magnesium oxide
- Under normal conditions (i.e. when the element is no hotter than 500 deg F., the magnesium acts as an excellent insulator
- These heaters are capable of overheating even in ideal situations, and once the temperature surpasses 500 deg F., the insulative characteristics of the magnesium oxide begins to fail, and may allow an arc to occur.
- The arcing results in significantly increased temperatures, high enough to melts the magnesium oxide into molten material which melts through the aluminum coil, allowing the molten material to be sprayed out of the heater (this failure does not trip the circuit breaker and the heater continues to run and the fan still turns, allowing the magnesium oxide to be released and sprayed around until there is no more left).
- None of the heaters discussed in this e-mail will pass the testing procedure that CSA will introduce in 2009 (the intent is to force manufacturers to design and manufacture heaters with elements that will not fail or allow molten material to be released if the temperature rises above 500 deg).
- The only known way to prevent the arcing is to plug these heaters into a GFCI protected outlet; however, it is apparently very rare to come across a 240 volt power source that has GFCI (because of the cost), and the heaters are not provided with built in GFCI protection because it could double or triple the cost of each unit.
Note: It is important to know that this particular alert is not referring to 120 volt portable heaters or 220 volt heaters rated under 3,000 watts nor is it referring to hard-wired, permanent heaters (even when 240 volt / 3,000 watts or greater).
The most important safeguard is to ensure that a portable heater is not running while unattended.
(A post I saw the other day about lopping plugs off electrical devices so they can be hard wired into the electrical system reminded me of this topic)