Danger: Using Lights for Space Heating

During this past week, hundreds of thousands of people experienced the polar vortex that swept across our country. In the process, many have had to figure out a way to heat spaces where there was no heat in order to keep pipes and pets from freezing. One of the things being done is using lights with high wattage bulbs. Clamp lights as well as any type of spot or work light are rated for use with a bulb of specific wattage. It is never a good idea to use a light rated for a specific wattage with a bulb rated for a higher wattage. For example, if your light is rated for 100 watts, do NOT use a bulb rated with a wattage greater than 100 watts. A higher wattage bulb will produce more heat, always in excess of the rating of the light itself. The problem lies in the fact that more heat results in a higher current draw. If the wiring cannot handle the current draw, it will melt and burn resulting in a fire, particularly if an extension cord is also used. A fire hazard will also arise if the light bulb produces enough heat to ignite combustible material in close proximity to the light. How far away should a light be kept from combustible material depends on the heat output of the light bulb. Recently, we were asked to investigate a fire involving a clamp type worklight and its use in heating a dog house. As it turned out, the light was rated for 150 watts and the homeowner installed a 250 watt infrared bulb to provide the necessary heat for their pet. At 120 volts, a 150 watt bulb will draw 1.25 amps whereas a 250 watt bulb will draw a little over 2 amps. These current levels are very low in comparison to other heat producing devices and were not a factor in this incident. On the other hand, the amount of heat produced at 150 watts is about 511 BTU/hr. At 250 watts, the amount of heat produced is 852 BTU/hr, a difference of 341 BTU/hr. This difference was enough to cause the plastic material in the dog house to melt and eventually ignite. The fire went on to cause damage to a deck and vinyl siding material used to cover the soffitt. Fortunately, the owner’s dog survived the fire and was unharmed.

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About rjhillconsulting
R.J. Hill Consulting is a forensic consulting engineering firm that specializes in performing failure investigations for attorneys and insurance companies. Mr. R.J. Hill is a registered professional (mechanical) engineer with over 37 years of experience, 33 years in private practice. Please visit www.rjhill.com to see the kinds of forensic investigations that Mr. Hill performs.

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