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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Air Conditioning in the Winter?

Whoever heard of air conditioning in the winter?  It’s cold outside and you need warm air, not cold to be comfortable, right? That certainly sounds reasonable.  After all, most people are using their furnaces at this time of  the year.  You might not be aware of it but, it is possible to create enough heat enough within an enclosure so as to require cooling instead of heating.  Most homes lose heat at a faster rate than can be replaced by supplemental sources (ovens, televisions, dryers, etc). As a result, some type of heating system has to be implemented in order to keep cold weather at bay.  However, in some office buildings, for example, the number of people and machines can easily produce enough heat to require space cooling in order to keep people comfortable.   Consider for example a 40 watt flourescent light bulb.  For each watt of power, the bulb produces 3.41 BTU/hr or 136.4 BTU/hr/bulb.  Most light fixtures are equipped with four bulbs. So, each fixture produces 545.6 BTU/hr. Imagine an office space equipped with 100 light fixtures. The total heat produced by all of  these fixtures is now at 54, 560 BTU/hr.  In terms of cooling, 1 ton of cooling is equal to 12,000 BTU/hr. The lights will require a cooling capacity of 4.5 tons. This doesn’t sound like  much but, when you start adding in other loads like people and computers, the heat output can be significant.

Tankless Water Heater Explosion

While investigating the cause of a tankless water heater explosion, the extent of the damage reinforced the mechanics behind the explosive force. Tankless water heaters are devices that put a large amount of heat into flowing water in a very short period of time. But, when the water stops flowing and the heat doesn’t, there can be a tremendous release of destructive energy. It is well known that as water is  heated in an enclosure, not only does the temperature rise but, the pressure also rises as well. Pressure cookers are a good example of how water can become pressurized and if caution is not exercised by the user, can be come a deadly force. In addition, explosions involving conventional water heaters and boilers are not unheard of. As a result, temperature and  pressure valves have been required equipment on these items for a number of  years. However, tankless water heaters don’t have relief valves. Since the amount of water to be heated is less than one gallon, (when water is not flowing) it doen’t take long to cause the temperature and pressure  to reach explosive levels. The tankless unit currently under investigation contains two small reservoirs in which heating elements are immersed. The reservoirs appear to be constructed of  a hard, plastic-like material, the properties of which are unknown. The point at which rupture occurs is  dependant on the properties of the material because it is the materal that is  subjected to the rapidly increasing pressure.

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