RVelectricity – Just Ask Mike (J.A.M.): Avoid space heater danger: What you need to know – Part 2

By Mike Sokol                

Welcome to my J.A.M. (Just Ask Mike) Session, a weekly column where I answer your basic electrical questions. If you’re a newbie who’s never plugged in a shore power cord (or ask – what’s a shore power cord?), or wonder why your daughter’s hair dryer keeps tripping the circuit breaker, this column is for you. Send your questions to Mike Sokol at mike (at) noshockzone.org with the subject line – JAM.

Dear Readers,
As promised, here’s Part 2 on how to avoid space heater danger. Last time we discussed the wattage and amperage draw requirements of various wattage space heaters, and discussed electrical fires that can result from heat-damaged outlets and how using skinny extension cords and outlet strips can cause a fire. You can review Part 1 here.

This week we’ll discuss the various space heater technologies available as well as potential fire hazards from flammable material placed too close to the heater or power cable.  But first, here’s an update on the home fire last year in my town that took the lives of a mother and her adult son:

An overloaded power strip caused a fire that killed a mother and her son last month on Snyder Avenue in Hagerstown. City Fire Marshal Doug DeHaven wrote in an email that the power strip overheated and ignited combustibles in the first-floor living room. After firefighters put out the blaze, they found the bodies of Tyson Kegarise, 41, and Debra Kegarise, 62, on the second floor of the duplex at 20 Snyder Ave. “The cause of death was listed on their documents as smoke inhalation and thermal burns for both victims,” DeHaven said. Two nonfunctioning, 9-volt battery smoke alarms were found in the debris, according to DeHaven.

UPDATE: I talked to the City Fire Marshal, Doug DeHaven, about this tragedy and he filled me in on more details. This occurred in an old house with a single electrical outlet feeding a string of 2 or 3 power strips in line. And each power strip had multiple things plugged into it, such as an aquarium, computer, floor lamp, and finally a space heater. This string of power strips had all sorts of combustible materials thrown on top of them such as papers and clothing.

Of course, the space heater on the end of this outlet string drew enough current to make every plug in this line heat up, which ignited the combustible material laying on top of it. The final part of this perfect storm is that the two smoke detectors in the house weren’t working. One of them was missing the 9-volt battery, and the other one had an ancient battery that was probably dead for the last decade. Such a tragedy that would have been easy to prevent. I’m not blaming anyone – I merely want to educate people to hopefully prevent another tragedy such as this one.

And here’s a really good reminder about smoke alarms from one of our readers:

Types of portable electric space heaters

Now, back to the types of portable electric space heaters available. First, let’s dispel the myth about efficiency. In reality, ALL electric heaters are 100% efficient. That is, if we put 1,000 watts of electricity into any of them, they’re going to put out 1,000 watts of heat. Anything less would violate a basic law of physics about conservation of energy. This isn’t some gas furnace with a chimney that has a lot of heat going up the flue. No, any electric heater always converts 100% of its electrical energy into heat energy.

But some types of heat feel a little different than others. So let’s divide them into two broad categories: ones that heat the air, and ones that heat you directly, radiantly.

A forced-air space heater will have some sort of resistance element internally along with a fan to move air past it. And that warmed air is pushed out into the room for you to enjoy. Most any other furnace you have in your home or RV will do the same sort of thing: heat the air, which then heats you up indirectly.

The second category of radiant space heaters work differently. Instead of moving  air past a heating element, they actually use the element to create infrared waves of energy. This is a lot like how the sun heats your skin – so a radiant heater kind of skips heating the air and heats up your clothing or skin directly. Because it avoids wasting a bunch of energy heating the air, you can feel a lot warmer with less wattage.

But is one type better than the other? While the radiant heater might feel toastier while you’re right in front of it, you actually have to be directly in front of it to feel the heat. But the air-heating variety just keeps pushing warm air out, which can circulate through the room and be felt by everyone and everything, including the water pipes in the wall that you don’t want to freeze.

Now let’s look at how the heating actually takes place

What about ceramic heaters? Well, most of them are air-type heaters with a fan. They can be very compact and quite safe, if a bit noisy. What makes them safe is the fact that the ceramic element draws less power the hotter it gets, so even if you drape a towel over one they won’t continue to get hot enough to catch on fire. It’s a self-limiting process that really doesn’t need a thermal cut-off switch since the heating element itself does the temperature limiting.

And what about those radiator-looking heaters? Well, they’re kind of combination radiant/air heaters since they have an internal resistance element that heats up oil, and the hot oil then heats the fins, which then do a combination of heating the air by convection plus heating you radiantly. Confused yet?

Remember that ALL electric space heaters pull an appreciable amount of electric current from your outlet, and none of them should be run unattended. And certainly you want to make sure you have operational smoke detectors both in your home and RV.

The thing that makes space heaters so difficult to use safely in your RV is that the NFPA (National Fire Protection Agency) recommends a 3-foot radius around them of non-combustible materials. And you want to select a heater with an automatic cut-off switch in the event it’s tipped over by you or your pet.

In addition, portable heaters with exposed heating wires like the one to the right can be VERY dangerous, since anything combustible touching the element will probably be set on fire in just a few seconds. This could be something as simple as a piece of tissue which fell on the heater. There are just so many ways all of these portable space heaters can catch on fire that it’s best to limit their use as much as possible.

So, to recap…

• Don’t run 1,500- or 1,800-watt portable space heaters continuously.
• If you do need to run a portable heater for more than a few minutes to take the chill off, run it on a half-power setting of 600 or 750 watts instead.
• Regularly inspect all electrical plugs and outlets for signs of overheating.
• Keep a 3-foot radius clear of any combustible material around them. That includes carpeting.
• Select a heater with an automatic tip-over shut-off switch.
• Never run any electric space heater unattended.
• Always make sure your smoke detector batteries are up to date (even if this is a 10-year version) at the beginning of every camping season and test their operation monthly. You’ll likely have 120-volt-powered detectors in your RV, but battery backup is important.

OK, everyone. Remember that electricity is a useful and powerful force, so we all need to pay attention to safety precautions while using it.

Let’s play safe out there….

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
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