RV Electricity – Portable space heater safety, Part 2

RV Electricity – Portable space heater safety, Part 2

By Mike Sokol

As promised, here’s Part 2 on space heater safety. Last week 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 month 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 just 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.

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

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’ll certainly 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 detectors have fresh batteries at the beginning of every camping season and test them monthly.

Let’s play safe out there….

Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. 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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9 thoughts on “RV Electricity – Portable space heater safety, Part 2

  1. Richard Baker

    Forced air space heaters include the fan wattage in the total watt rating. A 1000W
    Unit may only put out the 800W of heat…

    1. Mike Sokol

      Interestingly, if they have an 800 watt element and a 200 watt fan, they actually do heat up the room with 1,000 watts of heat. That’s because ANY electrical appliance that draws power, no matter if it’s 10 watts or 10,000 watts, heats up the room with that much electricity. As I’ve mentioned. all electrical heating is 100% efficient. So a 100-watt light bulb is actually a 100-watt heater, etc…

  2. Dave Jones

    I use both a RV dehumidifier and a small pump house type electric heater to control humidity in my Class C during the winter storage. The RV is plugged in to 30w shore power. I am not concerned about the dehumidifier as it using little power. My question is the electric heater. I have been plugging it into one of my interior outlets. For long term use, such as over the winter, would I be better off using a 12gauge appliance rated extension chord and plugging it in outside my RV so as not to put strain on my RV’s electrical system?

  3. Drew

    Kenneth,

    Probably the Cheap Heat system described above, followed by your propane furnace and finally the space heaters described in Mike’s article.

    Drew

  4. Wolfe

    Ken: *MY* opinion, which I’m sure someone will disagree with, is that *I* use a hot-oil radiator in my RV. It’s not as small as my forced air, but it’s a LOT safer with 90lb dogs bounding all over. The surface stays safe to the touch, much less flammables (and I do use it to carefully heat and dry towels sometimes… naughty me!). Mine has a thermostat and heats 500sf trailer pretty well if running most of the time. I have lousy hearing, so running TOTALLY silent is a requirement in my rig.

    I would NOT count on the safety of ceramic heaters over “glowing” heaters. ALL the same safety concerns and practices apply, and never count on ANY supposed safety device to replace wiser practices. The ceramic heaters I’ve used CERTAINLY can set fires if capsized or mis-used!!!

    Yes, radiant heaters heat “line of sight” and feel instantly warmer on your skin although not warming “around the corner” immediately. That said, they DO heat the air quite effectively because they warm EVERYTHING LoS — so the cold cabinets and walls get slightly warm and themselves heat the air. Radiant loses points for safety because something VERY close to the heater will catch fire VERY quickly.

    If you DO use a small forced air, I used to put mine on my counter where it won’t be kicked over — and yes, never above 800W setting.

    Be safe… and toasty!

  5. Drew

    Hi Mike,

    We have a fake fireplace in the rv that we love. The grounded cord has chromed looking plated blades on the plug. They seem very resistant to overheating and don’t discolor the way the brass colored ones do. I’ve also replaced the 30a plug on the shore power cord with one that has the same style chrome looking blades. This plug has not discolored and pitted the way my original did. It looks as though this coating or plated material is more resistant to overheating due to load

  6. LARRY MCGAUGH

    The best answer is none of them, you’re better off using something like the CheapHeat system that is hard wired into your RV. Because it’s designed for a 100% duty cycle and has the built in safeties you need, like high temperature and over current protection. You can leave your RV unattended and don’t have to worry about it overheating and causing a fire.
    Plus it hooks directly into your RV’s central heating system so it heats the entire RV including the mechanical area where your plumbing and storage tanks are located.
    You can find out more about this at http://www.rvcomfortsystems.com

  7. Kenneth Merry

    What is the safest of all these if you do wish to have an additional source of heat?

    1. Mike Sokol

      I’ve been in contact with a few portable space heater manufacturers about this, and there doesn’t appear to be any published statistical data on the relative safety of each technology. However, we can draw some conclusions based on general ignition principals.

      So, any radiant heater with an exposed heating element that reaches combustible temperature is in the most dangerous category. So open element radiant heaters as well as Vicor tube elements (looks like a glass tube over the elements which glow cherry-red) would be on the top of my “most dangerous” list.

      Intermediate danger would be units with a completely enclosed wire heating element and a fan to circulate the hot air. But it’s critical that this type of heater has an over-temp shut-off as well as a tip-over switch. That way if the fan fails or the heater is knocked on the side, it won’t heat up out of control.

      Safer than that would be the self-regulating ceramic heaters with a fan. The ceramic element draws less power as it heats up, so the temperature is self limiting. However, it needs to have a tip-over switch to shut it down if knocked over.

      Finally, I would consider the radiator style oil-fill radiant heaters to be the safest of all, as long as it has an over-temp and tip-over switch. There’s no exposed element, the surface never gets hot enough to ignite combustible objects (normally), and there’s no fan to fail.

      However, ANY heater on high setting can overload an extension cord or cause overheating of loose/corroded outlet. So I wouldn’t run any of these on the HIGH setting for more than 30 minutes, and NEVER unattended or while you’re asleep. On the 1/2 wattage setting of 600 or 800 watts, the danger of electrical overload is reduced, so it’s probably safe to run them at the lower wattage for hours at a time. But you still will want to periodically put your hand on the outlet cover to inspect it for heating. And NEVER run one on a power strip as they’re usually cheaply constructed and prone to overheating. More to study later, but that’s my WAG from years of experience with electrical things that heat up.

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