By Mike Sokol
Since much of the country is gripped by the coldest winter in a generation, this is a good time to remind you about electrical safety for using portable electric space heaters in your RV as well as your bricks-and-sticks house.
Now don’t get me wrong, portable space heaters by themselves are generally designed to be safe. And the ceramic versions are self-limiting in temperature and will reduce their own current draw if the airflow is blocked. But the problem isn’t the heaters themselves. It’s that the USA electric outlets weren’t designed to be heavy enough for the task of providing 1,500 watts continuously for hours on end.
Here’s why. A little Ohm’s law tells us that wattage divided by voltage equals amperage. So 1,500 watts / 120 volts = 12.5 amperes. Seems safe enough for a 20-amp outlet, doesn’t it? Well, the next piece of the puzzle is that circuit breakers and outlets are only rated for 80% of their stated amperage when run continuously. So that 20-ampere circuit is really only rated for 16 amperes of current continuously (0.80 x 20 = 16 amperes). So now you’re down to a 16-ampere outlet providing 12.5 amperes. But remember, that branch circuit could be using 14-gauge wire instead of 12-gauge wire, which means it should only be using a 15-amp circuit breaker. And 80% of 15 amperes is only 12 amperes. Yikes!
So a 1,500-watt portable electric space heater can put even a well-maintained electrical out right on the edge of failure. Now add in corrosion on the heater’s plug and the wall outlet, maybe throw in a too-small extension cord and possibly a power strip or two, sprinkle some flammable objects like newspapers around, and you have a sure recipe for an electrical fire.
How do I know this? Well, I reported on just such a fire last year near where I live. And I’ve heard of a few more recent house fires in my area that appear to be space-heater related. Read my past articles on space heater safety here (Part 1) and here (Part 2).
So what can you do about it? Well, first of all you need to carefully inspect the space heater’s plug for any signs of damage, overheating or corrosion. It’s not a bad idea to use a little fine emery cloth on the contacts to brighten them, and maybe some contact cleaner. Same for the wall outlet you’re plugging into. Make sure it’s not loose when you plug in and a spritz of contact cleaner is a good idea.
If there’s any sign of overheating or melting, have the outlet replaced immediately. And don’t use an extension cord on an electric space heater if at all possible. If you do need to use an extension cord it should be a contractor-grade cord built with 12-gauge wire and rated for 20-amperes. If you do have to run it unattended, see if it has a low power 600- or 750-watt setting. That’s way easier on the wiring and might be enough to keep the pipes (and possibly your toes) from freezing.
Finally, keep all flammable materials such as paper or fabrics away from the heater itself, but especially off of any extension cord plugs. That’s where the overheating and fires generally start. I don’t want to read about any more electrical fires caused by electric space heaters this season. It’s just too heartbreaking.
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 40+ 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.