Safe-Boat Smart-Boat: The safe onboard use of space heaters and extension cords

Recently one of our local vessels experienced a pilothouse-to-living quarters fire due to a portable electric heater and extension cord.

The pilothouse was subsequently removed and replaced with a new pilothouse and the interior was gutted and is presently being remodeled.

The only positives are that there was no loss of life or injuries and that this incident happened at the dock.

A qualified Coast Guard-approved marine drill instructor, Fred Mattera of Point Judith, RI is the owner/president of North East Safety Training Co. (NESTCo), which conducts fishing vessel drills and inspections and basic safety training workshops. A commercial fisherman for 40 years, Mattera is a member of the Commercial Fishing Safety Advisory Committee to the Coast Guard, and, since 1998, has been president of the Point Club, a fishing vessel mutual insurance group. He also has served on the board of directors for Sunderland Marine Mutual Insurance Co., the principal underwriter for the Point Club and more than 2,000 US fishing vessels, since 1998.

The downside, of course, is lost time and money.

What can we learn?  

This, unfortunately, is an often overlooked fire hazard that is always an overriding concern on boats.

The use of portable electric heaters is very common in our fishing fleets and admittedly problems caused by them are rare – largely due to improvements in these heaters and the education of users.

In this article, I will try to enhance and educate you further:  It is my contention that electric heaters and extension cords can be used safely, but only with proper precautions.

Heater choices  

The safest type of portable electric heater is the oil-filled radiator.  The oil diffuses the heat across the entire surface so nothing gets hot enough to present a fire hazard.

But these are the largest and most bulky of commonly found heaters and they depend upon convection for heat distribution.

Ceramic heaters operate at lower internal temperatures than heaters that use wire grids.  As such, they present less fire hazard than conventional heaters if tipped or if something accidentally comes in contact with the heater.

All portable heaters should be equipped with an over-temperature switch and some also have a tip-over switch for additional safety.

As a heat source with a small footprint, the ceramic heater is your best choice.  Most have a fan to distribute the heat.

The glowing infrared radiant heaters provide a warm fireplace-like glow and are inexpensive, but they are also the most dangerous.  Any contact with flammable material will cause a fire.

The quartz heater is basically one of the wire-wound radiant heaters with the element inside a quartz envelope, just one step above the old-fashioned type.

I would refrain from using any radiant heater on a boat.

Heater use  

Operate electrical heaters away from combustible materials and do not use a heater to dry wearing apparel or boots (gloves, clothing) that could fall on the heater and trigger a fire.

Never place electrical heaters on a table, bench, cabinet, or the like.

Electric space heaters typically have a rating of 1500 watts, and a low setting of 750 watts, with a few having three settings.

But those settings are based on the power used by the heater and do not tell you how much heat each unit makes for the power consumed.  That is rated in BTU’s and only a few give that information.

When purchasing a heater, if it does list the BTU’s produced, you want one that has the highest output for the 1500/750 watts being used.

The two designs that supply the most heat for the watts used are the oil-filled and the ceramic.

Powering the heater

Any electric heater will be drawing nearly the maximum rated load of a duplex outlet – possibly for an extended period – and be aware that boat sockets are not always of the highest quality.

A heater should always be the only thing plugged into an outlet leaving the other half vacant.

A slight warming of the plug while the heater is operating is normal, but if you notice any heating of the outlet itself, or if the plug gets hot enough to deform the plastic around the prongs, you have a wiring problem that must be addressed.

If you replace an outlet, buy one in the mid to upper price range and from a known manufacturer, as they vary in quality.

The same rules apply to your shore power plug.

Safe use of the full capacity of your shore power is dependent upon all equipment being in good condition, which isn’t always the case.  You should examine the plug to be sure that it doesn’t show signs of damage.

If the outlet is not in good condition it isn’t safe to use, especially when using heaters.  It should not show signs of overheating, cracking, or weathering.

One way to improve electric connections is by applying a small amount of dielectric grease (available at most home supply stores) to each pin of your power plug.

A 30-amp circuit will be running at close to maximum capacity with two 1500 watt heaters.  Add the other miscellaneous loads – like lights and appliances – and you are probably at or exceeding that limit.

It is wiser to use only one heater, or use two in different locations, but with each set to the low settings.

If you have a 50-amp power cord you can use two heaters safely at the same time.  If you do, make sure that each one is on a different electric circuit.

With 50-amp service, it is a good idea to install a separate circuit for each heater used.

Install a 15-amp breaker into the distribution box for each, using 12/2 wire, and install a single socket outlet for dedicated use on each heater.  These dedicated outlets are usually orange in color to indicate that they are on a separate circuit.

Extension cords, power strips

When there is no place to plug in the electric heater, what do you do?

You probably are tempted to use one or more extension cords to reach the nearest outlet, or add a power strip to get more outlets.

Most of us don’t think of this as dangerous, but the US Consumer Product Safety Commission declares extension cords among the most dangerous of electrical appliances.

What’s wrong with using an extension cord or power strip to run an electric heater and more electrical equipment?

If too many pieces of electrical equipment are plugged into the same outlet and they are all on at the same time, more current may be running through the outlet than it can handle – creating an electric fire hazard.

Tips for safe use

Here are several commonly experienced problems, and remedies, toward making onboard use of heaters and cords a safer proposition for vessel owners.

Overloaded circuits and what to look for:
  The outlet or wall is warm to the touch, the outlet is discolored, the circuit breaker frequently trips, and/or a burnt smell of insulation is noticeable.

Remedy:  An extension cord or power strip should only be plugged directly into an outlet (not into another extension cord or power strip, and not strung together in a series or “daisy-chaining”).  Extension cords without surge protectors are not recommended.

Extension cords and cords from power strips (or surge protectors) being used for heaters and electrical equipment should not be run under rugs or carpet.  The heat build-up is a potential fire hazard.

Overloaded extension cords can cause an electrical fire and what to look
for:  Extension cord is warm to the touch, discolored, or has a burnt smell.

Remedy:  Make certain the extension cord ratings are at least as high as the heater or appliance they power.  Best to use an extension cord with the same or larger wire size as the heater/appliance cord.

Consider the load – remember an electric heater draws more than a light bulb – and consider the distance from the outlet.  Use the shortest length of extension cord possible to minimize current loss or heat build-up.

Per the American Wire Gauge (AWG) system, the smaller the wire gauge number the more current the cord can safely handle.  For example and extension cord made from 12-gauge wire can safely handle more current than an extension cord made from 16-gauge wire.

Unwind/uncoil the extension cord fully before use to prevent heat build-up.  Also, since an extension cord is designed for temporary use (90 days or less) it is best to run a dedicated circuit and/or install well-located three-wire grounded outlets to minimize the need for extension cords.

Electrical shock from a short circuit due to ungrounded outlets and what to look for:
  An electric heater or equipment cord has a three-prong plug, but the nearest outlet only has two slots for the plug.

Remedy:  Never remove the ground (third) prong of a three-pronged extension cord or attempt to insert it into an ungrounded (two-pronged) outlet.

Grounding is a method to protect individuals from electrical shock by providing an intentional low-resistance path from the electrical system to the earth with sufficient current-carrying capacity to prevent the buildup of hazardous voltage.

Cord and plug-connected equipment must be grounded if located in a hazardous wet environment, or if operated at more than 50 volts.

Only use electrical extension cords listed by Underwriters Laboratories (UL).

Electrical shock from damaged extension cords and what to look for:
  Watch for damaged extension cords that have been knotted or kinked (causing the wire to break internally) frayed, cut, or burned.

Also, be observant of extension cords running through walls, under carpet or furnishings, through doorways, across walking paths, or that are draped over electrical equipment.  These all can become easily damaged.

Remedy:  Inspect extension cords for wear and damage before use.  Remove extension cords by pulling on the plug instead of the cord.  And damaged extension cords should be destroyed and discarded.  Avoid repaired cords – these are a weak link.

Electrical shock from extension cord contact with water and what to look for: 
Watch for electrical outlets within 3’ of sinks or other water sources; and that are outside, across a wet deck.

Remedy:   Extension cord use near sinks or wet environments should be plugged into an outlet with Ground Fault Circuit Interruption (GFCI) or you should use a supplemental GFCI to prevent an electrical shock.

Ensure that the only extension cords you use outdoors are rated for outdoor use with a built-in or supplemental GFCI.

In conclusion  

Hopefully, these safety tips on electrical heaters and extension cord use will heighten your awareness – and prevent a fire hazard on your vessel – as this year’s cold weather season winds down.  File them away for next winter – it will be here before we know it.


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