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How To Size, Layout and Install Electric Baseboard Heaters

February 15, 2009

Cadet electric baseboard heater

Milton asks:
I am currently adding the electric baseboard heaters to my home and I would like to know if the units require there own separate breakers or if they can be wired in such as multiple units on one breaker or on with other electrical receptacles. I have been unable to find a wire diagram for this issue.

You are permitted to wire the units together. However, you need to pay attention to the total wattage and not overload your circuit. The total wattage will also determine the wire and circuit breaker size. To determine the total wattage needed for a room multiply the length by the width of the room. Once you have that number multiply it by 10.

So, let’s say you want to install electric baseboard heat in a bedroom which is 10 feet long x 12 feet wide. So, the minimum total wattage needed is 1200 [(10×12)x10=1200]. This would require either 1 – 5 foot heater (1250 watts) or 2 – 3 foot heaters (1500 watts) at 240 volts. Electric baseboard heaters rated at 240 volts are approximately 250 watts per foot.

Determining if you need 1 or 2 depends upon the number of windows in the bedroom and furniture layout. You want to place the heater under a window because the heat will rise clashing with the cold from the window causing a natural convection and circulating the heat around the room.

You are NOT permitted to install the heater under a receptacle or in any area where combustible vapors, gases, liquids, or excessive lint or dust are present. You also need 12 inches clearance above the heater and 6 inches clearance on each side of the heater.

To determine the wire and circuit breaker sizes divide the total wattage by the voltage, which will give you the amperage. Let’s say you install the 2- 3 foot heaters, then 1500 watts divided by 240 volts = 6.25 amps.

According to the National Electrical Code® (NEC®) section 424.3(A) “Branch circuits supplying two or more outlets for fixed electric space-heating equipment shall be rated 15, 20, 25, or 30 amperes.” So, you will need to use a 15 amp breaker which requires 14 AWG wire.

According to NEC® section 424.3(B) “Fixed electric space heating equipment shall be considered a continuous load.” This means that you are permitted to fill the circuit breaker to 80 percent of the total load.

So, let’s say that you want to put an adjacent bedroom on this circuit as well. Let’s also say this adjacent bedroom is 10 foot wide by 12 foot long. If you wired the 2 bedrooms’ heaters together, then the total connected load is 12.5 amps. You are only permitted to fill a 15 amp breaker to 80 percent of the total load or 12 amps. So you need to increase the breaker size to 20 amps and increase the wire size to 12 AWG.

As for the thermostat, I recommend a wall mounted t-stat over a unit mounted t-stat. If your budget allows, I also recommend a programmable thermostat. Using the wall mounted t-stat will heat the room evenly. Using a programmable t-stat will allow you to turn your settings up and down automatically. So, you can turn the heat down to 62 degrees during the day while you are at work and set it to automatically adjust to 68 degrees just before you arrive home. This is also recommend to do while you are sleeping. This will save you money on your electric bill.

To wire the room simply install a cable from the breaker box to the t-stat and from the t-stat to the heater(s). The cable coming from the breaker box will connect to the line side of the t-stat and the cable going to the heater will connect to the load side of the t-stat. All electric baseboard heaters come with instructions on how to wire them.

If you are installing standard electric baseboard heaters, then you may install the wires at either end of the unit. However, if you are using the Softheat electric baseboard heaters, then you can only install the wires in the left end of the unit.

The most energy efficient electric baseboard heating system I recommend is the Softheat electric baseboard heater with a programmable, wall-mounted t-stat.

Regarding 120 volt heaters, I do not recommend using these as they use twice as much current than a 240 volt heater.

Wiring a Motion Sensor Light, Installing an Electric Baseboard Heater in a Closet and Grounding Your Electric Dryer

February 14, 2009

Question mark James Vida asks:
I’ve got 3 wires coming from a light sensor (red, black & white) and 2 wires + ground that come from my light. I know that I connect white-to-white and black-to-black, gnd-to-gnd; where does the red wire connect?

You should have 1 more cable with 3 wires in it which come from the switch or power source. The first thing that you need to do is determine which wire is the line and which is the load from your light sensor. After that ensure that the power is off and check it at the light with a voltage meter before beginning work.

Now connect all of the ground wires together, place a wire nut on them and tuck them into the box. Next connect all of the neutral wires together, place a wire nut on them and tuck them into the box. Now connect the black wire coming from the light to the load side of the light sensor. Next connect the black wire coming from the light switch or power source to the line side of the light sensor. Finally, install the light, turn on the power and test.


Joseph Casha asks:
I want to add a 3ft hydronic electric heater to an existing 2ft heater and use the same thermostat. The 2ft heater is in the bathroom and the additional heater with be located in a closet which is directly opposite the bathroom is there a specific wiring configuration I need to use. If so,can you give me a heads up on the correct wiring? Both heaters are 240volts.

I do not recommend this. The National Electrical Code® (NEC®) does not specifically restrict fixed electric space heaters from being installed in a closet, but NEC® section 424.13 states “Fixed electric space-heating equipment shall be installed to provide the required spacing between the equipment and adjacent combustible material, unless it is listed to be installed in direct contact with combustible material.”

It is also not recommended to control an electric baseboard heater from a thermostat in another room. The thermostat in the other room will not accurately detect the temperature in the opposite room with your new heater.


Taunya asks:
I’ve just changed the cord to my dryer but the green ground bolt is at quite a distance from the black, white and red hookups and the green cord won’t reach that far. I’ve grounded it to another screw and the frame of the dryer but I’m not certain that’s good enough?


In theory, this will work. However, I recommend connecting the ground wire to the green ground screw provide by the manufacturer. To lengthen the wire, simply strip a little more off of the outer sheath of the cable and push the cable further into the dryer’s wiring compartment.

Intermatic Recalls DT17C and DT17C8 Heavy-Duty Digital Timers Due to Shock Hazard

February 5, 2009

Intermatic DT17C 7-Day Heavy-Duty Grounded Programmable Digital Timer On February 5, 2009 Intermatic Inc., of Spring Grove, IL recalled approximately 200,000 Intermatic DT17 heavy duty digital timers. The recalled timers can have a faulty ground connection, posing a shock hazard to consumers. However, no incidents or injuries have been reported.

The recalled Intermatic DT17 heavy-duty digital timers are lamp and appliance timers. They were packaged as the “DT17C Heavy Duty Digital Timer” and the “DT17C8 Heavy Duty Digital Timer.” The timer is white-colored and measures 3 3/8” tall x 2 5/8” wide x 1 5/8” deep. Only products with date codes of “40Z” through “52Z” or date codes ending in “A,” “B” or “C” are included in the recall. The brand name “Intermatic” is molded on the front of the timer, and the model number (“DT17”) and date code are printed on the back of the timer.

These units were sold at retailers and electrical distributors nationwide from September 2005 through December 2008 for $15 to $25 and manufactured in China.

You should unplug the timer immediately and contact Intermatic to obtain a free replacement including shipping. For additional information, call Intermatic at (800) 704-3585 anytime, or visit their Web site at

Intermatic DT17C 7-Day Heavy-Duty Grounded Programmable Digital Timer - rear view