InspectAPedia®   -   Search InspectApedia

Electric heat wire and fuse sizes (C) Carson Dunlop AssociatesElectric Heating Baseboard Installation & Wiring

Electric baseboard heater wiring & safety
Electric baseboard heater output blocked
Electric baseboard heater manuals & sources

Electric baseboard heat wiring & location specifications:

Here we explain wiring sizes, ratings, fusing, and overcurrent protection for electric heaters and electric baseboards, followed by notes on the proper location for electric heating baseboards to avoid overheating or fires. Sketch at page top courtesy of Carson Dunlop.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

Electric Baseboard Heat Installation

Article Contents

...

Wiring and Overcurrent Protection for Electric Heating Systems

Wiring tips for electric heat (C) Carson Dunlop AssociatesBe sure to check and use the proper wiring sizes and overcurrent protection

for electric heat - for fire safety, as Carson Dunlop Associates' sketch demonstrates.

Watch out: Turn off power source to the heater before attempting installation, maintenance or repairs.

Lock, tape or tag circuit breaker or fuse so that power cannot be turned on by accident.

Failure to do so could result in serious electrical shock, burns or possible death. - King Electric cited below.

Special electrical wire for electric heating circuits 

By convention, electrical wiring used for electric heating circuits is coded with red or orange plastic exterior sheathing and contains internal conductors colored black (hot) and red (hot) as well as a ground wire.

The sketch above right addresses a common electric heat wiring detail where this special electric heating wire has not been used.

Since usually our electric heaters are 240V and require two hot wires, it's common for an electrician to run conventional 12-2 NM plastic electrical cable or BX armored cable to the heater.

In order to avoid confusion during future electrical work, the white wire of the black-and-white wire pair is wrapped with black electrical tape wherever its ends are exposed for wiring connections.

This tells future electricians that this is a "hot" wire, not a neutral wire.

Proper / Safe Overcurrent Protection for Electric Heat

Electric heat wire and fuse sizes (C) Carson Dunlop Associates

Electric 240V heaters also should be powered from circuit breakers using a common trip tie or fuses that are linked together - (we don't want just one leg of the circuit to be turned off or to trip off in an emergency).

Below is a table of typical electrical circuit wire sizes and circuit protection or breaker sizes for electric heat installations, adapted from information from Knig Electric, a manufacturer of electric heaters. The original source is cited at the end of the table.

Electrical Heat Circuit Wire Size & Circuit Breaker / Fuse Size
Total Heater Watts1 Heater Volts

Heater Amps2
=
Maximum Circuit Load3

 Circuit Wire4 Circuit Breaker / Fuse
1,440 W 120 V 12 A # 14 / 2 Single Pole 15 A
1,920 W 120 V 16 A # 12 / 2 Single Pole 20 A
2,880 W 240 V 12 A # 14 / 2 Double Pole 15 A
3,840 W 240 V 16 A # 12 / 2 Double Pole 20 A
5,760 W 240 V 24 A # 10 / 2 Double Pole 30 A
7,680 W 240 V 32 A # 8 / 2 Double Pole 40 A

Notes to the electric heat circuit sizing table above

Adapted from King Electric, ELECTRIC HEAT WIRING CIRCUIT SIZING CHART [PDF] King Electrical Manufacturing Co., cited in detail below, retrieved 2018/09/10, original source: https://www.king-electric.com/pdfs/helpful-hints-sizing-chart.pdf

Separately at ELECTRIC BASEBOARD FEET NEEDED we provide a chart showing typical number of linear feet of electric heating baseboard to heat average rooms of various sizes.

Definitions of terms such as Amps, Volts, Watts used in this article are given in detail

at DEFINITIONS of ELECTRICAL TERMS

1. Total Electric Heater Watts:

this is the total wattage of all of the electric heaters connected to a single electrical circuit of the size given in the table.

That electrical load might be by just one heater or by several heaters all on the same circuit. As you'll read below, for electric heater circuits the circuit sizing is performed assuming continuous operation.

2. Heater Amps

In the table we are showing the maximum electric heater size, measured in watts or Amps, that can be safely used when connected to the electrical circuit wire size and breaker size given in the last two columns.

Heater Amps

in this table is the maximum continuous electrical current loading, measured in amperes, that the electric heater will draw or create on the circuit.

Electrical circuit ampacity

is the amount of electrical current, measured in amperes, that the wire conductor can carry continuously without overheating. (Overheating electrical wires can damage wire insulation and is a fire hazard).

When the electrical current drawn on the heating circuit is equal to or less than the maximum circuit load permitted by wire size and circuit breaker rating, the circuit and breaker and heater have been properly matched.

3. Maximum Circuit Load

2014 U.S. National Electrical Code Section 210.19(A)(1) Conductors Minimum Ampacity and Size

210.19(A)(1) General. Branch-circuit conductors shall have an ampacity not less than the maximum load to be served. Conductors shall be sized to carry not less than the larger of 210.19(A)(1)(a) or (b).

(a) Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum branch-circuit conductor size shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load.

(b) The minimum branch-circuit conductor size shall have an allowable ampacity not less than the maximum load to be served after the application of any adjustment or correction factors.

For a dedicated electric heat circuit, the circuit ampacity must be not less than 125% of the continuous load.

  • Electric Baseboards:

    An electric baseboard heater producing a continuous load of 12A must be supported on a dedicated circuit with a rated capacity of 125% of 12A. 12 x 1.25 = 15A.

    This heater should not be on a 15A electrical circuit shared by other receptacles, devices, or loads because such a circuit would be overloaded and thus unsafe.
  • Portable heaters:

    No special loading calculation is performed by the installing electrician when wiring a normal residential receptacle circuit into which a portable cord-and-plug-adapter heater will be connected, because of the assumption that a portable electric heater is NOT intended for continuous use. That is, a cord and plug portable electric heater is for supplemental and temporary heat; it is not intended to serve as the primary heat source in a building.

    General purpose receptacle outlets of 15- and 20-ampere ratings in dwellings are included in the general lighting-load calculations of 220.12. No additional load calculation is required for such outlets.

    The U.S. NEC Article 210.19 (Branch Circuit Conductor Sizing) and Article 220.14(I), (J), and (K) (load calculations for receptacle outlets) are used together by the electrician to determine the conductor sizing and overcurrent protection required. The standard load calculation for a duplex receptacle is 180 volt-amperes.

See ELECTRICAL CODES to download copies of various electrical codes and standards.

4. Wire Type:

Assuming the electrician has selected the proper type of copper wire for the heating circuit.

Aluminum electrical wire sometimes found in older homes will be one size larger.

Watch out: while aluminum wire may already be present in some older homes, because of a serious fire hazard, we do not recommend using aluminum electrical wire for electric heat nor for other general use circuits in buildings. Details are

at ALUMINUM WIRING HAZARDS & REPAIRS - home.

...

Electric Baseboard Heat Installation Safety Details

Electric heat baseboard safety - fire clearances (C) Carson Dunlop Associates

Here are some suggested safety details to avoid a fire from electric baseboard heat.

Sketches courtesy of Carson Dunlop Associates.

Electric baseboard heat safety - outlet clearance (C) Carson Dunlop Associates

Fire Safety & Electric Baseboards or Other Fixed-in-Place Electric Heaters

  • Blockage by shelving, cabinets, etc. -

    See details at SAFETY CONCERN: COVERS over ELECTRIC HEAT CONVECTORS - or over fan boosted convector heaters
  • Curtains, Drapes, Other combustibles:

    Don't locate curtains or drapes over or in front of electric heaters. Keep drapes and curtains at least 10" (some sources including CDA say 8") above electric baseboards, and at least 3" in front of them.

    The reason for the 1" floor clearance is also to allow air to circulate. Circulating air both helps the heat to enter the occupied space and it also helps prevent the curtain from becoming too hot.
  • Electrical receptacles: As we discussed

    at ELECTRICAL OUTLET, HOW TO INSTALL, we don't place electrical outlets over or too close to the ends of electric baseboard heaters. (Sketch above .

    Also see ELECTRICAL RECEPTACLE HEIGHT & CLEARANCES
  • Thermal protection cutouts:

    For details about lectric baseboard heater overheating, UL Standards, & Safety Inspection using temperature monitoring equipment such as thermal scanners or thermography on electric heaters

    see ELECTRIC BASEBOARD HEAT INSPECTION
  • Older / Obsolete Electric Heaters May Be Unsafe

    For example see WESIX ELECTRIC HEATERS

...

Electric Heat Baseboard Blockages Reduce Heat Output

Is it safe to build cabinetry around a baseboard heater?

Storage cabinets for LP's covering part of an electric baseboard heater cuts heat output and may damage the reccords (C) InspectApedia.com Alison

Our reader asked:

Is it safe to build cabinetry around a baseboard heater, if so, how far above the heater should the cabinetry be placed.

For example, in this image, the cabinetry is built right on top of the heater. On 2020-05-30 by Alison

by (mod) - sSfety warnings when building a cabinet around heating baseboards

Fire Safety & Electric Baseboards or Other Fixed-in-Place Electric Heaters

Curtains, Drapes, Other combustibles near an Electric Heat Source

Watch out: Don't locate curtains or drapes over or in front of electric heaters. Keep drapes and curtains at least 10" (some sources including CDA say 8") above electric baseboards, and at least 3" in front of them. The reason for the 1" floor clearance is also to allow air to circulate.

Circulating air both helps the heat to enter the occupied space and it also helps prevent the curtain from becoming too hot.

Watch out: For hot water heating baseboards, radiators, convectors close to cabinets or shelving, the issue is more one of heat damage to nearby items.

The cabinet in Alison's photo isn't curtains as noted in the article above but the photo does point out other concerns, such as the risk of heat damage to the cabinet contents, depending on what's stored therein.

Notice that there appear to be vinyl LP records on the bottom shelf behind that open door?

If that's what we're seeing, cooking your vinyl records over any sort of heating baseboard is likely to warp and ruin them!

There is also at least some blockage of heat flow out of the baseboard into the occuped space.

For an example of shelving custom built to fit safely in front of and around a hot water heating convector unit with minimum heat blockage,

see CONVECTOR BLOCKED by SHELVING / FURNISHINGS - safe when used at a hot water heating convector

For an example of covers that might be used to deliberately reduce heat out put from a radiator,

see RADIATOR BASEBOARD or CONVECTOR COVERS - safe when used for hot water heat radiators or baseboards or convectors (without electrical components)

...

Electric Heat Baseboard Installation & Wiring Manuals

Marley MD26 line voltage thermostat at a Home Depot store (C) Daniel Friedman at InspectApedia.com

Photos: a Marley MD-26 wall-mounted line-voltage thermostat used with electric baseboard heat.

Watch out: Before attempting to install your heater, verify that the power supply wires are the same voltage as the heater you are installing.

The best way to check for proper voltage is by using a voltmeter, testing between supply line 1 and 2. 240 and 120 Volt heaters are not interchangeable.

Connecting a 240 Volt heater to a 120 Volt circuit will reduce the wattage 75% making the heater feel barely warm.

Connecting a 120 Volt heater to a 240 Volt circuit will destroy the heater, could cause fire damage, personal injury or death, and, voids all warranties. - King Electric, cited below.

Marley MD26 line voltage thermostat at a Home Depot store (C) Daniel Friedman at InspectApedia.com

...


ADVERTISEMENT



Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Is it OK to mount electric baseboard against a vinyl siding apron?

Installing baseboard heater in three season room can I mount on wood floor against vinyl siding apron 350 sq ft On 2018-04-20 by Bruce wilson

by (mod) - vinul siding indoors is a hazard with electric baseboard heat

With apologies that I have to speculate because I don't understand why vinyl siding material would be indoors in a building, there could be an odor and off-gassing problem of placing a hot baseboard against vinyl material.

But the answer in general is almost always found in the installation manual for your heater. The manufacturer will give warnings about clearances from building features (such as curtains or electrical receptacles) and warnings about safe vs unsafe mounting surface for the heater.

Let's start there.

Why are half of the electric heaters in our air handler missing?

Heater coils in supply air opening, found half with heating coils, while half without heating coils.

Engineering is requested to re check for proper spacing of heating coils in supply air opening On 2017-07-13 by iqbal

by anon

Make sure the Thermostat wiring isn't Corrupt,

Sometimes thie wire heat up inside the thermostat and can cause Sparking,resulting in Insufficient Heating,Check this First!

by (mod) - check for a short in electric heater wiring.

Iqbal: it sounds as if the problem isn't an electrical failure but rather that you are not sure enough heaters have been installed in the air handler.

That's a question to take to your electric furnace installer.

Anon

Thanks for the suggestion , though I don't think that's Iqbal's question.

While a short in any heating thermostat wiring is an important defect, for electric heat wall thermostats a short in the thermostat wiring is a particular hazard since it's at higher voltage.

However a shorted thermostat won't give insufficient heat.

It'll give no heat, or continuous heat, and -

Watch out: it risks a fire.

...

Continue reading at ELECTRIC HEAT BASEBOARD DIAGNOSE REPAIR or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Articles on Electric Heat

Suggested citation for this web page

ELECTRIC BASEBOARD HEAT INSTALL at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to ELECTRIC HEAT

Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia

Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay.

Only one image can be added per comment but you can post as many comments, and therefore images, as you like.
You will not receive a notification when a response to your question has been posted.
Please bookmark this page to make it easy for you to check back for our response.

Comment Form is loading comments...

IF above you see "Comment Form is loading comments..." then COMMENT BOX - countable.ca / bawkbox.com IS NOT WORKING.

In any case you are welcome to send an email directly to us at InspectApedia.com at editor@inspectApedia.com

We'll reply to you directly. Please help us help you by noting, in your email, the URL of the InspectApedia page where you wanted to comment.

Citations & References

In addition to any citations in the article above, a full list is available on request.


ADVERTISEMENT