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I am thinking of installing three wall space heaters in the basement I am renovating. I currently have three cables coming into the basement:

  • 1 - 20amp for the bathroom GFCI that will power the fan,
  • 1 - 20a for all of the wall sockets and
  • 1 - 15amp for the bedroom and bathroom lighting

Here is the problem: I need a space heater for the bedroom, bathroom and two for the main living area.

My thoughts are because each unit pulls a maximum of 8.3amps that I can put two heaters on one 20amp breaker or do you think each heater would require its own dedicated 20amp breaker

What am I installing? This Cadet CEC163TW Energy Plus Wall Heater
1600 Watts at 240 volts; 1500 watts at 208 volts; 1000 watts at 120 Volts.
The cool thing about this heater is a unique power supply smart sensor auto-adjusts the heater voltage to match your voltage supply.

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    What makes you think you need the supplemental heat? What do you have for a primary HVAC system?
    – ThreePhaseEel
    Jan 17 '21 at 15:48
  • 1,000 W isn't much. Since you are going to have to run wires anyway, go for 240V - same wiring but you get (with this particular heater) 60% more heat. You do pay for the electricity, so long-term cost it's the same, but if you wake up cold one morning, you get to heat up the room much faster.
    – manassehkatz-Moving 2 Codidact
    Jan 17 '21 at 16:43
  • The current furnace HVAC doesn't have enough capacity to heat the entire basement. There is only one supplemental vent off the plenum. Naturally, the basement is cool during the year due to the floor temp of 52 degrees. So my only way of heating the rooms is with wall heaters.
    – Christopher Lond
    Jan 17 '21 at 16:54
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Wrong heater

I don't know what possessed you to pick that one, but you can get far cheaper Cadet heaters. A heater of that size should cost $50-100. All of them are 100% efficient - an electric heater that is less than 100% efficient is impossible.

That "cool feature" is actually 100% useless to the consumer. You know your voltage so you can buy a much simpler single-voltage heater that has fewer failure points. That "feature" is only cool to contractors, who get to stock only 1 heater and simply pass the feature cost on to the customer.

So I think I just saved you about $400 :) Now we can fund the circuit(s) needed to do the job.

This unit is 8.3 amps @ 120V. Because it is a heater, we must provision for 125% of that ampacity, so we must provision at 10.4 amps per heater. Welcome to 120V heating.

Not enough capacity on the circuits.

It must be hardwired. When a hardwired load is more than 50% of circuit ampacity, that circuit cannot have any receptacles. Even one on the wall circuit will be >50% ampacity (10.4 amps) and will require removal of all receptacles. Two just won't fit (20.8 amps).

So that means the bedroom lighting circuit can handle 1. (but the lights better be LED).

Use of the bathroom receptacle circuit is out of the question. That can only be used for bathroom receptacles OR loads inside one bathroom.

So we can't get there from here.

Since we have to run a new circuit anyway...

you can just run a 240V/20A circuit with #12 wire. That will be 4800W on paper and will support up to 3840W of heaters. (3840 x 125% = 4800).

Cadet baseboard heaters are laughably cheap. These are dog simple and will last 40 years.

2000W baseboard -- $65 due to demand, normally $50.
1500W baseboard -- $57 ditto.
1250, 1000 and 750W also available.
Add up to 3 thermostats at $15 each.

If you really want fan units, here's 3000W in one unit ($181) Or two 1500W fan units, $126 each. Or 1000W unit same price.

See how that "feature" doesn't make any sense when you know your voltage? It simply adds electronics that creates a failure point.

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  • The plan was to dedicate one circuit for each heater, if I were to use one single pole 20amp breaker. Due to the limitation of breaker space, I was attempting to do two heaters on one breaker and two on another. If what I am hearing I should use a 240v double pole breaker with 20amp wire that will support two heaters per breaker? That sounds like a very good idea. I will look into the baseboard heaters as well.
    – Christopher Lond
    Jan 18 '21 at 18:11
  • I used a single dedicated 20amp wire for all the outlets in the basement bedroom and main living area. The bedroom and bathroom lights use a dedicated 15amp breaker. The bathroom has its own 20amp breaker that is connected to the GFCI outlet but not the ceiling fan BUT can the fan be on the same circuit? The lighting in the main living area is on a separate circuit.
    – Christopher Lond
    Jan 18 '21 at 18:18
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    @ChristopherLond A 240V/20A circuit will support up to 3840W of 240V heaters. Arranged any way you please. Three 1000s will work, with spare room enough for another 750 also.
    – Harper - Reinstate Monica
    Jan 18 '21 at 20:40
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    A bathroom recep circuit can only power things that are in that same bathroom.
    – Harper - Reinstate Monica
    Jan 18 '21 at 20:41
  • Yes, the bathroom has a dedicated 20amp circuit that will be for the GFCI. it sounds like I will need to run a separate 12/2 for the exhaust fan / light as well
    – Christopher Lond
    Jan 19 '21 at 12:39
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You're gonna a bigger boat. According to code, a bathroom requires it's own 20 amp dedicated circuit.

I looked up the amp draw on the heaters you mentioned and I think you might have not interpreted the ratings correctly: 1) at 120 volts, the heater will produce 1,000 watts at 8.3 amps 2) at 240 volts, the heater will produce 1,600 watts of heat at 6.7 amps. 3) at 203 volts, the heater will produce 1,500 watts of heat at 7.2 amps.

So even if it was code legal, connecting permanently installed electric space heaters on a 120 volt circuit would seriously overload the circuits. Also bear in mind that electric space heaters are considered a "continuous load" and must be derated by 20% IE: even though 120 volts x 20 amps = 2,400 watts, you can only load that circuit up to 1,920 watts (2,400 * 80%).

Is it practical to run additional cables from your main panel? Running those cables at 240 would enable you to run 2 heaters on the same cable.

Not meaning to be too assertive, but at the end of the day, think about what you're doing: Trying to add 4 space heaters that has high power requirements to existing wiring! They will also be expensive to operate.

I know they are a lot more expensive, but have you considered a mini-split system? They are very efficient and as a bonus you get A/C as well.

Sorry, but I think you'll need a bigger boat.

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  • You misunderstood, I currently have a dedicated 20amp wire going into the bathroom and I am thinking if that wire can power only the fan and the GFI outlet. The bathroom light will share the same 15amp circuit as the bedroom light. I am not sure that I will need a separate 20amp wire for the heater but based on your answer it sounds like I will.
    – Christopher Lond
    Jan 17 '21 at 16:57
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you can get 2 of your heaters on one 20amp 240v circuit.

these circuits should only be for heaters.

so yeah, 2 new wires going to the panel.

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  • Could I use a 40amp breaker with one #8 wire? One wire could handle all four? Will my standard residential electrical panel handle this?
    – Christopher Lond
    Jan 17 '21 at 17:39
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    @ChristopherLond Why bother? A #8 CABLE is more money than two #12s.
    – Harper - Reinstate Monica
    Jan 17 '21 at 21:06

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