I am installing three 1500 watt space heaters in my old house. They come in 110V and 220V. If both 110 and 220 have the same wattage, does that mean that I get the same amount of heat from either one? If that is the case, why would I want to install the 220V when 110 is cheaper and easier to install?
Thanks.
You need larger wire and a larger circuit breaker for 120, and 120 is a little less efficient (although at the typical distances in a residence the less efficiency means little or nothing).
Further, you cannot put as many on the same circuit if running them at 120 volts.
If your going to connect all three heaters to the same branch circuit that would be 4500 watts of power. It makes no difference whether you supply it with 120 volts or 240 volts the cost to operate is the same. The cost savings is in the installation. If you are going to supply the 4500 watts on one branch circuit at 120 volts then your load in amps is 4500/120 = 37.5 amps. The branch circuit conductors must be sized at 125% of the rated load. So that puts you at 37.5 x 125% = 46.9 amps. If you use NM-B (romex) cable as conductors you'll need 6 awg copper on 60 amp breaker..... Or if in conduit using THHN you will need 8 awg copper on 50 amp single pole breaker.
The problem with the above is I dont think you will find many juristictions that will allow you to supply 120 volt fixed heating on anything larger than a 30 amp single pole breaker for residences.
So even two heaters on one branch circuit exceeds 30 amps when calcualted as continuous load(125% of rated load). So you would need 3 branch circuits using #12 awg copper either as a cable like NM-b or in conduit (added cost) to supply these heaters with 120 volts.
Each circuit protected with 20 amp single breakers (3 total)
If you supply the heaters with 240 volts your load is only 18.75 amps. Conductors then would be required to have an ampacity of 23.4 amps. So using NM-B you would need #10 awg copper and 30 amp double pole breaker...or THHN in conduit would be #10 awg on 30 amp double pole breaker.
So at 240 volts you can put the heaters on one branch circuit. You will need one 30 amp double pole breaker (could use a 25 amp if you want) and some #10 awg copper wire either as a cable or wires in conduit.
Though #12 copper in NM-b cable or THHN is capable of 25 amps and would appear to ok we are not allowed to use the smaller guage wire as 12 awg copper is not to be protected at more than 20 amps...(unless we are supplying motors.)
Roger
You will get the same heat out of either the 120V or 240V heater of equivalent wattage.
The advantage in using the 240V heaters is that you can put them all on one 30A circuit using 10/2 wire. If all three heaters are in the same room, you can control them with one thermostat.
If you choose the 120V heaters, you need a seperate 20A circuit with 12/2 wire to each heater. This will use up three spaces in the breaker panel and three times the length of cable and three thermostats.
To add a bit to Roger's explaination:
424.3(A) ...Branch circuits supplying two or more outlets for fixed electric space-heating equipment shall be rated 15, 20, 25, or 30 amps.
(B) Fixed electric space heating equipment shall be considered continuous load.
210.19(A)(1) ...where a branch circuit supplies continuous loads...[the circuit] shall have an ampacity not less than the noncontinuous load plus 125 percent of the continuous load.
This explicitly rules out the possiblity of putting the heaters together on a 120V circuit, but allows putting them together on a 240V circuit.
For Roger or Ben:
I'm taking your suggestions to run a 10/2 w ground off a 30 amp circuit breaker so as to wires receptacles for 3 1500 kw heaters. Can you tell me wire the receptacles? Do I use 30 amp receptacles? Do I wire two of them to one leg of the 10/2 cable and the ground, and the other receptacle to the other leg and ground? Many thanks for your advice. Jerry
Baseboard heaters are normally direct wired. From the panel to a 2-pole thermostat. From thermostat to 1st unit. Unit 1 to unit 2, unit 2 to unit 3. All cables will be 10-2 with ground. Feed the circuit with a 2-pole 30-amp breaker.
Remark all the whites as blk or red with a magic marker. Connect all the bare grounds together and to the ground screw or wire in each heater.
the only other thing you have to watch out is the linevoltage termostat some have limted on amp rating AFAIK most are rated at 22 amp but however there are some thermosast that can rated much as 30 amp you may have to look around to see if they stock that high a amp rating.
[ 22amps @ 240 volts at 5280 watts ]
4500 watt @240 volts is 18.75 amps
Merci,Marc
Tags: 220v, 110v, baseboard, heaters, difference, branch circuit, pole breaker, continuous load, double pole, double pole breaker
