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-   -   Wire Choice 12/2 or 14/2 (http://www.diychatroom.com/f18/wire-choice-12-2-14-2-a-103633/)

Pentium 05-04-2011 11:51 PM

Wire Choice 12/2 or 14/2
 
Installing Baseboard Electric Heaters 120vac 1500watt units throughout home. To have choice of Electric or Oil Heat to save money hopefully using electric when the price of oil is unrealistic.

The breakers I will be installing are 20amp breakers, so I am guessing that I should go with 12/2 (20amp wire) instead of 14/2 ( 15amp wire ) since you probably want your wire rated equal to or greater than your breaker. 14/2 can handle 1875 watts, even though the heater for each feed from the breaker will draw maximum of 1500watts.

Another important detail is that the breaker box is at one end of my home and the furthest run is about 75 feet when you add up length + angles for the run. My concern with 14/2 is that under 1500 watts at 75 feet it will heat up even though its rated for 1875 watts. I am guessing I should install 12/2 to have a maximum 2500watt service to each heater, which will definately avoid a long run from heating up?

Should I go with my gut with 12/2 or go with 14/2, because 14/2 will be fine for that long run drawing 1500 of its 1875watt rating?

mpoulton 05-04-2011 11:59 PM

Your wire size must be matched to the circuit breaker. You cannot use #14 on a 20A breaker, you must use #12.

frenchelectrican 05-05-2011 12:20 AM

There the other thing you have to figure out the wattage requirement if you are going full baseboard heaters you will need to figure out about 10 watts per sq foot in your house and it may push the 100 amp service to the limit.

If you going to use quite few baseboard heater I will recomoned that you go with 240 volt verison so you can have more basebord heater on that circuit.

again becarefull if you use 120 volts 20 amp circuit I will recomened that you loaded up to 16 amp max { 1920 watts } while the 240 volts you can go much as 3840 watts on 16 amps therefore just give you a head up per NEC code the electric baseboard heater are condersing as contiounus use heater { I know thermostat will cycle it }.

otherwise check with the POCO sometime you may get a reduced rates if you run the baseboard heater at nighttime I know few do that.

Merci,
Marc

Saturday Cowboy 05-05-2011 01:39 AM

with heaters wire ampicity must be calculated at 125%.

mpoulton 05-05-2011 01:58 AM

Quote:

Originally Posted by Saturday Cowboy (Post 642428)
with heaters wire ampicity must be calculated at 125%.

I thought that was true for breaker ampacity, but not wire ampacity. No?

Saturday Cowboy 05-05-2011 03:08 AM

oh no! ur gonna make me look it up??? NOPE I got a homework assignment for you.

mpoulton 05-05-2011 03:14 AM

It's only a relevant difference in the case of special-purpose circuits like HVAC compressors and welders, where the OCPD may be larger than the conductor ampacity. If it ever matters to me, I'll look it up then.

Saturday Cowboy 05-05-2011 03:24 AM

U lazy slop, ask a question and then refuse to educate the DIY population, and make me do it 4 u??:furious: U called me on it, u do the leg work.


Check 424.3 B

210.19A & 210.20A

mpoulton 05-05-2011 04:12 AM

A brief survey of the wisdom of the internet (code book not accessible from the chair I'm in unless I lean reeeeealy far) indicates that the derating for continuous loads applies to both conductors and OCPD's, separately.

NJMarine 05-05-2011 05:42 AM

424.3(B) states something like: "Fastened in place electrical heating equipment shall be considered a continous load".

Speedy Petey 05-05-2011 06:05 AM

Why not use 240v heaters and double the capacity and use half as much wire???
One electric heater at 120v is no big deal. A whole house full of them makes absolutely NO sense at all.

A 20A/240v electric heat circuit can safely handle 3840 watts.

sirsparksalot 05-05-2011 01:15 PM

Quote:

Originally Posted by Pentium (Post 642402)
14/2 can handle 1875 watts...

1800-W, and after derating, only 1440-W

a7ecorsair 05-05-2011 01:37 PM

As others have said, you need to revisit your plan. If this is all new wiring you should do it in 240V. You do know that you can attach multiple units to one 240V circuit.

Piedmont 05-05-2011 03:33 PM

I'd revisit the plan another way.

A gallon of oil burned for heat produces 40.7kWh of heat. I pay $0.23 per kWh so I can either pay $3.70 to burn a gallon of oil or pay $9.36 in electricity to produce the same heat. You have to be rich to use electricity for heating.

I'd take the total of your electric bill and divide it by the kWh you used to get a realistic kWh you pay. I pay something like $0.11 per kWh but after transfer fees, renewable fees, taxes, I end up at $0.23/kWh in the end.

Reason being, fuel doesn't convert to electricity very well (it converts to heat extremely well) so power plants are usually at most around 40% efficient at turning the fuel they burn into electricity but you have to pay for 100% of the fuel they burn to get 40% back as electricity. Then there's around 7% loss in the lines transmitting it to ones house. It is typically the most inefficient and expensive form of heating... even with oil prices rising like crazy.

BTW not all fuel is created equal, propane and natural gas takes 1.6 gallons to have the same heat as a gallon of oil. So, if oil cost is less than 1.6x the cost of propane it's still the winner. That's one reason it's so hard to find a replacement for oil, nothing has the energy. One benefit of propane/natural gas is they typically don't require yearly maintenance which saves about $100 around here. Have you considered a wood or pellet stove?


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