# Electric Heater



## 99cents (Aug 20, 2012)

jordandunlop said:


> Hey guys I always get confused on this one. With an electric furnance or even a electric construction heater the amperage rated on the equipment must be multiplied by 1.25 to meet the right amperage and breaker size. CEC 62-114(8)
> Just so you know I am a Journeyman Electrician just needing a refresher.:thumbsup:


After reading that rule, I don't know if circuit loading for space heaters is any different than any other circuit using an OCPD rated as noncontinuous (the 80% rule).

The rule is simply telling you that you take the amps of your heater, multiply by 1.25 and then you are allowed to go up to get your industry standard breaker size.

I might be wrong. Space heating is %&@#ing confusing.


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## BBQ (Nov 16, 2010)

If it is like the NEC they force us to consider a heater as a continuos load even though it might not be. So yes, nameplate rating times 1.25 and move up to next size breaker.


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## wcord (Jan 23, 2011)

jordandunlop said:


> Hey guys I always get confused on this one. With an electric furnance or even a electric construction heater the amperage rated on the equipment must be multiplied by 1.25 to meet the right amperage and breaker size. CEC 62-114(8)
> Just so you know I am a Journeyman Electrician just needing a refresher.:thumbsup:


Brain farts happen:huh:
Yes you are correct. 1.25 is the magic multiplier

But only with electric heat that has motor (fan)
Baseboard wiring and breakers are allowed at 100%
and don't start thinking that electric hot water tanks fall into that rule!
Their wiring is at 125% like fan heaters
No time this morning to look up the rule numbers, sorry


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## aftershockews (Dec 22, 2012)

wcord said:


> Brain farts happen:huh:
> Yes you are correct. 1.25 is the magic multiplier
> 
> But only with electric heat that has motor (fan)
> ...


Crap, I have been using 125% when sizing circuits. I could have put 3 on 1-20 amp circuit the other day but split with 1 and 2. Ran 2 circuits.


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## jordandunlop (Feb 28, 2009)

Thanks for your input guys much appreciated:thumbsup:


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## 37523 (Dec 30, 2012)

> _multiplied by 1.25 to meet the right amperage and breaker size. _

In my older NEC, this is section 210.19.A 

For "Continuous loads" the conductor ampacity and breaker must be 125%. 

The phrasing is tricky. What about a mix of continuous and non-continuous loads? If you are taking an Exam, you need to study (or write it on your palm). 

Definition of "Continuous" is in Definitions, NEC section 100, 3 hours or more. 

My *loose* interpretation: 

A wire may be loaded 100% but not forever. Some hours at MAX temperature is OK, 24/7 service will slow-cook it. When that will happen, we load to only 80% of ampacity and breaker. 

"Continuous" is not rigorously defined. Some things can run 3 hours but hardly-ever. 

If the power has been out for days, baseboard heat may run a few hours to bring the house up to heat, but will then cycle 20 min on 30 min off, never again 100% on. And those few times it runs steady is when the place is cold, so wire is unlikely to burn. 

OTOH, a water heater may run for hours to re-fill, then again for hours as baths and dishes happen. In some households a water heater hardly gets a break. 

A kitchen range may max-out over 50 Amps but if you ran 50A or 12,000 Watts in a small kitchen for a couple hours you could poach an egg on the sink. The water boils in 10-20 minutes and you shut-off. Soup simmers 4 hours on low-low. The turkey takes 2 hours but the oven cycles off/on to hold 300. 

Electric furnace? If you are casting bullets, it's maybe 20 minutes per heat and cold for months. OTOH my friend had a pottery kiln that had to run for days non-stop. Before a show she would cook for a month straight. 

Construction heater.... well, if just run so carpenters can work, it will run 7 hours a day 20 days in a month, and then they move on. It sure may run "3 hours", but not for the life of the house. And there's usually somebody around if it smokes. OTOH at some point you need to bring the house up above 60 deg F for a week so the plaster or wall-mud can dry. And they like it _warm_. Nobody may be around 20 hours a day or over the weekend. I'd be conservative. 

A clue: I got a garage heater, 5,600 Watts. Or 23.33 Amps at 240V. Why 23.3? Because 125% of that is 29A, just a round-off from a standard 30A breaker. And FWIW, my dryer is 22A. These loads are probably sized for "continuous" 125% duty on standard-value wire and breaker. If an odd load times 1.25 looks sweet, the maker probably thought the AHJ could call it "continuous".


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## Speedy Petey (Jan 10, 2007)

aftershockews said:


> Crap, I have been using 125% when sizing circuits. I could have put 3 on 1-20 amp circuit the other day but split with 1 and 2. Ran 2 circuits.


The poster you replied to is in Canada. In the US fixed electric heat is considered a continuous load.
424.3(B)


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## sparky250 (Aug 28, 2012)

wcord said:


> Brain farts happen:huh:
> Yes you are correct. 1.25 is the magic multiplier
> 
> But only with electric heat that has motor (fan)
> ...


Your saying you can 100% load a breaker not marked for 100% duty??? I thought we still can only load the breaker 80% but can load the conductor 100%. What I have been doing ( under the new code ) is now 14/2 is good for 20A, so I am putting 4800W on it and a 25A/2P breaker.


" Where a service, feeder, or branch circuit is used solely for the supply of energy to heating equipment, the
load, as determined using Rule 62-116, shall not exceed
(a) 100% of the rating or setting of the overcurrent devices protecting the service conductors, feeder
conductors, or branch circuit conductors when the fused switch or circuit breaker is marked for
continuous operation at 100% of the ampere rating of its overcurrent devices; or
(b) 80% of the rating or setting of the overcurrent devices protecting the service conductors, feeder
conductors, or branch circuit conductors when the fused switch or circuit breaker is marked for
continuous operation at 80% of the ampere rating of its overcurrent devices.
(7) Service, feeder, or branch conductors supplying only fixed resistance heating loads shall be permitted to
have an ampacity less than the rating or setting of the circuit overcurrent protection, provided that their
ampacity is
(a) not less than the load; and
(b) at least 80% of the rating or setting of the circuit overcurrent protection.
(8) Notwithstanding Subrule (7)(b), where 125% of the allowable ampacity of a conductor does not
correspond to a standard rating of the overcurrent device, the next higher standard rating shall be
permitted. "


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## l0sts0ul (May 7, 2011)

It's the same calculation as a motor calc except you don't have the infamous "SHALL NOT EXCEED" (in a godly tone) caveat that throws a wrench in things from time to time. 

My rule? Err on the safe side and if there is. Chance t lad can run continuos for any reason, calculate and install accordingly. I'd prefer to be safe than sorry for the customers sake and my piec of mind. 

Dont forget motor calcs when figuring branch, feeder, and service numbers or you'll hate yourself later.


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## sparky250 (Aug 28, 2012)

l0sts0ul said:


> It's the same calculation as a motor calc except you don't have the infamous "SHALL NOT EXCEED" (in a godly tone) caveat that throws a wrench in things from time to time.
> 
> My rule? Err on the safe side and if there is. Chance t lad can run continuos for any reason, calculate and install accordingly. I'd prefer to be safe than sorry for the customers sake and my piec of mind.
> 
> Dont forget motor calcs when figuring branch, feeder, and service numbers or you'll hate yourself later.


I am still not understanding where it says we can load breakers to 100% for circuits that supply only heating loads.......


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## FastFokker (Sep 18, 2012)

sparky250 said:


> I am still not understanding where it says we can load breakers to 100% for circuits that supply only heating loads.......


62-114 Overcurrent protection and grouping

(6) Where a service, feeder, or branch circuit is used solely for the supply of energy to heating equipment, the load, as determined using Rule 62-116, shall not exceed
(a) 100% of the rating or setting of the overcurrent devices protecting the service conductors, feeder
conductors, or branch circuit conductors when the fused switch or circuit breaker is marked for continuous operation at 100% of the ampere rating of its overcurrent devices; or
(b) 80% of the rating or setting of the overcurrent devices protecting the service conductors, feeder conductors, or branch circuit conductors when the fused switch or circuit breaker is marked for continuous operation at 80% of the ampere rating of its overcurrent devices.

(7) Service, feeder, or branch conductors supplying only fixed resistance heating loads shall be permitted to have an ampacity less than the rating or setting of the circuit overcurrent protection, provided that their ampacity is
(a) not less than the load; and
(b) at least 80% of the rating or setting of the circuit overcurrent protection.

(8) Notwithstanding Subrule (7)(b), where 125% of the allowable ampacity of a conductor does not correspond to a standard rating of the overcurrent device, the next higher standard rating shall be permitted.


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## sparky250 (Aug 28, 2012)

FastFokker said:


> 62-114 Overcurrent protection and grouping
> 
> (6) Where a service, feeder, or branch circuit is used solely for the supply of energy to heating equipment, the load, as determined using Rule 62-116, shall not exceed
> (a) 100% of the rating or setting of the overcurrent devices protecting the service conductors, feeder
> ...


So are we looking at 
62-114 Overcurrent protection and grouping

(6) Where a service, feeder, or branch circuit is used solely for the supply of energy to heating equipment, the load, as determined using Rule 62-116, shall not exceed
(a) 100% of the rating or setting of the overcurrent devices protecting the service conductors, feeder
conductors, or branch circuit conductors when the fused switch or circuit breaker is marked for continuous operation at 100% of the ampere rating of its overcurrent devices??

Almost all of the breakers we order here in Canada are rated for 80% duty.


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## l0sts0ul (May 7, 2011)

Listen. You can never load a breaker above 80% unless its is marked as such. This is why we have duty cycles, deratings etc. 


If your space heating load is x amount of amps, you must multiply by 1.25 for the FLA and go to table 2 for the conductor size. Then go to table 13 to find the next available breaker size if the fla does not fit an already set breaker size. 

Does that help?


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## Stickshaker (Jun 29, 2012)

jordandunlop said:


> Just so you know I am a Journeyman Electrician just needing a refresher.:thumbsup:


Then why does it say Master Electrician under your name?:blink:


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## rubeshares (Jan 18, 2013)

It's funny sometimes how we forget things we already! But anyway, it seems everybody has reminded you what to do.


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## bennysecond (Jan 18, 2013)

l0sts0ul said:


> If your space heating load is x amount of amps, you must multiply by 1.25 for the FLA and go to table 2 for the conductor size. Then go to table 13 to find the next available breaker size if the fla does not fit an already set breaker size.


Don't limit him, maybe he wants to run it in free air or Al, :thumbup:


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## anthonydavis4188 (May 16, 2012)

rubeshares said:


> It's funny sometimes how we forget things we already! But anyway, it seems everybody has reminded you what to do.


Ha ha ha:thumbup: Thats true.


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## l0sts0ul (May 7, 2011)

Yay! I want a post point too


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