Continuous Load Circuit

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tryinghard

tryinghard

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California
Is Article 210 specifically the code to qualify how to circuit a continuous load?

As example in 2002 424-3(B): "The ampacity of the branch-circuit conductors and the rating or setting of overcurrent protective devices supplying fixed electric space-heating...shall not be less than 125% of the total load"
and 2005 424-3(B): "Fixed electric space-heating equipment shall be considered continuous load"
 
When your dealing with when and where to apply the term continuous load
do not over look the definition in article 100.
 
tryinghard said:
Is Article 210 specifically the code to qualify how to circuit a continuous load?
Click to expand...

If I understand your question correctly I would say that 210.19(A)1 is the section in Article 210 that mandates how to size branch circuit conductors when they supply a load that is considered continuous .
 
ibew441dc said:
If I understand your question correctly I would say that 210.19(A)1 is the section in Article 210 that mandates how to size branch circuit conductors when they supply a load that is considered continuous .
Click to expand...

So 424-3(B): "Fixed electric space-heating equipment shall be considered continuous load" means I shall [must] use 210-19(A)1 to install the circuit because it is continuous.

So a branch-circuit size for a 4000 watt heater is calculated at: 1.25 x 4000 = 5000/240 = 20.83A, can this be a 20A circuit or does the fraction .83 cause it to be 30A?
 
tryinghard said:
So 424-3(B): "Fixed electric space-heating equipment shall be considered continuous load" means I shall [must] use 210-19(A)1 to install the circuit because it is continuous.

So a branch-circuit size for a 4000 watt heater is calculated at: 1.25 x 4000 = 5000/240 = 20.83A, can this be a 20A circuit or does the fraction .83 cause it to be 30A?
Click to expand...


220.5(B)

I didn't write it , I just accept it.
 
tryinghard said:
So a branch-circuit size for a 4000 watt heater is calculated at: 1.25 x 4000 = 5000/240 = 20.83A, can this be a 20A circuit or does the fraction .83 cause it to be 30A?
Click to expand...

Put your meter on it. What? It's 243 volts? That's okay, the poco can deliver up to 10% more or less than the nominal voltage.

5000/243=20.5 round down and use a 20a two pole. All set!
 
ibew441dc said:
220.5(B)

I didn't write it , I just accept it.
Click to expand...

I'm not so sure this article can apply because it's used only for "computing branch-circuit, feeder, and service loads".

I tend to agree with you but how does your answer with my example apply differently than installing dwelling units according to the 3VA or even non-dwelling to 180VA?

There have been great discussions here that Article 220 is for calculations only and not to install, even though most of us do install non-dwelling recept.'s honoring the 180VA calculation. The interesting thing is we are supposed to use Article 220 to install feeders and services :-?

I think NEC needs to clarify how to apply "continuous load", the 2002 424-3(B) version was clear. Maybe 210-19 needs an (A)(2) for clarity of specifically how to apply a continuous load?
 
jerm said:
Put your meter on it. What? It's 243 volts? That's okay, the poco can deliver up to 10% more or less than the nominal voltage.

5000/243=20.5 round down and use a 20a two pole. All set!
Click to expand...

I would use this but maybe Article 220 does apply and if so 220-5(A) tells me I "shall" use 240V.
 
In summary correct circuit sizing for fixed heaters see:
424-3(B) "Fixed electric space-heating equipment shall be considered continuous load"

Now follow the trail for installing a continuous load:
210-19(A)(1) Conductors, "Branch-circuit conductors shall have an ampacity not less than the maximum load to be served. Where a branch circuit supplies continuous loads...the minimum branch-circuit conductor size...shall have an allowable ampacity not less than...125 percent of the continuous load."

210-20(A) Overcurrent Protection, "Where a branch circuit supplies continuous loads...the rating of the overcurrent device shall not be less than...125 percent of the continuous load."

Notice its not 80% (the reciprocate of 125%) of branch-circuit rating like what's stated in 210-23(A)(1)

An example circuit of a 3000W 240V fixed heater is:
Conductors: 1.25 x 3000 = 3750 so 3750/240V = 15.6A, #12 THHN
Breaker: 1.25 x 3000 = 3750 so 3750/240V = 15.6A, 20A

An example circuit of a 2000W & 1500W 240V fixed heaters is:
Conductors: 1.25 x 3500 = 4375 so 4375/240V = 18.2A, #12 THHN
Breaker: 1.25 x 3500 = 4375 so 4375/240V = 18.2A, 20A

An example circuit of a 4000W 240V fixed heater is:
Conductors: 1.25 x 4000 = 5000 so 5000/240V = 20.8A, #10 THHN
Breaker: 1.25 x 4000 = 5000 so 5000/240V = 20.8A, 30A
 
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