80% max. ckt load

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Bill W

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Another thread got me wondering. Does the ckt. begin after the ocpd, or does it include the ocpd? So, if I were expecting, say, an 18A receptacle load, and chose to use a #10 terminated on a 20A breaker, would I be in violation. Please cite code. And no 30A breaker due to 20A spec. receptacle. I say no violation.
 
Bill W said:
So, if I were expecting, say, an 18A receptacle load, and chose to use a #10 terminated on a 20A breaker, would I be in violation. Please cite code. And no 30A breaker due to 20A spec. receptacle. I say no violation.
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Would the load be continous?
210.19
 
celtic said:
Would the load be continous?
210.19
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Assume yes. The exeption there seems tricky.I'm not sure a standard, say, square D QO 20A CB is rated for 100% load. I have had breakers on an 18A load w/ 12/2 wire trip after a short period of time.
 
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Bill W said:
Assume yes. The exeption there seems tricky.I'm not sure a standard, say, square D QO 20A CB is rated for 100% load. I have had breakers on an 18A load w/ 12/2 wire trip after a short period of time.
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Assuming you have a 20A CB that is listed for operation at 100 percent of its rating....and you load it up to 18A (90% +/-)...and use a #10....

Have you considered the voltage drop?
There is no prohibition on INCREASING a conductor for a given CB rating (of course, assuming you could fit a 500MCM under a 20A CB screw ;) ).
The code states the minimum allowable conductor size and OCP device.

I would be looking at the rating of the receptacle...
Table 210.21(B)(2) Maximum Cord-and-Plug-Connected Load to Receptacle ~ for one recept.

Table 210.21(B)(3) Receptacle Ratings for Various Size Circuits ~ for more than one recept.
 
So, 210.3 Tells me the branch ckt. rating shall be determined by the ocpd, even where conductors of a higher ampacity are used. And 210.19 tells me 125 % of continous load must be applied. Therefore a 20A ocpd cannot supply an 18A continously loaded receptacle under any circumstances. Right?
 
Bill W said:
So, 210.3 Tells me the branch ckt. rating shall be determined by the ocpd, even where conductors of a higher ampacity are used. And 210.19 tells me 125 % of continous load must be applied. Therefore a 20A ocpd cannot supply an 18A continously loaded receptacle under any circumstances. Right?
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Right.
210.23(A)(1) sums it up nicely:
Cord-and-Plug-Connected Equipment.
The rating of any one cord-and-plug-connected utilization equipment shall not exceed 80 percent of the branch-circuit ampere rating.
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Looking a bit further, 201.23(A)(2) addresses Utilization Equipment Fastened in Place....50%.
 
OK, so I have a 10KW range. 10000/240=41.67 amps. What size cord and plug do I use and what size CB?
 
infinity said:
OK, so I have a 10KW range. 10000/240=41.67 amps. What size cord and plug do I use and what size CB?
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Didn't that post run on for like 10 pages
 
infinity said:
OK, so I have a 10KW range. 10000/240=41.67 amps. What size cord and plug do I use and what size CB?
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Not sure but my quick response is 220.55. Not over 12kw use column C=80% increasing 5% for each kw over 8 3/4. So, 10kw/240=41.67/.85=35.4
 
celtic said:
Didn't that post run on for like 10 pages
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I was just wondering as I got a call today from a customer who needed one hooked up. I was wondering how I would comply with the 80% rule? I figured a 50 amp circuit with a 50 amp receptacle and cord set. Now I'm not so sure. :confused:
 
infinity said:
I was just wondering as I got a call today from a customer who needed one hooked up. I was wondering how I would comply with the 80% rule? I figured a 50 amp circuit with a 50 amp receptacle and cord set. Now I'm not so sure. :confused:
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see my last post?
 
Bill W said:
Not sure but my quick response is 220.55. Not over 12kw use column C=80% increasing 5% for each kw over 8 3/4. So, 10kw/240=41.67/.85=35.4
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I forgot about applying demand factors to ranges and I haven't looked at table 220.55 in quite some time. So if I remember correctly, 1 range at 10KW would allow me to use Column C. For one appliance the maximum demand in KW would be 8KW according to the table.

8000/240=33.33amps.

Now the question is does this require the 80% factor or can the CB and conductors be sized based solely on the 33.33 amps?
 
Bill W said:
Not sure but my quick response is 220.55. Not over 12kw use column C=80% increasing 5% for each kw over 8 3/4. So, 10kw/240=41.67/.85=35.4
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Where does the NEC indicate that 5% is added to under 12kw?
 
celtic said:
Where does the NEC indicate that 5% is added to under 12kw?
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That confused me as well. Column C is labeled not over 12KW which would fit the range in my question.
 
infinity said:
I

Now the question is does this require the 80% factor or can the CB and conductors be sized based solely on the 33.33 amps?
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210.8(A)(3)
For ranges of 8 3/4 kW or more rating, the minimum branch-circuit rating shall be 40 amperes.
 
celtic said:
210.8(A)(3)
For ranges of 8 3/4 kW or more rating, the minimum branch-circuit rating shall be 40 amperes.
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So although 33.33amps(125%)=41.66amps, this would not apply to this 10KW range which could be on a 40amp circuit.
 
infinity said:
So although 33.33amps(125%)=41.66amps, this would not apply to this 10KW range which could be on a 40amp circuit.
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I'll admit, I'm no expert on electric ranges - I don't think I've ever even hooked one up, all gas in my area - but it would appear that 40A is what you need...CB, wire, cord and plug.
 
infinity said:
I forgot about applying demand factors to ranges and I haven't looked at table 220.55 in quite some time. So if I remember correctly, 1 range at 10KW would allow me to use Column C. For one appliance the maximum demand in KW would be 8KW according to the table.

8000/240=33.33amps.

Now the question is does this require the 80% factor or can the CB and conductors be sized based solely on the 33.33 amps?
Click to expand...
I don't think so. I read it as add 5% to the 80% for each kw over 8 3/4, perhaps I should have chosen 90% rather than 85%, but I still calculate at least 35.4 or greater. I'm often wrong, especially when I'm sure I'm right.
To Celtic: in the notes...
 
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