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Old 08-15-2011, 07:34 PM   #1
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Confused about dryer circuit


Hey guys,

When looking through the code book it states to use 5000 VA or the nameplate whichever is higher in determining the dryer load. I understand that this is to be used when calculating the loads on a home when you will be installing a new service, etc.

My new dryer draws 26A. When looking in the code regarding branch circuits it says that the conductors and overcurrent device should be sized no smaller than 125% of the load. I have 10/3 NM protected by a double pole 30A breaker. This is what came with the home and may have been sized right for the original dryer. My calculations tell me that I need larger conductors and a larger breaker. Also the code states that cord and plug connected equipment shouldn't draw more than 80% of the circuit rating. Of course my 26A draw exceeds that too.

Am I looking at this right or is 10/3 protected by a 30A breaker standard installation for all dryers?

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Old 08-15-2011, 07:44 PM   #2
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Confused about dryer circuit


That is the standard installation

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Old 08-15-2011, 08:14 PM   #3
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Commercial dryers would use a higher rated breaker, same for wiring, but since you are not installing a commercial grade dryer (I hope you didn't get one of those beasts, because they are loud), go by the standard that has always been done on home type use dryers.
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Old 08-15-2011, 08:25 PM   #4
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Confused about dryer circuit


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When looking in the code regarding branch circuits it says that the conductors and overcurrent device should be sized no smaller than 125% of the load.
It certainly does NOT state this as a blanket statement.
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Old 08-15-2011, 08:27 PM   #5
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Confused about dryer circuit


210.19(A)(1) General. Branch-circuit conductors shall have an ampacity not less than the maximum load to be served. Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum branch-circuit conductor size, before the application of any adjustment or correction factors, shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load.
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Old 08-15-2011, 09:43 PM   #6
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Confused about dryer circuit


So Petey....how would you size this circuit? Wouldn't you consider the nameplate amp draw as continous?
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Old 08-15-2011, 09:51 PM   #7
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Confused about dryer circuit


Quote:
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Wouldn't you consider the nameplate amp draw as continous?
For a residential dryer? Absolutely not. Why would you?

Do you know what the NEC definition of a continuous load is?

Quote:
A load where the maximum current is expected to continue for 3 hours or more.
Key word: EXPECTED
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Old 08-15-2011, 09:52 PM   #8
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So Petey....how would you size this circuit?
30 amps and #10 wire.

The only caveat is the "one cord and plug connected load 80%" rule. For 26 amps though I think you are fine.

Last edited by Speedy Petey; 08-15-2011 at 09:55 PM.
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Old 08-15-2011, 10:15 PM   #9
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Confused about dryer circuit


Ok, thanks Petey. I guess my problem is determining if something is expected to draw maximum current for three hours or more. Yes, I am aware of the definition of continous. I was just thinking that my wife seems to do laundry all day sometimes and it seems as though the washer and dryer are on constantly. I see your point though. Thanks for your help.
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Old 08-15-2011, 10:40 PM   #10
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Confused about dryer circuit


If it shuts off for only one second every 2 hours and 59 seconds it is not a continuous load.
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Old 08-15-2011, 10:46 PM   #11
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A fan motor, irrigation pump, pool circulation pump, riser pump in a hi-rise for potable water, those would run continuous. Such as a pool circulation pump, it would run for 8 hours or more. A fan motor, such as what we had on board ship, run all of the time, and only time we would shut them off, is if we were doing PM on them, or during General Quarters for a ship's emergency, or NBC drill.

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Old 08-15-2011, 10:56 PM   #12
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I think I have a better understanding now. Thanks guys
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Old 08-16-2011, 01:06 AM   #13
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Confused about dryer circuit


Majorty of the electrique dryers are not contiounus load due the heating element will cycle as the termosat demand so it will kick on et off so I treat this as non continous load { the commercal dryers are diffrent story }

#10-3 NM with ground will suit this just fine with 30 amp breaker. { our French verison will have either 24 or 32 amp breaker depending on model et conductor size }

Merci,
Marc

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