Question for brickeye

stash-hdyJanuary 26, 2013

Brickeye, Read your answer on another question on breaker size for an oven. The oven I bought has the following specs in the manual. Is the 30 amp breaker the correct size as listed in the manual? The 80% comment makes me question the 30 mp breaker size.

Amp Rating at 208V -

30

Amp Rating at 240V

30

Bake Wattage

2100W

Broiler Wattage

3600W

Convection Wattage

2500W

KW Rating at 208V

5.4

KW Rating at 240V

7.2

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brickeyee

If you need 7.2 kW you need a 40 amp circuit.

    Bookmark   January 26, 2013 at 3:44PM
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stash-hdy

brickeyee thanks,

What is the significance of the 208V in the oven mauual, I assume I have 240V in my house? My present oven wiring is 3 wire - white, black and red.

This post was edited by stash-hdy on Sat, Jan 26, 13 at 17:17

    Bookmark   January 26, 2013 at 5:07PM
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brickeyee

208 V appears in some larger building like apartment buildings.

It is referred to as a 'wild leg' (or ;high leg') derived from 3-phase power.

    Bookmark   January 26, 2013 at 6:40PM
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btharmy

The 208v. listed in the install instructions is most likely refering to the 120/208v. 3 ph wye systems found in commercial office environments where an oven will be installed in a break room or catering kitchen. Not the hi leg of a 240v delta system. Nobody would/should connect it to the high leg of a 240v system?

    Bookmark   January 26, 2013 at 7:46PM
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stash-hdy

Thanks again, the oven I am replacing has a 50 amp breaker both were installed when the house was new. I bought a 30 amp because of what was in the manual, I will get a 40 amp and install that. Appreciate your time

    Bookmark   January 26, 2013 at 8:27PM
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petey_racer

An oven such as this is not considered a full load continuous load. Meaning it is NOT expected that the whole unit will draw a full 30A for 3 hours or more.
A 30A breaker would also be FINE.

    Bookmark   January 27, 2013 at 8:45AM
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brickeyee

Since there is nothing to limit the period of power draw, it IS a continuous load.

    Bookmark   January 27, 2013 at 1:03PM
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stash-hdy

Ok guys should I use a 30 or 40 amp breaker. My wife during the holidays will be using both ovens for a good portion of the day. Last thing I want is an unhappy wife because the oven stopped working. 30 or 40 amp breaker??

    Bookmark   January 27, 2013 at 1:41PM
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btharmy

The key to a range NOT being a continuous load lies in the NEC definition of "continuous load".

It states-
"A load where the maximum current is expected to continue for 3 hours or more."

The simple fact that the oven portion of the range turns on and off in order to maintain its set temperature rules it out as a continuous load. Not to mention, all available burners would also have to be on, and set to their maximum setting, at the same time for at least 3 continuous hours.

This post was edited by btharmy on Sun, Jan 27, 13 at 16:46

    Bookmark   January 27, 2013 at 4:23PM
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brickeyee

Since there is no hard limit on the range that limits it to 3 hours or less, it does not met the rule.

Nothing prevents you from leaving the door open, turning all the burners on, and using the range as a heat source.

    Bookmark   January 27, 2013 at 4:45PM
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petey_racer

"Since there is nothing to limit the period of power draw, it IS a continuous load."

Sorry Brick, you are completely wrong here.
There is NOTHING in the NEC that states to be a continuous load the load must not be able to run for three hours or more. In fact the load can ABSOLUTELY run for three hours or more and still NOT be a continuous load.

The key word here is "expected" as btharmy clearly points out.

    Bookmark   January 27, 2013 at 4:46PM
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petey_racer

A related note would be to ask why then is a 12kW range allowed on a 40A circuit?
The same philosophy applies.

    Bookmark   January 27, 2013 at 4:49PM
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stash-hdy

30 or 40 amp breaker???

    Bookmark   January 27, 2013 at 7:32PM
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petey_racer

If the wire is at least #8cu then either.

    Bookmark   January 27, 2013 at 7:47PM
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stash-hdy

thanks

    Bookmark   January 27, 2013 at 8:50PM
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greg_2010

Doesn't the manual trump everything? It states 30 amp so you use 30 amp.

    Bookmark   January 28, 2013 at 8:26AM
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brickeyee

Not if it is an outright violation in some cases.

You would need to examine the full lab listing (UL or other) to determine what the manufacturer is certified as.

The manual is just a summary of the listing, often written by people with no real idea of what they are doing besides operating the product (how the controls work, how to clean the surfaces, etc.).

Look at the other question that has a gap in the instructions that leave a hole in the branch circuit requirements.

X below 7.2, Y above 7.3.
What do you use FOR 7.3?

    Bookmark   January 28, 2013 at 9:33AM
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