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Old 07-13-2011, 12:00 AM   #1
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#12 internal wiring in a GE 4500w water heater


why would a company internally install #12 guage wire when it needs #10 guage (4500w or 18.75A). My breaker will not protect the internal wiring.

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Old 07-13-2011, 12:48 AM   #2
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#12 internal wiring in a GE 4500w water heater


Welcome!

#12 allowed internal to the device - circuit the heater is plugged into must be #10.

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Old 07-13-2011, 12:59 AM   #3
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#12 internal wiring in a GE 4500w water heater


code requirements for fixture wiring different than in wall requirements.
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Old 07-13-2011, 08:48 AM   #4
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#12 internal wiring in a GE 4500w water heater


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why would a company internally install #12 guage wire when it needs #10 guage (4500w or 18.75A). My breaker will not protect the internal wiring.
Different ratings on the insulation allow for higher amperage loading.

FYI, the actual amperage rating (at 60C) on the #12 used in Romex is 25A, but the NEC sets the limit at 20A for most uses.
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Old 07-13-2011, 02:55 PM   #5
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#12 internal wiring in a GE 4500w water heater


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Originally Posted by pdolph View Post
why would a company internally install #12 guage wire when it needs #10 guage (4500w or 18.75A).
Where are you fining where it says it "needs" #10ga???
Not in the NEC I hope.
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Old 07-13-2011, 08:48 PM   #6
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#12 internal wiring in a GE 4500w water heater


The 4500 watts is more than likely the total load of both elements. A water heater is wired to operate only one element at a time.
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Old 07-13-2011, 10:02 PM   #7
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#12 internal wiring in a GE 4500w water heater


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My breaker will not protect the internal wiring.
That is not the purpose of the breaker.
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Old 07-13-2011, 10:10 PM   #8
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#12 internal wiring in a GE 4500w water heater


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The 4500 watts is more than likely the total load of both elements. A water heater is wired to operate only one element at a time.
Nope it is 4500 watts per element. If they both were to operate at the same time (which they don't) the load would be 9000 watts.
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Old 07-13-2011, 10:14 PM   #9
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#12 internal wiring in a GE 4500w water heater


Manufacturers design and construct their internal wiring, protection devices, and controls to standards not found in the NEC. For example, my GE wall oven draws 30A at 240 volts, hence the external wiring from the breaker to the connection box is #10 Cu wire. The internal wiring in the oven is #16 gage, and uses very special, extra high temperature rated insulation. This is perfectly legal, because NEC does not control wiring internal to the device.
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Old 07-13-2011, 10:32 PM   #10
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#12 internal wiring in a GE 4500w water heater


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Originally Posted by HouseHelper View Post
Different ratings on the insulation allow for higher amperage loading.

FYI, the actual amperage rating (at 60C) on the #12 used in Romex is 25A, but the NEC sets the limit at 20A for most uses.
The actual ampacity of #12 is determined by such factors as type of wire, the ambient temperature in which it is used, and the application not the insulation rating. For example 12 ga. can be used for up to 41 amps in chassis wiring, less than 20 amp in high temp application, or 9.3 amps for transmission lines. The temperature rating of the insulation is determined by environmental factors such as high temperature of ovens not the amperage that is used.

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Old 07-13-2011, 10:55 PM   #11
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#12 internal wiring in a GE 4500w water heater


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The actual ampacity of #12 is determined by such factors as type of wire,
Are you referring to the core material?
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Old 07-13-2011, 11:09 PM   #12
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#12 internal wiring in a GE 4500w water heater


core material composition, high silver, copper, aluminum, etc
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Old 07-14-2011, 07:10 AM   #13
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#12 internal wiring in a GE 4500w water heater


Haweye I do not know what you mean by the words "actual ampacity". In the NEC, wires are rated for allowable amperage, which is simply referred to as the ampacity. And for all wires, one of the factors that determines the allowable current flow (ampacity) is the insulation. See the following link for "Ampacity of Copper and Aluminum Wire" http://www.allenelectric.com/referencedata/ampacity.htm.

Note that for example that for #8 wire, using the 60 degree C rated insulation, the ampacity is 40A. The same copper wire using 75 degree C insulation is rated for 50A. The same wire using 90 degree C insulation is rated for 55A. The other factors you mentioned (free air versus conduit, number of wires in the conduit, outside temperature, type of wire, application) also are part of determining the ampacity, but to state that the insulation is not part of the ampacity determination is incorrect. The point of all the computations is to determine how hot the wire is expected to get, and to prevent the insulation from melting. The insulation melts or burns long before the copper, so you are protecting the insulation from excessive heat, hence the use of higher temperature rated insulation in ovens etc.
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Old 07-15-2011, 12:46 AM   #14
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#12 internal wiring in a GE 4500w water heater


You can have wiring with the same insulation temperature rating used in fixture wiring,romex, and chassis wiring all with different "allowable amperage" depending on application. The high temp requirement for the oven is due to the ambient heat generated by the appliance not by the amperage through the wring nor does the high temp rating increase the allowable amperage of the particular wire size.
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Old 07-15-2011, 09:12 AM   #15
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#12 internal wiring in a GE 4500w water heater


Haweye, you really are a skeptical guy. "nor does the high temp rating increase the allowable amperage of the particular wire size.". I posted a table taken right out of NEC that shows that the allowable amperage for a particular wire size (I chose #8) is greater for 90 degree C insulation than for 60 degree C insulation, but you don't believe it. This is true for all wire sizes.

The reason the allowable amperage goes up with higher temperature insulation is that the temperature reached by the insulation depends on several factors, ONE of which is the amperage. Heat loss generated by wire resistance is I * I * R, where I is the current (amperage), and R is the resistance. So as the current increases, the heat loss increases, and the temperature seen by the insulation goes up, meaning you need higher temperature rated insulation. Insulation temperature also goes up if the wire is in conduit rather than free air, if the environment is hot (read oven), or if you have several wires close to each other. But current always effects insulation temperature.

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