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Old 12-20-2012, 02:12 PM   #1
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Change heater plug


I have a 240v garage heater that came with a NEMA 6-30P plug. I have no more panel space or outlets for it. Can I swap the plug for a 50-10P and plug it in my weldor outlet?

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Old 12-20-2012, 02:37 PM   #2
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It is dangerous and improper to connect an appliance to a circuit of greater amperage than the appliance was intended to have, whether by using an adapter or by swapping the power plug. If the instructions does not specify the maximum amperage circuit for the appliance, the plug that came with the appliance will also imply said maximum amperage, since plugs come in different amperage ratings.

Should physical mishandling, wear and tear, or rust/rot cause damage to an appliance, its being connected to a circuit of too great an amperage could allow unusually large fault currents that create a severe fire hazard.

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Old 12-20-2012, 03:22 PM   #3
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I'm sorry, I don't understand. The unit uses a max of 20 amps. The breaker is 50 amp. Why is that not a good idea? Thanks.
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Old 12-20-2012, 03:32 PM   #4
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Change heater plug


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Originally Posted by davenk32 View Post
I'm sorry, I don't understand. The unit uses a max of 20 amps. The breaker is 50 amp. Why is that not a good idea? Thanks.
Because the breaker does not adequately protect the appliance or its cord from overload.
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Old 12-20-2012, 03:39 PM   #5
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Change heater plug


With a breaker rated that much above what the heater, and the cord are rated for the the whole cord could be on fire and melting and still not trip the breaker.
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Old 12-20-2012, 03:40 PM   #6
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Is it a only function of large amperages? If I plug a 2 amp device into a 15 amp circuit wouldn't that cause the same situation?
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Old 12-20-2012, 04:20 PM   #7
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Change heater plug


Your missing the point, if the heater is working perfect then everything will be fine.
If there's ever a short, or anything goes wrong with the heater the power will just keep coming to it until it completly catches on fire. There's no safety factor.
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Old 12-20-2012, 04:29 PM   #8
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For example, suppose your cord is rated for 30 Amps, and you use it on a circuit capable of providing 50A. So long as your heater is working properly and drawing just 30A or less, everything's fine.

Now suppose there's a short in the heater (maybe it gets bumped and a couple of the heating elements contact each other) and the total current draw goes up to 45 Amps. The breaker won't trip (45 < 50), but the power cord is now carrying 50% more current than it's rated for.

Since P = I^2 * R, the cord is now dissipating 2.25 times (1.5^2) as much power (heat) as it was designed for, not to mention the sparking taking place at the short.
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Old 12-20-2012, 04:36 PM   #9
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Old 12-20-2012, 04:37 PM   #10
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Got it. Thanks. How about if I replace the cord and the plug?
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Old 12-20-2012, 05:06 PM   #11
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Got it. Thanks. How about if I replace the cord and the plug?
There's internal wiring in the heater, a thermostat or two, probably a couple of switches... all sized based on 30A maximum current.
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Old 12-20-2012, 05:12 PM   #12
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Originally Posted by AllanJ View Post
It is dangerous and improper to connect an appliance to a circuit of greater amperage than the appliance was intended to have,
Is this code ? or just best practice ?

Whilst I can see the safety aspect of it !
It would be impossable to enforce,

Cause that would mean I couldnt plug a 1 amp load
into a 10 amp circuit !

See what I mean !
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Old 12-20-2012, 05:36 PM   #13
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Change heater plug


If you are not using the welder, you could replace the 50 amp breaker with a 30 and change the receptacle.
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Old 12-20-2012, 05:41 PM   #14
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Change heater plug


Quote:
Originally Posted by dmxtothemax View Post
Is this code ? or just best practice ?

Whilst I can see the safety aspect of it !
It would be impossable to enforce,

Cause that would mean I couldnt plug a 1 amp load
into a 10 amp circuit !

See what I mean !
But that 1 amp load will be connected to the plug with #16 or #18 wire, not the #28 or #30 wire that can handle 1 amp.

Seasonal example: All the Christmas light strings I've seen lately have the fuses right in the plug, before the skinny wiring that goes from bulb to bulb.
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Old 12-20-2012, 05:42 PM   #15
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Change heater plug


Quote:
Originally Posted by dmxtothemax View Post
Is this code ? or just best practice ?

Whilst I can see the safety aspect of it !
It would be impossable to enforce,

Cause that would mean I couldnt plug a 1 amp load
into a 10 amp circuit !

See what I mean !
because the cord and plug and design of, say, a clock radio, is all made and designed to be plugged into up to a 20 amp circuit.

A heater designed to be plugged into no more than a 30 amp circuit, should not be modified by changing the plug so it could be inserted into a 50 amp circuit.

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#2 - If you follow my advice and something bad happens see # 1
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