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Discussion Starter · #1 ·
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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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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Discussion Starter · #3 ·
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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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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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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Discussion Starter · #6 ·
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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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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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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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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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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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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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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Discussion Starter · #16 ·
Thanks to you all. I'm convinced not to take the risk.
It just never occurred to me that a light bulb or clock radio would be built that heavily (20 amps).
Thanks again.
Dave
 

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Those small load doohickes are UL listed to be safely connected to a 20 amp circuit.

Could you imagine if we had different plugs and circuits for 5, 10, 15, and 20 amp widgets?
 

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The heater was designed, listed, and spec'ed to utilize a 30A circuit, the cord and the cord end that came factory installed. Manufacturer specs over-ride the NEC, thus, changing the cord, the cord end, or plugging this into anything other than a 30A circuit, is against code.
 
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I once saw the results of someone switching a plug on one of those large computer room computers. They did this because an appropriate outlet was not available. They also miswired the plug connecting hot to ground and thus wrecking about $40,000.00 worth of computer equipment.

Note this company had their own in-house electrician and the person could have easily called to have the proper outlet installed. (The person who did this no longer works there.)

Bottom line: Various plugs are on equipment for a reason. Call an electrician and have the proper outlet/circuit installed. It might just be the least expensive route to go! (Not only wrecked equipment, but fire or electrocution possible as well.)
 
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