Logic behind the 125/250 30A socket??

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Old 01-06-10, 03:09 PM
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Logic behind the 125/250 30A socket??

Trying to understand the 125/250 recepticle on generators and other things. Is it mainly used as a connection for generators? I dont see many appliances using it (but I live in cave). You can buy a cord that plugs into it and splits it into 2-15A 110 recepticles (y) for $12 which I could see useful on a job site, but there are usually 2 110 20A recepticals right next the this one on the generator? Can you wire it to a GFCI recepticle?

Sorry, just an "Andy Rooney" ever wonder....minute.
 
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Old 01-06-10, 03:24 PM
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Some appliances, like a dryer, are 240 volt and 120 volt therefore require a neutral. So your 125/250 volt receptacle and plug will have 4 slots (hot, hot, neutral and ground) instead of a 250 only receptacle which would only have 3 slots (hot, hot, ground)
 
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Old 01-06-10, 03:26 PM
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If you connect it to a jobsite fused power distribution unit (PDU), you can get four 15A 120V circuits. Otherwise it would be connected to a generator transfer panel to temporarily power a building. A few larger machines could use 30A directly like a big heater, air compressor or a small welder.
 
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Old 01-06-10, 03:35 PM
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Example almost all clothes dryers in the US are 120v. Then the manufacturer adds either a gas heating unit or a 240v electric heating element. Therefor you need a 120v line for the dryer and a 240v line for the electric heat. This way the same parts in both a gas dryer and electric dryer and some of the parts are also used in washing machines. Much more economical for the manufacturer to need fewer parts in inventory and have them cross compatible.

On the generators though they are also building in the same power supply you have to your house. A 240v service with a grounded center tap. That makes hooking up to your house easier.
 
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Old 01-06-10, 03:58 PM
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Can the circuit be GFCI protected? It should be given you have the 4 wires, right? Or is the 120 GFCI protected and the 220 not? Can a 220 be gfci? With 2 hot and no nuetral how is voltage leak sensed, the ground? But its not connected to the nuetral bar...
 
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Old 01-06-10, 04:04 PM
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Otherwise it would be connected to a generator transfer panel to temporarily power a building. A few larger machines could use 30A directly like a big heater, air compressor or a small welder.
When it powers a building from generator does it use the 110 or 220 leg? Is that the way to think about it? 110 @ 30 amps = 3300 watts vs 220 @ 30 amps =6600 watts??
 

Last edited by Tolyn Ironhand; 01-06-10 at 05:03 PM. Reason: fixed quote
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Old 01-07-10, 08:43 AM
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Originally Posted by sandyharry View Post
Can the circuit be GFCI protected?
I believe all generators must come with GFCI protection now.

It should be given you have the 4 wires, right?
No. Some generators only output 240V some only 120V and some both.

Or is the 120 GFCI protected and the 220 not? Can a 220 be gfci?
If GFCI is built in to the generator it would likely cover both.

With 2 hot and no nuetral how is voltage leak sensed, the ground? But its not connected to the nuetral bar...
It senses a current leak. For any circuit to function, current must flow in a loop. The GFCI measures current flowing out on one wire and current flowing in on the other then trips if there's a mismatch. It does not matter if we call one wire "hot" and the other "neutral" or "hot and hot", or "black and red" the principle upon which the device works is the same. Current out = Current in.

When it powers a building from generator does it use the 110 or 220 leg? Is that the way to think about it? 110 @ 30 amps = 3300 watts vs 220 @ 30 amps =6600 watts??
It uses both. Thinking of it in terms of wattage is very useful because that measures the actual power without getting caught up on the voltage and amperage.

Most power companies and generator manufacturers in the USA and Canada have standardized on 120V and 240V now, so the power in your example is 3600W and 7200W. You can get two legs of 120V at 3600W each (7200W total) or one 240V circuit at 7200W or some mixture of the two that does not exceed 7200W total.
 
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Old 01-08-10, 07:51 AM
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With one L14-30R you could split that with an off the shelf Y cable into 2 20-amp 110 sockets.

Coleman 3ft., 10-Gauge Generator Cord w/Y Adapter | Generator Cordsets + Plugs | Northern Tool + Equipment

This requires #10 wire for the 30A. What amp at 110 can you split off of a L14-20R which uses #12 wire?
 
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Old 01-11-10, 09:40 AM
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My generator has a 120-volt, 30-amp receptacle. It's for powering an RV.
 
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Old 01-11-10, 10:04 AM
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Originally Posted by sandyharry View Post
With one L14-30R you could split that with an off the shelf Y cable into 2 20-amp 110 sockets.
This cord should have 20A fuses or breakers inline with the 5-20s, which it may have in the splitter assembly that just can't be seen in the picture.

This requires #10 wire for the 30A. What amp at 110 can you split off of a L14-20R which uses #12 wire?
20A -- fuses would not be required in this case because the 20A generator breaker protects the circuit at the proper ampacity.
 
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Old 01-11-10, 12:42 PM
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Originally Posted by ibpooks View Post
This cord should have 20A fuses or breakers inline with the 5-20s, which it may have in the splitter assembly that just can't be seen in the picture.
-Good point never thought about that otherwise you would have 30A flow.....I think there are rectifiers or some other circuitry in the cord assembly that limit the output to each



Originally Posted by ibpooks View Post
20A -- fuses would not be required in this case because the 20A generator breaker protects the circuit at the proper ampacity.
-Interstingly they dont make these cables as there doesnt seem to be a market for these given most generator outlets are 125/250 30A vs 20A whihc are the duplex 110 recepticle.
 
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