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-   -   How to fry a microwave oven: (http://www.diychatroom.com/f18/how-fry-microwave-oven-119606/)

Thurman 10-09-2011 12:05 PM

How to fry a microwave oven:
 
So I've had this 5550 watt generator for a few years now, used it a few times in my business. Then I go and by another travel trailer. So, I decide to see if the generator would support the TT being as I may want to go somewhere with no hook-ups. The generator came with a 25 ft. cord which plugs into the four-blade, twist-lock receptacle labeled "120v/30amp--220v/50amp". The cord has a normal looking 110v receptacle such as a home duplex receptacle and is clearly labeled "110 volts AC". I tried to run the TT from the regular outlet labeled "110 volt" on the generator, but it will not support the A/C unit in the TT. So I turn off everything in the TT, so I thought, fire up the generator and plug up the TT's power cord. As soon as I walk into the TT I smell smoke and see it coming from the microwave and a small table fan. Rush to unplug the power cord, but too late. The microwave and table fan are fried. Thankfully I did turn the TT's fridge off. Then I start checking out everything. The power cord is clearly labeled "110 volt" on the female receptacle end, and "110v/220v" on the large male four-blade twist-lock male plug. But when I take the male plug apart it is wired wrong. Black and white are to the terminals which would give it 220 volts with the ground correct, no fourth wire. So what I had was two hot wires giving 220 volts, a ground, and no neutral. All is correctly wired now, the TT works fine with the generator and I'm looking for a new microwave for the TT. Lesson learned, but wanted to warn others who may have an extension cord that came with their generator: Check to assure the cord is wired correctly for your use.

AllanJ 10-09-2011 12:45 PM

Was it intentionally feeding 240 volts into hot and neutral for 120 volt circuits, or was it a loose neutral problem (no neutral) allowing the voltages to seesaw on both sides of the line?

Thurman 10-09-2011 05:48 PM

Ironically the cord that came with the generator did not have a "molded" male plug on one end. It was one of the "DIY" type plugs you buy at a big box store and put on yourself, that should have been a warning. The generator has two (2) duplex receptacles labeled "110v/20amps", and one large four-blade twist-lock type receptacle labeled "120v/30amp and 220v/50amp". The four-blade twist-lock male plug was wired with the black to one "HOT" leg, the white to one "HOT" leg, no wire at the neutral leg, and the green to the ground. This led 220 volts to the other end of the cord which has a standard 110v female cap, looks the same as one part of a duplex receptacle. Therefore there was 220 volts at the female end with no neutral. The cord itself is 10/3 cord. There is no provision for wiring this up as 220v with two (2) "HOTS", a neutral, and a ground. I'm thinking now that someone had rigged this cord after it left the factory. The photos I saw on the internet of this unit, with cord, show a molded male cap on one end and plainly state that it is a "110v/20 or 30 amp" cord. Done is done now, new microwave coming soon. I'm very thankful that nothing else was damaged.

mpoulton 10-09-2011 06:21 PM

Wow. So that's a 3-conductor (including ground) cable, with no red wire? There's no safe/code compliant way to provide both 120 and 240V from that, then. I made a cord like that once, with 240V on a normal 120V female end, because I run a portable welder and plasma cutter that have 120V 15A plug ends but will operate on 240V with greater output. I painted it red and marked warnings all over it!

That mis-wiring is about as bad as the submersible pump I bought that came from the factory with hot and ground reversed.


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