120 to 220V transformers? For 3000W Generator

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9,568
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Ontario, Canada
Anyone use a step up transformer on a 120V generator to plug into 220V generator panel? We have a seperate generator panel wired for a 220V generator that has the basic functions of our house wired through it. The generator panel has a switch to seperate it from the main panel. Do I have to worry about 1 phase vs 3 phase power? I suspect I do as I think each side of the 120V panel is one leg of the 220 coming into the house. The main issue is that our well pump is 220V, every thing else of importance is 120V in the house. Maybe the best solution is just use the transformer to run the pump seperate from the panels at all? We have a big hotwater tank to use as water storage. Thanks, Ian
 

IndyIan

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9,568
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Ontario, Canada
Watts remains the same, at either voltage, amps get cut in half. Our only real loads are the fridge, freezer, and well pump, everything else is gas or we don't have it. Lights are all CFL's, hydronic heating with tiny pumps, etc...
 
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12,385
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Northern CA
The vast majority of North American home wiring is single phase. The 220-240 volt service is opposite sides of one phase and the 110-120 is from one leg of that phase to the neutral connection. This may help. http://www.batteryjunction.com/sevenstar-3000.html Problem is that if you want 110-120V also then you need some more wiring. I think you could go from one side of the 240V out to ground for 120V but I'm not an elecrocutionist. Assuming (a dangerous word) that your generator has enough capacity, your idea of running the pump voltage up-converter as a separate load off the generator and bypassing the panel sounds like a good approach. How much power does the pump take to start.
 
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Duvall WA - Pacific NW USA
You are correct. But a small 3000W (peak?) generator will have a tough time powering much more than a fridge and a few small items, so stepping up to 230 doesn't seem to make sense.
 
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Southeast Alabama
Locked roter amperage is 3 to 5 times running amperage. As a rule of thumb 1 HP = 746 watts plus the 3000 peak generator is just that. No way in the world that you can run what you describe!
 

IndyIan

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 Originally Posted By: SrDriver
Locked roter amperage is 3 to 5 times running amperage. As a rule of thumb 1 HP = 746 watts plus the 3000 peak generator is just that. No way in the world that you can run what you describe!
The well pump is 1/2hp, about 400W, times 5 makes 2000W. So I guess if the fridge and freezer were on at the same time plus a couple hundred watts of other stuff starting the well pump might overload the generator for a moment which I'm not to worried about. Its a EF3000iSE yamaha and rated 2800 continuous and seems to have a massive flywheel. I tested it before we bought it running a 1500W hair dryer and starting up my 1500W mitre saw and it had no trouble even when nearly stalling the saw jamming it through 2x12's, even in economy mode which drops the rpms to match the load. Also the well pump only has to handle 40-50ft of head to start which is not making it work to hard as its good for 300ft+. It would be nice if it had more peak power but its what I've got for now. XS650, I found that transformer but I wonder if it has the capability to do 3000W through one plug? In and out. Even if it doesn't do the whole house, having around just to run the pump alone is worth the money...
 
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12,385
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Northern CA
 Originally Posted By: IndyIan
XS650, I found that transformer but I wonder if it has the capability to do 3000W through one plug? In and out. Even if it doesn't do the whole house, having around just to run the pump alone is worth the money...
If your pump only takes 400W running, you could use a smaller transformer and only run the pump off of it. A 15 Amp 120V outlet can handle 1800W which should start your pump OK.
 

IndyIan

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 Originally Posted By: XS650
The vast majority of North American home wiring is single phase. The 220-240 volt service is opposite sides of one phase and the 110-120 is from one leg of that phase to the neutral connection.
So it sounds like I'm good with the 220V single phase output of the transformer, the generator panel is set up to use 220V input, using 220V for the well pump but still have 110V circuits usable as well for parts of the house. I'll ask my electrician just to make sure of what I'm thinking of doing.
 

JHZR2

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New Jersey
well a 220V is two phases of 110 separated by 90 degrees, right? What he intends to do is just hop one of the two phases to 220 via transformer. I think you do not have enough conductors to then properly operate a normal 220 device. Am I mistaken? The next step would be 208V legs which are 120 degrees out of phase and form a 480V system, right?
 
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Ohio
 Originally Posted By: JHZR2
well a 220V is two phases of 110 separated by 90 degrees, right?
Nope, 180 degrees. Sounds plausible, but do make sure your 220 side of the transformer is center tapped, and that center tap will need to be connected to the neutral bus bar, otherwise, you could end up with more than 120 volts on one 120 volt line and less than 120 on the other.
 

IndyIan

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Yikes this is complicated! So what I need is the 220V outlet on the transformer to have atleast 3 conductors? One ground and 2 live ones? I'll have to look at the plugin for the generator into the panel when I get home, I think it might have 4 conductors but atleast 3 if my memory is right. I'm not in a hurry to do this thankfully, as I have quite abit to learn before I buy anything...
 
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Ohio
 Originally Posted By: IndyIan
Yikes this is complicated! So what I need is the 220V outlet on the transformer to have atleast 3 conductors? One ground and 2 live ones? I'll have to look at the plugin for the generator into the panel when I get home, I think it might have 4 conductors but atleast 3 if my memory is right. I'm not in a hurry to do this thankfully, as I have quite abit to learn before I buy anything...
A typical 220 volt connection should have 4 connections: Two hot leads that have 220 VAC between them, a neutral lead which would have 120 volts between it and either of the hot leads, and a ground. If you use your transformer, the 220 volt side of the transformer must have a center tap, which would be the neutral. The lines coming from your utility pole carry the 2 hots and the neutral, and the transformer on the utility pole is center tapped. If you don't have the center tap, you'll have BIG problems.
 

IndyIan

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I finally looked up what a center tap is, I don't know why I didn't right away... Must've had a pre-google flashback. I'll make sure the transformer has one, I guess many 220V appliances wouldn't need a center tap? So a small transformer might not come with one... Thanks for your patience! Ian
 
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11,458
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Illinois
I'm still trying to figure out why you want to use a step-up transformer. If you have a breakout box, don't you have 220v going into the box, with the 110v loads split between the two legs? Go look at your breaker box where the commercial power comes into your home. You have two black wires, that have 220v across them, and the white neutral. If you can see the copper conductors, you can see that they alternate so every other 110v breaker is on one of the black wires. The next breaker is on the other one. The voltage between any one black wire and the white neutral is 110v. That's why a 110v breaker takes up only one slot in the box. Any 220v breakers, such as A/C or your pump take up two slots because they connect to BOTH sides of your commercial power, for the 220v between the two hot wires. This breakout box you mention, isn't it wired in the same fashion? Perhaps it should be if not. That way, you can have 110v and 220v circuits coming out of it. So can't you just find 220v in that breakout box you mention, and wire to the circuit for the pump, and not mess with the transformer? The transformer is a parasitic load, even when you are not running the pump. So why throw away all that energy when you already have 220v from the generator and perhaps from the breakout box itself.
 
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11,458
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Illinois
Of course, when I did this, I just added a 30A circuit with a L6-30R and made a special male-male cable to go from my generator to my breaker box. If my commercial power went off, I switched off the main, switched off any circuits I didn't want to feed in the house, started the generator and then switched on the 30A breaker to that L6-30R. I supposed I should have used a four conductor circuit, but I figured if the utility co can only use three, as long as I grounded the gen set outside, I could also use three conductors to feed the power to my home. It worked great and didn't back-feed into the utility system since my main breaker was switched off. I don't think it passes code, but it works and is safe. That's certainly a lot simpler than your breakout box and transformer solution. Theoretically, I could have turned on any circuit in my home. I simply didn't have enough to run an A/C or electric range with my 5500W generator.
 

IndyIan

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Ontario, Canada
My well pump is 220V, its about 100 feet from the house and 120ft down so we needed to got to 220V. Also the generator panel plug in outside is wired to accept 220V, I should've got our electrician to wire it for 120V but I didn't think of it at the time. He assumed our generator could do 220V. I think the generator panel solution is the code's way to prevent backfeeding into the grid. There is a switch that breaks the connection to the main box/grid while connecting the generator to the generator panel. I guess it also makes it more idiot proof as none of the big loads go through the generator panel making it harder to overload the generator. The transformer at the generator solution is simpler for my wife to do, just plug in the transformer, then plug it in, flip the switch at the panel and turn the key on the genny, continue life as normal... I wouldn't even really care about the well pump running as we have big hotwater tank, but we have a small collection of livestock which would go through the water in our hotwater tank in 1 or 2 days. According to wikipedia there are transformers that are quite efficient with little dead load but I don't know if the $100 7 star 3000W version is one of them. I'll have to do some research.
 

JHZR2

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My question would be if you need a phase shifter to get you 180 degrees out. I am nogt getting past the fact that you need to have an additional conductor to properly provide 220V properly, since each leg is ONLY 120V, not 240V. I havent done the math to verify it...
 
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8,986
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Marshfield , MA
the original 220 feeds for my electric range and dryer were 3 conductor cables, 2 hots and a bare ground wire. In the panel, the neutral and the ground buses are tied together. The 220 baseboards are wired in the same fashion. The feeds are 12-2 romex. The newer electrical codes dont allow this anymore. Gotta be 3 conductors plus the bare ground.
 
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