120V Generator to 240V Transfer Panel

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  #1  
Old 10-07-15, 07:42 AM
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120V Generator to 240V Transfer Panel

I recently completed a new cabin in the north woods of Wisconsin.

I had the electrician install several key circuits (fridge, gas furnace, well, and several lighting circuits in a small transfer panel which has an interface connection in the garage.

I currently own a new (never used in a power emergency) Honda 3000is (120V 3000W max.(25A) 2800W rated (23.3A)) .

Since this generator is only 120V, can I SAFELY feed both sides of the transfer panel from the same 120V source? I would need to construct an interface cable between the generator and the interface port in the garage to do this. I realize that this setup could not power any 240V devices and I would have to carefully control which transfer circuits were energized at any given time so as not to strain the generator.

Is it safe to do this?
I could also build two interface cables-----each one feeding a different line in the transfer panel and then just alternate the interface cables when needed.

Comments please.


Thanks,

Bob
 
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  #2  
Old 10-07-15, 08:02 AM
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Yes you can do this with a generator cable or inlet configured to power both poles of the panel. I'd probably make the jump in the inlet box and use a standard 20A 120V inlet and 20A 120V extension cord cable. That way you can use off-the-shelf parts in case you need to grab one from the local hardware when your specialty one ends up lost. If your generator has the 30A 120V RV style plug, go ahead and use that one as cords and inlets are widely available in that style.

The only one of those loads that could have trouble is the well pump. Pump motors are notoriously hard to start with generators.
 
  #3  
Old 10-07-15, 08:13 AM
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Thanks, Ben.

The well pump is 240V so it is already a no go.


Bob
 
  #4  
Old 10-07-15, 03:24 PM
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Go buy at least a 5000 watt 5500 surge minimum generator and the whole problum goes away.
Sell yours on Craig's List to off set the cost.
My 5000 watt would run my water pump, mini split for heat and A/C, lights, TV.
If is shut a few things off for a while I even had hot water.
 
  #5  
Old 10-07-15, 03:38 PM
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I have a Yamaha 120 volt only generator. Rather than a transfer panel I have an auxiliary circuit breaker panel fed through a transfer switch. I wired everything to accept a standard 240/120 input and then I changed the twist-lock receptacle on the generator to a four-wire model, L14-30 with the X and Y terminals in parallel. This outputs to the transfer switch through a standard 4-wire interconnect cable and inlet connection but when the generator is connected it parallels the input of the circuit breaker panel. The one thing to be careful of in this method is that you cannot have any 3-wire (multi-wire) branch circuits using a shared neutral or else the possibility of overloading that shared neutral could become a real hazard.

I see no reason why you could not do the same with your transfer panel and a standard 4-wire interconnect cable.

The best part of my arrangement is that if you or a subsequent owner ever have a standard 240/120 volt generator available it will plug right in with no rewiring necessary even using the same interconnect cable. It IS a good idea to add a label to the generator stating the 4-wire receptacle is only 120 volts with both line terminals in parallel.
 
  #6  
Old 10-08-15, 02:08 AM
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Don't make custom modifications at the inlet on the house or anywhere in the main electrical panel. Make a custom cord for your generator and jump the hots together there.

It's generally cheaper to build a quality custom cord instead of modifying a off the shelf generator cord. Get some 10/3 SOOW cable, NEMA L5-30P(?) male plug and NEMA L14-30R female plug. When connecting up the NEMA L14-30R, add a jumper between the two hot legs. Shop on eBay, and you can make up an excellent 30 foot cord for about $65.

To be safe, make sure you don't have any MWBC wiring, but a 2600 watt (rated, according to my info) generator probably would not be capable of overloading the neutral to a dangerous level, even under the worst condition.
 
  #7  
Old 10-08-15, 06:50 AM
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Since this generator is only 120V, can I SAFELY feed both sides of the transfer panel from the same 120V source?
Do you have any multiwire (shared neutral) branch circuits in the transfer panel?
 
  #8  
Old 10-08-15, 02:19 PM
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Make a custom cord for your generator and jump the hots together there.
In my experience this would be extremely difficult to do in any manner that did not require splicing outside of the plug or connector body. Further, this special interconnect cable could ONLY be used with a 120 volt source feeding a 240/120 panel. By changing (or adding an additional receptacle) the generator receptacle to a four-wire type you can have a standard interconnect cable which can also be used with a 240/1210 generator with no modifications whatsoever.
 
  #9  
Old 10-08-15, 05:56 PM
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Jumping the hots is very easy and cheaper and simpler. (Not my pic, but an example)
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  #10  
Old 10-09-15, 08:48 PM
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That picture appears to be type SJT cable and of a size much smaller than I would ever use for a generator interconnect cable, maybe #16 or maybe #14 at the largest. I use #10 type SOOW cable and the individual conductor's insulation virtually fills the round entry to the screw connections on the plug and connector bodies. No way I could add that jumper.
 
  #11  
Old 10-10-15, 09:34 PM
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You like to argue. It was an example of the wiring, not the wire. I already said use 10/3 SOOW in my original post.
 
  #12  
Old 10-10-15, 10:28 PM
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bg...... Furd brought up a valid point, although the cord idea is a good one, you cannot fit two #10 wires in one slot. Those plugs/receptacles are designed for only one #10 wire per screw terminal.
 
  #13  
Old 10-11-15, 01:05 AM
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If you take a look at that style plug, most of them are perfectly able to accommodate a wire on either side of the screw that clamps down the wire between the two metal plates. This is just like many better quality outlets that allow two wires to be held under one screw/plate.

The hole (in the clear plastic) is also over-sized and able to handle a pair of 10 ga wire on most of these plugs. This is probably because they are sharing housings and internal construction with the 50 amp parts. I have seen some where the hole is indeed too small so it depends on the model plug, but the better ones will accommodate them.

Anyway, I don't have anything more to add unless the OP shows up again needing further advice or help.

Have a good weekend.
 
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