We live in a rural area where electrical service from the local utility is sometimes interrupted for a few/several days by winter storms - accompanied by high winds - that blow down large evergreen trees across electrical transmission lines.

So, (to ensure we have residential electrical power during an extended power outage) we have two "paired" Honda EU2000i portable gas generators. They’re both small, red and quiet. We have a small “pairing” cord set from Honda that allows us to connect two of these generators together (aka “pair” them) for approximately twice the output amps.

The Honda generators have a round 3-prong female receptacle/plug on the face of the generator to accept a round 3-prong male plug from a power cord (to connect the generator power to a load).

We also have a 30 amp Honda "Gen Tran" - Generator Transfer Switch that has been professionally installed to the breaker box in the garage (for the house).
The 30 amp Gen Tran Switch (part # 32310-189006) has 10 circuits, and a male 4-prong locking plug power inlet to receive the female end of a 4-prong power cord that is connected to a generator power supply.

Note: Each circuit on the Gen Tran Switch must be individually, manually moved from “Line” to “Off,” and then to “Generator Power,” in order to safely transfer generator power to a specific electrical circuit in the house without back-charging the line coming into the house from the utility pole. Then, when utility power is restored, each circuit powered by the generator must be individually, manually switched back to “off,” and then to “line.”

Here’s the challenge/question, and it involves wiring/creating an adapter to allow the round 3-prong female generator outlet to be connected to the 4-wire power cord that plugs into the Gen Tran Switch:

We have a “4 wire, 10 gauge, 25’ power cord” (purchased from Home Depot) to connect the "paired" generators to the Gen Tran Switch.
The respective female/male ends of this power cord are both round 4-prong, and wired as follows • Green “Ground” • Red “Y” • Black “X” • White “W”

The round 4-prong female end of the power cord plugs into the male prongs on the face of the Gen Tran Switch just fine, but the 4-prong male end of the power cord won’t plug into the round 3-prong female receptacle on the generator.

So, I will need to wire/build an adapter (with a Round 4-prong FEMALE plug on one end, and a Round 3-prong MALE plug on the other end) in order to be able to connect the "paired" generators the Gen Tran Switch. I plan to use an 18" piece of 10 gauge 4-wire, and two locking plugs, to create the adapter.

On the adapter, how should the 4-wires be connected to the 3 terminals for the wires on the male end of the adapter? My un-informed layman’s approach would be to either:

A. Amputate the green wire from the 3-prong male plug (that will be plugged into the generator) altogether, or alternatively to B. Wire the Green Ground wire and White neutral wire together...

... And then, in either case, to wire the remaining “Y” to “Y” and “X” to “X” for both ends of the adapter.

Thoughts or recommendations?

  • 1
    Don't think this is possible. The three prong plugs are for 120 V and the 4 prong are for 240 V. Recommend you ask the electrician who installed the GenTran switch to change the 4 prong receptacle to a 3 prong. And please, don't connect neutral and ground - this is unsafe.
    – Mark
    Commented Jan 5, 2015 at 5:32
  • Can you post a photo of the three prong plug?
    – Tester101
    Commented Jan 5, 2015 at 11:05

1 Answer 1


I looked up the Honda EU2000i Owner's manual, and it appears these generators are only rated for 120 volt output.

Honda EU2000i Generator specifications

I couldn't find much detail on the transfer switch you mentioned, but from what I could find it appears to be a 120/240V transfer switch.

If you were to connect the generator to the transfer switch, only half of the circuits would work, and you'd not be able to power any 240V loads. This is because the generator is designed to only supply 120 volts, whereas your home (and the transfer switch) work with a 120/240V system.

If you really want to proceed, which I wouldn't recommend. The adapter cord would have a standard 20 ampere three prong plug ("hot", "neutral" ground) on one end, and a four prong ("hot", "hot", "neutral", ground) plug on the other. The wiring would be as follows:

  • Three prong "hot" to four prong "X".
  • Three prong "neutral" to four prong "neutral" (W).
  • Three prong ground to four prong ground.
  • four prong "Y" not used.

With this setup, only the circuits labeled "A" on the transfer switch will work (or maybe only "B" will work, depending on the internal wiring).

My recommendation; based on the fact that you seem to indicate that the power in your area is somewhat unreliable, is to purchase a larger 120/240V generator. This should plug directly into the transfer switch, and will power both legs (A and B), as well as supply 240 volt loads.

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