| My small generator only has 5-15 receptacles with common 120v output and I | need to wire this to a L14-30 receptacle on a transfer switch to provide | 120v power to both sides of the switch so I can use all 10 circuits. I | don't see a problem with this but I can't find anything about it after | many hours of searching the web. So what I plan is to use 2 120v outputs | from the generator and just double up the neutral and ground and then put | each hot lead on the separate hot leads of the the L14-30 thus giving the | same 120v to each side of the transfer switch. The generator is only 2300W | max, so I'm sure there won't be a problem using 12 or 14 AWG scrap | extension cord (SOJT 600V) for this. I'm trying to confirm I'm not missing | something. The generators ground is not common with neutral and the | transfer switch is a Connecticut Electric EGS107501A. I've already wired | the switch in and it works fine from the line side. Just need to get the | generator side hot.
Is the generator producing only 120V or is it producing 120/240V?
If the power source is 120V only, then in theory, by attaching that 120V source to both sides of a 120/240V system, the neutral could see the sum current of both legs. OTOH, your generator is so small that, even if it is just 120V only, we're looking at no more than 20A. As long as you use AWG #12 CU, it should be OK to connect your 120V hots to both sides of the system at the transfer switch. The switch MUST be an open-transition switch, which all small ones are. I can hardly imagine you getting one that is a closed-transition switch.
Not that you'd even want to operate them on a 2300W generator, but I am sure you know this means your 240V appliances will see no voltage difference to speak of, if your generator is 120V only.
FYI: my comments are not so much for the OP (he knows this stuff and is just looking for little things he may have overlooked like one duck out of row) but rather, for the newbies that might be reading this thread.
BTW, isn't SOJT only 300V? Without the J then it would be 600V. But you aren't putting in 480/277 so the SOJT should be OK for 120V or 120/240V.