I have an electric Power generator and have a manual transfer switch to use a Power generator when the utility power is out. So the electric power generator is used as is with bonded neutral when used stand alone, but must be set to floating neutral when connected to the transfer switch, per the instructions from the manufacturer. I originally installed a switch to the screw on the case, but it is rated to 250V 20 Amps, but my generator has a max of 240V 50 Amps 9KW.
It is difficult to find a small enough switch for 240V 50 amps AC that can fit inside the generator housing. I was thinking if I can use an isolation switch like those used for car batteries that are rated at 500 amps, but at 12 DC Volts.
The bonding cable is the top right white cable screwed on the casing.
Battery isolation switch
The transfer switch has the neutrals connected along with ground to the home.
Best Answer
The root problem is you are modifying an appliance that is UL-listed, thus, voiding the UL listing. And further, you create a situation that Code really does not like, where a procedure is essential to safety. Code wants interlocks to be mechanical.
Assuming this thing has an internal GFCI to keep you honest, the problem is on the other side: when you've disconnected it from the house and are now using it portable, and you forget to restore the N-G connection. Again the internal GFCI will protect you here, if it exists and works - but not every outlet has GFCI. In fact the company has a page on how to disconnect the N-G bond for powering a refrigerator (which often trip GFCIs).
I am a huge fan of "permanent wiring done temporarily", so I would just bolt on a small box and put the appropriate wrenches in that box, and simply follow the factory procedure for removing/reapplying the N-G bond.
If you had to use a switch, I agree, a 12V switch is probably insufficient. Your best bet that's readily available is 30A snap switches intended for water heaters etc. If it's 2-pole, parallel it. (still a codevio, but more suitable for the service).