Kiwi
Perhaps where you live a generator neutral cannot be isolated from the frame but every generator I have installed or inspected in Victoria has had an isolated neutral and connected to 3 pole transfer switches. In my 26 years here I have not seen a 4 pole transfer switch installed. As I said My answer is CEC perspective.
I started out as a motorwinder and the two generators we fixed while i worked there could be isolated but I cannot say if they were permanent or portable use.
I have seen that most Portable generators are bonded to the neutral and if used as a permanently installed generator then would require a 4 pole transfer switch. Now you have me thinking about a 5kw transfer switch and plug for connection to a portable that I hooked up 13 years ago. The generator is seldom located at the house but at the owners workplace. That generator might be bonded to the neutral??
