Bonded or Floating Neutral for generator?

[Larry Caldwell]

An Automatic transfer switch needs to be connected to a generator that has sufficient ampacity to serve all the connected loads at the time the switch automatically transfers. Otherwise you run the risk of damaging a small generator.



The Duramax generator can handle about 30 amps at 240 volts. I would reccommend a dedicated panel for the required loads you want on the generator and just transfer the the dedicated panel loads for standby circuits. Then you can use a less expensive transfer switch. 30 amp instead of a 100 amp transfer switch.

Edit: Or install panel interlocks that lock out the utility main breaker in off position and have the interlock allow a breaker for the generator to be turned on. Then turn off breakers in main panel that the generator does not have enough ampacity to serve, Manually start generator.

A transfer switch does not eliminate the need for load management. That's a big reason an automatic transfer switch should be limited to a really big generator.

I have a 60 amp transfer switch, but my generator will not handle the well pump and the water heater at the same time. If the water heater is on, the well pump will not start, and short cycles, which will damage the starting contacts. If I have to run both at once, I have a dedicated pump generator with no interconnect. You have to unplug the well pump from a 240v socket and plug the pump into the generator for it to work. Generally I can just twiddle breakers to load manage - heat a tank of water, then flip over to the pump to take a shower. In case I am not available, there is a load management page taped beside the transfer box to indicate what breakers to use and when.

 

[Larry Caldwell]

Totally unrelated to the original question, I saw a video of someone trying to charge an EV with a generator, and failing. IIRC, the car required a bonded neutral to accept the connection, and the genset had a floating neutral.

 

[etpm]

A transfer switch does not eliminate the need for load management. That's a big reason an automatic transfer switch should be limited to a really big generator.

I have a 60 amp transfer switch, but my generator will not handle the well pump and the water heater at the same time. If the water heater is on, the well pump will not start, and short cycles, which will damage the starting contacts. If I have to run both at once, I have a dedicated pump generator with no interconnect. You have to unplug the well pump from a 240v socket and plug the pump into the generator for it to work. Generally I can just twiddle breakers to load manage - heat a tank of water, then flip over to the pump to take a shower. In case I am not available, there is a load management page taped beside the transfer box to indicate what breakers to use and when.

I seem to recall seeing a switch that is made for a situation such as yours. Two loads overload the power source so the switch turns off one load when the other load turns on. Actually it prevents one load from turning on until the other load is turned off. I can't remember where I saw this but I'm sure a web search will find several examples. I think I'll look in the morning and report my findings.
Eric

 

[stumblinhorse]

Totally unrelated to the original question, I saw a video of someone trying to charge an EV with a generator, and failing. IIRC, the car required a bonded neutral to accept the connection, and the genset had a floating neutral.

The genset used stand alone, not plugged into a house, would required the neutral to be bonded. If used correctly plugged into a structure, the structure provides the bonded neutral and ground.

Most newer inverters/gensets it is an easy modification, and somewhere in this thread I mentioned I would probably add a switch to my genset to bond or float the neutral as needed.