Two generators to a house panel

[Davebones]

I was asked if you can plug two (2) 5500 watt , 240 volt portable generators into a house panel . I never saw this done for a house . Know you have to Sync power house generators for the grid . Can this be done ?

 

[petersonra]

I was asked if you can plug two (2) 5500 watt , 240 volt portable generators into a house panel . I never saw this done for a house . Know you have to Sync power house generators for the grid . Can this be done ?

Normally you would NOT synch them to the grid. They would only be used when the grid is down. You would need a transfer switch to isolate them from the grid.

You can buy inverter type generators that can be synched together.

https://www.electricgeneratorsdirect.com/Honda-EU7000IS-Portable-Generator/p14017.html

Rather than buying two 5500 W inverter generators you might want to consider buying a larger more permanently installed unit that is already hooked up to a transfer switch and to a source of fuel such as natural gas.

 

[charlie b]

Not unless the generators have a paralleling and synchronization component built into their control systems, and that is unlikely. I don't know if you can get a third party device that can manage the process on synchronizing and closing in the second generator. Even if you do safely close in the second generator, the degree to which they will evenly share the load will depend on the respective settings (and control thereof) of their speed governors and excitation currents. Overall, not a good idea.

 

[JFletcher]

I agree with both of the above posters. even if you could find third-party synchronization gear, it's likely to exceed the cost of the generators by a magnitude of order.

an 11 kilowatt generator would be a much better. if they already have the two 5.5 Portables, they're going to be limited to running just one of them to the panel, and using extension cords off the receptacles from the other

 

[Tony S]

I looked in to this in the UK.

Two 7kW 240V Ph→N generators to be synchronised for a small workshop out in the middle of nowhere. The costs just spiralled making the idea a non-starter. Two 7kW generators were marginally cheaper than a 15kW set but the cost of the control swayed the argument.

Another option I looked at was splitting the installation in to two halves, I didn’t like the idea and so never mentioned it.

 

[kwired]

Not unless the generators have a paralleling and synchronization component built into their control systems, and that is unlikely. I don't know if you can get a third party device that can manage the process on synchronizing and closing in the second generator. Even if you do safely close in the second generator, the degree to which they will evenly share the load will depend on the respective settings (and control thereof) of their speed governors and excitation currents. Overall, not a good idea.

A few years ago that answer was true. I think you are starting to see small portable generators with inverter output that can connect multiple generators together to develop higher overall output.

 

[ggunn]

A few years ago that answer was true. I think you are starting to see small portable generators with inverter output that can connect multiple generators together to develop higher overall output.

That's what I was going to say. Some generators now produce DC and use an inverter on the output. Synching genny inverters should be no big deal; we connect PV inverters in parallel all the time.

 

[JFletcher]

A few years ago that answer was true. I think you are starting to see small portable generators with inverter output that can connect multiple generators together to develop higher overall output.

With smaller generators like one or two kilowatt that is true. The link that Bob left to the Honda 7000 / 5500 w inverter generator shows that it can be parallel to another one, however the parallel kit is not yet available for them.

since the inverter generators lack any type of synchronization gear, or the ability to maintain the same speed on more than one generator, they have to be paralleled from the DC side, then run through the inverter. I don't see a technical reason why three or more could not be paralleled in such a fashion.

 

[gadfly56]

Not unless the generators have a paralleling and synchronization component built into their control systems, and that is unlikely. I don't know if you can get a third party device that can manage the process on synchronizing and closing in the second generator. Even if you do safely close in the second generator, the degree to which they will evenly share the load will depend on the respective settings (and control thereof) of their speed governors and excitation currents. Overall, not a good idea.

What if you get two ATS's and split the loads? Or two manual transfer switches and split the loads?

 

[Davebones]

The question I got was they thought they could just take two portable generators and just plug them in to their house panel . They are talking about turning off their main to do this . Didn't mean that they were to Sync to the grid . When I wrote in my original question I said " Know you have to Sync power house generators for the grid " I was talking about power plant generators being Sync to the grid . From what I've read from the answers this is something they really shouldn't try to do ...

 

[JFletcher]

It'll be pretty much impossible to synchronize non inverter house generators together. There is no way to know if they are perfectly in Phase with each other, no way to keep their frequencies identical, no way to ensure they split the load equally.

I think about the worst possible scenario would be to plug in the second generator with it being 90 or 180 degrees out of phase with the first, you're going to make very expensive paperweights out of any load that is plugged in, not to mention probably fry the generator windings before the breakers can trip.

Your options are inverter generators that can be paralleled easily, two house panels and basically two separate electrical systems, or running extension cords off the second generator while the first powers the house panel.

As far as I know only Industrial size generators are ever synched to one another, and the gear to do it is not cheap... May exceed the cost of your customer's house.

 

[Davebones]

Well as Paul Harvey used to say " Now you know the rest of the story " . I was asking this morning how he planned on doing this and he showed me the Generac 6877 parallel kit . From what I saw he has to use the same type inverter generators and he'll only get 30 amps at 120 volt out of it ...