Which inverter to back feed to sub-panel?

[scanchain]

I am looking for a 1500W (3000W surge) 12V DC to 120V AC inverter to back feed electricity to the sub-panel. Has anyone successfully used one?

One major consideration is that the neutral and ground are bonded together in the main panel so I presume we don't want these to be bonded together on the inverter to prevent ground loops? Where can I find such an inverter? I don't find this information in the specs.

I will be using an interlock plate to prevent electricity from being fed back to the grid.

 

[wyliesdiesels]

Is this for a backup power source?

What is the power source? Batteries solar or?

Why do you want this? What is the purpose?

The neutral should be isolated in the subpanel.

 

[scanchain]

Is this for a backup power source?

What is the power source? Batteries solar or?

Why do you want this? What is the purpose?

The neutral should be isolated in the subpanel.

It's as a backup power source. I will be tapping the 12V terminals from the Chevy Volt.

The neutral is not bonded to ground in the subpanel; but they are bonded in the main panel.

 

[wyliesdiesels]

It's as a backup power source. I will be tapping the 12V terminals from the Chevy Volt.

The neutral is not bonded to ground in the subpanel; but they are bonded in the main panel.

The bonding in the main is fine.

Do you only want to power the subpanel with the inverter?

 

[scanchain]

The bonding in the main is fine.

Do you only want to power the subpanel with the inverter?

Yes. In an outage, this will only power the subpanel. The interlock plate will be in the subpanel.

I guess my question is also : is there generally any bonding between ground and neutral in a gasoline generator?

 

[slow]

Is a 120 volt inverter all you need, or do you need a 120/240 volt split phase inverter, (ie, no MWBC and all critical circuits are either 120 or the entire sub panel is 120 volts)

Depending on the size of the generator they may or may not have the neutral ground bond.

 

[scanchain]

Is a 120 volt inverter all you need, or do you need a 120/240 volt split phase inverter, (ie, no MWBC and all critical circuits are either 120 or the entire sub panel is 120 volts)

Depending on the size of the generator they may or may not have the neutral ground bond.

120V is all I need. I would probably put the circuits I want to run on the same phase.

I don't plan to run 240V equipment. There are no 240V circuits on the subpanel.

 

[Lightning rod]

Not to derail,but you may need to think about this
Never done a house but helped a buddy on his boat
He used a modified sine wave inverter at first and some of the electronics
Didn't like it
Switched to a pure sine wave and all was well
For some reason some electronic boards don't like modified sine wave

 

[rlitman]

Not to derail,but you may need to think about this
Never done a house but helped a buddy on his boat
He used a modified sine wave inverter at first and some of the electronics
Didn't like it
Switched to a pure sine wave and all was well
For some reason some electronic boards don't like modified sine wave

That is because the modified sine wave has awful harmonic distortion.

 

[scanchain]

I do plan to select a pure sine wave inverter.

I am hoping someone had done a similar project before (back feed 120V AC to a subpanel in the house from 12V DC) and could share which inverter was used.

 

[wyliesdiesels]

Yes. In an outage, this will only power the subpanel. The interlock plate will be in the subpanel.

I guess my question is also : is there generally any bonding between ground and neutral in a gasoline generator?

Depends on the generator.

Almost all portable generators have the neutral bonded to the frame.

 

[scanchain]

Depends on the generator.

Almost all portable generators have the neutral bonded to the frame.

I am curious. If this is the case, how do people normally back feed electricity from a portable generator to the house? Won't the neutral be bonded to ground at two points (assuming the frame is at ground)?

 

[wyliesdiesels]

I am curious. If this is the case, how do people normally back feed electricity from a portable generator to the house? Won't the neutral be bonded to ground at two points (assuming the frame is at ground)?

They remove the bond on the generator.

I imagine theres many setups out there with the bond still in place cause the person doesnt know.

But the bond must be removed to ensure safe operation.

 

[scanchain]

Just saw you can buy 3-pole transfer switches. But these are not cheap.

https://www.electricgeneratorsdirect.com/power/gfi-transfer-switches.html

 

[American Locomotive]

An inverter that doesn't internally bond its ground and neutral leads would not be safe. Switchmode inverters are almost always isolated power supplies, meaning their output power is not referenced to earth.

There is exists only one spot in the inverter that's always at 0v potential, and that is its internal neutral connection. The output ground connection needs to be internally tied to the inverters neutral in order to have a place for fault current to go.

If your inverter's ground was floating (not bonded to anything), and you had a fault in some equipment in your house, the fault current would not flow to earth ground because the inverter's neutral is not referenced to earth ground.

 

[nsula_country]

This will stir the pot!

I have done this before. NOT CODE!!! Used 6 TelCo batteries wired in parallel and a 120v 2000w inverter to ride out 4-5 days of outage after a hurricane. Backfed inverter through a subpanel in shed to main panel at the house. Have since acquired a 5500w generator.

Turn off main. Turn off all 2 pole breakers. Make a cord to plug into the inverter receptacle with flying leads on other end (suicide cord). Use a 2 pole 20a breaker and jumper both phases together. Land 120v from inverter (pure sine) to 2 pole breaker with jumper. Land neutral and ground to panel buses. Turn on jumpered 2 pole breaker and turn on inverter. The 120v inverter will feed both phases of the entire panel/panels...

Turn off/remove said 2 pole breaker before turning main back on. Otherwise it's a dead short!

This information is for educational purposes only. DO NOT TRY THIS AT HOME!

CT

 

[slow]

Make sure your inverter is setup to have a neutral/ground bond as stated above. I just read my datasheet on mine. Mine is, it is a Xantrex Statpower PROsine 1000 ($600 1000 watt pure sine inverter, with UL 458 approval) Most of the cheap inverters, I can't even find a datasheet on.

I can't recommend the 120/ on both legs either, but in a severe emergency, that idea may have crossed my mind as well.

edit: I have never backfed by panel with it.

 

[scanchain]

This will stir the pot!

I have done this before. NOT CODE!!! Used 6 TelCo batteries wired in parallel and a 120v 2000w inverter to ride out 4-5 days of outage after a hurricane. Backfed inverter through a subpanel in shed to main panel at the house. Have since acquired a 5500w generator.

Turn off main. Turn off all 2 pole breakers. Make a cord to plug into the inverter receptacle with flying leads on other end (suicide cord). Use a 2 pole 20a breaker and jumper both phases together. Land 120v from inverter (pure sine) to 2 pole breaker with jumper. Land neutral and ground to panel buses. Turn on jumpered 2 pole breaker and turn on inverter. The 120v inverter will feed both phases of the entire panel/panels...

Turn off/remove said 2 pole breaker before turning main back on. Otherwise it's a dead short!

This information is for educational purposes only. DO NOT TRY THIS AT HOME!

CT

Could you please tell me the brand/model of your inverter? Does it have ground and neutral bonded together?

 

[Fixin'Stuff]

It's as a backup power source. I will be tapping the 12V terminals from the Chevy Volt.

I don't know anything about the specs of a Chevy Volt, but:

Are the 12-volt terminals in the Volt rated for continuous draw of that kind of current? 1,500 watts at 12 volts is 125 amps. Since there is some power lost in the inverter, it will actually draw more current it is outputting.

Another question would be, does the Volt have access to all of the battery banks of the car via the 12 volt terminals, or just a small subset of the batteries in order to get just 12 volts?

 

[nsula_country]

Could you please tell me the brand/model of your inverter? Does it have ground and neutral bonded together?

No idea. Haven't used it in years, its somewhere in storage. Also, no idea if bonded internally. I think it had a ground lug on the outside of the case. It was an import inverter from Sams club, modified sine wave, about $90. Microwave oven did not like it! Ceiling fans, television, satellite receiver and CFL bulbs were ok.

I made note of PURE SINE. I did not have one, but would ONLY use a pure sine wave inverter. Modified sine inverters are cheap for a reason.

CT

 

[scanchain]

I don't know anything about the specs of a Chevy Volt, but:

Are the 12-volt terminals in the Volt rated for continuous draw of that kind of current? 1,500 watts at 12 volts is 125 amps. Since there is some power lost in the inverter, it will actually draw more current it is outputting.

Another question would be, does the Volt have access to all of the battery banks of the car via the 12 volt terminals, or just a small subset of the batteries in order to get just 12 volts?

The 12V battery is being charged from the traction battery through a DC-DC converter. If I remember correctly, the DC-DC converter's rating is 2kW. So when there is a draw of 1500W, most of it would be coming from the DC-DC converter.

The thing I like about this setup (if I can figure out how to get it to work) is I don't have to worry about the gas growing stale. The engine in the Volt is very efficient at charging the traction battery. And because the traction battery acts as a buffer, the engine only needs to run intermittently even if the traction battery is depleted.

Here's a discussion

http://gm-volt.com/forum/showthread...Home-in-the-event-of-a-power-outage-emergency

 

[bmh]

EVExtend makes a kit and sells the inverter for the Volt.

 

[scanchain]

EVExtend makes a kit and sells the inverter for the Volt.

Yes, I think they are including the Sunforce PSW inverter. I haven't read anyone backfeeding to the subpanel.

And I have also read inverters which have HOT at 60V and Neutral at 60V. It will be a disaster if such a neutral gets bonded to ground at the main panel.