Is it safe to connect a Xantrex Prowatt 2000 to my home's main panel?

hekghekg Registered Users Posts: 4
Hello.  I live in a condo where my main panel is actually a subpanel and I bought a pure sine wave xantrex inverter and I want to connect it to a 20amp 240v breaker so that it powers both phases of my condo in case of a power out emergency.  

I would be using a generator disconnect bracket in between the breakers to prevent my 20 amp breaker from being turned one while the main breaker is also on in order to prevent backfeeding back out to the grid.  I'm clear on this part.

Now, I know that this inverter is only 2000 watts at around 15 amps and the outputs on it are only two 120v gfci outlets.   My thinking is to create a cable with one end as a standard 120v plug without the ground and the other end an L14-20 240v plug to connect to the 20 amp breaker that I have designated on my subpanel.   In the 240v plug I would have to bridge the two hots in order to send power to both phases of the subpanel.

So far this is all theoretical because I have not tested it out yet and my biggest concern is the whole live neutral or bonded ground thing.   Has anyone tried anything like this and am I planning anything wrong here?

In my mind this all seems like it should work fine but this is my first time trying anything like this and I do not want to fry anything in the process.

Any help, ideas or suggestions would be greatly appreciated.  Thanks guys!


  • BB.BB. Super Moderators, Administrators Posts: 31,176 admin
    STOP... DON'T DO THIS in this way... It is unsafe, generally illegal, can injure/kill somebody, and void your house/fire/liability insurance.

    There are manual transfer switches and hardware that can interlock panels--But you have to have the right LISTED hardware to do this (and probably a licensed electrician). You will not find any (that I can think of) that would bridge the two phases together when on 120 VAC inverter power.

    What you can do is:
    1. wire up a second sub panel+transfer switch to connect your inverter and power some circuits.
    2. wire up a manual transfer switch to your existing panel
    3. other options.
    The simplest and less amount of work is to purchase a manual transfer switch and wire it to the circuits you would like backed up.

    You (or your electrician) wire up the external transfer switches to your local panel and to your AC inverter, and you should be good to go.

    There are some things to be careful about when using 120 VAC to power "both" phases (120/240 VAC split phase power)... Basically, you have to understand how the neutral is wired in your condo...

    Many places will wire a Black+White or Red+White for 120 VAC circuits. Sometimes, you will find Black+Red+White in one set of Romex (or old knob and tube) wiring. With red+black "hot" wires, they are 180 degrees out of phase--So that when you use power on Black+White, the power on Red+White will "cancel out" the current in the white wire (i.e., 10 amps on black and 8 amps on red will give 10-8=) 2 amps on the white.

    If you wire the blk+red to the same 120 VAC source, the current will add instead (10 amps + 8 maps = 18 amps on white). You have to understand how your condo is wired, and if the circuits you want to back up have a common neutral or not (i.e., you cannot run 120 VAC to blk+red on a common neutral circuit).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • hekghekg Registered Users Posts: 4
    Ok I understand.  I think the transfer swtich to my subpanel is the way to go for me.  Thanks alot Bill  :)
  • hekghekg Registered Users Posts: 4
    Bill I happened to stumble on this video which shows somebody that did pretty much what I had planned to do with the exception that he's using his car to power the inverter instead of a battery bank and his inverter does not have GFCI outlets.  

    Is this completely wrong to do even though he's using that main breaker interlock to prevent backfeeding into the grid?  

    Thanks again
  • BB.BB. Super Moderators, Administrators Posts: 31,176 admin
    edited July 2016 #5
    I should correct myself... Yes, you can easily connect 120 VAC across the Blk+Red behind a (as in the above example) a drier double pole breaker. That would do it "automatically" and is exactly what I did with one of the external breaker setups wired back into my home panel (120 VAC genset and 120/240 VAC main panel).

    What he did with the drier cord is called (in slang) a "suicide plug" -- the plug is "hot" from the AC inverter.

    Will it work, yes. Did he do it, yes. Is it legal, no. Is there the possibility of issues (somebody turns on main breaker while AC inverter is plugged in and/or running?), yes.

    Can it be done for a one time emergency (keep your family warm, pipes from freezing, etc.), yes. Should you make long term plans doing this--Not a great idea. Get the external breaker panel or build out a real sub panel--Highly recommended.

    If you are going to use a fairly large genset sometime (will work with smaller AC inverter too--Just do not turn on all breakers at the same time or your will overload your inverter)--You can get a whole house Genset Meter Base adapter/transfer switch:

    I try not to harp on safety--A "red box" warning post. And then a discussion of the details.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • hekghekg Registered Users Posts: 4
    Thanks again Bill.  I understand alot more now :)
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