Results 1 to 4 of 4

Thread: How to get 240V split phase for off-grid

  1. #1
    Join Date
    Dec 2010
    Location
    I can see Mexico from my back yard
    Posts
    210

    Default How to get 240V split phase for off-grid

    Can you wire any of the smaller, say 300 watt, inverters together to get 240V split phase or is a 120v/240v transformer the cheapest way to do this?

    I'm trying to come up with a way to bootstrap my grid tied array during an extended power outage. I don't really expect one, but it's better to be prepared and not need it than the other way around.

    I'm already wiring in a generator inlet with lockout so I can bring my house up off grid during power outages, but I'm trying to figure a way to do it with an inverter instead.

    I have a Prosine 1800 that I use in my workshop and I can dig up a 1-2,000 watt transformer. That's probably the way I'll go, but I'm trying to make sure I consider all of the available options.

  2. #2

    Default Re: How to get 240V split phase for off-grid

    In general inverters not designed to be "stacked" won't; there's no way to synchronize the frequency. Using an autotransformer is best.

    But back-driving a grid tie inverter from an off grid one has more than its fair share of problems too. There's more than one thread about it on the forum. Synchronization troubles, over-powering problems, et cetera. Some have done it with generators too. It's also likely to void any warranty as it is clearly not "intended use".

    Maybe you want to look into the new Xantrex 600 Volt charge controller and a small, stand-alone emergency off-grid set-up. Still cheaper to use a gen for emergency power.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  3. #3
    Join Date
    Dec 2010
    Location
    I can see Mexico from my back yard
    Posts
    210

    Default Re: How to get 240V split phase for off-grid

    One of the advantages of micro-inverters is they will drop out one at a time as you approach the voltage cut off. This is due to slight manufacturing differences in cutoff voltage plus differences in the lengths of wiring.

    I know several people who have successfully tested bringing up Enphase inverters using backup generators. In fact I've yet to hear about anyone that was unsuccessful at trying this.

    From what I understand, the only remaining concern is the voltage limit. I believe the voltage drop in the wiring as well as the transformer will be sufficient to protect the Prosine/etc.
    I can always modify the transformer windings if needed.

    As I said, this idea is for extended power outages. I won't bother with it for typical outages that only last a few minutes to a couple hours.

  4. #4
    csulto Guest

    Default Re: How to get 240V split phase for off-grid

    I have enphase as well and are looking for the same thing. I have seen some 240v inverters at The Inverter Store but I am not sure how picky Enphase is about the voltage.

    I was considering a generator as well but if I was going to use that I might as well just have a large generator and be done with it. A solar "primer" for the Enphases would be ideal.

Similar Threads

  1. 240V dual phase inverter?
    By Dill in forum Off Grid Solar & Battery Systems
    Replies: 54
    Last Post: February 1st, 2014, 21:46 PST
  2. stacked vs split-phase vs transformer
    By ChrisOlson in forum Off Grid Solar & Battery Systems
    Replies: 7
    Last Post: October 29th, 2012, 17:36 PDT
  3. Sanyo Split system? for off grid
    By Jcrabtree in forum Off Grid Solar & Battery Systems
    Replies: 21
    Last Post: August 4th, 2011, 18:26 PDT
  4. Three phase power to grid tie inverter
    By NZRR in forum Advanced Solar Electric Technical Forum
    Replies: 6
    Last Post: January 11th, 2011, 10:26 PST
  5. Can I backfeed 2-phase 240V through one 1" knockout?
    By psablo in forum Grid Tie and Grid Interactive Systems
    Replies: 8
    Last Post: November 26th, 2009, 16:20 PST

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •