Inverter voltage vs. panel voltage and balance???

kj8olotkj8olot Registered Users Posts: 4

Ok - need a bit of assistance on this one - I have an off-grid system with a pure sine wave inverter with 240VAC out...

Running that into a 2 pole breaker - I am finding that I am getting 240 across both sides of the breaker - BUT - as soon as I switch the break ON - it then throws the voltage to one pole - and the other is dead...what am I missing?

Also - I now realize that the inverter has no earth ground - and the place that I would normally have a ground off the plug - has nothing wired to it internally - SO - what do I need to do to get the voltage to remain 120VAC across both poles AFTER I switch it on and not have the imbalance of voltage?

Thanks in advance - Jim

Comments

  • kj8olotkj8olot Registered Users Posts: 4

    BTW - my guess is that I can not split the phase of the 240 VAC - or use BOTH outputs of the inverter to accomplish what I want - OR really need to have a split phase inverter? Thought I had that - any assistance is appreciated!

  • VicVic Solar Expert Posts: 2,969 ✭✭✭✭

    Hi Kj8olot,   Welcome to the Forum.

    One quick guess.   Many power panels that are supplied by Inverter manufacturers (or with MidNite Panels),  use an Inverter Bypass Breaker set.   This breaker set has a Lockout feature  --  a mechanical blocking device that prohibits both breakers being in the ON position.   Does your double breaker have such a blocking device?  The wiring on these breakers can be a bit confusing.

    Also,  you mention measuring across the terminals of the breaker.   When a breaker is in the ON position,  there would no voltage across it,   as the two terminals of one breaker (or one side of it),   represents a connection  --  a short.   There should only millivolts voltage drop across a good breaker that is in the ON position.

    Little time now,  perhaps I am misunderstanding the situation that you are seeing ...

    FWIW,   Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • kj8olotkj8olot Registered Users Posts: 4

    Hi Vic - thank you for the response - when I drop turn off the main power breaker (to prevent the power coming back on and back feeding into the inverter) I have a double pole single throw breaker that feeds the panel from the inverter - then when the inverter is turned on (prior to flipping the breaker in the panel) I do measure 120 VAC on each terminal of the breaker to ground - BUT - when I turn it on the thus 'feed the panel' - it then only supplies 240 VAC on one leg of the breaker - making me believe that I can't 'split' the phase to each side of the panel circuitry...not sure if that helps - let me know - thank you in advance - and I have to take off for part of the day now too....let me know and I will work hard to clarify!

  • EstragonEstragon Registered Users Posts: 3,490 ✭✭✭✭✭

    You say this is off-grid, so the "main power breaker" has to be turned off to prevent backfeeding from what? Other inverter(s)? Generator(s)?

    It might help if you could post a link to the inverter you have, and maybe pics of the panel and breaker.

    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mcgivormcgivor Solar Expert Posts: 2,759 ✭✭✭✭✭

    The explanation is confusing, if the output of the inverter is 240VAC, 2 wire there is no way of splitting phase, the confusion is because in the first post it's stated the is no ground to the inverter, but in post 3, it's stated the voltage measured to ground is 120V from each terminal to ground.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • BB.BB. Super Moderators, Administrators Posts: 28,853 admin

    Can you give us the brand/model of inverter (or a link to it)?

    Do you have three wires out (in North America, that would be a black and a red wire, both hot. And a white neutral wire)? or do you just have two wires out (no neutral)?

    The three wire would be the typical 120/240 VAC 60 Hz split phase north American Standard. Two wires would be the "rest of the world" with just 230 VAC (and typically 50 Hz) output.

    In either case above, you may also have one more wire, a green wire safety ground (typically connected to the chassis of the AC inverter).

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • kj8olotkj8olot Registered Users Posts: 4
    edited March 16 #8

    Ok - sorry to be 'confusing' and yes, I am backfeeding the main panel in my home when I loose power...thus the reason for killing the main on my panel so that if and when the power company powers back up - it does not backfeed - that's #1 and also - why I am measuring voltage to the ground/neutral bar in my panel

    #2 - I have an inverter like this https://www.amazon.com/Holdwell-AC200-240V-Power-Inverter-5000W/dp/B071RD1Q35/ref=sr_1_8?crid=3MAF19855WFTT&keywords=48vdc+to+240vac+inverter&qid=1552693059&s=gateway&sprefix=48+vdc+to+240%2Caps%2C233&sr=8-8

    #3 - The output on the inverter only has black and white going to the output receptacle - no other wire for ground as normally found on our USA systems - so that's why I made the above comment.

    #4 - if my original musing is correct above - I have a single phase inverter that I can not feed the panel with a 240 double pole breaker as I originally thought - this is why I can not split the voltage across both 'legs' of the panel - that's the only thing I can come up with...

    Hope that clarifies things - let me know if you need additional info - thanks in advance for your kind assistance

  • mcgivormcgivor Solar Expert Posts: 2,759 ✭✭✭✭✭

    The inverter is single phase, the only way to achieve split phase would be through the use of an auto transformer or like. The use of a transfer switch, auto or manual, is needed to prevent potential conflict between sources and or backfeeding the grid, which could put line workers in danger. Furthermore doing this may potentially void home insurance should something go wrong due to the lack of compliance, if applicable. Additionally there may be requirements for permits and professional installation. Always play safe and adhere to the requirements of the authority having jurisdiction.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • BB.BB. Super Moderators, Administrators Posts: 28,853 admin

    Yep, as McGivor saids, a single phase 240 VAC 50/60 Hz inverter... No 120 VAC unless you use some sort of transformer.

    What are your needs/expectation?

    Do you want an automatic switch over of the entire home? (i.e., automatic transfer switch plus auto-start/auto-shutdown on the inverter).

    Or are you looking for a manual transfer switch? There are manual transfer switches that let you switch a limited number of circuits (kitchen, bedroom, sump pump, etc.) manual between main and backup power. Here is a common unit (wire to genset or AC 120/240 VAC split phase inverter, or to a 120 VAC single phase inverter if you do not need 240 VAC).

    https://www.homedepot.com/p/Reliance-Controls-10-Circuit-30-Amp-Manual-Transfer-Switch-Kit-310CRK/205793178

    There are higher end (more expen$ive) AC inverters that can do the auto transfer from mains to AC backup power, and even recharge the battery bank from the inverter (really inverter-charger). And even inverter-chargers that will have AC1 mains & AC2 Genset inputs and protected AC out. (you wire your critical load circuits to the protected subpanel).

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
Sign In or Register to comment.