Help with the inverter

Hi guys i have a 6kw setup and im looking for inverter im kinda newbie in this, so i'm looking for some advice. I would like to hear ppl with experience with cheap inverter and with some good inverter. I have seen a few with 2 year warranty so they will probally last 3-4 years at a really low price, but maybe im wrong and i will have to change them every 2 years and it would be better if i just buy a sunny boy, xantrex, outback, etc. I just want some guidance.


thanks for your help,
Nap

Comments

  • mike95490mike95490 Solar Expert Posts: 8,471 ✭✭✭✭✭
    Re: Help with the inverter

    Is this inverter for grid-tie, or off - grid use ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators, Administrators Posts: 29,736 admin
    Re: Help with the inverter

    Sounds like off grid inverter.

    Are you looking for tsw or msw inverter?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Help with the inverter

    off grid and whats the different between tsw or msw?
    thanks for answering and helping
  • BB.BB. Super Moderators, Administrators Posts: 29,736 admin
    Re: Help with the inverter

    Here are a couple of Inverter FAQ's:

    All About Inverters
    Choosing an inverter for water pumping

    Basically, the first choice between expensive and cheap inverters is TSW (True Sine Wave) or MSW (Modified Sine aka Square Wave) type inverters.

    TSW is basically like the 120 VAC you get out of your home wall outlet from the utility company. A sine wave.

    MSW is a modified form of a square wave. (+150 vac, 0 vac, -150 volts, etc.). Because of the sharp edges (leading/trailing edges) and the flat top at the peak voltage (crest of the waveform)--Many devices that have capacitors, inductors, diodes, electric motors, etc. don't like MSW very well... Tends to make the devices run hot and use more power than the normally would use (wasted energy upwards of 20%).

    Now, roughly 80% of your 120 VAC stuff will work fine, and around 10-20% can overheat, have a short life, or not work properly. A few may even fail immediately.

    What may not work well--Small wall transformers/power bricks (chargers, laptop computer adapters, DVD players, sometimes battery chargers for power tools, etc.). Some electric motors may overheat (refrigerator, other small/high duty cycle) and fail early (or may not). Things with timers may not time correctly (electronic timers).

    And much of your stuff may work perfectly fine or a bit degraded (microwave ovens may take longer to heat, some CFL lamps may buzz a bit, etc.). TV's, Radios, etc. may have buzz in background.

    Now, TSW inverters an be 10x as expensive as MSW inverters ($$$/Watt).

    Once you have made the above decision--then you can look at cost/brand/reviews and see what looks good for you.

    Typically, input voltage is also a major factor in your choices...

    Roughly 1,200 watt or smaller inverters can work OK on a 12 volt battery bank. If you see 2,000-5,000+ watt 12 volt input inverters--probably should stay away from them.

    If you have larger power requirements.... 24 volts is good upwards of 2,400 watts. And above 2,400 watts, you should be looking at a 48 volt input inverter. You are probably going to find fewer "cheap inverters" in the 24-48 volt devices).

    Some folks have addressed the TSW/MSW question by getting a smaller TSW (such as 300 watt) for running the small/sensitive equipment. And use a large MSW inverter for motors/floodlight/etc.

    If this is off grid and you don't have time / inclination to play the will it or won't it work 100 miles from the nearest store--Highly suggest you get a good quality TSW inverter.

    Questions?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Help with the inverter

    thanks for the info it was really helpful. I have to say i must go with the True Sine Wave. Do u guys know a good tsw off grid inverter for 6kw setup. There is other thing, what is better 2 inverter of 3kw or 1 inverter of 6kw?

    Also thanks for the help guys this is really helping me on taking the final decision.
  • BB.BB. Super Moderators, Administrators Posts: 29,736 admin
    Re: Help with the inverter

    That is a tough choice... There are Inverters, Inverter/Chargers, Inverter/Chargers/AC Generator transfer switch support, "search mode" to reduce stand by loads, 120/240 VAC Split Phase systems (or 120 VAC output only that would need a 120:240 VAC transformer), surge power ratings, etc...

    Here are two vendor/models that have very good reviews and are "high function" units.
    Download the glosses and user manuals, look at price and features... Then come back with questions on what you may need for your specific application.

    I have mixed feelings about "combination units" (inverter/charger/transfer switch all in one). When everything is working well--they can be fantastic units.

    When you have problems--the can be a bit of pain in the butt to diagnose and repair.

    Again, not saying these are "the one" for your application--but they are good quality, fair priced, high function units. If there are things you don't need--then you can look at other units and see how they may better match your setup.

    Also, with any inverter/charge controller/electronic power system today--Their realistic life is probably 10-15 years--And for any E device (not just inverters)--They will probably be pretty much unrepairable 10 years from now and when they fail--you will need to perform a full swap out (electronic parts like microprocessors, power electronics, memory, etc. have very short production life these days and are almost impossible to purchase as spares 10+ years from date of manufacture)...

    Am I being conservative or "Chicken Little"--Take your guess... My suggestion is to have money in the bank to buy new units 10+ years from now. If they last longer/don't cost much to repair--you are still ahead of the game. Also, batteries have a definite service life of 4-15 years--Depending on quality of batteries, how they are used, and maintenance performed. And plays heavily in the cost estimate of $$$/kWH for off-grid power ($1-$2+ per kWH for off-grid power costs vs $0.10-$0.20 per kWH for grid power is not a bad starting guesstimate).

    Off grid power is terribly expensive (in the US, it is probably 10+x more expensive for off-grid power vs utility power--so conservation and attention to details during the paper design phase can save you lots of money).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,471 ✭✭✭✭✭
    Re: Help with the inverter

    A single 6Kw inverter is large and expensive

    You might be better served by getting a pair of 3KW, that communicate with each other, and manage loads, by shutting down on, if there is less than 2Kw of load. This saves battery power, but the 2nd inverter is ready to turn itself back on if the system demands it.

    How will you be recharging the batteries ? Some inverters have a charger built in, some don't

    Vendors - the board host:
    Arizona Wind Sun


    I'd suggest 48V battery bank. You cannot easily get 6KW out of a 12V battery bank.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Help with the inverter
    Nappolean wrote: »
    Hi guys i have a 6kw setup and im looking for inverter

    6kw of what? Solar PV?

    You don't buy 6kw of inverter just because you have 6kw of PV unless you are doing grid-tie.

    For off-grid you have to size the inverter according to what the loads will be, not according to how much PV or battery you have.
  • rplarryrplarry Solar Expert Posts: 203 ✭✭✭✭✭
    Re: Help with the inverter

    Not sure why someone would say that 12v systems cannot supply more that 1200 watts or so. I have 2 Outback 2800 watt inverters and a 1600 AH battery bank connected with a short run of 4/0 cable which has worked flawlessly for over 7 years now. Having a 12v battery bank makes it easy to use 12v appliances like water pumps and VHF radios, etc. I like having 2 inverters, if I have a problem with one I can still run my house on the other until I can get other repaired, or replaced.
    My suggestion would be, don't go with a cheap inverter, stick with name brands, you will be happier in the long run.
    Larry
  • BB.BB. Super Moderators, Administrators Posts: 29,736 admin
    Re: Help with the inverter

    I am the guy that talks about the 1,200 watt recommended maximum inverter for a 12 volt system... The big issue is the amount of current and voltage drop.
    • 2,800 watts * 1/10.5 volt cutoff * 1/0.85 invrtr eff * 1.25 NEC factor = 392 amp minimum circuit
    That is above the rating of a single 4/0 cable.

    If you assume 313 amp max current, 11.5 battery voltage under load, and 10.5 volt cutoff--a 1 volt drop. The maximum one-way cable length would be about 25 feet with ~8% losses.

    If you assume 4kW to 4.8kW surge (which the battery must still supply current for)--the numbers look even worse.

    On the other side is charging current... If you assume that typical 60 amp maximum charging current from a solar charge controller and 5-13% charging current--Your 1600 AH battery bank would require 2-4 solar charge controllers. A 48volt battery bank would only require 1 charge controller (1/2 or 1/4 the cost).

    Again, not saying it cannot work--It is just you are spending a lot of money on copper cabling, special fusing, and charge controllers vs what a 48 volt battery bank would require (upwards of 1/4 the copper and charge controller costs).

    If your loads are less than 2,800 watts (times 2 because you have two inverters) because few people load their inverters to 100% rated load for long periods of time--I can certainly understand the system works well for your needs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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