Inverter selection

Jonesz
Jonesz Registered Users Posts: 18 ✭
in Solar Beginners Corner #1
Have been searching and reading but am still confused. I will have a simple system in my fifth wheel RV to replenish battery power I use when boondocking. The basic system will be 1 Kyocera 135W panel, a morningstar 15A mppt controller and 2 UB121100 batteries with total 220AH rating. I want to buy an inverter whose basic function will be to power my TV (on occasion) charge laptop, ipod etc. I am thinking that I would not have to use my microwave, toaster etc. when boondocking. So that being said I understand that "bigger is not necessarily better" due to idling power consumption and of course initial cost So what I am thinking is that smaller inverter paired with a somewhat larger (say a 600W Xantrex prowatt TSW)converter may be the way to go. But I really don't know that I even need the 600 W and if it should be a sine wave rather than a modified wave inverter. Any help greatly appreciated.
Jonesz
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #2
    Re: Inverter selection

    Take a look at MorningStar 300 watt (600 watt 10 minute surge) 12 volt TSW inverter--It has several modes that most small inverters do not--Search mode (looks for >6 watt loads before "turning on") and a remote DC inhibit (a digital on/off remote switch so you can place the inverter power switch in a convenient location). You may still need a DC master switch to turn off all power to the inverter for storage (if your solar panels are covered during storage--the inverter still does draw a bit of current in standby/search mode).

    The MorningStar is a good one to study the specs. on and see if you can do better for your needs.

    Regarding TSW vs MSW:

    All About Inverters
    Choosing an inverter for water pumping

    If you can justify the costs, I would recommend going TSW for the first/main/smaller inverter. There is enough small electronics/equipment that don't like MSW (small wall transformers for various chargers and many computer/electronics power supplies) and can overheat/fail.

    You can always get a large MSW for running power tools in an emergency (small battery banks really cannot support very large loads anyway).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Jonesz
    Jonesz Registered Users Posts: 18 ✭
    #3
    Re: Inverter selection

    Thanx for the good info Bill, I read the articles The Morningstar looks like a good one and I am thinking 300W would look after anything I ask of it. Also really like the 55mAmp on standby. The only thing I can see against is that it is the same price as an Xantrex 1000 prowatt sine and almost $100. more than I can buy the 600W Xantrex for. So I guess the sawoff is Morningstar with better efficiency and reduced standby power usage compared to either Xantrex Prowatt with higher power output. And that in a nutshell is my dilemma. I am thinking that the morningstar may be the best buy for me in the long run. Seems there are different quality levels of Xantrex inverters as these or the lower end of their price range.In your experience would you say that 300W will look after most of my needs. As I say I would forego the Microwave, toaster and coffee maker which can all be replaced by propane appiances when I am boondocking. Boondocking to Shorepower ratio about 50-50 when we are snowbirding.
    Jonesz
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #4
    Re: Inverter selection

    With small off-grid Solar RE systems--Conservation/Efficiency is almost always worth throwing money at...

    But--if you can live with the standby loads/using a large DC power switch and a "regular" inverter--You certainly can save money with other units.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Jonesz
    Jonesz Registered Users Posts: 18 ✭
    #5
    Re: Inverter selection

    Thanx Bill- I will likely go with the Morningstar 300W-I like the idea of the auto Standby feature , efficiency and low draw when operational. I am also thinking that the 300W output is closer to my maximum requirements and therefore in its' sweet spot so to speak. Maybe if I stick to my conservationist guns in power usage this inverter may save me from further upgrades in my PV array.
    Jonesz
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #6
    Re: Inverter selection
    Jonesz wrote: »
    ...Maybe if I stick to my conservationist guns in power usage this inverter may save me from further upgrades in my PV array.

    You will be the first. :p;):D

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #7
    Re: Inverter selection

    We run our entire house on a 300 watt sure sine, and have for ~ 5 years, and we are very happy. Our major AC loads are CFL lighting, paddle fans, laptops, sat modem etc. (we don't have a TV.) It runs very efficiently, makes no noise, induces no noise into radios etc. Unlike most small inverters you can do a true system ground (grounded neutral) with it as well. As for an RV application, I can't imagine needing a bigger inverter.

    Tony
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  • Jonesz
    Jonesz Registered Users Posts: 18 ✭
    #8
    Re: Inverter selection

    Thanx for the other thumbs up Tony! Nice to hear from someone who is operating their setup with this inverter.
    Jonesz
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  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    #9
    Re: Inverter selection

    Can this inverter work without the system ground? I located my shed on asphalt pad, and it might take me a while to pierce it to the proper depth.
    icarus wrote: »
    We run our entire house on a 300 watt sure sine, and have for ~ 5 years, and we are very happy. Our major AC loads are CFL lighting, paddle fans, laptops, sat modem etc. (we don't have a TV.) It runs very efficiently, makes no noise, induces no noise into radios etc. Unlike most small inverters you can do a true system ground (grounded neutral) with it as well. As for an RV application, I can't imagine needing a bigger inverter.

    Tony
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #10
    Re: Inverter selection

    Most inverters will work just fine without any grounding at all (DC or AC side)...

    Grounding is done for several reasons:
    1. everything at equal potential. Water pipes, electrical conduit, your 120 VAC lines are never more than 120 VAC above earth ground (i.e., prevent high voltage line crosses on the utility pole from causing house fires, etc.).
    2. Static charges (a large insulated tower can develop hundreds of volts of static charge) and grounding to earth lighting current.
    3. A few appliances need Earth Ground (or similar) to function correctly (florescent lights may not start reliably, spark type gas flame ignition devices may not function correctly, etc.).
    Improper Inverter grounding may case problems... Typically, MSW inverters do not have internal isolation between DC input and AC output. If you earth ground the battery ground, and try to neutral bond the AC "Neutral"--you usually create a dead short through the inverter and smoke them immediately.

    TSW type inverters, typically, have an internal isolation transformer. You can DC ground the battery post, and AC Ground the Neutral wire (which copies the way NEC code works in North America).

    Ground the AC output on an isolated TSW inverter is not always a good thing... If you are working with hand tools/in wet areas--having an isolated output actually reduces the possibility of shocks/shorts on the AC output. Since neither the L1 or L2 lines are ground referenced (i.e., bonded neutral)--there is no way to get a shock from L1 or L2 to "ground".

    For a small RV, cabin, or portable installation with a TSW inverter--I would not bother with AC grounding and only DC ground if there was a chance of lightning at the location... If you are wiring up audio equipment (i.e., portable stage)--You may want to bond the neutral of the inverter to ground/stage ground so that all the electrical equipment is grounded as designed (some, older?, audio equipment has been known to energize microphone and such when faults occur).

    There are a lot of issues about grounds--and it is difficult to have a one size fits all answer. But for portable/small inverters (and gensets)--everything usually works just fine without a ground rod driven into the earth.

    It is when you have long cable runs/complex setups/lighting/water piping/utility power present/etc. when things get complicated and you need to review what you are installing and what the safety/system needs really are.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #11
    Re: Inverter selection

    The Suresine 300 doesn't care if the AC side is grounded, it is available to do so just for the added shock prevention in a hard wired system. It might make a difference for example on a GFCI protected circuit however. (not grounding)

    Tony
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