what to look for when buying an inverter

[reelnative]

im thinking of going 24volt input, and in the 4000 range, are these ones comming out of china any good or just a waist of cash, I see some good deals on ebay on them.

is there some better name brand ones out there or are they most all the same.

also I see most say pure sound wave is that a plus?

can you run more then 1 if you want more power or do you  need to just get a bigger unit

[Barn Owl]

You might have to wait for Sean (Our Odyssey) to chime in on this one. I feel he is the is the expert on these questions, and the best at explaining it in a way everyone understands it. Try searching for his post on this topic. He gets these questions a lot.

[Jerry32]

I would think 4KW would be all thaat you would want as that can suck your batteries down in a hurry. I use a 4KW and it takes care of my needs.  Jerry

[bevans6]

Everything you need to know is in the search feature, writ by Sean...  some short layman's answers:

Pure sine wave duplicates most correctly the waveform produced by the electric company for it's grid, and is best suited to supply things like electric motors (AC units, refrigerators) some delicate electronics, and microwave ovens.  Things that convert the 120 volt to something else (most TV's, computers, other small gadgets that use "wall-warts") will often work fine on cheaper modified sine wave inverters.  So if your use includes AC units and home style refrigerators, a pure sine wave inverter will suit you better.  Note that anything will run on almost any inverter, the motors just run less efficiently, use more power, create more heat and wear out faster.  Timers and clocks might not be accurate, things might be noisy, stuff like that.

4,000 watts is a lot, but you need to size your inverter to your load.  You need to determine your load by your anticipated use.  AC units are usually the critical application - if you need to run one, two or three AC units, that kind of sets your power requirement and almost everything else gets lost in the noise.

At that power use level, you need to look for inverters that are designed to tie into a 120 volt distribution system, not ones that just have several 15 amp fused outlets on the front.  It does you no good to have a 4000 watt inverter and try to run a 20 amp AC unit if the largest supply the inverter has is fused at 15 amps at the outlet.  Also at that power use level you need to plan the battery system carefully, the wiring will be large gauge, the fuses will be large, the switches will be large.  You may plan to run the inverter only when the bus engine is running - but sure as god made little green apples you will have times when the inverter is on and the engine is off, or idling and not supplying power.  Plan for that as well.

You can buy inverters that are made to be "stacked".  That means you can tie their outputs together and they synchronize their output waveforms to add together.  Not all do this.  You need to also look for the UL or CSA approvals on all units, but some cheap stackables around lately are not approved.  These might include the import ones you've seen on Ebay.

Brian

[Sean]

Brian, you have mad search skilz

My opinion on low-priced sine wave units from China and elsewhere is that it is hit and miss.  You might get a good one, or you might get a dud.  For the price, it might be worth the gamble.  If you "de-rate" or oversize the unit, you will lower the risk.

Right now I favor Magnum units, although the older Xantrex/Trace SW4024 is still the "gold standard" for pure sine inverters, and if you could find one (about $1,500 or so factory-refurbished), that would be my recommendation.

If you need more power than a single unit can provide (or just prefer the redundancy of two smaller units), then you either need to be able to divide the load between them, or you need to buy ones that have a "stacking" capability, which involves synchronization software and an interface cable to connect them.  Usually not found on cheaper units.

HTH,

-Sean
http://OurOdyssey.BlogSpot.com

[bevans6]

Sean, I actually just wrote that off the top of my head, my old Electric Circuits teacher would have said "now, after 35 years, you start paying attention and remembering things..."   

Presumably, based on your comment, I passed?  Passing grade used to be a C...   

Brian