Multiple Inverters

[Shadow]

I've been considering ordering an Inverter, probably the Outback 3648 for just over $1700.00. My plan has always been to have the fridge and deep freeze on thier own inverter, just so I dont have all my eggs in one basket if trouble arises. And that inverter would probably be this one..http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230019876799&ssPageName=ADME:L:DBS:US:11 but then I got thinking why not order 4 of them and have 4400 watts for $1000.00 as opposed to 3600 watts for $1700.00? I could have one for the basement, one for the kitchen, one for the fridge and freezer, and one for the remainder. All off one battery bank.I realize there will be some losses, and lots of connections but what other problems will I encounter?The way I look at it when you go off grid, if your inverter fails it shuts down your whole system, this is what I'm trying to avoid. All comments welcome.

[altosack]

The Exeltech XP1100 is an excellent inverter; I have the 24V version (I paid $600 4 years ago and it was worth it). And that is a most excellent price, usually the 48V version is $900 each. Exeltech will fix any of their inverters, no matter what's wrong with it, for $100.

You already know about the losses (40W continuous for 4 inverters, or 1 kWh/day; there is no sleep mode on this inverter), and the wiring difficulties (it will be a big complicated switching system, maybe if you wired it 2 x 2 instead of 4 x 4...).

Normally I would say, no way, don't do it, just get one big reliable inverter with a smaller backup unit, but these little guys are as reliable as they come. As long as you don't mind a little hands-on, I'd say go for it; I love the idea of redundancy. I wish I was in the position to take advantage of this offer, but I'm in the process of moving off the mainland (US).

Let us know how it turns out !

Dave

[harrie]

Hi Shadow, I have bought one of the 48 volt 1100 inverters and it is on the way, I didnt think I could go wrong at that price. Keep us informed if you plan on stacking, I for one would be interested how it worked out. Good luck.

[Volvo farmer]

I went with one Outback 3524. I don't have much planned for backup except a generator that I can put in bypass mode and remove the inverter if need be. If things got really bad, I have a couple of cheap 12V 1.2 KW MSW inverters laying around that I could patch in with some rewiring of batteries and panels.

How are you configuring your system? Are you putting the batteries inside the house near the distribution panel? Four inverters might work in this situation, though a good point was made about idling losses. My quick research shows four Exeltech 1100 inverters are going to draw four times the idle current of one Outback 3548, 80W vs. 20W. That's about 1.5KW/day you're throwing away or 300W of solar @ 5 sun hours. 300W of solar runs about $1500 nowadays so now the Outback is now the more cost effective option. If you're doing homebrew wind or hydro, perhaps my calculations do not apply.

I like redundancy as much as the next guy. Get a generator for backup, you're going to need it anyway if you are off grid. Outback can overnight you a control board if you take a lightning hit or something. The wiring, DC breakers, AC breakers  and distribution from four inverters is going to be a rat's nest of a mess. My opinion is to keep it simple, stay with one inverter, two stacked if you need that much power.

Electric fridge AND freezer? I'd like to know what kind of monster system you're planning on building to do that.

[nothing to lose]

Depends on how you set stuff up also perhaps.

 Idle losses would be if they are on but not in use, but there may be a little drain still if turned off but connected to batteries. I was a bit suprised to see that in a manual for one. I think it was just a few Milliamps, probably keeping the caps etc.. charged on the circuit boards.

If your only going to turn it on when in use, idle loads of 20watts or so should not apply except when turned on. So say if the inverter switch is near the basement light switch, turn on the basement inverter when you go down to the shop, run tools ect.. a couple hours, then turn inverter off when returning upstairs I think that might be better than an inverter 3X's the size always on. Also, how much do you need that inverter on? Just 4hours Fri,Sat, night or 12 hours everyday. That would make a differnce perhaps.

If you plan to have them all on all at once all the time, then I would say one large one would be better, or 2 half sized if you want one for backup.

One nice thing I think about having the important always on stuff like frig/freezer on it's own seperate inverter is that if batteries are getting low you can shut off the rest of the house on the other inverter if you want and maximize the run time for the fridge/freezer.

I don't mind roughing it at times myself, so I could live a weekend without power as long as my food don't spoil, personally I'd rather do that than run a feul powered genny unless I had to.

Due to a bad year I have not started building my new house as planned, but I plan 4 inverters. 1 is the absolute loads I never want without power, Fridge/Freezer maybe 1 computer etc...  2 is the 240V deepwell, it will only be ran to fill a large storage tank as needed and mostly durring excess power times. 3 is the rest of the house. 4 is the shop area. How many hours a week do I need a 5k inverter to run a lathe, welder, aircompressor and other high load tools anyway? So 75-90% of the time inverter 2 and 3 will be turned off. For me then I think this is better than getting one large 10K to run everything.

Not everyone wants or needs the same thing, but that's what I want, and all powered by wind.

[robl]

For what it's worth, Outback permits configuring their inverters to permit one to carry a 120/240 load and then wake up any number of sleeping inverters as needed. The trigger to cascade the next inverter is approx. 1KW. That's how my rig is set up, although we only use two inverters. During thunderstorms and extended absences we actually isolate the second unit completely (ac, dc, control lines) in case of catastrpohic damage to the primary unit.

Rob

[Shadow]

Hi Volvo, Thanks for the input, I think youre right I should stick with my original plan and get an Outback. I currently have a back up generator, a Lister aircooled 2 cylinder with a 7.5 kw gen.But it runs about 1800 rpm and is very noisy. So its for emergency only. I've ordered a Lister clone, 6/1 which runs about 650 rpm and will be run on vegetable oil.I'm really debating whether to bother with solar panels at all, the cheapest ones in these parts are still just under 10.00 a watt, so for the price of 2 hundred watt panels I can almost pay for the Lister engine and gen head. Which in turn gaurentees me power sun or rain.And with free fuel it can run as much as needed. I raised my eyebrows when you commented fridge and deepfreeze!? Is this not common? Why do you need a monster setup for those two? Mind you those two items will be our biggest power draw, but still its not that much.I have two wind turbines that seem to constantly be putting between 500-2000 watts each into a 1060 amphr battery bank so I'm hoping I dont have to go much bigger than that.

[Volvo farmer]

Ohh.... wind.....

To me 1KW/hour constant is a monster system. I have no wind power yet, I make maybe 4KWhr/day on a good day with solar. You're making six times that. Nevermind, you can run a fridge and freezer all you want on 20+KWhr/day.

If you've got that much wind, I'd totally forget about solar panels. DanB hasn't hooked his back up since he put up the 20 footer and he told me hasn't missed them at all.