Small Backup Power System for House

Blikbok

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I'm not looking to take it completely off-grid. Basically, I'd like to be able to run my electric-start gas heater without grid power because winters are cold around here. Additionally, it would be nice to tie into the UPS which keeps the computer equipment up, and also recharge some flashlights. It'd be neat to post to CPF during the outage /ubbthreads/images/graemlins/smile.gif I also don't want to run directly off a generator.

The two faces of the roof are E/W, but the ground slope is towards the south, so there are no trees or buildings blocking my southern sun. I may be able to hoist a small PV array, but covering the roof may not be practical.

Any suggestions?

(edited for clarification)
 

LitFuse

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I don't think there is any way you're going to be able to run an electric heater without a generator. As far as the rest of the stuff (computer, charging lights) I would look at eBay for a nice, big (used) UPS. There are some really good deals there if you look around a bit.


Peter
 

Blikbok

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I've edited the main post-- it's a gas heater with a 12v starter, just like the water heater.

If I divide my electrical loads into three layers of decreasing priority, the only thing in the critical layer would be that electrical starter, and maybe the blower fan. If I don't have power, I don't get heat. /ubbthreads/images/graemlins/frown.gif
The middle layer would be my computer gear, communications gear, and chargers for flashlights, radios, and phones. It's nice to have, but not essential.
The bottom layer is all the other stuff in the house.
 

Darell

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LOCO is more like it.
I hope Brock will pop in here soon. He's the guy you're after for this kind of thing. You're sure you don't want to power two electric cars, huh? /ubbthreads/images/graemlins/smile.gif
 

Blikbok

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If you have any for sale, then yes. /ubbthreads/images/graemlins/smile.gif I commute <30m each way to work, with no stoplights in between. Plus, they I'd quickly convert them to as many LEDs in the signals as possible.
 

Brock

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Where to start. I had a smaller system, then it grew.

I started with a large old computer UPS, it was rated 550w continuous. Once the battery died I found out it ran on 12v, so I added a 105A deep cycle marine battery. All was good.

Then I wanted to add the freezer to the mix but the little UPS wouldn't start it so I went to a Trace DR2412. It is a modified square wave 2400w inverter that runs on 12v. That was good for a while. Then I found out all sort of things don't run so well on modified square wave MSW and I also had a couple of 240 loads I wanted to run. At this point I was about to build a new house, so I upgraded again.

My third try and current system consists of 2 Trace SW2512, they are 2500w each and are "stacked" to output 240. I stuck with 12v since I had a bunch of 12v equipment and a good 12v generator. I currently have 8 T125 batteries rated about 225a @ 6v, so my current battery bank is set up for 900a at 12v or just over 10kw of storage. I also added some solar panels to the mix. With an SB50 solar controller.

Now I wish I had gone with larger inverters, 2 5548 inverters and 20 to 30 kw of battery, maybe someday. I also have a small 2.5 kw gas genset and a 750w 12v smaller genset.

So lessons I have learned. Get the largest size inverters you can afford, for what you might need. I like the Trace SW line because they can be generator or grid interactive (I believe the new Outback line is similar). For instance my genset can only supply about 8 amps per side and the inverters can make about 20 amps per side. The inverters can add the 8 amps from the genset to the 20 amps from themselves and supply a 28 amp load. You can also set how much power they take from a genset. I have mine set for 8 amps. If I am running a 12 amp load the genset passes the 8 amps to the load and adds 4 to get the total 12 amps. If I am only running a 4 amp load the inverter still pulls 8 amps from the genset, but passes 4 to the load and charges the batteries with the other 4 amps. If I have no load the inverter uses all 8 amps for charging. It does all this by itself. It also has controls to start and stop a generator, but my old genset doesn't have the controls.

I could go on for hours.

I guess the biggest thing is to figure out how much the largest load you want to run and for how long without firing up a genset.

Oh I would strongly recommend a sine wave inverter over a square wave.
 

Blikbok

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Brock, You rock! I'm gonna have to buy and induction ammeter. I really want to start the furnace and run the blower without the generator. The electronics would be nice, but they aren't an essential nor constant load.

I'm also going to try and get some sunlight readings in various areas so I can see if there is enough to justify a solar panel. I don't have fantasies of running the whole thing off solar, but if it can slow down the overall discharge rate, I'd be happy. I remember the ice storms in 98, and all I could hear were generators. I want to avoid being a nuisance or attracting attention.

Though maybe I could eventually have a system large enough to run conduit to the neighbors and charge them per KWH. /ubbthreads/images/graemlins/smile.gif
 

Brock

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[ QUOTE ]
Though maybe I could eventually have a system large enough to run conduit to the neighbors and charge them per KWH.

[/ QUOTE ]
LOL, sounds like a plan.

So if all your really concerned about is the blower for the furnace I would suggest maybe a "prosine". They are the baby brothers of the larger units like I have. They are sine wave so they can run anything and even have a built in 3-stage charger

http://www.xantrex.com/products/product.asp?did=545

They come in two sizes 1kw and 1.8kw Again I would recommend the 1.8, just in case you want to run a larger load. Also even if a motor draws say 400w running it will generally draw about 4 to 6 times that to start. So the larger inverter will start motors much easier. And in the long run it's better to have the inverter running at 50% rather then 75% of load.

The disadvantage is you can't stack them to get more power or 240v, although you could get a 120/240 x-former for a dedicated 240 load, that is if you have one.

Oh, one more thing, does the furnace have a glow plug? That probably draws more then the blower, although it is for a very short time and usually the blower is already running.

One of the other things I did was run an 80 amp fused #6 line from my battery bank up to the front edge of the garage, then I attached those to jumper cable ends. So I can back a car out of the garage and let it idle and connect it to the battery bank. Even at idle it charges my bank at about 35 amps. I have never had to use it that way, but it is one of those "just in case" things. Also a car idling is actually more efficient then my little lawnmower/generator setup, and a LOT more quite. I have used it to jump start one of our cars though /ubbthreads/images/graemlins/wink.gif
 

Blikbok

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Okay, I found out the heater does have a pilot light.

Thank you for all your help, Brock. A few questions, if I may?

First, since this is my first house, I don't see myself there forever. I don't see a system of even the small scope I am planning as a big feature for future buyers. Is it unreasonable to expect to dismantle the system and move it to a new house? What parts would be safer left behind?

Second, I see how in just about every arena, money is actually saved by buying (reasonably) larger initally and not losing on a trade-in or trade up. If invest in the good inverter, will it be easy to start with a few batteries (since I have a small load now) and add sets in the future, if I reside there longer or increase my load?

Third, it looks like the inverted you linked to kicks on when the grid fails. How would the backup system operate on sagging or dirty power from the grid? Would that be the battery charger's job?

(I like the idea of tying the car into the home system.)

Right now, it looks like all critical appliances will be in the basement: heater, blower, computers. That should simplify things. So right now, I'm gonna talk to my electrician about getting measurements and estimating my UPS needs. Adding up my maximum possible loads (according to the components' labels) doesn't break 1KW. So I may be able to scale back my plans. Xantrex doesn't list prices, so I'm figuring this stuff may break the bank. But I don't want to go cheap with electrical infrastructure.
 

Brock

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First I have to say looking at the prosine, they don't have a built in charger. I thought they did, but they don't. So you would either need to get an external charger, or solar panels, or something.

I would definitely make the system portable since most people wouldn't want to deal with it. Fortunately most furnaces actually have a 120 plug right on them and then plug in to a dedicated outlet right next to them. This is good because it is easy to just plug that in to your inverter without messing with anything. So you don't really need to do anything with that part.

Getting power around the house is a different story. You could let your electrician know you will be putting in a backup power source and ask them to put certain loads on a sub panel. Usually a sub panel can be run from the main panel or from a different source, like inverter, or most commonly a genset. This would be the only thing really left in the house, but the cost of adding a sub panel right away would be about ½ that of doing it after the fact. And you could let them know which outlets you want on the sub panel.

Yes you can start with a small battery bank and then if you need a larger one, replace it later. The catch here is you can't or shouldn't add batteries to an existing battery bank. Old and new batteries don't mix well. Battery banks are going to be the biggest pain in your system, and usually last between 5 to 15 years depending on the battery type and how you treat them.

Think of the inverter like a large UPS. You would take a wire from your main panel, run it through the inverter to the sub panel. If the inverter sees power from the grid it just lets it pass through to the sub panel to power the loads. Then if it sees the grid fail, it automatically starts and powers the loads in the sub panel, and once the grid is back up, it switches back to the grid. It also will disconnect from the grid if it sees low voltage or over voltage to protect you loads on the sub panel. I have mine wired like a UPS. Meaning there are physically plugs that power the sub panel. They can be plugged in to the main panel, the inverter outlets or the generator outlets. And the inverter can be plugged in to the main panel or into a generator outlet in my shop. Typically I leave my inverter plugged in to my main panel outlet and my sub panel plugged in to my inverter. The only time I usually switch it is plugging the inverter in to my generator outlet if the power goes out.

Take a look on Ebay. I know you could get a SW2512 for less then 2k new and about ½ that used. Just do a search on Ebay for inverter. The catch is you will see a thousand smaller 100 to 300 watt units. If you add "Trace" or "xantrex" or "prosine" to the search it will narrow it down a lot.

Going back to the type of inverter I think I would have to recommend a PS or SW line now because of the battery charging part. They would automatically charge the bank from the grid and a good rate and be fully automatic. A good 3 stage external charger will cost $300 to $500, so remember that when looking at prices. The disadvantage is it is hardwired and not as portable, but you can hard wire normal plugs to it like I did.

Now since most of you loads will be in the basement, you could avoid the sub panel and plug things directly in to the inverter via extension cords. That will also save you some $, but you loose the built in look, that is if you care. Again think of it like a large UPS.

Check out some of the links on my stuff page.

http://www.uwgb.edu/nevermab/stuff.htm

I like Mr. Solar and or Backwoods. I bought most of my stuff from them. On Backwoods there is a "newsletter" part where people sell their old stuff when they are upgrading, you can get really good deal there.
 

Blikbok

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Looks like a good start. I'll check out the links.
My first step looks to be a UPS, to protect and power the PC's, then an inverter and batteries, then a PV panel or two. I definately like the idea of using the car as a temporary DC power source.
 

Brock

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The battery backup thread forced me to take some pics

Here is my little setup, first the batteries, 8 Trojan T125's, 6v at 225amps, set up for a 12v system at 900 amps or 10kw.
battery1.jpg

They feed the two inverters that turn the 12vdc in to 120vac sine wave. The inverters can supply 5kw at 240v. I put a D battery in-between them for size reference.
inverters.jpg

The inverters in turn feed the dedicated loads around the house. That panel is on the left, I have two more panels, besides these, one in the garage and one on the third floor.
panels.jpg
 

mrorange

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Now thats a nice setup. If you don't mind me asking, what's an approximate cost for that setup? I would love to do something similar, but I'm intending to sell my house in a year or so and don't want to put a ton of $$ into a system I would have to leave. I have been thinking of just a simple backup generator and manual transfer switch, at least then when I move, I could take the generator with me....
 

_mike_

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I have a 9kW portable generator running from a 16HP V-twin B&G Vanguard engine setup to use my 350 gallon propane tank. The generator itself cost about $2800.00 (propane ready)when I got it 8 years ago. It goes to a manual transfer switch. Our hot water tank and furnace are propane but both need some electricity for their ignition and fans, the cook stove is all propane and needs no electricity...along with our wood burning stove.

My computer is hooked up to an APC Back-UPS 500 and my DSL router is plugged into an APC Back-UPS ES 350. The big drain for me are my well pumps. However, the generator handles everything I need. Obviously we don't do laundry or use the dish washer. I have had this setup for roughly 8 years (except the DSL router). I have never had any problems with any of my equipment. Even when I didn't go through the APC for my computer and just ran it off the generator.....no problems.

You would not know the power is out when I'm running on the generator...except for the noise. If I had to move, the only thing I wouldn't take with me is the transfer switch. Not too much of a financial loss there as it was only about $200.00.

mike
 

Brock

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The eight batteries are about $75 each. The inverters are the killer, they run about $2500 each. I did all the wiring myself, probably another $500 for panels and extra wiring while I was building.

I could easily move the gear, but I couldn't move the built in wiring.

I would say for a smaller system I would get 2 or 4 batteries and a Trace (xantrex) PS2512 inverter. The batteries would run about $150 - $300 and the inverter would be about $1800. You could go with a cheaper sine wave inverter, I believe the prosine (xantrex) 1800w 12v unit is about $1000, but has no built in charger.

The PS 2512 is actually the same inverter I have, but mine has all the controls and the ability to sell back to the grid and has a separate input for a generator and can actually start and stop a generator as need by the batteries.

I also have 2 siemens 75w solar panels ($300 each) and 2 solarex 43w panels ($150 each) connected to a solar boost 50 ($400).

Xantrex has bought out most of the other inverter companies, so they have the largest selection at this point.
 

mrorange

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Brock, what part do the solar panels play in your system? Are they very efficient in your area? I looked into solar panels some time ago and from what I could gather, they were not all that efficient in my area (SW Ohio) a good part of the year. Do they help keep your battery bank topped off?

Sportsmansguide has what appears to be a pretty good combo available right now, a 5000W continuous/6250 surge Coleman generator plus home hook up kit with a transfer switch, junction box and cords for $629.97 (buyers club price) You can split the cost into four payments too /ubbthreads/images/graemlins/grin.gif

http://www.sportsmansguide.com/cb/cb.asp?a=93697
 

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