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12-03-10, 04:53 PM | #1 |
Lex Parsimoniae
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Automatic AC transfer switch
Generator Transfer Switch These things are designed to kick in the aux power when the grid fails.. But, I want to twist that idea around and built a switch that kicks-in when there is aux power available. It would work like this.. 1.When the sun came up and hit the PV and got the batteries charged up a bit, 2. a battery voltage monitor circuit would turn on, 3. and apply DC (Batt+PV) power to a 12VDC to 120VAC inverter. (The inverter is my Dump-Load). 4. The AC output of the inverter would disconnect my computer (wifi router etc) from the grid. 5. 10 msec later, it would connect the PC to the inverter.. 6. When the clouds come in, the batteries keep me going for a while.. But when they start getting low, the battery voltage monitor circuit will switch off DC to the inverter. 7. The relay pops back into NC and the PC is back on the grid. I wonder if someone makes these things? I've seen some PV charge controllers that have a 'load' output. Some of them don't provide a lot of amps on those terminals, but they could be used to switch the inverter in and out.. Comments please: Cheers, Rich |
12-03-10, 06:49 PM | #2 |
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I know that there is a company that makes a battery charging / grid tie inverter. They are obviously expensive though as you get the best of both worlds.
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12-03-10, 08:15 PM | #3 |
Lex Parsimoniae
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I'm thinking just build the switch harness, so I can pick n chose what kind of inverter,
charger and etc that I want to use. Right now, I'm putting together a 400W PV powered battery charging setup. The plan was to use the batteries with inverters to power sump-pumps during outages. But, I'm thinking maybe I could take some stuff off the grid? Maybe the 10 hours a day this PC is drawing 180w could be cut in half.?. Maybe my (133w) refrigerator could get some of it's juice from the sun? After the batteries are charged, why waste the incoming photons? The nice part of this scheme is, no GTI is used. No power is going to go out on the grid. But, your electric bill will be reduced.. |
12-04-10, 08:35 PM | #4 |
Lex Parsimoniae
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I found it! And it's affordable..
Iota ITS-30R Automatic AC Transfer Switch 30 Amp http://www.iotaengineering.com/pplib/30rman.pdf Pretty neat little gismo!! Almost exactly as I envisioned it.. |
12-04-10, 10:48 PM | #5 |
Master EcoRenovator
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wow that is cheap. I was thinking I'd need to build one. It would be nice to get my fridge running partially on solar and the rest of the day on A/C. Right now my battery has been topped out since march and I've just thrown away 45 watts worth of generating all summer...
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05-11-12, 04:55 AM | #6 |
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Are you sure the Iota auto AC transfer switch does exactly what you need? The description for this device says that it "will sense the presence of available supplies and automatically select the proper one." The description does not define how the switch decides which AC source is "the proper one." I assume it means that if one AC source stops, it will switch to a second AC source. Has anyone used this particular auto AC transfer switch for the application like Xringer's?
Thanks, Frank in Pittsburgh |
12-04-10, 11:48 PM | #7 |
Lex Parsimoniae
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I don't know what the compressor pulls, but my fridge runs at 133 watts.
These two new panels could run both my fridge and the little freezer in the basement.. These new inverters they are making now seem to have a good resistance to high start-up current. Heck, they use them from drills and saws now.. |
12-20-10, 07:09 PM | #8 |
Lex Parsimoniae
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Check out these IOTA switches in use..
auto power using relay - Solar Electric Power Discussion Forum by Northern Arizona Wind & Sun I'm getting interested in buy one of those cheap Ebay inverters again!! |
12-29-10, 06:43 PM | #9 |
Lex Parsimoniae
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I just ordered three of these 30A IOTA switches for my little solar-battery back-up system.
I plan to use one of the switches to power this PC and a few CFLs, just so I'll be able to put the excess power (after charging) to good use. This PC is on a LOT of hours.. I'll also need to discharge the bank down a bit once in a while, so the back-up will power the PC at night too. Just enough to see 80-85% SOC. I guess it's not good to keep the bank on float all the time.. |
12-29-10, 07:34 PM | #10 |
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All that is needed is a relay.
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To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her... |
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