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keastvol
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# Posted: 4 Feb 2013 10:22am
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My cabin is wired up for AC and is powered by a generator 2000I during the day through a breaker box. My question is can I back feed my cabin using a small battery bank and a invertor and plug it directly into a wall outlet to power a few lights and and DVD player at night? Would it be strong enough to supply power thrpough the entire cabin? Only 200 sq/ft.
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Dillio187
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# Posted: 4 Feb 2013 10:45am - Edited by: Dillio187
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yea that would work, but obviously won't be code and could expose male plugs as a possible shock hazard. I do similar except I have a separate outlet for my generator power, which I can use to plug in items directly, or what I usually do is plug my battery charger in and recharge my battery bank.
My inverter is hard wired into the panel through a breaker.
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keastvol
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# Posted: 4 Feb 2013 10:59am
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I never thought about hard wiring the inverter to the panel. What size panel, inverter and battery would I need.
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Dillio187
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# Posted: 4 Feb 2013 11:38am - Edited by: Dillio187
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I just use a small 70 amp panel, but it really depends on how many circuits you'd need.
I highly recommend the Morningstar SureSine 300 inverter, more than enough power for lights, a tv, and smallish appliances. It will even surge to 600 watts for 15 minutes. There are other good small inverters as well made by Samlex that are pure sine wave, I would stay away from the cheap Walmart style modified sine wave inverters. solar-electric.com has both types of inverters, and is worth the time to browse and research.
As far as batteries for a small cabin system, it's hard to go wrong with a couple 6V golf cart batteries wired in series, you can get them at Sam's club for around $75 each. They are a true deep cycle battery.
You can see my small system in the below photo. If you look close, you can even see the 14-2 Romex coming out of the inverter and disappearing into the insulation. It just patches into a 10amp breaker up in my box, which then feeds the rest of the panel and cabin.
FWIW my cabin is a shade under 200sq ft (16x12) and this setup has worked great! Good luck.
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rayyy
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# Posted: 4 Feb 2013 11:42am
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if your feed wire to this panel is being plugged into your generator's 120 volt outlet,you could just unplug it from there and plug it into your inverter's 120 volt outlet.This would assure you that you wouldn't accidently ever fire up your generator at the same time your inverter is on line.The sorce of your electric will be from one or the other but never both.
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Dillio187
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# Posted: 4 Feb 2013 12:00pm - Edited by: Dillio187
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good point rayyy, and a good idea if you plan on directly powering the cabin from the generator. I don't do this as I have a separate outlet just for the gennie, it also happens to be next to the window I put the AC unit into.
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keastvol
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# Posted: 4 Feb 2013 12:01pm
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Sorry, What size solar panels would I need. I only use this cabin on weekends a couple times a month. How long would the charge last on two 6V batteries as you suggest. Only a couple CFL lights and a small TV. How long does it take to charge if I fully drain them.
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keastvol
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# Posted: 4 Feb 2013 12:08pm
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What type of charger and solar panels would you recomend for this type of system. I dont want to spend too much.
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Dillio187
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# Posted: 4 Feb 2013 02:48pm
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it's not recommended to drain deep cycle batteries below 50%, and realistically you should keep them above that. It really depends on the draw.
Ideally you would want to charge those batteries around a 10% rate, or 22 amps.
There are a wide array of panels and charge controllers that could meet your goal, but solar and 'cheap' are not two words that really go together all that well.
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bldginsp
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# Posted: 5 Feb 2013 08:13am
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If you backfeed any electrical system through an outlet on a 20 or 15 amp circuit, be aware that you run the possibility of overloading that circuit. The wires in that system become your feeders, and #12 or #14 wire can only handle 20 and 15 amps respectively. With just a few lights and a DVD you may not have a problem but later if you add more, then a little more, you could start to overload the wiring. If the circuit connects to a breaker box via a 20 or 15 amp breaker, that breaker should trip if it gets overloaded.
But the better path, as suggested above, is to use your inverter to feed the breaker box just like the generator does. Using a plug to switch from the generator to the inverter is a good idea from a grounding and bonding (safety) perspective. One danger of having two power sources hard wired on one breaker box is that you can backfeed neutrals and/or grounds into the unused power source while the other is being used. To avoid this, a transfer switch is used which, when thrown, disconnects the hots and neutral from one power source and then connects the hots and neutrals from the second power source to the breaker box. With a transfer switch, the two cannot be simultaneously connected. But transfer switches are expensive, so Rayys idea to use a plug which you must disconnect from one before connecting to the other effectively does the same thing for the cost of a plug and two outlets.
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mhooks1973
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# Posted: 9 Jul 2024 11:40pm
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I have a cabin that I plug into on a 30amp power pedastal near the road. The power goes out frenquently and I'm wondering if I can backfeed the power pedestal with my inverter. I assume that will energize my cabin with my 4 x 1200W batteries. My only quesiton is what happens when the power comes back on? Issues or no?
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gcrank1
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# Posted: 10 Jul 2024 12:03am
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You absolutely need a Transfer Switch!
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darz5150
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# Posted: 10 Jul 2024 02:34am - Edited by: darz5150
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Quoting: gcrank1 You absolutely need a Transfer Switch!
Quoting: mhooks1973 Issues or no?
Crank is 100% correct.
The "issue" you ask about, can kill someone trying to restore your power. Or YOU.
Don't do it
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travellerw
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# Posted: 10 Jul 2024 04:52pm - Edited by: travellerw
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Sorry.. I'm not %100 clear on something.
Is your cabin connected to an external grid?
If not and its just the generator, then the answer changes a bit. You still need to take some precautions to ensure you don't fry a device (the generator or battery bank), but you don't need to worry about killing someone back down the line. Only yourself or someone in your cabin!
When we first built our cabin, we powered it similar to what you are asking (external generator, portable power station at night).
Before the input line entered the breaker panel we had a switch that switched input between the generator or a plug just below the breaker panel. The portable power station was plugged into that plug with a double headed cord. This way we could switch between the 2 while keeping them isolated. Because we were not using any high powered devices (no microwaves or hairdryers or even toaster), we just used a cheap transfer switch from Amazon. Like this one.
https://www.amazon.ca/Baomain-Universal-Changeover-SZW26-20-D202-2D/dp/B07SKNMY9P/ref =sr_1_10?crid=IJ61HILIT6L6&dib=eyJ2IjoiMSJ9.AqUb3Tp4ZeHPVz-IGeyg2DJE3EXYXPUQbhbuW0Pvo 20xORMqwjwjRquAJeOQs_Y9DoX68yC-asju_4sPEVGQZTZ5KrWGANxBVlCHUhOoM8GnshoW2axywD7oIxcYjg S673BfaMTvQe7A-FAISW-PzHUIB4oPWfdQtHN0XPHn4DK_kZTJxWRJoTRUtZS1NpqnJSbjqVnbU8w4yTlh_x7 kLae47dc7ilqpYU1ZD1vKng6DDM-qg6haUNqcplbOrJpZzaSdwodiWF--1Dy8ANb_1OFYj6poDIzGx_fjRr_0 b0M.q946cK9K9YYzNZ_wCE8k_8bdeXMxF2Cn5B9VtDDdH3s&dib_tag=smacab-20&keywords=transfer+s witch&q id=1720628504&sprefix=transfer+swi%2Caps%2C640&sr=8-10
I really don't want to be "That Guy", but with all that typed and said. You really should have a decent knowledge of AC electrical before doing stuff like this. It is 120V and has more than enough potential to kill you or injure someone else if you do it wrong.
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Tim_Ohio
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# Posted: 10 Jul 2024 05:43pm - Edited by: Tim_Ohio
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ff
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ICC
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# Posted: 10 Jul 2024 07:36pm
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Quoting: mhooks1973 I have a cabin that I plug into on a 30amp power pedastal near the road. The power goes out frenquently
I interpret that to mean there is a grid connection. If there is a grid connection and a generator, as well as batteries and an inverter and you have to ask, "what happens when the power comes back on....", then you should hire an electrician and keep everybody around you safe. As others have said, 120 volt AC power can kill and some knowledge is needed to set this up correctly.
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Fanman
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# Posted: 10 Jul 2024 11:33pm
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Quoting: gcrank1 You absolutely need a Transfer Switch!
Or an interlock on the panel, which is a lot cheaper and simpler to wire. Basically, you backfeed one breaker on your panel and the interlock doesn't allow that one breaker to be turned on unless the main is turned off. I have a (homemade) interlock on the panel at my house, but at the cabin I use the hillbilly suicide cord into the laundry machine outlet... definitely not to code but I'm the only one who touches it.
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gcrank1
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# Posted: 11 Jul 2024 12:51am
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It also may be that the '30a' pedestal has well more than 120vac inside it.
People die Every Day messing about with electricity.
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ICC
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# Posted: 11 Jul 2024 01:49am - Edited by: ICC
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but I'm the only one who touches it.
Not to pick on anyone, or start a war, but may be more or less true today, but not tomorrow or some day in the future. I am aware that everything I leave behind when I die, the good, the bad, the indifferent, will have to be dealt with by somebody. The chances of the existence of the cord being a danger to someone else probably is very small but I see such things as potential booby traps for the unknowing.
Once again, no malice to anyone is meant by my comment. Just food for serious thought in case of a "what if..."
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darz5150
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# Posted: 11 Jul 2024 03:18am
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Try to keep in mind that there are not any do-overs or rewinds when it involves something that can kill someone. There's only..... Could've, would've, should've.
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paulz
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# Posted: 11 Jul 2024 04:37pm
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Quoting: Fanman Or an interlock on the panel,
Interesting. With millions of installs there must be many who rely on backup power when the grid goes down. At my grid city house it’s just flashlights. The fridge is the only thing that may suffer but it always gets restored before that.
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Tim_Ohio
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# Posted: 11 Jul 2024 07:02pm - Edited by: Tim_Ohio
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Quoting: keastvol My question is can I back feed my cabin using a small battery bank and a invertor and plug it directly into a wall outlet to power a few lights and and DVD player at night?
I do this at night, but I have a portable generator that is set up to be plugged into the twist-lock receptacle I installed on the outside of the cabin that is directly wired into the cabin electrical panel, complete with breakers. When I go to bed, I shut off the generator and unplug it. Then, I plug in a chord set up to be connected to a cheap inverter, which is then energized by a charged 12 volt car battery. It allows me to charge my cell phone through the night and turn on any LED lighting from the switches, including the porch light, if needed.
I like this set up, since I don't leave anything that will walk away.
Everything is kept out of the weather and the twist lock is sealed with a rubber seal around the plug. Also, everything is oriented so there is no suicide connection because of the orientation of all of the plugs...females on all of the energized equipment. But, I never have anything energized before installing the chords, so it really doesn't matter in my case. Also, it's a good practice to have no load (nothing turned on) when starting any of the electrical sources. The inverter I have is a cheap, modified sine wave inverter which has not caused any problem with charging my phone.
Here is a photo of the weatherproof twist lock receptacle. I was installing the ground rods at the time . Since there is a solid rock shelf about 4ft down, I had to trench and install the rods bent at 90 degrees. I could not drive them into the rock shelf.
Ground_rod_install_1.jpeg
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gcrank1
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# Posted: 11 Jul 2024 09:03pm - Edited by: gcrank1
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Yep, RV type plug on the wall to feed inside is the way to do it for a simple, yet safe system. 
Working on just such now for our new cabin. The RV receptical (fed by gen OR grid power, hardwired) will feed inside the PSW inverter which has an internal transfer switch. If the gen isn't running the inverter runs off the battery, when the gen gets fired up it shuts down the inverter and does a pass through of the gen 120vac.
Seamless
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paulz
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# Posted: 12 Jul 2024 11:54am - Edited by: paulz
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Quoting: gcrank1 feed inside to my PSW inverter which has an internal transfer switch
Hmm, so your inverter has an ‘IN’ a/c socket by the outs, like the ones I looked up? Pretty neat, had me taking a quick look at mine, not that I would ever need it.
Oops, I was misreading the image I saw. The input is the screws next to the sockets?
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Tim_Ohio
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# Posted: 12 Jul 2024 12:24pm
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Quoting: gcrank1 The RV receptical (fed by gen) will feed inside to my PSW inverter which has an internal transfer switch. If the gen isn't running the inverter runs off the battery,
Gcrank1, do you mind sharing the details of the inverter you use that transfers automatically. I might like to get one. Thanks, Tim
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gcrank1
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# Posted: 12 Jul 2024 12:47pm - Edited by: gcrank1
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Not a simple 'plug-in' for the external 120vac, grid or gen, but is a simple hardwire from 'source' to inside the inv.
Some of these type inv. with the auto transfer also have a built in bat charging function (you will have to check if LFP compatible though if you are usually on grid and doing essentially a back up you could easily use LA bats).
Mine may have been discontinued but there should be others. And mine is psw 12v/1000w, but a 1500w min. would probably be better for a smallish place.
Cooper Bussman mdl 12-110-1000
Bought it online, think maybe Amazon a couple years ago. Mfr date is 29/June/2015
Btw, it is chunky, bigger and more weight than any other 1000w inv. Ive seen.
Im sure they come in 24vdc also.
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ICC
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# Posted: 12 Jul 2024 01:02pm
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Sounds like it is a low frequency inverter. They use a heavy iron core transformer and are superior for high surge motor starting. More expensive than the more common high frequency inverters. I believe also longer lasting.
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Brettny
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# Posted: 12 Jul 2024 02:51pm
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I also have a inverter with an automatic transfer switch. It's a xantrax freedom x1200, no charging capability with this one. My setup will consist of a remote start generator in a shed hard wired useing underground wire to my inverter under the cabin. At the push of a button I have full 120v 30a available. When I want to switch back to battery/solar power I just have to push the button again. The button is on a key fob.
I also have a 12v30a charger connected to the generator output so any time the generator is running my batteries are charging. No plugs to move, no breakers to flip and not even a cord to pull.
Generator is a champion 4500w inverter.
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travellerw
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# Posted: 12 Jul 2024 04:32pm - Edited by: travellerw
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Quoting: Tim_Ohio Gcrank1, do you mind sharing the details of the inverter you use that transfers automatically. I might like to get one. Thanks, Tim
There are quite a few inverters with that function. Victron has numerous models! Xantrex, Go power, Mastervolt all have similar offerings.
I will caution about some of the Chinese brands like Growatt, PowMR and even Renogy (and many other clones). They are affordable and have built in ATS, but have some serious shortcomings.
1. Standby power is REALLY high (so high idle draw at night). About 50W just idling.
2. Cannot disable battery charging easily. When the ATS kicks in, the battery is being charged (at high amps). If your generator is not big enough, this can cause problems.
3. VERY limited settings for battery charge voltages (too low for proper care of FLA batteries).
4. No power correction or supplement function. i.e. if your generator dips and causes a brown out, the inverter does not supplement (many other brands have this function)
However, they are beasts when it comes to providing power. I use ours to run my AC, welder or my log splitter without issues. I bought it for fun as I only had experience with big brands and wanted something to "play" with. Eventually I will swap it out for a Victron Multiplus unit (yup, twice the price).
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gcrank1
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# Posted: 13 Jul 2024 08:43pm - Edited by: gcrank1
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More info on mine:
60 Hz (Likely the output feq)
87% efficiency
1000w constant/2000w surge
Up to 16vdc input
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