Categorizing my step-by-step solar/generator cabin power

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Small Cabin Forum / Off-Grid Living / Categorizing my step-by-step solar/generator cabin power

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rmak Member	# Posted: 17 Feb 2014 10:37am Reply OK. Reading and studying off-grid power for my little recreation cabin. I have some gaps in my knowledge and seeking help here. My plan is to first buy a Honda generator with my portion of our income tax return. Next, I want to buy two deep cell batteries and wire the cabin up with plugs and lights. Since I want AC current (I think) I also need a converter to run power off the batteries at this stage. My plan is to run everything off the batteries and either charge the batteries with the generator, or run things off the generator part time. This is where I'm confused. How (and what do I need in simple terms) do I change from battery to generator power, or do I need to? I think if I want extra power sometimes I need to plug into the generator power without going through the batteries, but as I said, I'm confused about this. After saving for the solar part, I believe now would be the time to get some panels and charge controller, and complete the set up. However, I just saw a youtube video about another piece of equipment that switches from generator to solar power, so I am confused at this stage as well. Please, simple explanations are the best for me. Am I approaching this step by step power system in the right order?

Dillio187 Member	# Posted: 17 Feb 2014 10:50am Reply the item to switch between 2 different AC power sources is called a transfer switch. To convert from DC to AC (house) power, you need what is called an inverter. I would advise to not go cheap on an inverter and get a nice pure since wave inverter at whatever wattage you determine you need. Many people (myself included) skip the transfer switch and just use the generator to charge their batteries when needed. I have 1 outlet in my cabin near my batteries which passes through the wall out to my generator. That way I can plug my charger into 1 socket, and run something else from the other while the generator is running.

bldginsp Member	# Posted: 17 Feb 2014 11:05am - Edited by: bldginsp Reply I'm no expert on this, but I think you are asking the right questions. Here's what I know: Both the solar panels and the batteries are DC, the generator and the power system in the cabin are AC. You could use a DC system in the cabin, but I'm told DC switches, lights etc. are very expensive so it's cheaper overall to use AC in the cabin (I think). Yes you need a charge controller from the panels to charge the batteries. Then, you take DC power off the batteries into an inverter (not 'converter') which switches the power over to AC. I think (not sure) that there are charge controllers that have terminals for wires for the solar panels and batteries AND for connecting to an inverter. From the inverter you run feeders to your main distribution panel (circuit breaker panel). Always separate your grounds and neutrals in the distribution panel, but connect them at the furthest upstream point. That's a separate subject, for safety you must know your grounding and bonding. The generator can be tied directly to the distribution panel, but the big issue here is, do you tie both the inverter and the generator to the distribution panel at once? Here is the limit of my knowledge, but I do know that if you connect a generator to your home system where you have utility power, you must use a main transfer switch. This switch simultaneously disconnects the utility power to the house, and connects the generator. Then, when you switch it the other way, it disconnects the generator and reconnects the utility. In your house, you don't want your utility power connected when you use the generator, because it would backfeed into the grid and run your neighbors refrigerator or kill a lineman attempting to repair the wires (literally). But with your solar system, would the generator, connected to the distribution panel which is also connected to the solar/battery inverter, pose a backfeed threat? I don't know. Dillio- would you explain your last paragraph in a bit more detail for us off-grid dummies- the outlet to outside the building for connecting the generator goes to where- the charge controller I assume, and while the generator is running, you just use the system as normal? In this case, generator power goes from generator to charge controller to inverter to AC system? Transfer switches are expensive.

rmak Member	# Posted: 17 Feb 2014 12:05pm Reply Thanks...inverter, not converter. A few questions for Dillio: 1) I believe the Honda generator has a 12 volt charger separate from the AC power plugs. Just checking that that is the one you are hooking to the battery or batteries. 2) What's the cost of a good inverter? What's a "nice pure wave inverter"? Is that a brand name? 3)If I'm just charging the batteries, can I run generator only power, such as vacuum cleaner? Using those higher draw appliances are why I think I would need to run direct from the generator. I was thinking about a separate set of plugs running directly to the generator for those purposes. This might be what you are saying. I'm just trying to be clear.

Dillio187 Member	# Posted: 17 Feb 2014 12:57pm - Edited by: Dillio187 Reply Quoting: bldginsp Dillio- would you explain your last paragraph in a bit more detail for us off-grid dummies- the outlet to outside the building for connecting the generator goes to where- the charge controller I assume, and while the generator is running, you just use the system as normal? In this case, generator power goes from generator to charge controller to inverter to AC system? Transfer switches are expensive. I have an outlet on the outside of my cabin with a power inlet for my generator. It's cabled through the wall to a regular outlet inside the cabin (which I have mounted upside down to differentiate) and from this outlet, I plug my 12V battery charger in, which charges my batteries. The other outlet can be used to power a fridge, fan, vacuum, or other high draw AC item. All of the other outlets in my cabin are powered direct from my inverter and panel. Quoting: rmak A few questions for Dillio: 1) I believe the Honda generator has a 12 volt charger separate from the AC power plugs. Just checking that that is the one you are hooking to the battery or batteries. 2) What's the cost of a good inverter? What's a "nice pure wave inverter"? Is that a brand name? 3)If I'm just charging the batteries, can I run generator only power, such as vacuum cleaner? Using those higher draw appliances are why I think I would need to run direct from the generator. I was thinking about a separate set of plugs running directly to the generator for those purposes. This might be what you are saying. I'm just trying to be clear. 1.) The Honda 12V charger is a relatively weak charger. I think it's 2 or 3 amps, pretty measly. A nice external charger is highly recommended. 2.) Regarding a good cost, it depends how much you need to supply. For my little cabin, I use a 300W pure sine wave inverter from Morningstar. They are built like a brick and really tough. They are about $200. Google Morningstar SureSine 300 for more info/purchasing. 3.) you have it exactly.

rmak Member	# Posted: 17 Feb 2014 01:21pm Reply Gocha! Switching the plugs around is a neat trick! I'm thinking I'm going to power just three things from solar Lights Cell phone docking station charger laptop For everything else I'm going to use the generator. Our cabin is on our property and used for recreation and occasional sleepovers, so we don't need to depend on power to survive. Any thoughts on number of batteries, photo cells and other component size?

MtnDon Member	# Posted: 17 Feb 2014 01:30pm Reply Quoting: bldginsp the generator goes to where- the charge controller I assume, and while the generator is running, you just use the system as normal? In this case, generator power goes from generator to charge controller to inverter to AC system? NO. CC only use power from PV panels or a wind or hydro generator. A generator can be used to power a battery charger like any ones you can plug intp 120 VAC at home.

MtnDon Member	# Posted: 17 Feb 2014 01:40pm Reply Quoting: bldginsp Transfer switches are expensive. TS-30 30 Amp Automatic Transfer Switch at amazon is good for most folks with small off grid systems and a generator

rmak Member	# Posted: 17 Feb 2014 01:44pm Reply I'm going into my stupid question phase, but just so I'm clear. I won't need a transfer switch if I'm installing a separate set of plugs that go directly to the generator; while running lights and a few things from solar alone. Does that sound right?

bldginsp Member	# Posted: 17 Feb 2014 02:29pm Reply That's correct. From what MtDon and Dillio say, you are basically using the generator separate from the solar setup altogether, except that you are using it to charge the same set of batteries using a separate charger, not the charge controller that charges the batteries from the solar. So, my only question is, is there any problem with having the batteries connected to both the solar charge controller and the generator-supplied battery charger at the same time? The batteries could be getting charged from two sources at once, I suppose. Will one charger damage the other, or will the batteries suffer having two charges on them at once?

creeky Member	# Posted: 17 Feb 2014 05:52pm Reply If you have sun (it's long summer days) and you have a small system with 1 watt of solar panel charging for every 10 amps of battery (12v system here) you may never need your generator (so, say you have two 150 amp 6v deepcycle batteries... you would want 150 watts solar charging.) If you're only coming on weekends and the panels have all week to charge up the batteries, you can use fewer watts of panels, but . 1 watt to 10 amps is a general rule of thumb. If you want to use a vacuum cleaner and power tools etc then you need a genny (if you have a small battery/solar setup). Dillio's solution is a good one. Just wire one outlet for the generator power and plug your heavy draw devices in there. You could even skip the solar panels and just charge your batteries off of the genny. Gets expensive after awhile, but... Getting fancier: a transfer switch automatically puts the generator power to all plugs/switches and will charge your batteries with a battery charger. (As Dillio has noted. The DC output on the Honda generator is not really useful for charging a battery bank. It's more a charge your laptop kind of thing) a good low cost solution: http://www.bestconverter.com/Powermax-30-Amp-Transfer-Switch_p_436.html good folks. and the powermax transfer switch is 65 bucks and of know good quality. For battery charging look at the powermax charger "boondocker." It's well suited to small offgrid applications. And. For Bldginsp. Your batteries don't care if two or one charger is charging them. Your solar charge controller may taper back if it sees the batteries you're charging are at a high voltage. It will think it doesn't need to supply as much power. But chances are, if you're running your battery charger, it's because it's dark/cloudy out and you need to charge the batteries... is their an "obviously" emoticon?

bldginsp Member	# Posted: 17 Feb 2014 10:14pm Reply Ok, so lets see if I got this straight- Solar panels to charge controller. Charge controller to batteries. Charge controller to inverter, or direct from batteries to inverter? Inverter to a number of circuits. Generator without transfer switch, simply plug in what you want, like separate charger for batteries (connected to batteries simultaneously with solar charge controller), and plug in separate circuits apart from those powered off the inverter for lights, vacuum, etc. Generator with transfer switch will power circuits coming off inverter, so you don't have to have separate circuits. But the power to the battery charger needs to be one separate circuit, since you wouldn't have that powered off the inverter. Still not quite seeing what the wiring looks like at the batteries themselves- do the wires coming off the batteries lead to terminals where you hook up connections to charge controller from solar, battery charger from generator, and perhaps feeders to the inverter? Anyone got a nice photo of their wiring setup between all these components?

MtnDon Member	# Posted: 17 Feb 2014 10:35pm Reply Quoting: bldginsp Charge controller to inverter, or direct from batteries to inverter? ...assuming it's a PV setup... Charge controller INPUT from PV panels Charge controller OUTPUT to batteries CC never gets connected directly to an inverter Inverter INPUTS connect to batteries with fuse in (+) as close to batteries as possible. (Type T is best for this, but expensive. Type ANL will do the job mostly... the job being short circuit protection, not overcurrent.

MtnDon Member	# Posted: 17 Feb 2014 10:38pm - Edited by: MtnDon Reply Quoting: bldginsp Anyone got a nice photo of their wiring setup between all these components? Here's one way That is from this other place The CC connects to the buss on the left. The inverter connects to the buss on the right. Each series string of batteries connects to the buss (24 VDC system)

MtnDon Member	# Posted: 17 Feb 2014 10:43pm Reply Quoting: bldginsp Generator with transfer switch will power circuits coming off inverter Upper scale inverters may include the automatic transfer switch. Ours is the Outback VFX-3524M

MtnDon Member	# Posted: 17 Feb 2014 10:47pm Reply I like buss bars for a few reasons that include; ... neat and tidy, no nest of snakes wiring ... easy to disconnect one or two battery strings and leave other(s) connected ... if sized generously they have little noticeable resistance ... neat and tidy Note that shortly after that photo was taken rubber covers were fitted to the long bare portions of each buss bar.

MtnDon Member	# Posted: 17 Feb 2014 10:49pm - Edited by: MtnDon Reply wiring diagram for the above... note this shows pretty much everything except the T-fuse for the inverter, which is between the (+) buss and circuit breaker #4 and

MtnDon Member	# Posted: 17 Feb 2014 10:57pm Reply Quoting: bldginsp Inverter to a number of circuits. With a simple inverter there may be circuit breakers inside the unit. Other inverters that do not have included protection should be wired through a service panel with typical home breakers / circuits.

MtnDon Member	# Posted: 17 Feb 2014 11:00pm Reply Quoting: bldginsp Generator without transfer switch, simply plug in what you want, Be careful to not have any circuit "cross connected" or "double connected" to the inverter output and the generator output at the same time. That is one reason I do like automatic transfer switches. The ATS removes the consequences of a brain fart from the equation.

bldginsp Member	# Posted: 17 Feb 2014 11:47pm Reply Excellent, Don. Clean setup, well executed. I was glad to see the insulators on the bus bars, I must say, even though I'm sure it's all behind lock and key. I assume leads from a generator powered bat charger would just tie to the busbars, same as CC and inverter, correct? So lets talk a little grounding and bonding theory. You've got a separate grounding busbar for the grounds coming off the CC and inverter. Those are grounding electrode conductors I assume, to protect against lightning and to keep all potential with the earth equalized. As well the positive side has a fuse as close to the batteries themselves as possible to guard against short circuit, but not overcurrent. What's missing from the picture is any ground fault protection, an equipment grounding conductor bonded to the neutral (negative) at the source. If current gets loose off the positive, and energizes something, for instance some metal siding, there is no low impedance path for return current to get to the negative bar to spike the amperage and burn the fuse. By now you can tell I haven't dealt with these systems at all- I suppose this is accepted methodology- I've just been trained to look for fault current return path. Of course a 'compliant' system will have the grounds on the AC side of the inverter, and the grounds bonded to the neutrals at the upstream breaker panel or perhaps inverter itself, providing ground fault protection for the circuits. So I suppose everything on the line side of the inverter is considered, more or less, service entrance conductor which is essentially unprotected against ground fault. Only way to really protect it is to include a breaker as far upstream as possible, include equipment grounds and bond them to the negative. But maybe that creates other problems with DC. Anyway it's not required of course, I'm just trying to figure the logic of what protects best in this situation. In some cases the NEC writers can't find a good way to protect against certain possibilities, so they leave it be, trusting (or hoping) that the installers and users will know where the danger lies and guard against it appropriately on a case by case basis. Your neat and well organized work shows that kind of attention, wish I could say that for all the installations I see. Thanks for the info and pics.

MtnDon Member	# Posted: 17 Feb 2014 11:57pm Reply Quoting: bldginsp I'm sure it's all behind lock and key. I assume leads from a generator powered bat charger would just tie to the busbars, same as CC and inverter, correct? Yes, to the lock. The only time the battery bank is open is when I check Sp Gr, add water, etc. Other than things like that there is no need to open it. The CC is alone to the left in its own compartment and the inverter to the right, by itself. nd yes, to adding something like a stand alone battery charger; connect to the buss.

MtnDon Member	# Posted: 18 Feb 2014 12:07am Reply Quoting: bldginsp missing from the picture is any ground fault protection, At the time of the design the only situation that called for a DC side GFCI was if the PV panels were installed on a metal roof. I am not certain if things have changed with respect to GFCI and DC. NOTE: The long distance from PV panels to batteries meant that an exception came into play. The exception is that no ground wire was needed between the panels and the CC. The NEC didn't name a distance, I don't recall the exact wording, it was one of those things that can give you 2 different answers from 2 different inspectors. IIRC, if the separation of the panels and CC is more than approx 50 feet the ground wire is exempt, with conditions. There can not be any metal piping close by the wire run, no metal fencing like chain link or barbed wire close to the PV system wire run. Grounding rods at both ends were needed. I have two at each end, 10+ feet apart. There might be some other conditions I forget. Anyhow that saved the cost of the third wire.

bldginsp Member	# Posted: 18 Feb 2014 12:07am Reply If the inverter does not have breakers and simply feeds a breaker panel, do the inverter manufacturers bond grounds and neutral at the inverter, or leave it to the installer to do so at the sub panel? The NEC is trying to get away from bonding ground and neutral at sub panels altogether, but I don't see how it's avoidable in this case if the inverter manufacturer hasn't done it. Do you know?

MtnDon Member	# Posted: 18 Feb 2014 12:10am Reply Quoting: bldginsp I suppose everything on the line side of the inverter is considered, more or less, service entrance conductor Correct. FYI, everything from the pole the panels mount on to the output wires of the inverter qualify for federal tax credits. In NM all that was also exempt from sales tax.

bldginsp Member	# Posted: 18 Feb 2014 12:13am Reply Did we lose you altogether, rmak?

MtnDon Member	# Posted: 18 Feb 2014 12:16am - Edited by: MtnDon Reply Quoting: bldginsp If the inverter does not have breakers and simply feeds a breaker panel, do the inverter manufacturers bond grounds and neutral at the inverter, or leave it to the installer to do so at the sub panel? I can't say for certain about all brands, but the Outback, upper line Xantrex and I believe all Magnum inverters do not have an internal bond. I have the bond in the main service panel that is nearby outside the inverter enclosure. Since the original installation I have added a sub at the barn we built later. That is NOT bonded as the main panel is bonded. I realize the schematic also does not show the AC side lightning arrestor.

MtnDon Member	# Posted: 18 Feb 2014 12:19am Reply Quoting: bldginsp Did we lose you altogether, rmak? I think we went beyond what was asked for

bldginsp Member	# Posted: 18 Feb 2014 12:29am Reply But perhaps not beyond what is needed. Every aspect of what we discussed here bears directly on the safety of the system. I hope all off grid elec system installers understand it as well as you, Don.

rmak Member	# Posted: 18 Feb 2014 05:45am Reply Quoting: bldginsp Did we lose you altogether, rmak? Not entirely, but I'm running hard to catch up! Don't worry. If someone else can get good information, the thread is doing it's purpose. I never saw ground wires, lightning protectors or dc circuit breakers in a system before. Are these needed on a simple set up? Are dc circuit breakers like the ones in cars? How many amp circuit breakers are used?

Bret Member	# Posted: 18 Feb 2014 07:51am Reply This is great conversation. A question, if you don't mind. I am building an off grid cabin 16x20. 500 watt system to handle lights.small pump, ceiling fan. Are there any advantages to keeping everything DC? That would eliminate the expense of an inverter, but would add expense of heavier gauge wire. I can always add a small inverter if needed. Any thought would be appreciated. Bret

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