HELP needed; Wire size for minimum voltage drop, etc.; full house 12v lighting off-grid

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  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Hi caribocoot,
    Can you advise on UPS charge controller/inverters? I'm looking a couple: http://www.photonage.com.au/advance-...h-p-11113.html
    and http://www.petech.com.au/fusion-commercial-ups.html
    Please let me know if anyone else could look into this. Sounds ideal for my requirements, I could even install PV panels at a later date and use the unit to charge batteries overnight. Victron make a similar unit Phoenix MultiPlus, probably better quality at a price but don't seem to have PV input.
    Thanks
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    So you've changed your mind about the 12 Volts? That first one is 24 and the second is 48.
    I like the specs on that first one with its built-in solar charge controller. But I have to say I've never seen any units like it or any other equipment by the same company so I know nothing of its quality or performance.

    Perhaps some other forum member has some actual experience with them? I know one fellow here uses commercial UPS units, but probably not that brand.

    These are not full-time type it seems (like are used to keep power pure and constant on computer servers) but emergency back-up systems only. They won't sell to grid like a hybrid GT system would.

    Is that what you're looking into now?
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr
    So you've changed your mind about the 12 Volts? That first one is 24 and the second is 48.
    I like the specs on that first one with its built-in solar charge controller. But I have to say I've never seen any units like it or any other equipment by the same company so I know nothing of its quality or performance.

    Hi Caribocoot,
    Based on advice including yours, 12 volt semms to be more temperamental & sensitive especially on the battery bank, cable loss, etc. so have now decided to ditch the 12v wiring and supply all lights with 240v mains from either 24v or 48v inverter and use DC drivers from the 240v to the 12 volt. I'll use the 4mm2 wire for the connections from each DC driver to each set of lights lights. This will enable me to use standard switching, standard 2.5mm2 twin & earth and keep the bulbs happy with controlled 12v. Other appliances will also run from inverter. Does this not sound better than my initial plan? :) Simplicity is probably the key here as you've also indicated. Voltage drop in 12v wiring is a major concern and that's why I've ditched the 12v wiring idea. In terms of radiation, etc. 12v wiring would have been great but it comes at a cost with issues added.
    The second choice does state 'solar energy compatible' but doesn't say if the solar just reduces the 240v use or also charges the batteries. Would that be automatic, within the unit? The charge controller is probably powered from the main 240v but if batteries reduce the 240v input wouldn't this effectively give the same end result?

    Perhaps some other forum member has some actual experience with them?
    These are not full-time type it seems (like are used to keep power pure and constant on computer servers) but emergency back-up systems only. They won't sell to grid like a hybrid GT system would.

    Is that what you're looking into now?

    I know they wont sell to the grid but we already have a GT 2.2kW in place so the UPS should complement that in terms of the ability to control the battery charge from different sources. I can hopefully use batteries during the day, maintained by solar input, to power most of the loads. Any more power needed should come in from the grid through the UPS. The batteries should then be fully charged overnight, when little output is required. I hope the UPS can be programmed to treat the battery bank as the primary supplier and use mains as backup. This souds like the opposite of what it's designed for but will hopefully work!?
    What do you think? if this isn't the case perhaps it's time someone made a unit that would do it.
    The battery bank, if 24v 440Ah should be suitable for the max charging current of 50A.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr
    Sascha wrote: »
    Hi Caribocoot,
    Based on advice including yours, 12 volt semms to be more temperamental & sensitive especially on the battery bank, cable loss, etc. so have now decided to ditch the 12v wiring and supply all lights with 240v mains from either 24v or 48v inverter and use DC drivers from the 240v to the 12 volt. I'll use the 4mm2 wire for the connections from each DC driver to each set of lights lights. This will enable me to use standard switching, standard 2.5mm2 twin & earth and keep the bulbs happy with controlled 12v. Other appliances will also run from inverter. Does this not sound better than my initial plan? :) Simplicity is probably the key here as you've also indicated. Voltage drop in 12v wiring is a major concern and that's why I've ditched the 12v wiring idea. In terms of radiation, etc. 12v wiring would have been great but it comes at a cost with issues added.
    The second choice does state 'solar energy compatible' but doesn't say if the solar just reduces the 240v use or also charges the batteries. Would that be automatic, within the unit? The charge controller is probably powered from the main 240v but if batteries reduce the 240v input wouldn't this effectively give the same end result?

    You've got it: 12 Volt has its applications, but they are limited in scope and nature.
    I suspect "solar energy compatible" means little more than that you can charge the batteries from solar, which of course you could. Charged batteries will not require power from mains, so in the event of longer-term outages you could have at least some power.
    I know they wont sell to the grid but we already have a GT 2.2kW in place so the UPS should complement that in terms of the ability to control the battery charge from different sources. I can hopefully use batteries during the day, maintained by solar input, to power most of the loads. Any more power needed should come in from the grid through the UPS. The batteries should then be fully charged overnight, when little output is required. I hope the UPS can be programmed to treat the battery bank as the primary supplier and use mains as backup. This souds like the opposite of what it's designed for but will hopefully work!?
    What do you think? if this isn't the case perhaps it's time someone made a unit that would do it.
    The battery bank, if 24v 440Ah should be suitable for the max charging current of 50A.

    "Use the batteries during the day ..." To what end? It won't save anything because the amount of power taken from the batteries will require more than that amount to recharge them. The UPS units are definitely not meant to consider batteries a primary power source; almost no system does if there is AC available. And as I said in the first part there is no advantage to it.

    The only possible advantage to shifting in and out of battery mode is if you have Time Of Use billing with a big price difference so that you could buy electric to recharge the batteries cheaply, then run off them when rates are higher. This is rather unlikely.

    Typically batteries require about 20% more energy to recharge than they supply.
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr
    "Use the batteries during the day ..." To what end? It won't save anything because the amount of power taken from the batteries will require more than that amount to recharge them. The UPS units are definitely not meant to consider batteries a primary power source; almost no system does if there is AC available. And as I said in the first part there is no advantage to it.

    The only possible advantage to shifting in and out of battery mode is if you have Time Of Use billing with a big price difference so that you could buy electric to recharge the batteries cheaply, then run off them when rates are higher. This is rather unlikely.

    Typically batteries require about 20% more energy to recharge than they supply.
    Thanks Cariboocoot,
    Our rates are $0.11AUD/unit between 9pm and 7am and we can sell back to the grid @ $0.47AUD/unit. If I could use the batteries during the day to some extend this would hopefully sell back units during the day. Is it worth considering I'd use 20% more power to charge the batteries then they can produce? The way I see it; We are already nearly breaking even as our power bill was around $5 for two months compared to $280 before we installed solar. It obviously varies with seasons and at peak (in summer I used a portable air-con (big consumer, I know) to cool my distributor van when stationery, almost every day when hot, this will change when I insulate the garage), our bill was $80. With the added 1000w of solar going through the UPS or whatever setup I decide to get, maybe standalone charge controller and inverter, we should be pushing some units back into the grid offsetting this agains the cost of such system. I just thought the UPS is easier to integrate solar & mains charging, battery bank and also inverter. Not to mention the independence we would gain in case the grid goes down. I still prefer being on the grid as there is no need for us to go totally off grid but I also like the independence power cost savings and contributing to being 'green'.
    Would I be better off with individual components as opposed to the all-in-one UPS?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    So it's $0.11 from 9 PM to 7 AM to buy. How much is it to buy from 7 AM to 9 PM? And is the sell rate the same all day and night?

    On the whole, straight GT is better because all the power the panels produce will go somewhere; either to your use or sell back to the grid. If you had a hybrid GT system that merely maintained batteries and could sell all the panels produce above that it would be best if you want the back-up.

    Otherwise you'd have to charge a substantial bank at night and then discharge it through a GT hybrid inverter during the day to gain from the buy/sell difference.

    When you've got grid and a utility that will buy at a good rate going from panel right to GT is best. Batteries deteriorate over time, used or not. The more and deeper they are cycled the faster they deteriorate.
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr
    So it's $0.11 from 9 PM to 7 AM to buy. How much is it to buy from 7 AM to 9 PM? And is the sell rate the same all day and night?

    On the whole, straight GT is better because all the power the panels produce will go somewhere; either to your use or sell back to the grid. If you had a hybrid GT system that merely maintained batteries and could sell all the panels produce above that it would be best if you want the back-up.

    Otherwise you'd have to charge a substantial bank at night and then discharge it through a GT hybrid inverter during the day to gain from the buy/sell difference.

    When you've got grid and a utility that will buy at a good rate going from panel right to GT is best. Batteries deteriorate over time, used or not. The more and deeper they are cycled the faster they deteriorate.

    The buy back is flat rate for whatever we overproduce but capped at 2.2kW. I can't send units back to the grid at night because the provider would cancel the contract which is based on solar (damn sun doesn't work at night). My savings with the additional off-grid would be based on using as little grid power as possible so, in an ideal world, we return a max of 2kW to the grid while using the off-grid. Cost per unit during the day varies depending on season but averages $0.25/unit (carefully distributing loads to mainly us off-peak shoulder) + flat 14 hour day rate $0.21 all weekend.

    Ideal setup: The UPS (or alternatively individual components) would be connected to grid/GC, maintain/charge batteries at night through mains power and during the day maximise solar & battery bank stored power to supply most loads and minimise the use of grid power in order to sell as many units as possible, up to the max 2kW.
    The 2kW technically can't be exceeded unless we upgrade the GC system as the UPS won't turn the meter backwards, only minimise load on mains and maximise use of the off-grid solar.
    My head is about to explode!
    Considering our consumtion is near 0 when taking into account the GC produces nearly as much as we use now (without the off-grid), the additional solar should be able to sell nearly all power it produces.
    I know battery banks need careful and extensive maintenance & monitoring but the beauty of this would be the independence if the grid goes down.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    If you want to do the battery-based time shifting, the easiest thing to do is use a timer to disconnect the AC from whatever inverter set-up you eventually choose and allow it to reconnect (activating the built-in charging system) after the rates change. If you add solar to it, you will need to adjust the exact time so that you make use of battery power after the sun goes too low to support the loads and the batteries have drain, say, 25%. A step above that is to use a Voltage controlled switch to reconnect the AC whenever battery Voltage drops below a point which indicates approximately the maximum discharge you wish to allow. This would also allow it to recharge from AC if there isn't enough sun. If you use both the VCS and timer, you'll need some method of low-Voltage disconnect to protect the batteries from being discharged too deeply.

    I hope that didn't make your head explode. Again. :p
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr
    I hope that didn't make your head explode. Again. :p

    I compare my head to a PC, not enough storage though so need to frequently defragment, reboot and or shut down. Schnapps works well to achieve those and your advice helps to prevent the reboot, etc.. :)
    If you want to do the battery-based time shifting, the easiest thing to do is use a timer to disconnect the AC from whatever inverter set-up you eventually choose and allow it to reconnect (activating the built-in charging system) after the rates change. If you add solar to it, you will need to adjust the exact time so that you make use of battery power after the sun goes too low to support the loads and the batteries have drain, say, 25%. A step above that is to use a Voltage controlled switch to reconnect the AC whenever battery Voltage drops below a point which indicates approximately the maximum discharge you wish to allow. This would also allow it to recharge from AC if there isn't enough sun. If you use both the VCS and timer, you'll need some method of low-Voltage disconnect to protect the batteries from being discharged too deeply.

    So, in laymens terms, do you suggest I steer clear of the all-in-one UPS and get an inverter, charge controller, etc.?
    If I put an AC disconnect switch or a simple timer on the UPS mains input it should register a power cut and use the battery bank, during the day also the solar charge controller. The battery bank would then supply the in-built inverter and any loads connected.
    In any case, I know I'll have to carefully monitor the whole setup several times a day to get used to the cycles and once I'm confident just keep an eye on it once a day and do battery maintenace once a week or so.
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr
    But I love my LED Christmas lights! :D One tenth the power of the old bulb strings, and I prefer the way they look. Can't say the same about the "standard bulb" LED's. Not yet, not here.

    Hey Cariboocoot, I've just received my light strips; 5 meters each with 44 key remote and when I plugged them it put a grin across my whole face.:D
    Great little gadgets and well worth it at just over $20 a pop, delivered. How can they make them so cheap??? The remote even has DIY buttons to program patterns. They'll be great under each step overhang on our staircase for indirect & safe lighting and I'll definitely get a few sets for the Christmas tree.
    'You beauty!', as they say here.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Great! Nothing like that "happy clam" feeling when something works out, eh? :D

    Oddly the Canadian phrase is: "Beauty, eh?" :p
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Hi Cariboocoot,
    I've just purchased 2 x Victron MultiPlus PHOENIX INVERTER/CHARGERS PURE SINE WAVE 24V/3000W/70 AMP. Price was good at $3125 for both, will sell one unit as I only need one. The normally retail @ $4400, chepaest I found it was $2970 + shipping so I think it's a good buy given they are much better quality units than the chinese or the indian made ones I was considering.
    I will also get a Victron BMV600 battery monitor to start with.
    Question: Given it has a max 70A 24v, 4 stage charge controller onboard would this be too much for a 440Ah 24v battery bank? Should I be aiming for 660Ah 24v (12 x 220Ah 6v batteries)?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr
    Sascha wrote: »
    Question: Given it has a max 70A 24v, 4 stage charge controller onboard would this be too much for a 440Ah 24v battery bank? Should I be aiming for 660Ah 24v (12 x 220Ah 6v batteries)?

    The answer is in the question: max 70A.
    That means the most it will put out is 70 Amps, not it's going to shove 70 Amps into the batteries whether they need it or not. That would be (70 * 100 / 440) about 15% charge current at most and it's not going to happen often providing you don't discharge the batteries too far so there's no worries.
    On the plus side it could also do the bigger battery bank if you wanted (a little over 10%).
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Thanks Cariboocoot. Now back to wire size I guess. What wire/cable size thickness should I use for the batteries, parallel, in series and also battery bank to charge controller/UPS approximately 1 meter above battery bank?
    8 x 6v/220Ah connected as; 2 x 4 batteries in series to get 2 x 24v/220Ah each and then parallel connect them to get 1 x 24v/440Ah.
    TM terminal type M (twin marine).
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    The inverter/charger manual should have recommendations for wire size and fusing based on its operating current. I can only give you an estimate calculated by the Watt capacity and nominal system Voltage. In metric size you'll be looking at something around 50mm2 (approximately 0 AWG).

    All the battery wiring should be the same size ideally; it makes it easier and guarantees no problems with interconnects "choking current". Purists will point out that since you will have two parallel strings of batteries the interconnects need only be 1/2 size (26mm2) because each string will only need to handle half the total current.

    Speaking of the two strings, be sure you use "diagonal wiring", method #2 here: http://www.smartgauge.co.uk/batt_con.html
    The idea is to connect the positive inverter & controller wiring to one string and the negative to the other to ensure even current flow through both.

    And while we're talking about trying to achieve the ideal, there really should be one fuse per battery string (in addition to the controller and inverter fuses/breakers) just in case something goes wrong. One of the strings could short, causing the other to discharge through it heavily and suddenly.
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Thanks, I assumed 0 gauge would be the best way to go.
    I've come accross the 'smartgauge' site before, most probably from one of your previus threads. It's a good site with heaps of info. I was going to use method 4 to make sure all is balanced.
    I didn't know the interconnects had to be fused though but you've explained it and it makes sense. One learns something new every day!
    Should something like this do the job; http://www.ebay.com.au/itm/ANL-FUSE-HOLDER-0-2-4-GAUGE-100A-300A-Gold-Plate-/260698157943?pt=AU_Car_Parts_Accessories&hash=item3cb2d23377 ?
    Do I need these on each connection, positive and negative or just positive? :confused: Just having a blank moment regarding basics so appreciate your input as you obviously have the knowledge and I do assume a lot.
    At this stage should I bite the bulet and get a pair of hydraulic crimping pliers, a few meters of 0 gauge, a number of 0 gauge copper lugs and fuse holders with fuses?
    Simply hammering the lugs down (like some DIY auto wiring dudes suggest) probably won't do if I want to sleep at night.
    What fuse rating is best for 6v 220Ah batteries and would they have to be a different rating for series and parallel?
    The shopping list is getting bigger and I'll soon have moths in my wallet. :cry:
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    It isn't the battery interconnects that need fuses, it's each battery string. You only need to fuse the positive side (standard practice) because you only need one circuit protection device to protect a circuit; the current is the same throughout. The parallel battery strings are what necessitate the change because it introduces a second circuit on the battery system: the parallel string.

    Blue Sea makes these nice battery terminal fuse set-ups that bolt directly to the battery (see pic). You can probably find them locally at a marine supply store.

    In addition to that you want a fuse (or breaker) on the (+) line to the inverter rated for its peak potential draw (best to go with the manufacturer's recommendations). Another will be needed on the (+) line from the charge controller to the battery.

    The sizing of wire and circuit protection isn't a matter of the battery bank so much as the expected current to and from the battery on the circuit. The inverter will have a maximum draw and recommended fuse size. Likewise the charge controller should have similar specifications. It's hard to go wrong using the manufacturers' recommendations.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Forgot to mention; for connecting crimp ends to wires you need to use a proper tool. Here's a hammer-down type that NAWS sells: http://www.solar-electric.com/hacrtoforlal.html
    There are lever-action types as well, but of course they cost more. Don't rely on just mashing them with a hammer or squeezing them with pliers. You really do need to put the right "dents" in the right places, just as you suspected.
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Doh, as I said; blank moment. 'Should have read the word STRING, not just battery!
    The fuse set-up's pictures are a good idea to keep the bank tidy. I'll look for them. So the fuse rating for the strings should be?
    Am I better off buying screw in terminal connectors or crimping lugs?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Basically the individual battery string fuses would be 1/2 the inverter fuse rating or a bit more. So if your inverter calls for a 150 Amp fuse you'd have that and a 75 to 80 Amp fuse on each battery string. Some might recommend the whole rating on each one, and I'm good with that too; if something is going to go wrong here it's going to go wrong in a big way so even 150 Amp on each would pop. Like if you drop a wrench in the wrong place.

    I think you're better off with crimped ends on wires. The screw-down connectors may not be available in the wire size you need, and you may not get the connection tight enough.

    There's been quite a debate on the forum about soldering lugs after crimping them. A couple of us prefer this method and have had no trouble with it. Others decry it as having inherent flaws. But you do have to do it right. A bad connection, no matter what type, is a bad connection and that means trouble.
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Hi Cariboocoot,
    Can you please advise on isolator switches and/or fuses for my setup;
    24v440Ah battery bank; 4 x 6v/220Ah batteries (in series) = 24v/220Ah x 2 (parallel) = 24v/440Ah. Does this requre two fuses, one each string before parallel wire connection?

    Battery bank connection to UPS/charge controller/inverter 3000w/6000w. Is the magafuse included in the UPS/charge controller/inverter 3000w/6000w sufficient or should I add isolator switch? If so what kind & rating?

    Should the mains input and/or output to and from the UPS/charge controller/inverter 3000w/6000w have an isolator switch?

    If I connect 24v/1000w PV solar through a 3 stage charge controller to the battery bank to complement charging during the day, what is recommended for optimum safety in terms of fuses and isolator switches?

    I apologise if I come across as ignorant to previous advice regarding separate components but it would be good to have all info at hand to make a shopping list.
    I've ordered 25ft of 1/0 gauge cable + 40 x tinned copper lugs/terminal connectors for all battery inter-connections and connection to UPS + 2 x fuse holders & 200A fuses for the two strings and also a 14t hydraulic crimping tool.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    As mentioned, if you have multiple strings of batteries (as in this case) it's a good idea to have a fuse on each string. Those Blue Sea post fuses are great for this.

    You really do want some sort of high-current disconnect on the inverter. Whether you use one of the standard battery switches (Blue Sea again makes good ones) or the breaker type depends largely on how accessible the built-in fuses of the inverter are. Sometimes they have fuses, but you can only get at them by taking the thing apart. Not so good.

    If you're going to have the AC output go to loads that you also want to be able to run from another AC source you'll need an AC transfer switch in between so the loads can be switched from one power source to the other.

    A charge controller's output should also have a disconnect and circuit protection on it. This needs to be rated as to the output potential of the controller. 1kW of 24 Volt PV will have a potential from 30 to 40 Amps, depending on the exact performance conditions. Even if the charge controller has a 60 Amp capacity you may want to wire & protect for the full capacity, just in case. Again, the controller should have the information on this as recommended by the manufacturer. You can probably find the manual on line before you buy and read it to get some idea what you're in for (one of the great things about the 'Net).

    Ignorant? Pshaw! I've been learning this stuff for 50 years and I'm still learning stuff! ;)
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr
    Ignorant? Pshaw! I've been learning this stuff for 50 years and I'm still learning stuff! ;)

    I wish I had you 50 years of experience but at my age (44).:p

    The UPS unit has the following protection built in;

    a) output short circuit
    b) overload
    c) battery voltage to high
    d) battery voltage to low
    e) battery reverse polarity detection
    f) 230 v AC on inverter output
    g) input voltage ripple too high
    h) temperature to high

    On the installation diagram it shows an RCD on the AC output, which I will install. Is this what you mean by 'high-current disconnect on the inverter'? If so what rating for 3000w/6000w output?
    The AC transfer switch also sounds like the way to go. If for nothing else at least I can simply swith to AC direct in case the UPS fails.
    Our GC solar system has a separate DC isolator switch. Would you recommend the same between the battery bank and the UPS? If so, would a 2 gang be good to enable isolation of the two strings independent and what rating should they be? Would I then still need the fuses on each string?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    The high-current disconnect is a switch capable of turning off the DC IN as needed. It has to be high current because the Amps drawn there could be more than 250. The Blue Sea units are capable of 350 Amps: http://www.solar-electric.com/blseabaswon3.html Great way to connect/disconnect without big sparks! But it is not circuit protection, so you'd also need a fuse as per the inverter's specs (probably 300 Amp).

    Switches don't take the place of fuses. Even if you used one of the double switches http://www.solar-electric.com/basw1300amp.html (allows use of either battery string or both or off) you still need the circuit protection.

    It's easy to understand a basic circuit: power source, load, wires that connect them. It get difficult when you have inter-acting circuits like two strings of batteries powering one load or several parallel panel connections to one controller.

    With the parallel battery strings, each one becomes another circuit which can feed either the inverter or the other string when connected together. Ideally the current flows from both to the inverter and back in an even discharge (and reverse from the controller for charge). But there is then the possibility that current can flow from one battery string to the other, especially if something has gone wrong. That's what the terminal fuses help protect against. The other "main" fuse is to protect the "intended" circuit through the inverter. The controller has its own protection as this is another circuit which interacts with the others.

    And I'll mention that for brevity's sake I tend to use "fuse" as a synonym for any type of circuit protection (i.e. fuse or breaker). It's shorter and easier, until I have to write this explanation. :roll:
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr
    With the parallel battery strings, each one becomes another circuit which can feed either the inverter or the other string when connected together. Ideally the current flows from both to the inverter and back in an even discharge (and reverse from the controller for charge). But there is then the possibility that current can flow from one battery string to the other, especially if something has gone wrong. That's what the terminal fuses help protect against. The other "main" fuse is to protect the "intended" circuit through the inverter. The controller has its own protection as this is another circuit which interacts with the others.

    And I'll mention that for brevity's sake I tend to use "fuse" as a synonym for any type of circuit protection (i.e. fuse or breaker). It's shorter and easier, until I have to write this explanation. :roll:

    Thanks Cariboocoot for letting me 'pick your brains'. You've explained this one well!
    I'll admit when I said DC isolator switch I meant the RCD breaker, which is probably not meant to be used as a switch but can be. You probably have similar devices instead of fuses; trip switch & reset/test button in a waterproof housing accessible from the transparent front latch opening.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Certainly the GT installs have to have that sort of thing. Out here in cabin country it's a bit more "RV meets house" as to the method of installation. :p
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Sure, your regulations are probably just as tight (on paper) as ours but seeing that people here do their own mods on cars as far as chopping a Land Cruiser in half and relacing the back end with a tray top, never to be put over the pits to be tested. Would like to see what the insurance company has to say if anthing happened but then again; auto insurance isn't compulsory here and no yearly testing like the UK for example. The 'REGO' covers damage to others but saying that, I don't think someone with such mods would be treated lightly in case of an accident. AUS is 'cowboy country', a term used often for incompetent trades people, cutting corners, etc.. You probably know the type I mean, they are everywhere so not just AUS! We are at a point were people don't trust any trades because they have been had by one of the cowboys.
    I meant; I could use the RCD to also disconnect the circuit rather than installing an RCD and a switch. this way it would act as a fuse but also switch if needed.
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Hey Cariboocoot, Ive just checked the time in Canada. :roll: You don't sleep much do you?
    Me neither! :cry:
  • BB.BB. Super Moderators, Administrators Posts: 29,639 admin
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Just to be clear--What is an "RCD"?

    I thought it was a "residual current device" or what we would call an AC Ground Fault Interrupter.

    Are you asking about installing one on the DC side or the AC side?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SaschaSascha Solar Expert Posts: 121 ✭✭✭✭
    Re: HELP needed; Wire sze for minimum voltage drop, etc.; full house 12v lighting off-gr

    Sorry Cariboocoot,
    RCD is a residual current device. I should have said RCBO (Residual Current Circuit Breaker with Overload protection). The box is a 'RCD cover with enclosure' one housing the AC isolator and one housing the DC isolator. we just generally call them RCD. :(
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