Two Aims 6000 Watt 48 Volt inverters to One Sub Panel.
SrTxsRoy
Registered Users Posts: 9 ✭✭
Hello. I am new to Solar and I am building an off grid place for retirement. I wanted to have to have a large enough system to run a typical small home with a window unit ac. I wired the cabin with one Square "D" 6 Circuit Panel and had it spray foamed insulated so I hope I do not need to add an additional panel. (Cabin is 16 x 40 one bedroom/bathroom, with open concept Kitchen/Livingroom) I am installing (4) arrays that each array output is at 96 volts at 9 amps. ( Actual total output 3700 watts from (4) Arrays) They are being ran through a midnight combiner to output 96 volts at 36 amps. Using an Outback Charge controller for 1000ah 48 volt battery bank setup. (actually (32) 125ah agm batteries made into 8 battery banks) I have two Aims 6000watt 48 Volt PSW Inverters and want to run the hot from each to each side of the Bus. I am hoping that I can connect the two Neutrals at the Neutral bus bar in the sub panel. I have grounded the Sub Panel to a ground rod. (Neutral bus not grounded) If not can anyone tell me what I need to do to complete my setup. I have spec information for all my equipment. Your time and help would be most appreciated. Roy
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Looks like you have more power than you'll need. Not a lot of fans of Aims inverters (efficiency , poor life span) here and 2 - 6000 watt will be much more inverter than you would want to run short of having a bakery! While I can't run everything at once, I have an 1800 watt inverter (had planed on a 3500-4000 watt inverter). I live in a 16x60 mobile home and run a window air conditioner as well as using a water heater (not recommended gas would be better), washer, toaster oven, dehydrator... I have a bit larger array 5000watt, but a much smaller battery @650 ah 24 volt (about a third of yours)
8 battery banks, which I suspect is one battery bank made up of 8 strings, will likely be problematic in the long run. It will work fine until one battery has a problem, then the other batteries will be drawn down trying to bring up the single battery. With AGM's it will be hard to trouble shoot.
Unless you are in a very sunny location, I would suggest discussing your energy needs and uses. I suspect you would be better served with a larger array, smaller battery bank and a single, smaller, better inverter. It reads as if you have already purchased this equipment. If you have a single 6000 watt inverter should be all you need in general, I guess a full size oven running with a water heater would bring it over the wattage, but that's a huge load and you would still be close!
Do you have any 240v loads, and if so, what are they?
If I understand correctly, your neutral isn't tied to ground anywhere (eg. in the inverter(s)), so is floating?
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
My suggestion would be to wire just one inverter into the panel and keep the other as a spare. It supposedly surges to 18000w, so if the window air conditioner is your biggest load, you should be fine with one. If not, it should prompt a re-think of loads for off-grid living.
It also looks like the inverter has a relay based ground-to-neutral switch. Do you have a generator, and if so do you know if it's grounded/neutral bonded?
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Hello Roy, Welcome to the Fourm.
If you could possibly return both of the AIMS inverters, would suggest you doing so. If they have not been mounted, and no knock-outs removed, a return may be possible.
As Photowhit mentioned there have been a number of off-gridders here, who have not been very happy with various AIMS inverters. Although, in fairness, there have been many fewer of these in the past year, or so.
AIMS makes many different inverters, but, if the one that Estragon found is the one that you have, the Idle power consumption is simply astonishingly HIGH. A single one of these inverters would consume in 24 hours about as much as do entire homes of many of us living off grid. It would difficult to imagine in what type of system an inverter with self-consumption would be a good fit.
Regarding your 32 ea AGM batteries, most likely, these 125 Ah batteries are 12 V. If that is the case, then you seem to be planning on running eight strings of four batteries each. This is considered to not be the best design choice, for a number of reasons -- the massive number of interconnections, difficulty in getting the strings to share charge and discharge currents well, the difficulty in choosing THE battery that best represents THE representative temperature of the bank for the RTS/BTS, and so on.
If you could return the batteries, and try to find a battery that meets the design goal of your system, based upon the loads that it will need to supply in a SINGLE string of batteries, you would probably be far ahead.
As you probably know, the off grid systems that perform most reliably for a long period of time, are those what have been carefully designed based upon the LOADs that they need to supply ... easy to say, and a bit time-consuming to do.
Do you know all of the loads that the system will need to supply, how long these loads will be on, the peak total load for the system, and approximately what time of day these loads will run? This will help size everything. Measuring the actual demand of the load on a Kill-a-Watt meter, or similar can be a large help.
Perhaps a bit too much attitude on my part.
A system that would supply 30-ish KWH per day, is a very large and usually a very expensive system, too.
FWIW, IMO, and so on. Vic
...but most places have an average yearly solar isolation of around 4 hours per day, or the max incoming wattage would be around 4hours x 2775 watts or @11Kwh. So even if you were using the energy as it was created you would have 11 kwhs on average. Stored energy comes with an additional @20% cost as only about 80% of the energy presented to the battery is stored. All this before the inverter efficiency, which on the Aims is around 88% peak. (some other peak around 95%)
I don't know if you care, but it doesn't look like Aims has any 6000 watt inverters that are code compliant, I went to their site, and breezed through the manual and didn't see any mention. It isn't required unless NEC needs to inspect your system or you want to carry insurance on the home, in which case I would ask them.
It actually sounds like you have a very well insulated very efficient cabin, I'll bet you will find you have a greatly reduce electrical usage.
First I want to first thank everyone for the feedback. I wish I had consulted on a forum or met with someone who had a system before I started out.
Due to cost my batteries were purchased on craigslist from a battery shop that was about 300 miles away which I drove and picked them up. They are used batteries but I was assured with proper care that they should last me at least five to seven years. It was my intention that when they needed to be replaced to buy new with a matched set of batteries all produced all having the same batch number and date code.
The panels also were bought through craigslist from a second source that were selling new old stock. They still have there warranty and are brand new panels but were manufactured several years ago and had never been sold. I bought them at about a third of their cost. The aims on the other hand I bought new through Amazon but at going back to the seller today found the date in which I could return them has past.
I have been piecing items together for the last several months. It may be a considerable loss but if it it is detrimental to use the Aims I am willing to purchase an alternative inverter or two.
As to code, being totally off grid I was not as concerned at being technical as much as being safe. I do not wish to act foolishly. I also did not sit down with the chart that I saw online to actually calculate my needs but as I said earlier referenced my former electric bills. I have used all LED lighting in my cabin and researched to buy the most energy efficient appliances to keep the loads down. I realized that the system was not the most efficient due to my purchases and thought that to error on being oversized would be a good thing.
Photowhit, I did not take you as being harsh. But reading your last reply it sounds like you have dealt with many novice builders and having taken the time to be educated about what you are doing. That you are tired of people trying to attempt something without first getting educated themselves. I can understand and appreciate that. I spent what I thought was a good amount of studying prior to starting my build, but see now I still jumped in too soon despite my studies. I have a friend that felt that I was going to be disappointed with solar power meeting my needs and I wanted to be sure to have plenty of power.
Thank you Vic for the advice. Before spending more money what recommendations would anyone make as to brand/size of inverters with my current Solar Power Panels (3700 watts, 4 strings at 96 volts at 9 amps) and or suggestions for battery Brand/size/Bank Configuration for 48 volt system? If you need I can post names and specs of Panels, and Batteries, inverters, charge controllers etc...
Also I have not bought it but do intend to buy a Kil a watt meter to check and verify loads at my outlets. I also have three inline amp/volt meters to install. Again I do appreciate your time. Roy
Think we have all made similar mistakes and paid the price of education, suggestions here are offered free of charge to those educating themselves, to prevent the disappointments most have experienced. The best starting point is an accurate inventory of all loads, then move on from there, for example using the Aims unit along with another smaller inverter for off peak times at night, could be one solution.
900W 3 × 300W No name brand Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal as a backup system.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergencies and welding.
I think you are realistic and will have an easier time switching to solar than others. Once being on solar we do tend to 'load shift' trying to use the energy when it's being produce and not dipping into the stored energy when we know we have been, or will be needing the stored energy. I don't have a generator, and that can provide some needed relief during long cloudy periods. I didn't ask, will you be using wood or gas for heat? Water heating? This is typical to save laundry as a daytime load, using a front load machine saves energy as well, your gas dry will give you a smoother transition to solar. I like to cook during the day with a crock pot, chili a couple days ago, pulled pork likely Monday...
Something you might look into is using a high efficiency Mini Split Air conditioner. I suspect with your well built, well insulated cabin, air conditioning the whole place would work out well, and have the advantage of less energy use and much less noise.
Many bargain hunters here! So understand the desire to save money. Hard to beat current low prices on new solar panels, 29 cents a Kwh for pallet load quantities, Grade 'A' New, UL listed panels. Thought I got a great deal 5 years ago at 76 cents a watt for new grade 'B' panels. Hard to imaging they can go much lower! In addition their is a 30% tax credit (off any tax liability in the US) Don't think you can take the tax credit on used panels or batteries. In the future you might consider forklift batteries, they are mass produced and offer a pretty good bang for the buck in deep cycle batteries, though they are among the highest maintenance batteries. Wish I knew of a source for inexpensive quality inverters!
Charge controllers are rated at output amps, so your 3700 watt array, even at NOCT values will be maxing out a 60 amp charge controller, I think you can get close to 5000 watts cost effectively on a 80 amp charge controller. You can have 2 (or more) controller feeding the same battery bank. I have 2 now and will have a third shortly, just put up a small east facing array to spread out my charging profile.
Kill-A-Watt meters are great to figure out how much energy is use, particularly on things that have thermostats! Fridge and freezers, Window air conditioners are hard to pin down.
Sadly, there are many gaps in your design.
Aims inverters are not stackable (you know that now)
Used AGM's are nearly always, expired, pulled from float service, Telcom plant backups. You can expect only a couple months service,
Parallel battery banks are not optimum, even more so when low IR agm batteries are employed
The new Magnum PT-100 controller might be a feasible replacement for the 60A controller
Your inverter/charger needs to be generator ready, or you need to have a 240V generator powering a 240 48V forklift or golf cart charger. The charger must be rated for use with AGM sealed batteries, or you have to become the charger brains and monitor when to
terminate the charging.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
The controller I have is an outback 80 amp 150 volt charge controller. (I can purchase another and add two additional 96 volt arrays to bring my total up to about 5500 watts. (each string of panels are just under 1000 watts) I still have (8) panels that are not setup) I have an Eco tank-less water heater that is run on propane and a front load washer. Do not have the dryer yet but it will be LP when purchased. my old one was electric so I passed it on to someone else.
Ok I am going to replace the Aims inverters. Any brand recommended? And is it better to have two stacked to feed the buses or tie the buses together and buy a larger inverter or at least a large one that is split phased? (When starting I thought having two inverters if one inverter failed I still had power. Wanted to maintain the fridge and minimal lighting so to limp along while repairing/replacing damaged equipment.)
After figuring my electrical use/needs I will post my findings and see where I should go next.
Roy
If you can return/sell the inverters, even if you have to eat a reasonable restocking fee, I would do it. They look more appropriate for a large marine application like a big power yacht. If not, just be aware of the big tare loss. If you use one for the barn make sure you turn off all the barn loads when not in use, or better yet, turn off the inverter. You don't want to run the inverter just to keep some electronics in the laundry appliances lit.
As others have pointed out, the batteries are likely to be problematic. It is what it is though, so we should focus on doing the best we can with what we have. On the bright side, you will get a lot of knowledge and experience with loads etc and will be in a much better position to make replacement choices when the time comes.
A big problem with AGM is there is no good way to accurately measure state of charge. We can get a reasonable idea by measuring resting voltage (no loads or charging for several hours) though, so before hooking them up as a bank, I would:
1. Lable each battery with a number to identify.
2. Measure and record resting voltage for each battery.
3. Charge each battery individually and fully. You will probably have to do this again, so get a good multi-stage 12v charger. Note any batteries that seem to charge unusually quickly, unusually slowly, or get unusually warm while charging.
4. Repeat step 2.
If you get this far with no problem batteries there's a decent chance of making a bank that might work for a while. If you find some problem batteries, maybe you still have some recourse to the seller?
The main thing is to get the batteries in as close to the same state as we can, and with no outright bad ones. If they go into a bank with some weaker than others there's a good chance of ruining the weaker ones prematurely. Once in use, you will want regularly measure and record individual battery voltages and repeat the separate charging exercise for weaker ones.
The generator is likely a portable type, on wheels, designed to run tools etc on remote job sites?
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
I don't see a huge load, I think your energy use will be surprisingly low, wonder how you are using close to 40Kwh's a day now. Perhaps you are in an all electric home, In power eaters, electric heat and air are usually #1 & 2, Water heater and refrigeration tie for #3, They account for much of a homes energy use.
In a solar home, there is an advantage, in that air conditioning is most needed when you have a lot of available power. In a tight small home (which you have described), you should be in pretty good shape. When setting things up look for those power hungry things. Old Plasma TV's could use 200+ watt for a large screen, New 55" LED TV's are in the 60-70watt range.
Some odd things do require more energy that you might image. CPAP machines may use upwards to 120-150 watts (and some in the 40-60 watt range) and they typically run at night off stored energy, This can be a load larger than a refrigerator! I suspect most living off grid, just learn to look at the amount of energy each thing uses.
Glad you are looking ahead and developing a system that will meet your needs. I do think it takes some time, some of use came into solar when Solar panels cost $5+ per watt. I suspect, us old timers, all have a pretty good idea of what is currently running in our homes and rarely leave a rom without turning off the light. It's odd for me to have more than a couple light on at any one time. I know people in grid connected homes who seem to turn on lights and leave them on until they go to sleep...
Can only be fed with a split phase power source ( a 240V inverter)
The split phase panel shares a return wire between the 2 phases, and assumes a large portion of the return current will be out of phase and cancel out, allowing a smaller return (neutral) conductor. Things will burn if the 2 legs are jumpered in the electrical panel.
If you have a split phase panel in, you should/must use a split phase feed. That can be from a Balance Transformer ($500) run off a
single phase inverter, or a split phase 240V inverter. Somethings are not safe to "MacGyver" into working.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
Mike, I asked here about and switched my 240 panel to 120, I don't think anyone though there would be a problem. Of course I'm only running 15 amp service to it from a 1800 watt inverter.
To clarify, you're talking about shared neutral on branch circuits, right?
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Mike you suggested the Magnum Charge controller. Is the Outback I have something I should not use? It is rated for 80 amp and 150 volt and can charge 4000 on a 48 volt bank. I can also add another and run them in parallel if I need to add more panels.
(Also note do not jumper buses on panels. Gotcha)
Mike maybe I am miss-understanding split phase. The panel I bought and wired my cabin with is a Homeline Square "D" 12 circuit 6 space 100 amp breaker panel and it is listed as single phase 120/240. But it has 6 circuits that is split with three on each bus for the hot and a neutral bus. Is this different from the split phase you mentioned above?
Photowhit you asked about heat. I have a wood burning stove for when needing heat. I am in Texas and we tend to need more ac through out the year but we do have times that heat is needed. When I retired I moved into my cabin no electric, no heat, no water and no insulation. The first week there winter blew me a kiss with 20 to 30 degree temps through the nights. I had my bed sucking the heat out from my body. I borrowed a propane stove and then bought the wood burner and thankfully it will crank out the heat. Oh and I do have a Samsung 52 in Plasma TV. Other wise everything has been researched for energy efficiency.
Now about panels I thought a string was panels wired together versus individual pans going to a combiner or charge controller/battery bank. I am also a little puzzled about panels being faced differently. I thought you wanted all to face south and dependent on time a year angled about 23 degrees for efficiency also dependent on latitude where panels are located.
Okay Estragon sounds like I need to change the batteries too. So you think that since I already have them use them til I lose them and then buy something that requires more maintenance but will prove to be longer lasting.
As to the generator you are correct I bought it to run tools for building and setting my place up. But I found it to be very efficient. I use roughly 5 gallons and it will last aprox 14 hrs. I have been really impressed. it advertises 10.5 hours on a half load but I have been running my house on it. The only real load though has been the ac. My fridge and stove are being delivered next week. I also do not have my water heater connected yet. It will be LP as so will the Stove.
You use terms like "two additional 96 volt arrays" When I think you mean "strings" they can be hooked up to the same charge controller, they face the same directions... I would use string, also either the total wattage vs Voltage. We would understand that each string must have very near the same voltage, and wattage would give us an indication of additional power.
Something I learned here, is you don't necessarily want to have all the power coming in at once. If you were grid connected, where the maximum power in total for the day makes perfect sense, it's not necessarily so with off grid installations. Since you will be using power during the day, and the less stored energy you use the better. It is often nice to have South East and South West arrays. You will still have near max during 'solar noon' but the curve will have longer tails. This is also a better charging profile if you are over paneled. Flooded Lead acid batteries can only charge at about 13-15% of their capacity per hour and the last 10% or so the battery accepts current even slower.
I think the understanding hit me listening to Dave taking about other advantages to solar tracking. Thanks Dave (or whom ever it was) Just yesterday I setup a small South Eastern facing array for just this reason.
I'd hook the Kill-A-Watt up to the plasma and chart it for a few hours. If it very high (I'd bet over 120 watts and suspect even more, depending on when it was made) If you don't need 4K there have been some great deals on efficient 55" LED TVs!
no funny tricks, and the inspector was quite happy on the first round.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
Regarding sharing a neutral bus bar between two AC inverters... It depends. Most pure/true sine-wave inverters have "isolated outputs" (transformer isolation) and can share a common/ground bonded AC neutral (the white wire in north America).
Most modified sine/square wave AC inverters do not have an isolated AC output. If you ground reference or try to share the AC Neutral and/or earth ground the AC neutral, the inverters will short out and fail (the specific warning is you cannot both have a negative ground battery bank and an earth bonded MSW inverter. The common installation is the ground the DC negative output and let the AC output "float").
And regarding split phase 120/240 VAC power. In North America, we have basically a center taped transformer on the power pole. There is a Black/White/Red connection. We have 120 VAC from Black to White, and Red to White. And 240 VAC from Black to Red. The center tap White is generally tied to ground (cold water pipe, ground rod, etc.) at both the pole transformer and at the house main panel (yes, the neutral is tied in two different locations--In general it works fine because there is no copper cable from the pole ground to the house ground. And since one transformer feeds a handful of houses, each house it tying White to Earth Ground--A bit problematic in theory, but what our code requires).
If you have one 120/240 VAC split phase output TSW/PSW AC inverter--Each hone will need its own 120/240 VAC panel. You can Bond the AC neutral together in the panel, and common ground reference (ground rod/cold water pipe, etc.) together for each panel.
If you have two 120 VAC TSW/PSW AC inverters, you can share one panel (common AC neutral, Black bus bar to one PSW Hot, and Red bus bar to second PSW/TSW AC inverter Hot). And make the two AC neutrals bonded on the same bus bar... It should work OK, but I would suggest not doing it. You will not get 240 VAC from Black to Red with two unsynced AC inverters. So, having a 120/240 VAC split phase main panel is of little practical use.
Also, it confuses the installation. Somebody working on the main panel may not realize there are two AC inverters has power sources--And they could try to pull 240 VAC out later, or get shocked when they only turn off one of the two AC inverter, etc... Just an personal opinion on my side. I do not like complexity/confusion--Years down the road, somebody may get bit.
-Bill
It will take a while. You may find some of the batteries are in pretty good condition (resting voltage at 12.8v in step 2). You want to focus on the weaker ones. I do think it's worth a shot unless you find batteries with a resting voltage less than 12v or so
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Hey Bill I appreciate the info on the panel and split phase. I had no intention of running 220 from the panel just did not want to waste having one half of the panel from being used so I Intended to have two 50 amp inverters in one panel.
I will update after I get my chart filled out.
Thank you all. Roy