somebody double check these figures (sanity check)

So after crunching kw/h numbers for what seems like over a year I came up with the following for my cabin: my usage per month in the winter over the last three years was 200 kw/h per month this is due to occasional heat tape use for the water pipes when the temps dip hard -20C (-4F) at night.
I chose a 3.6kw array with a 600 a/h 48 vdc bank. winter peak solar hours are 3.5 for this area. Solar controllers are morningstar ts60-mppt x 3, and inverter is a MS4448PAE with BMK,/AGS.
Currently we only go up on the weekends, and the only load while gone is a 4 cubic feet refrigerator and nothing else as the pipes are drained each week. daily use works out to about 8 kw/h so I am hoping for enough battery and panel to cover at least 2 days without the diesel generator firing up, though my muddling away seems to indicate possibly three with very limited if any sun. can anybody confirm these rough calculations?
Sign me: a former Marine living on Fuji and muddling his way though life
18 JA solar 200 watt panels, morningstar controller(s) and a
magnum 4448 inverter with all the usual junk that goes with it. and a
600 a/h 48 volt battery bank
Comments
1kw for fridge , what else is using power ?
And maybe your inverter is sucking too much at idle
|| 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 ,
However if you have grid power , stick with that . Easeyer and far Cheaper !
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
If gas fired tables aren't available, or you don't want to replace the tables for other reasons (eg. sentimental value), maybe it would be possible to retrofit a gas or diesel fired hydronic heating system into the tables, or the floor below. Something like this:
https://www.eberspaecher-na.com/products/fuel-operated-heaters/product-selection/coolant-heaters/hydronic-s3.html
This might also work as an alternative to electric heat tape for some or all of the water line?
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
Output is a function of water temp, flow rate, pipe size, floor material, etc., but ~25 btu/hr/sq.ft. is a reasonable OOM guess. I did mine with 16"O.C. spacing as it's just for supplemental heat. If doing it again, I'd do closer for more even heating.
I don't think natural convection would give enough flow, but it doesn't take a lot of pump to circulate. I have 4 zone pumps plus HX pump, on-demand propane heater, and lights running easily on a 300w inverter. I run it for an hour or two maybe a couple times/day to take the chill off. Solar heat wouldn't work too well in my (mid-Canada) climate. Seems like we haven't seen sun for weeks, and when we do it's brief and low in the sky.
Your bank appears to be 3 strings in parallel. Wiring would normally create the parallel connection close to the batteries (with string fuses in the case of > 2 strings), then a single (big) +/- wire to a breaker then +/- bussbars. The controllers would connect (via breakers) to the busses.
Adding battery string(s) is possible, but gets unwieldy. Some strings end up getting better charged than others, so you have to monitor individual strings carefully. If flooded, it also gets to be quite a chore checking SG and watering. Generally it's best to get bigger cell, lower voltage batteries so you get your design capacity with one or two parallel strings.
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
Is the line insulated with the tape between the insulation and pipe? If so, the tape should self-regulate down to what's needed to maintain just above freezing temp. If the pipe isn't insulated, most of the heat will be lost to surrounding air (or water/ice).
Is the line supplying water from a well or other downhill source? If so, you may be able to pump to a holding or pressure tank, and let water drain back to source between cycles, which may reduce or eliminate the need to run heat tape.
Just some thoughts
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
would make verification of current ballance a much simpler task, maintenance is important to avert supprises. The controllers outputs would probably be better connected to a common point on the busbar but spaced apart (negative and positive ) so as not to favor a single battery, for example both positive and negative connected in the center, same goes for the inverter connections. Understandably the diagram above may be a representation of actual layout, with 3 battery strings it's wise to have individual fuses for each string to the busbar, in case of a battery failure the fuse would prevent the other strings dumping all their current into one in fault, not a common thing to occur but a possibility.
With the TS60 's use the battery sence input at the same point as the output connections this will keep the controllers in sync with regards to transition voltage, having MS View software will be an asset, it allows finer adjustments and monitoring, if you don't already have it.
Just some thoughts.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
L-16 floor scrubber batteries are a choice, golf cart batteries are another option.
|| 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 voltage sense wires if commoned to the same point will ensure the controllers follow each other more closely, one point worth adding is, that if remote temperature sensors are used they would all have to be at a single point as well, as different temperatures will offset voltage output. My suggestion is ask tech support at Morningstar, they will suggest the best arrangement, they are extremely helpful.
The cost of off grid will far exceed grid even at a dollar per Kwh, perhaps double that when life expectancy of batteries and equipment are included.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
MicGivor's link is very nice with lots of meters listed. However, not all meters in the list are DC Current Clamp type DMMs.
For our solar power systems, I highly suggest you get the DC Current Clamp DMM/Meter (also usually does AC Current Clamp too).
It is great to be able to just zero the DC current clamp meter (DC C.C. meters have "zero drift" and can require re-zeroing every few minutes) and clamp it on a cable to measure the DC (or AC) current flow.
Many of the meters in the above link are AC current clamp meters with AC/DC volt meter functions too.
For example, here are a couple of low/medium priced AC/DC Current Clamp DMMs:
https://www.amazon.com/gp/product/B019CY4FB4
https://www.amazon.com/gp/product/B07546L9RT
-Bill
I have both the Klein and Uni-T DC clamp meters. Like them both. The one thing I like the Klein meter more for is the magnet feature on the back of the unit, It will stay put on a metal surface. Otherwise the Uni-T unit is a great value and a nice slim, handy size.
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Changing to the self regulating heat tape/trace and foam noodle should help at lot. I redid all my supply lines except the main to be contained inside the cabin using pex and sloped for ease draining down. The old copper stuff in the crawlspace was a mess anyway, having obviously been frozen a number of times. Main supply drains back between fill cycles, so my only heat trace is where the line goes through ice as backup in case air pressure system fails to push water down far enough.
Definitely wait for the (hopefully distant) demise of existing bank before thinking of replacement. My comment was just to point out the challenge of going to more than a couple of strings. Once you've addressed the excessive loads, you may find the existing works fine.
Doing a breakeven on solar is tough when future grid cost assumptions are little better than a WAG. If they're likely to stick with big ongoing maintenance/capex bills, having an option available makes some sense. For the other stuff, figure ~8yrs for decent well maintained FLA batteries, 10yrs for electronics, 20-25yrs for panels/racking/breakers/wire etc. Off-grid, that typically seems to work out to ~ $0.50 - $1/kwh.
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
so this past winter was as follows... average temps were running about 20 degrees on average in the daytime and about 0 at night. Blocking in the bottom of the house however severely limited the need for the heat tapes. my avverage overnight drain on the battery bank was 18 percent with 82 percent remaining. I had three or four times when it dipped down to 70 percent remaining after 3 or 4 days of poor production. this was running the two fridges 24-7 as well as ceiling fan, LED lights, the occasional water pump and the weekly kerosene fan heaters (about an hour each) when we first arrived on friday nights. This was running the heat tapes on a 15 on 30 off setting through the coldest parts of the night. later after I had enough data i eventually stopped turning them on at all as it was maintaining just above freezing under the house 33 to 38 degrees depending upon time of day. i did keep the heat tapes for the on demand water heater going through the night though as they have a 12" section that is not under the house and is exposed to the elements. but I double wrapped them and they shared one piece of 3 foot heat wrap between them. about 1/4 of the way through the winter Ihad to ditch my old fridge as it did not like swaping between 100VAC/50Htz to 120 VAC/60Htz the few times I ran on mains to allow the batteries time to completely charge only did it once and the fridge crapped out. the new one has had no issues to date though and I have done it twice to it. now to see how it works in the summer.
Ken, if you have mains power why did you not just let t he 4448 Inverter do the charging vs plugging the fridges into the Mains?
KID #51B 4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada
West Branch currently to meet code I had to have a disconnect outside of the inverter that mechanically disconects 100%. So the mains go into the disconnect as does the inverter. I was demonstrating the disconnect to a friend when I fired the refrigerator....it was a small 80liter unit that was about 25 years old and came with the cabin, so I was not surprised.
Running solar this winter last months bill was 1247 yen or about 10 bucks. in the past it was over 250 USD in the winter. between the mods i made to the house, and not using the mains I have for a fact saved about 600 over the last three to four months. summer will not be as drastic as no kotatsu or heat tapes, but it will still run around 60 to 100 per month.
Tepco is following through with their plans on chargeing independantly for repairs for the mountain cabins and vacation homes So I expect a really rude letter in the near future when they go to levy some bills to pay for some repairs as I will tell them to unhook.
Hopefully they'll let you unhook on reasonable terms.
I had a rental I expected to be vacant for some time, and asked to have water shut off. Aside from wanting to avoid fixed charges, I had heat turned down and didn't want frozen pipes. They said "no, the bylaw doesn't allow it". I read the bylaw, which does allow it. When I pointed this out, they changed their reply to "yes, we can turn it off, but we don't want to, and the bylaw doesn't give you any ability to make us".
Oddly enough, the bylaw doesn't even impose a duty to actually supply water on the utility, just a bunch of duties on property owner in support of the utility.
As renewables grow in some places by enough to be more than just a nuisance to utilities, I suspect there will be more moves to impose sunk costs as exit charges on grid cord-cutters.
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