Ok my original plan was to install a solar geyser and did a lot of research around it and still don't have all the answers on that.  When eskom started cutting the power the wife and kids forced me to move over to the a pv installation. I did not have a big budget to go for all the bells and whistles so  I had to settle for a lot less than what I need.

The first thing i realized is that i will have to redo my DB, my house is very old and still had the old fuchs Circuit breakers. i don't think they worked correctly. I split the DB in 2 eskom and solar. I installed 2 Earth leakages because I wanted both sides to be safe. The Stove; Geyser, Swimming pool; borehole and the inverter feed would be on the 1st earth leakage. the plugs and lights will be connected to the inverter output through an earth leakage. This setup did not work the 1st earrth leakage tripped immediately when i turned the second one on, I did split the neutrals. mbut could not solve the problem

I removed the 1st earth leakage and is worried because my swimming pool and borehole is not on an earth leakage. 

I installed 2 330w Solar panels in series to a mecer 3kva inverter with 4 batteries connected in series for 48v. after using the system for a day i realized something was wrong the sysem kept on switching back to utility after about 10mins. I checked and found that one of the supplied batteries are dropping below 5v as soon as the load is connected. The battery in question is a second hand battery that was borrowed to me. 

My need is to be able to run the lights and plugs for the time Eskom is off.  about 2.5 hours. My normal load during the day is around 300w(fridges, fishtanks; wifi routers) and when the kids are home 500w maks load 2kw( i still have to teach them to use the gas stove to boil water).  during the last couple of days with good sun I manually monitored the system and it was running of the panels and when the bad battery would drop it would switch back to eskom there are times where the panels supply all the power for the house. 

 

After this long spiel my question is as follow. Where can i purchase 100Ah batteries for less than R2k yes i know they will not be the best and they will not last 5 years but  that is what i can afford

What can i do to put my swimming pool and borehole back on an earth leakage to make the installation safe.

When the inverter is running the earth and neutral is not connected how can i connect them without using the normal earthing box?

 

I cant believe i do not have one reply 😥

 

 

I was browsing through the site and found this drawing from a 2015 post.

I am installing a 3Kva Mecer inverter 48v. My wiring will be 99% the same as this drawing 

is this Earth Bonding of the inverter output correct and does it work. i do not want to blow up the inverter.

Hi @Krokkedil,

I think that the old timers are a little nervous to respond on this.

There are many rules and regs around mains wiring and they are important since faults could kill you or burn your house down.

I think you should be worried if you have no earth leakage trip on your primary grid supply - this is unsafe and not compliant.

Apart from that I think you need to accept that you have a steep learning curve coming your way.  If not, you need to contract some help to get it done.

Here's some things to look into in respect of the batteries:

• How much power do you need to supply when the grid is off - how many watts and for how long?
• You need to be highly realistic about what needs to stay available since batteries are very very expensive.
• Multiply the amount of watts (say average of 1000 or 1kW) by the number of hours (say 2.5hours) and get the number of kW/H (2.5kW/h in my example) that you need to supply from batteries.
• Now double that - since you don't want to run the batteries down more than 50% - and divide by the system voltage (48) and you nave the number of Ah of batteries you need - so 5000Wh/48v = 104Ah
• So you need to buy 4 high quality deep cycle batteries of at least 104Ah capacity (in this example).
• Looking after those batteries is a whole story on its own - charging, not discharging too much by mistake, keeping them balanced (same voltage) - lots of stuff to geek out about.  Something like a Victron BMV702 can really help.
• Shorted batteries can start a big fire in short order.  You need FUSES.

Now about Solar PV:

• Your Mecer inverter specs are very important to read and understand.  Since you must design your solar array to fit into its specs.  Otherwise you will likely release the magic smoke that makes it work.  Look at:
• Maximum DC voltage it can cope with.  Make sure that your panels in series the "Voc" doesn't exceed this.  Give yourself 10-15% headroom
• It will have a minimum and maximum voltage for the MPP charger to work and an nominal or optimal voltage.  Add up the nominal voltages of your panels and make sure you are near the nominal voltage the inverter wants to see.  I wonder if this is what is happening now - since two panels in serious will give you somewhere around 70-80V or so which is probably too little.
•  Don't expect to get 300W from each panel routinely.  Sometimes it will by much much less.  I expect you need more than 2 panels.
• You'll need to get enough watts out of the panels to charge your batteries in a reasonable time.  In my example calc you might need to put 1.25kW into your batteries.  You will take more from the PV to get that done.  So if we guess you need 1.5kW and you are getting 300W from your panels in total you will take 5 hours to charge the batteries up from 50% discharged.

As for the wiring:

• I think you should consult an electrician about this.  But in principle:
• Earths should all be bonded together both sides of the inverter and make sure your earth is sound.
• Isolator/trip going into your inverter per the inverter spec.
• Isolator/earth leakage/trip coming out of your inverter - you have a 5kW inverter so a 20A trip sounds right but check the inverter docs.  Its its own source of power so needs all the same safety provisons that you have on your incoming power from Eskom.
• Keep the neutral on the output side separate from your grid neutral.  (And the live, of course).  BE careful in an old house since previous work may have taken short cuts and neutrals could be connected somewhere in the roof or elsewhere so check with a multimeter - with the power off of course.
• Don't connect inverter output neutral to earth.  You sometimes hear about that which I think is a practice to do with the US 2 phase system.
• There are special regulatory requirements for a dual supply setup like this around labelling, each board with a main switch and others.

 

So this is just input from someone just get started and to give you somewhere to start with seeking education.  There is tons of info on this board if you read patiently.

Perhaps it will provoke others to correct me or elaborate.

 

What @Elbow said, but re-examine why you are doing what you are doing.

There is an Irish saying when you ask for directions.

"If I was going there, I wouldn't start from here".

You have to be clear what your goal is.

If it's a 2kW peak load for 2,5 hrs, when ESKOM load sheds, a generator is hands down more suitable/reliable and cheaper than solar. (No batteries)

If its to save money on the bill, a grid tied inverter is the way to go. (No batteries)

And by the way, a solar geyser (No batteries) trumps a grid-tied inverter.

Batteries are way down the list, plenty of boxes to tick before you get there.

So if I was you, right now with you existing equipment, this is what I'd ask an electrician to do.

I'd change my lights to LED's by one more cheap battery to make up your 48V and just run your lights off this . That means your batteries wont work hard and they will be on float mostly. Not great but, getting something for your investment. If you can get the same make of battery as your other 3. Use what you've got until they are dead, which wont be long, but you may as well.

Use your battery budget to buy a small generator.  Don't split the rest of your system, just mark the MCB's that power your critical loads. Install a gen chop over switch. Then before you fire up the generator, trip the unwanted MCB's. Flip the gen switch and fire up the generator.

Please heed what @Elbow said about the earth leakage.

Solar geyser is probably your wisest next spend.

 

 

 

On 2018/12/31 at 2:00 PM, Krokkedil said:

I cant believe i do not have one reply 😥

 

 

Perhaps cause most people are on holiday?

I already purchased the the 2 PV 330w panels the Inverter and Batteries.

i don't want to go into to much detail now but the original plan was a solar geyser. I know this would have cut my electricity bill by about 30%. 

Because of the load shedding the plan was suddenly changed to PV backup. The supplier of the equipment gave me the wrong stuff and when I stripped after 4 weeks I was the bad one. 

I wired up my DB as per the above picture today. The 1st  EL trips as soon as I turn on the stove or the geyser. I removed the geyser and stove and connected them directly after the main CB.  I spoke to an electrician and he told me this is allowed I will look at the SANS doc when I have time.  The Swimming pool and Borehole is now back on EL

Just for Info, I am a qualified technician in electronics. Although this is my first HYBRID inverter installation. 

My biggest concern was the bonding of the earth to the neutral. I had a look at the grounding box that is sold to to this. It is actually an electronic board that gets a signal from the inverter that pulls in a relay that then bonds the earth to the neutral. And for this little box you pay R250-R850 depending on where you buy it from. 

I did the earth neutral bond after the inverter and will also be bonding all my equipment panels, batteries and inverter to the main earth in the DB of the house. 

I will be purchasing a new 100ah battery this week and will then check the system again, Today the power in our area was off, the solar panels provided enough power for the kids to still play games on the playstation. I think if the battery is replaced it will make a huge difference.

 

1 Question. 

1. What is the 20% DOD voltage for AGM batteries

 

 

 

 

 

 

 

11 hours ago, SilverNodashi said:

Perhaps cause most people are on holiday?

I hate typing on a tablet.

On 2018/12/28 at 9:38 PM, Krokkedil said:

... 100Ah batteries for less than R2k ...

The tend to go for +-R1850 incl - if you shop right, the 105ah "training" batteries.

They can last +-5 years IF you handle them with extreme care, seldom go below a SOC of 80% (20% DOD), DOC of 90% even better, till you need them.

If you take them to 50% DOD / SOC - then maybe 150-250 cycles.

To get the right SOC / DOD, you must have a BMV battery monitor, properly configured for the batteries.

I received 8x 200Ah batteries from a friend who replaced his with pylontech batteries. 

The batteries were never used below 75% and the system is working like a charm.

He has a raspberry Pi connected to his system that he uses to monitor the system. I  have a spare Pi but no software. Who is the distributor of the software. 

Thanks to all who helped thus far