2 minutes ago, Gerrie said:

If the water heaters have no neutral then you do not need to worry about that, but you still need to split the Eskom and inverter neutral as they must be isolated from one another ( the changeover actually do that). If loads are on inverter the inverter neutral must be used or if loads are on Eskom than Eskom neutral must be used.

Yup very clear .... thanks for everything, one more problem, now how do I turn water into wine..... this shutdown is threatening my stocks......or is it not that type of shutdown that can be solved with a few switches.......

15 minutes ago, JohnMarc said:

this shutdown is threatening my stocks.

As long as you save one cold one, when you finally flick that switch you can stand back and enjoy that sun power. 😎

 

20 minutes ago, JohnMarc said:

 

3 minutes ago, Gerrie said:

As long as you save one cold one, when you finally flick that switch you can stand back and enjoy that sun power. 😎

 

You'd be most welcome....thanks for everything 

1 hour ago, JohnMarc said:

how do I turn water into wine

CS Lewis wrote that the turning of water into wine, in itself, is something we do all the time. It just takes a really long time (as it has to go by way of grapes, fermentation, etc).

In terms of my own stock, I bought 24 cans of beer and 12 bottles of other things (cider, etc), The idea being that there'd be one drink for me and the wife for 18 days out of the 21... and since we had a bottle of wine as well that'd see us through. Then the 21 days became 35... and now we're literally sharing a can each day. We did however discover a bottle of Brandy... and Coke-a-Cola is still sold at the shops... so it seems we're good for another week or so 🙂

 

2 hours ago, JohnMarc said:

I would like to avoid reinventing the wheel if possible and effectively switch from # Phase to a single phase supply. 

Will you have panels connected to your inverter or only batteries?

 

On 2020/04/18 at 7:40 PM, Gerrie said:

I can’t see a problem with feeding only one  of the three phases from a inverter, I have done similar before with a single phase generator feeding a three phase installation during load shedding. We had a manual change over switch, and switched off all  non-essential circuit breakers before powering the critical loads. I actually looped all three phases to have generator power but just manually switched off all three phase breakers and non-critical loads.

Hi Gerrie, this is a common practice, and works nice when using a generator, but please rethink this approach. Now you are dealing with a Solar system, and you want to disconnect it from the loads when the Grid is available.

 

2 hours ago, Gerrie said:

As long as you save one cold one, when you finally flick that switch you can stand back and enjoy that sun power. 😎

In your setup above, @JohnMarc, will only enjoy the sun power when the grid is off, for the rest of the time, the solar system will be disconnected from the loads, doing nothing, except for waiting for a power outage. 

EDIT: Just as with the generator, if the power goes out, there will be a period of no power when Either John has to manually switch over the switch to connect the Inverter output to the loads. 

Connecting his 5KVA unit to 1 phase only, and having the critical loads connected to the same phase will offer constant usage of the available PV power as well as uninterrupted automatic changeover from grid to battery power. I am still of opinion doing it this way would be the best, but if John is willing to have these interruptions, there's not much more I can contribute. 

6 hours ago, Jaco de Jongh said:

Hi Gerrie, this is a common practice, and works nice when using a generator, but please rethink this approach. Now you are dealing with a Solar system, and you want to disconnect it from the loads when the Grid is available.

Hi Jaco, This thread started as backup on 1phase with outages, but I only confirmed to JohnMarc that it is indeed possible to feed 1 x essential phase during outages with a inverter, but I then went further and said it is even possible to feed all 3 x phases with power as long as 3ph loads are turned “off” and as-long its under the 5KVA capacity of inverter.

This in my opinion would be the most cost effective way of having back-up on all his single phase loads during outages. I know a generator would be be far cheaper but it that comes with it’s own disadvantages.

7 hours ago, Jaco de Jongh said:

 

7 hours ago, Jaco de Jongh said:

you want to disconnect it from the loads when the Grid is available.

Disconnecting it from the loads was not really the aim when grid is available, but a changeover switch makes it possible to even do so. He could even run this 24/7 with a decent battery backup and panels if he really wanted to. 

 

7 hours ago, Jaco de Jongh said:

In your setup above, @JohnMarc, will only enjoy the sun power when the grid is off, for the rest of the time, the solar system will be disconnected from the loads, doing nothing, except for waiting for a power outage. 

This is true what Jaco said, I also believe it can be a white elephant if not utilized to recover some cost. 

 

7 hours ago, Jaco de Jongh said:

Connecting his 5KVA unit to 1 phase only, and having the critical loads connected to the same phase will offer constant usage of the available PV power as well as uninterrupted automatic changeover from grid to battery power. I am still of opinion doing it this way would be the best, but if John is willing to have these interruptions, there's not much more I can contribute. 

I also agree with having one dedicated phase permanently on inverter could be a better longterm option. I think that would require a specific type of inverter and will require a more in-detail design.🙂

7 hours ago, plonkster said:

Then the 21 days became 35... and now we're literally sharing a can each day. We did however discover a bottle of Brandy... and Coke-a-Cola is still sold at the shops... so it seems we're good for another week or so 🙂

We realized how many odd bottles we had that ended up in the cupboard, when I used to empty the cooler box in the good old days when we were still free. Those came in handy now and the cupboard has less clutter, but my one bottle of Jameson gets watched with hawk eyes because this lockdown might stretch a bit further.😁

1 hour ago, Gerrie said:

Disconnecting it from the loads was not really the aim when grid is available,

In your design above, it was unavoidable. You would have used either grid or inverter. So when the changeover in your design was set to Grid, the inverter would have been disconnected from the load.

1 hour ago, Gerrie said:

I think that would require a specific type of inverter and will require a more in-detail design.🙂

Not at all, any 5 kva unit for that matter can be used in this application, no special or in dept design needed.  

I haven't been very clear and should have laid out my expectations of the system that I am installing, Halfway there, the batteries are installed (48v 220 Ah) the Invertor is installed (connected to the batteries) BMV 702 is installed and all working well..I am in the process of sourcing solar panels and will install those later

... Now want to connect to the board.....

I am looking for an interrupted power supply for when (not if) Eskom start playing their games again. All options are still on the table but when Eskom switch us off I simply want to have uninterrupted power. When the grid comes back on I am happy to use Eskom to charge the batteries and get ready for the next shut down.....

41 minutes ago, Jaco de Jongh said:

In your design above, it was unavoidable. You would have used either grid or inverter. So when the changeover in your design was set to Grid, the inverter would have been disconnected from the load.

Is this an issue I should be aware of....... are you saying that with the inverter disconnected I would not be charging my batteries Maybe you can help find a 3 phase changeover diagram so I can apply some of my own grey matter to the issue and have a better understanding of the points you raise

 

As this system takes shape there is still one question I haven't managed to get an answer on, that is on the battery side why is a fuse and a breaker necessary, surely just a dc breaker would have the same protection a fuse would offer

1 hour ago, JohnMarc said:

that is on the battery side why is a fuse and a breaker necessary, surely just a dc breaker would have the same protection a fuse would offer

I am not sure why the breaker is needed. In general we only install DC fuses. Normally on the POS as well as NEG wires. For your inverter I would recommend 125 - 160amp fuses. A DC breaker with that kind of rating will be pretty expensive compared to a fuse. 

18 minutes ago, Jaco de Jongh said:

I am not sure why the breaker is needed. In general we only install DC fuses. Normally on the POS as well as NEG wires. For your inverter I would recommend 125 - 160amp fuses. A DC breaker with that kind of rating will be pretty expensive compared to a fuse. 

Is the breaker there as a way to isolate the battery bank from the inverter? If we assume I go the breaker route then are the fuses still required

8 minutes ago, JohnMarc said:

? If we assume I go the breaker route then are the fuses still required

No, either one of the 2 is sufficient.

18 hours ago, JohnMarc said:

All options are still on the table but when Eskom switch us off I simply want to have uninterrupted power.

Hi JohnMarc, The above is a big statement 😁

So I’m going to through a big spanner in the works. The discussion about the manual changeover switch was a very simple way of doing things but it comes with the “schlepp”. Sombody needing to flick that switch manually and you might not be at home. I used to get phone calls from wife and kids phoning me while I‘m in a meeting, saying ; there’s load-shedding how do we operate the inverter?

My system - Off-Grid, I have a cheapy 4KW inverter with small 120AH 48V gel bateries and 6 x 330W panels (DIY cost R35K) I installed a contactor as changeover switch (Main one) and I went further and installed a second changeover contactor (critical one). I then installed a sonoff switch that allows me to operate any of the two contactors from my phone. The sonoff’s are great it have timer seting on it, so my solar system is pre-set on times when to come on-and-off everyday. 

Now I’m sure there are nice inverters on the market that can do this automatically, yours might be one of those.

It might be worth your while looking into something like this, depending on your needs, as you mentioned there are times when your away from home, this might be a solution and I’m sure similar can be done even with your 3phase to 1phase system.

The contactors I used is called modular contactor, In you case you can check out electo mechanica hager part ESC464. I bought different brand on on ebay at a third of the price.

Now the un-interupted supply function, when my system switch, it happens in about 30ms. You do not need to shut-down computers it is instant, I have two gaming pc’s thats on 24/7 and the wife is also now with her pc working from home. So there is no issue. If my inverter gets overloaded for whatever reason it falls back to grid and nobody even knows it switched. It all just how you wire the thing😉

I fear we may have overcomplicated things with all this talk of a changeover.

The OP said he has all the essential loads on L1 already. If he does want to expand from that, this is what I'd do:

1. I'd install the inverter/charger on L1, as I normally would. I would use the inverter's already built-in changeover switch so that when the power fails, the loads are picked up automatically.

2. I would split L2 and L3 as well, so that the three-phase loads and the water heaters are on one side, and the single phase loads are on the other.

3. I would then put two changeovers on L2 and L3, that allows the single-phase loads on them to either feed from the grid, or to feed from L1.

Now the outcome is that when the grid fails, the essentials stay up. Should I need one of the others to run, I have to manually flip those switches. At least I don't have to do that in the dark.

For the purposes of this discussion I assumed L1 gets the inverter/charger. If it is one of the others, then just rotate it around. From the inverter/charger's perspective it does not matter what phase it is on, as long as you don't screw up the rotation.

Edited April 21, 20206 yr by plonkster