Hello

My grandmother is in an old age home and I want to help her to get through load shedding. Her flat's DB box is in the hallway, so the easiest is to install a inverter that is powered from a wall socket. Based on available stock and price, we will be installing a 1kW RCT Axpert inverter. I will install separate red plugs for all the appliances that need to be on the inverter. This will prevent somebody to accidentally plug a high load appliance on the inverter. 

What is correct way to protect the "red plug" circuit? Obviously there must be a circuit breaker to protect against short circuit. There should also be an RCD to protect against earth leakage. The neutral on the output side of the inverter should be bonded to earth. 

Does this inverter do automatic bonding?

If it does automatic bonding, I should be able to install a RCD on the output of the inverter without causing nuisance trips of the two RCD (on in the main DB and one on the output of the inverter). 

If not, what is the correct way to do earth leakage protection with this install? 

Hi @ErickvWyngaardI like your design philisophy and I can see you are touching the right bases in terms of both functionality and safety.

1. In terms of the grid input input, if the plug connection is quite a  distance from the inverter, add a double isolator at the inverter. Also remember that when the inverter is in Line mode, it will supply both load and charge a flat battery. Be conservative what you allow the maximum charge current to be, as not to exceed say the 16A rating of the plug circuiy. 

Also add a 2 x  220VAC red indicator lamps, one on grid input, and one on load output. It will make life very easy for you to remotely ask grandma the state of the machine, if need be. 

2. The protection on the red plug load circuit will be an RCD and a circuit breaker to match the wire size of the red plug circuit. 

3.you wont know wether there is automatic bonding. But there is a test you can perform when you install it, to verify wether it has. If it turns out no, then  10 amp din mount Omron relay 3 pole will need to be added onto your little db box. We will discuss wiring detail when applicable.  During ELD testing, you need a Plug Tester to verify safe working of ELD. RCD test button on its own is not good enough. 

4.go for it, make your GrandMa happy ❤️

Edited March 11, 20232 yr by BritishRacingGreen

11 minutes ago, BritishRacingGreen said:

Hi @ErickvWyngaardI like your design philisophy 

1. In terms of the grid input input, if the plug connection is quite a  distance from the inverter, add a double isolator at the inverter. Also remember that when the inverter is in Line mode, it will supply both load and charge a flat battery. Be conservative what you allow the maximum charge current to be, as not to exceed say the 16A rating of the plug circuiy. 

There is no chance that a 1kw inverter as per this unit can even get to 10A let alone exceed the 16A rating of a normal 3 point socket. 

Not in line mode or bypass or during charging 

Edited March 11, 20232 yr by Scorp007

9 minutes ago, Scorp007 said:

There is no chance that a 1kw inverter as per this unit can even get to 10A let alone exceed the 16A rating of a normal 3 point socket. 

Not in line mode or bypass or during charging 

That is of course true, after all its a small 1000w machine. 

Edited March 11, 20232 yr by BritishRacingGreen

I just want to say good on you!

We have put in a solution for my mother. It is not as elegant as yours, but it gives her light and TV and allows her to charge phones. Crucially for her, she has a bedside lamp. We also added a flat lying one plate gas stove and an old fashioned kettle, so she can make tea or warm up a meal. 

This may not  be a lot when you say it out loud, but in fact it makes a big difference to her. She can read a book (in bed!), she can watch TV, do her knitting, have a cuppa. She's way better off. 

Many of her neighbours still sit in darkness during load shedding. Ok... First prize is to end load shedding, but what we've done for my mother cost under 20k, and it puzzles me that those neighbours have to sit in darkness or burn candles when their situation could be made more comfortable for not a huge outlay. 

So well done! You are making a real difference. 

NB! I don't think what my mother has is going to last 10 years, so there is more outlay to come. But it will be in increments rather than one go.

Edited March 11, 20232 yr by Bobster.

4 hours ago, Bobster. said:

I just want to say good on you!

We have put in a solution for my mother. It is not as elegant as yours, but it gives her light and TV and allows her to charge phones. Crucially for her, she has a bedside lamp. We also added a flat lying one plate gas stove and an old fashioned kettle, so she can make tea or warm up a meal. 

This may not  be a lot when you say it out loud, but in fact it makes a big difference to her. She can read a book (in bed!), she can watch TV, do her knitting, have a cuppa. She's way better off. 

Many of her neighbours still sit in darkness during load shedding. Ok... First prize is to end load shedding, but what we've done for my mother cost under 20k, and it puzzles me that those neighbours have to sit in darkness or burn candles when their situation could be made more comfortable for not a huge outlay. 

So well done! You are making a real difference. 

NB! I don't think what my mother has is going to last 10 years, so there is more outlay to come. But it will be in increments rather than one go.

I can just agree with you on why so many people still sit in darkness during LS. 

Some years ago I did a test during non LS times measuring the power a 1 bedroom flat consumes for LED lights in a 1 bedroom flat with 2 people. This was normal use and switching on a light ad lib. The power consumed worked out at 10kwh per month. I was using a brick 750W inverter connected to a lead acid battery. I never measured the input power to keep the battery charged. 

Now if one used a 200W panel, controller, 1x100Ah LA battery and a small 220V charger if days are cloudy this can cost as low as R6500. For this use a lead acid could easily last 3-5years due to low discharge rate. Scrapping the panel and controller can cost R5100. 

18 minutes ago, Scorp007 said:

 

Now if one used a 200W panel, controller, 1x100Ah LA battery and a small 220V charger if days are cloudy this can cost as low as R6500. For this use a lead acid could easily last 3-5years due to low discharge rate. Scrapping the panel and controller can cost R5100. 

Still have 200Watt panel, 20A pwm charge controller and 600 Watt inverter I started with. Best money ever spend. Paid R15/Watt then. 2013

 

Edited March 11, 20232 yr by Chris Louw

22 hours ago, BritishRacingGreen said:

 

1. In terms of the grid input input, if the plug connection is quite a  distance from the inverter, add a double isolator at the inverter. Also remember that when the inverter is in Line mode, it will supply both load and charge a flat battery. Be conservative what you allow the maximum charge current to be, as not to exceed say the 16A rating of the plug circuiy. 

Also add a 2 x  220VAC red indicator lamps, one on grid input, and one on load output. It will make life very easy for you to remotely ask grandma the state of the machine, if need be. 

2. The protection on the red plug load circuit will be an RCD and a circuit breaker to match the wire size of the red plug circuit. 

3.you wont know wether there is automatic bonding. But there is a test you can perform when you install it, to verify wether it has. If it turns out no, then  10 amp din mount Omron relay 3 pole will need to be added onto your little db box. We will discuss wiring detail when applicable.  During ELD testing, you need a Plug Tester to verify safe working of ELD. RCD test button on its own is not good enough. 

Thank you for the reply

1. The plug will be close to the inverter, within arms reach, so I don't think it is necessary to install a circuit breaker.

I will probably set the charge amps to 2A AC (to charge a 200Ah @ 12V battery in 4 hours). With a maximum of 4A AC for load, even a 2.5mm2 cable will be sufficient.

2. Agreed

 3. I know the 5kW Axpert King does automatic bonding, so chances are that the 1kW will also do it, but I will test it.

What is the product code of the Omron relay that you are referring to

Thanks

13 minutes ago, ErickvWyngaard said:

Thank you for the reply

1. The plug will be close to the inverter, within arms reach, so I don't think it is necessary to install a circuit breaker.

I will probably set the charge amps to 2A AC (to charge a 200Ah @ 12V battery in 4 hours). With a maximum of 4A AC for load, even a 2.5mm2 cable will be sufficient.

2. Agreed

 3. I know the 5kW Axpert King does automatic bonding, so chances are that the 1kW will also do it, but I will test it.

What is the product code of the Omron relay that you are referring to

Thanks

OMRON C4-3-230AC, available from ACDC, 3 changeover poles, 230vac coil, contacts are 10A rated.