Hi All,

 

Wanted to get some advice on weather to go with 1 system or 3 separate systems.

Im going to be building a house with 2 small cottages(rentals). I have a single phase Eskom 80amp coming in.

I was going to run 2 x 8 kw invertors and all 3 houses on 1 system.

I was told by the guys im buying the equipment from i wont be able to meter the cottages usage(which are rentals) if i have 1 system. and I should setup 3 separate systems.

not sure which way to go here. Any advice?

 

Kind Regards
Zeo

 

 

You should be able to use sub-meters for the rentals.

1 minute ago, WannabeSolarSparky said:

You should be able to use sub-meters for the rentals.

This is the way. An inverter is not the best device for measuring.

Thanks all for the reply. 

This is what im looking at doing. 

The non-essential loads in the rentals will be direct Eskom only. Eventually will move them behind the solar system when i can afford to.

Any advice and input is much appreciated.

 

You need a few of these, will solve all your metering needs and you would not need to pay third parties for tokens or use.

This stackable power meter realizes smart management with overload protection, metadata monitoring and electricity statistics.

Just look long and hard at your pricing if you're supplying tenants electricity through battery backup. Make sure your tariffs reflect the cost of storage per kWh over the life of the batteries. Their time of use could make or break the financial viability of your system. Personal thinking would have been to give each sub-unit its own off-grid battery inverter and changeover after the meter, eg. a 3kVA 24V for essentials, and give them each the option to add backup batteries at their own expense.

33 minutes ago, GreenFields said:

Just look long and hard at your pricing if you're supplying tenants electricity through battery backup. Make sure your tariffs reflect the cost of storage per kWh over the life of the batteries. Their time of use could make or break the financial viability of your system. Personal thinking would have been to give each sub-unit its own off-grid battery inverter and changeover after the meter, eg. a 3kVA 24V for essentials, and give them each the option to add backup batteries at their own expense.

Thanks...Will definitely take this into consideration.

If there's one system serving three dwellings, then it is possible that one person/family could drain the system more than the others do. So, for example, tenant A is being frugal. tenant B is using the oven all night long and doing some bitcoin mining on the side, and since everybody is connected to the same battery, tenant B will consume battery power to the detriment of tenant A and the main household. 

So there's your answer really.

The systems for the cottages need not be as big as the system for the main house, and you should be clear with the tenants about what is being backed up and that they have to manage the load. Inverters are current limited on the output side, and if they exceed that limit then the system will trip. So plugging in hot plates (for example) is not a good idea.
 

Hi @Zeo786

Sounds like the guys selling you the solar either want to sell you more inverters or have no idea how to manage the power usage of the cottages. I would definitely recommend centralising everything as much as possible.  

I am assuming that the cottages will be running single phase and each would not drawing more than 63A and that they will be feeding from the main house DB Board to a sub-db in each of the cottages.

My suggestion would be to install a Ewelink Smart Breaker switch in series with the breaker for each of the cottages in the main house DB and connect them to your wifi. 

https://www.robofactory.co.za/smart-switches/167-63a-1p-smart-circuit-breaker-with-monitoring-ewelink.html?gclid=Cj0KCQjwlK-WBhDjARIsAO2sErTMG4_til-QFtk8omHLBC7PA8GoJInn9iBQMIXy5IQO-fX8ky0nGPUaAkg7EALw_wcB

You can tell from an app on your phone what each of the cottages is drawing at any specific time as well as the monthly power usage is for each of the cottages.

It also allows you to set a maximum amperage before it will kick out the relay 

I have a very similar setup. I have a cottage and a staff kitchen all running of 1 x 8kw inverter.

If you integrate them into Home Assistant you should be able to change the maximum amount of power that can flow through them when there is load shedding using the Home Assistant Automations. ie. If there is 0hz grid frequency set the maximum amps through the switch @ 10A for example. This assume that you connect the inverters up to home assistant as well.  I haven't done this personally as yet as I have no requirement as I just send them a message if they are drawing too much power. 

I have another automation that changes the colour of smart light bulbs installed in the cottage and staff kitchen so that everyone knows when there is load shedding happening and this seems to solve the issue.

 

Edited July 11, 20224 yr by Sc00bs
Had to change link for smart switch

You can get the Smart Switches for half the price directly from China as well if you have the time

14 hours ago, Sc00bs said:

Hi @Zeo786

Sounds like the guys selling you the solar either want to sell you more inverters or have no idea how to manage the power usage of the cottages. I would definitely recommend centralising everything as much as possible.  

I am assuming that the cottages will be running single phase and each would not drawing more than 63A and that they will be feeding from the main house DB Board to a sub-db in each of the cottages.

My suggestion would be to install a Ewelink Smart Breaker switch in series with the breaker for each of the cottages in the main house DB and connect them to your wifi. 

https://www.robofactory.co.za/smart-switches/167-63a-1p-smart-circuit-breaker-with-monitoring-ewelink.html?gclid=Cj0KCQjwlK-WBhDjARIsAO2sErTMG4_til-QFtk8omHLBC7PA8GoJInn9iBQMIXy5IQO-fX8ky0nGPUaAkg7EALw_wcB

You can tell from an app on your phone what each of the cottages is drawing at any specific time as well as the monthly power usage is for each of the cottages.

It also allows you to set a maximum amperage before it will kick out the relay 

I have a very similar setup. I have a cottage and a staff kitchen all running of 1 x 8kw inverter.

If you integrate them into Home Assistant you should be able to change the maximum amount of power that can flow through them when there is load shedding using the Home Assistant Automations. ie. If there is 0hz grid frequency set the maximum amps through the switch @ 10A for example. This assume that you connect the inverters up to home assistant as well.  I haven't done this personally as yet as I have no requirement as I just send them a message if they are drawing too much power. 

I have another automation that changes the colour of smart light bulbs installed in the cottage and staff kitchen so that everyone knows when there is load shedding happening and this seems to solve the issue.

 

Thanks this will really help. Going to add this to my configuration.

16 hours ago, Sc00bs said:

If you integrate them into Home Assistant you should be able to change the maximum amount of power that can flow through them when there is load shedding using the Home Assistant Automations. ie. If there is 0hz grid frequency set the maximum amps through the switch @ 10A for example. This assume that you connect the inverters up to home assistant as well.  I haven't done this personally as yet as I have no requirement as I just send them a message if they are drawing too much power. 

This is an elegant solution. What happens if the 10A is exceeded. EG I am drawing 9 and then decide to turn on the kettle. Does the smart breaker trip?

16 minutes ago, Bobster. said:

This is an elegant solution. What happens if the 10A is exceeded. EG I am drawing 9 and then decide to turn on the kettle. Does the smart breaker trip?

If you exceed the specified maximum on the switch it disconnects. 

You can set a maximums  for power/Amps & Voltage as well as minimum power &  voltage. 

The things I am not sure of are:

- How easy it is to change the OPS settings from Home Assistant so you could reduce the load allowed during load shedding

- What the process is to restart the connection after it has been disconnected. 

Would need some investigation to work that out.

Just been thinking about it a bit more, you wouldn't need to change the switch OPS settings, you can just do it in an automation in Home Assistant or Node Red. 

Monitor the power being drawn through the breaker switch.

If there is load shedding (0hz grid frequency) and the limit is exceeded, disconnect the switch

Reconnect after 5 minutes or whatever time you decide.

Not too complicated to setup 

Sonoff also have some new smart stackable switches that would do pretty much the same thing

https://itead.cc/product/sonoff-smart-stackable-power-meter/ 

 

20A per cottage isn't really enough power though in my opinion. 

 

1 hour ago, Sc00bs said:

Just been thinking about it a bit more, you wouldn't need to change the switch OPS settings, you can just do it in an automation in Home Assistant or Node Red. 

Monitor the power being drawn through the breaker switch.

If there is load shedding (0hz grid frequency) and the limit is exceeded, disconnect the switch

Reconnect after 5 minutes or whatever time you decide.

Not too complicated to setup 

If I have it right the APP just switches off the device used and resets again when the current drops. This is on the OPS setting.

Hi All, so it seems my supply has changed. Im actually getting a 3phase supply in. 

What I wanted to know is will i be force to get the sunsynk 3 - phase 12kw? The balance wont be correct as the main house will consume much more than 4kw.

or is there another solution?

Sunsynk 12kW can do 100% unbalanced, or perhaps it should be 200% unbalanced, because it can do up 6kW in one phase, as long as the total is below 12kW.

On 2022/07/12 at 4:09 PM, Scorp007 said:

If I have it right the APP just switches off the device used and resets again when the current drops. This is on the OPS setting.

Hi @Scorp007

If it switches the switch off there will be 0 current, not sure how long it waits before it resets and switches it on again, can't see any setting in the app for how long it waits

11 hours ago, Zeo786 said:

Hi All, so it seems my supply has changed. Im actually getting a 3phase supply in. 

What I wanted to know is will i be force to get the sunsynk 3 - phase 12kw? The balance wont be correct as the main house will consume much more than 4kw.

or is there another solution?

Hi @Zeo786

You do have the option of only using one phase of the 3-Phase supply. 

@P1000 is correct, max power per phase you can do on the 3-phase Sunsynk is 6kw so if you go over 6kw on a phase it will either pull from Eskom on that phase or overload the inverter and trip out if you are off-grid at that stage (load-shedding etc).

In my opinion, if you don't have any requirement for three phase power it would be better to get 1 x  16Kw single phase, you would have much less chance of overloading the inverter and price is only slightly more expensive than the 3-phase.