3 Phase power house hold, power backup options

[BlackSnow88]

Good day

I am looking for advise on how to approach my future power needs with a 3 phase powered house with 2 DBs, one down and up stairs.
My plan is to start with a power backup system (For load shedding reasons) and later expand it for Solar to either supplement or go totally off-grid.

So my delemma is that most advises seem to be around single phase inverters, but I am not sure how can a single phase inverter setup be used in a 3 phase home, or should I get a 3 phased inverter from the start?

 

[Sinbad]

Depends. Can you move all your critical (stuff you want to run off the backup) loads to a single phase? If so, do that and just use a single phase inverter on that phase.

 

[RonSwanson]

Not a dilemma at all, there are 3-phase inverters available (the cost is obviously higher), and in some cases 3 or more inverters can be paralleled in a 3-phase config.
The biggest question though is whether you actually need/use all 3 phases. What is you monthly consumption in units / kWh?

 

[Tim_vb]

My suggestion to keep the basics on in load shedding

1. reduce power consumption - solar geysers, inverter air cons not heater, gas stove, led for all lights
2. separate essential power from non essential power into different DB or at least separate circuits on DB
3. install a good quality single phase inverter with a minimum of 5kw capacity on the essential circuits. If these are on different DBs then you will probably need one inverter per circuit. Assuming each DB is on a single phase OR at least all the essential circuits can be put on a single phase

 

[BlackSnow88]

Depends. Can you move all your critical (stuff you want to run off the backup) loads to a single phase? If so, do that and just use a single phase inverter on that phase.

I guess we can tell the electrician to move essentials to one phase.

Not a dilemma at all, there are 3-phase inverters available (the cost is obviously higher), and in some cases 3 or more inverters can be paralleled in a 3-phase config.
The biggest question though is whether you actually need/use all 3 phases. What is you monthly consumption in units / kWh?

I may have not mentioned that this is a new build, so we don't have consumption stats or billing as yet, I am trying to plan ahead and prepare for future expansions

 

[Lupus]

Why do you need 3 phases? But as Sinbad said you can just move the critical load to a single phase.

 

[BlackSnow88]

Why do you need 3 phases? But as Sinbad said you can just move the critical load to a single phase.

Well for 1. the electrician is pretty certain we need 3 phases, I guess to cater for all the potentially "power hungry" devices that might be, pool pumps and so forth.
2. From a billing perspective city power charges the same whether single or three phased.
3. In future if one acquires an EV or anything of that nature, 3 phase will provide much quicker charge speeds.

What I will consider is moving essentials to one phase, only other thing is that we have DBs per floor, does that then mean two inverters, one per DB? as I would imagine things like lights and plugs are on the respective floor's DB

 

[Lupus]

Well for 1. the electrician is pretty certain we need 3 phases, I guess to cater for all the potentially "power hungry" devices that might be, pool pumps and so forth.
2. From a billing perspective city power charges the same whether single or three phased.
3. In future if one acquires an EV or anything of that nature, 3 phase will provide much quicker charge speeds.

What I will consider is moving essentials to one phase, only other thing is that we have DBs per floor, does that then mean two inverters, one per DB? as I would imagine things like lights and plugs are on the respective floor's DB

Actually City Power doesn't charge the same for single phase and three phase, it's more expensive. Besides a pool pump what else is power hungry?

 

[BlackSnow88]

Actually City Power doesn't charge the same for single phase and three phase, it's more expensive. Besides a pool pump what else is power hungry?

Well according to their technical representatives and the tarrif schedule (link) it is the same charge rate for residential <= 80A

Other than the pool, the aircons, the geysers (though there's solar geyser installed), cant think of anything else ATM.

 

[Lupus]

Well according to their technical representatives and the tarrif schedule (link) it is the same charge rate for residential <= 80A

Other than the pool, the aircons, the geysers (though there's solar geyser installed), cant think of anything else ATM.

Well that is from 2019, but even in 2019 you paid more for the capacity fee

 

[Sinbad]

Well according to their technical representatives and the tarrif schedule (link) it is the same charge rate for residential
Other than the pool, the aircons, the geysers (though there's solar geyser installed), cant think of anything else ATM.

You can pull 12kw from a single 60A phase. 16kw from 80. Only time you need 3 phase is when you're pulling more than that, or running three phase specific equipment like a borehole pump.

 

[itareanlnotani]

I've had/done offgrid 3 phase in a household setting. I'd suggest go with single phase though - costs are higher for 3 phase, and you probably don't need it.

Figure out which circuits in the house you need to run, chat to an electrician, and work out a plan.

You probably won't be feeding back, but can setup a ups type system to keep light and other circuits (plugs) online when Eskom/ muni goes down.

My setup at the time, was a Growatt 10KW 3 phase inverter, which was then tied to 3 x Victron Multiplus which shared a battery.

 

[BlackSnow88]

Well that is from 2019, but even in 2019 you paid more for the capacity fee

View attachment 1182296

Granted, I think we can agree that R110 difference may not be enough reason to switch to single phase, there’s ways to recover that difference.
And I dont think this thread is about convincing anyone about why single phase is better than 3 phase, the installation is aleady 3 phase, “We are in Church, might as well pray”