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3 phase residential balancing


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Hi all, to start let me make it very clear that I’m no electrician or engineer - so should anything I say sound weird I reserve the right to plead ignorance. 

Now, I have a 3 phase power supply and use around 30kWH per day (25 - 37 max). I have 2 x 150l geysers (one used far more than the other so let’s say 8kWh & 3kWh respectively), a pool pump (6kWh / 8kWh if I need Some extra filtration of my pool), 8kWh of ‘essentials’ which is basically all plugs and lights and an oven (3kWh every other night) with a pool heat pump I run from a little in to Spring until a little in to Autumn (7kWh once pool at temp). 
 

I recently installed a 5kWh Deye hybrid and 9.6kWh Pylontech battery bank with 13 x 410w JA mono panels (5330 watts). All is running beautifully however there is a but... or a few. 
 

1) I only got the one inverter and so put all plugs and lights + oven and pool pump (and by implication heat pump in summer) on to this phase. All works fine but that leaves just 1 geyser for each of the two remaining phases (one of which is seriously underutilized). So PROBLEM 1 - phase balancing concerns me. 
 

2) my battery bank is full around 12h30 so I figure I’m losing around 4 / 5 kWh of power each day. And I don’t think I can slap a geyser on to this phase as well (refer PROBLEM 1). So PROBLEM 2, unoptimised system. 
 

3) my oven saps my battery bank so going to move this to a non PV phase. Not really a problem as easy fix. 
 

My intention is to

1) add a second deye inverter on to a second phase and parallel. I’ll put the pool pump (and in summer the heat pump) plus the lesser used geyser on this phase. I’ll put all the PV through this inverter and time everything to run during PV hours. My array will cater for the power draw and I will set battery to switch to grid at 90% SOC (should it be a cloudy day I don’t actually want the batteries drained for the geyser or pool kit). I think this will solve the phase balancing issue  


QUESTIONS

Can one parallel just 2 phases of a three phase supply (and leave the third purely on grid?)

How important is phase balancing if I have no 3 phase equipment? What if I had nothing on 1 phase? With PV am I not effectively eliminating any draw on said phase in any case? (As far as it would concern the supply of electricity to my residential area)

2) I’ll leave the essential (back-up) dB as lights and plugs on phase 1. Batteries work perfectly. 250w - 600w hourly draw (average around 350w) and takes me from sun down to sun up with discharge to around 40 / 45 / 50% depending on previous night cooking requirements. This phase will then draw constantly through the parallel battery bank (if I understand correctly the other phase with all the PV will cover pool kit and geyser. Excess will flow in to batteries and charge / supply power to this phase as required) 

QUESTION

Does this mean the batteries are having to work harder than otherwise or if there is sufficient Pv is it really just a pass-through?

3) phase 3 will have main geyser and oven once moved. 
 

For the future I can see myself adding an ITS heat pump on to phase 2 and moving the spare geyser to phase 3... but effectively switching both geyser elements off and using only the heat pump (I may use one geyser as prefeed or run in serial but still researching this). Again I’m worried about phase balancing. The purpose of this change would be to cover all my energy needs with my currently installed PV system - while not having EVT tubes etc (and not really having easy roof space to expand or use in any case). 
 

by doing this phase 1 would be around 8kWh. Phase 2 around 6 - 11kwh (also reducing pool pump size). Phase 3 would be just oven (with geysers on circuit but turned off) - so say 3kWh every other day. 
 

thanks! Any input very welcome. 

Edited by iMercury
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  • 4 weeks later...
On 2020/08/15 at 11:04 PM, iMercury said:
On 2020/08/15 at 11:04 PM, iMercury said:

3) my oven saps my battery bank so going to move this to a non PV phase. Not really a problem as easy fix. 

So PROBLEM 1 - phase balancing concerns me.

Why?

On 2020/08/15 at 11:04 PM, iMercury said:

So PROBLEM 2, unoptimised system. 

 

On 2020/08/15 at 11:04 PM, iMercury said:

3) my oven saps my battery bank so going to move this to a non PV phase. Not really a problem as easy fix. 

Number 3) won't help improving this.

 

On 2020/08/15 at 11:04 PM, iMercury said:

Can one parallel just 2 phases of a three phase supply (and leave the third purely on grid?)

If you mean using 2 phases from 3 then yes, why not.

For all your other questions and remarks about unbalanced phases; I wouldn't bother to much. It is not your problem but you energy supplier's (Eskom?) . Everybody is taking from the three phases as they please and the end result will be a quite well balanced grid in most cases.

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You can parallel the 2 phases ( load  side )  in your DB board effectively  ignoring one incoming phase. Cannot do so on the supply side that will result in a big bang.   HAve one phase as maintained supply ( plugs lights ) and the other direct Eskom supply - Geysers, oven etc 

 

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On 2020/08/15 at 11:04 PM, iMercury said:

2) my battery bank is full around 12h30 so I figure I’m losing around 4 / 5 kWh of power each day. And I don’t think I can slap a geyser on to this phase as well (refer PROBLEM 1). So PROBLEM 2, unoptimised system. 

Using something like the Solic200 or Apollo GEM will ensure the power that would otherwise be exported can be redirected to a load like a Geyser, in effect the Geyser can become a massive store of energy like a huge battery, but just storing heat rather than electricity.

Depending on you requirement, the Solic 200 unfortunately does not have a timer function but the Apollo GEM has but is more expensive, although it does have two channels, so yuo could add two geysers.

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Do you actually need 3 phases into what seems like a normal size home?

I use 30kWh/day on average and even 40+ when its cold all on 1 phase.

You are paying a fortune to have the 3 phases if you do not have a specific requirement for 3 phase power.

It would be cheaper to just ditch 2 phases than buying another inverter, panels etc.

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