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3 Phase cause I like pain...


Nate

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Hi guys

I've been trolling this and other forums for months and I have been in analysis-paralysis phase for almost two years. The kicker is my Eskom bill jumping a couple of months ago for a reason I am yet to figure out. Regardless, this has changed my approach to this whole exercise so might have been a good thing procrastinating. 

I have three phase in the house and even though I do not have three phase loads in the house I do have 3ph loads in my workshop which is out of scope for this consternation. I am not convinced going single phase is the way to go so I am sticking with 3ph. But this complicates things... 

I am 'writing off' the cost of an inverter + battery + installation - with capacity to get me through load shedding - as a base cost of living in SA. Just like insurance and a fence around our properties it's one of the things we pay for to make up for all the other benefits we get. Once past this point I look at payback periods etc. 

So initial install I was looking the SunSynk 12KW 3Ph inverter with the 5.5KWh Hubble battery. From this forum it looks like a winner and the fact that it supports unbalanced load swayed me from three single phase inverters. Challenge is, even with the 6KW capability on one phase, I do not like the odds of someone switching on a stove while the geyser timer is on. I could have the stove on one phase and the geyser on another but I just see things going very wrong... I would love someone correcting me on this assumption. 

So back to single phase inverters and will probably go for the SunSynk/Deye options. Add to this as many panels I can fit into my initial budget as I recon offloading most of my daytime load to solar and dumping excess in my 200l geyser works to start off with. I will look at more batteries later but realistically I will never get off grid with my workshop activities so I am all about getting as much out of solar as possible, realizing there will be a ceiling. 

I bought my house with my DB setup for a single phase generator: so one phase has my geyser and stove. The other two phases runs everything else so when I swap over the changeover switch it bridges the input of these two phases from the generator and the stove/geyser phase is dead. The plan is to get two Inverters for the two phases with everything and leave the stove and geyser as is on the last phase.

So here is my plan attached, high level. Couple of things that I am worried about; 

1) When supply dies, I see a neutral going back to the supply. Neutral can tickle you... ask me how I know.

2) I do not see a way of dumping excess into my geyser. I am sure this has something to do with connecting it to the non-essential side of an inverter but its a 4 KW element, with the potential of someone switching on a stove at the same time. So all of this through the inverter with whatever else is running on the plugs as well. Surely this will release the magic smoke?

3) I am sure I missed more... feel free to educate me.

3a) Will this pass CoC? 

Thanks all!

 

Backup power 16 Nov.jpg

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Two things:

You can put a smaller element on the geyser (1.5Kw) and also have a timer for it - e.g. switch on only during the day when PV is available.

That 5.5kW is too small for a 12kW SunSynk. You will need 3 of those, in order to have a good balanced system

 

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Its the current that kills ... not the voltage (single or 3 phase) ... and beware of the neutral ... for example ... if you disconnect the neutral at a light point and the switch in the room next door is switch on.

So long as the neutral is grounded ... you should be ok ... thats why the neutral bar and cabling is stolen in the sub station which creates a dangerous environment further down the line ... you end up with a high floating voltage ... which is why sometime I have seen smoke coming out light fittings and other devices when called out to a site. 

That is why  it is a good idea to always switch off the main switch when you see your light turn really bright or you can smell a burning smell.

 

 

 

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1 hour ago, PowerUser said:

Two things:

You can put a smaller element on the geyser (1.5Kw) and also have a timer for it - e.g. switch on only during the day when PV is available.

That 5.5kW is too small for a 12kW SunSynk. You will need 3 of those, in order to have a good balanced system

 

It's already on a timer; had a solar panel on it that popped last winter and I did not replace. Now the solar control panel is a glorified timer; I figured before I go solar water heating again ( I did not have a good experience), I'd rather install a heat pump and if needed add a couple of PV panels to cater for the ~1.5Kw draw. 

But in the interim, yes, downgrading the element is an option. It will take forever to heat up in winter tho so will have to rework my schedule. 

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59 minutes ago, isetech said:

Its the current that kills ... not the voltage (single or 3 phase) ... and beware of the neutral ... for example ... if you disconnect the neutral at a light point and the switch in the room next door is switch on.

So long as the neutral is grounded ... you should be ok ... thats why the neutral bar and cabling is stolen in the sub station which creates a dangerous environment further down the line ... you end up with a high floating voltage ... which is why sometime I have seen smoke coming out light fittings and other devices when called out to a site. 

That is why  it is a good idea to always switch off the main switch when you see your light turn really bright or you can smell a burning smell.

 

 

 

So yes, an on-switch anywhere will complete the circuit and your neutral anywhere is not so neutral anymore, I get this. What I've never quite grasped is if neutral is grounded, how does this not complete the circuit to ground? Where is ground picked up in the first place? 

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5 hours ago, P1000 said:

Perhaps the goodwe ET 10kW is an option? It can handle 100% unbalanced loads:

https://powerforum-store.co.za/products/goodwe-10kw-3-phase-hybrid-inverter-2-mppt-hv-battery

It won't work with the Hubble battery, though. You have to look at the BYD or Pylon HV options.

I had a look but could not find any literature about unbalanced loads on the Goodwe - I had the same situation on the SunSynk for that matter. On the SunSynk it was 100% unbalanced but to a maximum of 50% of the entire inverter capacity so 6KW max on a phase. I would assume the same applies here so 5 KW. Might be a tad shy.. 

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9 hours ago, Nate said:

I had a look but could not find any literature about unbalanced loads on the Goodwe - I had the same situation on the SunSynk for that matter. On the SunSynk it was 100% unbalanced but to a maximum of 50% of the entire inverter capacity so 6KW max on a phase. I would assume the same applies here so 5 KW. Might be a tad shy.. 

Looks like it might actually be worse for the Goodwe - 33% on each phase. I think I have misunderstood exactly what "100% unbalanced" means.

 

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Hi @Nate

I can only speak from my own personal experience, I had a similar situation as my Eskom supply is 3 Phase.

I have a Sunsynk 8kw inverter and my daily consumption is in the 50-60kw/hr range.

I decided that it is better to have my loads in one place rather than split up across the phases as it make sense to me to group all my loads on one phase and my total load from Eskom was never going over 60A. 

The conversion to single phase is relatively easy for an electrician, my electrician bridged the phases and it did not involve rewiring the whole DB Board so you could get your stove and lights onto one phase relatively easily. 

In regards to your workshop, it is possible to run 3 phase devices of a single phase supply using a VSD, it has the added bonus of giving you more control over the supply and allowing for soft starts etc so I would not rule out running that of single phase. I have a 3phase booster pump running of my inverter. 

https://cfptechnologies.co.za/product-category/variable-frequency-drives/#shop

 

From what you described, depending on your load peaks, I would probably convert everything to single phase (except maybe the workshop but would try to do that as well using VSD's), install 1 x 8kw Sunsynk and leave space for a 2nd in case you decide you need to install one later. Get all the large loads onto smart DB switches and have them switching on one at a time and so you can see how long they are pulling loads for.  

My base load is around 1kw and my system is happy running a 2kw borehole pump, a 3kw geyser element and not tripping out when someone puts the kettle on 🙂 , main thing is to not go over the 12kw pass thru limit on the Sunsynk as that will cause an Inverter trip out (it will pull the extra 4kw from Eskom to make up the 12kw). Pulling some power to make up the shortfall for a few minutes if necessary is not a major issue. It is not unknown however for my family to trip my inverter when they put the airfryer, kettle, toaster and microwave all on at the same time!! 

 

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Thanks Sc00bs

Not looking to convert tho. I have my workshop on it's own cable and split from the house just inside my boundary wall so I can do anything I want to the house without impacting the workshop and it's three phase loads.   I use the three phase fairly extensively there so a VFD per device will probably cost as much as an inverter. 

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  • 1 year later...

Im starting with a 3 phase invertor right now too

and the question is can i run my 1 phase generator which powers the whole house 3 phases (fake three phases just a 220volts on every phase from gens 1 phase

so it could power up Inverter (all three phases would be that fake i told before) so the inverter charges the battery?

 

or i only need a 3 phase generator and there is no way of charging a 3ph Inverter with a 1 phase gen (options are: gen current goes to inverter grid, gen current goes to inverter aux-gen input, gen current goes to aux -mikroinverter )

Edited by Denveronly
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On 2023/03/26 at 12:42 AM, Denveronly said:

so it could power up Inverter (all three phases would be that fake i told before) so the inverter charges the battery?

If it's a set of 3 Voltronic off-grid inverters, I'm pretty sure that you have to have the correct phase for each AC-in. In other words, no fake 3-phase AC source.

However, I think that you could supply the generator to just one AC-in port, and that would charge the battery, and the inverters would supply real 3-phase to the house. The problem is can you get enough utility charging power from one inverter. If the average load power is higher than the charging power (ignoring losses for simplicity), then the battery will run down gradually or not so gradually, depending on the power difference.

But I have no experience with three phase set-ups.

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