Energy Matters Forums

[hsvz]

Hi All,
This is a Sydney based question.

Currently I have 3 phase power and gas hot water. I am trying to get my head around how the solar is connected to the 3 phase... does it connect to only 1 phase and an additional feedin meter installed ? If this is the case and being in Sydney we can only get 8cents / kwh and the buy about 23cents.

So what I am saying is I could be at a point of exporting power on one phase at a low paid rate and at the same time I could be using grid power on the other 2 phases at the high rate, which seems a bit silly to me.

Numerous quotes I have received sort of imply the above but most of the salesmen I ask aren't electricians they are just out to get that bottom line signed.

One salesman said I need 3 inverters

At the end of the day I was looking at a 3kw system, now I am confused - it sounds like 3 off 1kw systems would be better to cover the phases ?

Any help will be appreciated.
Glenn

[Tracker]

There has been some discussion about 3phase connections in the past on here

Gordon is correct.. Try and search for "3 phase".
Things have changed a bit since losing the 60c FIT, when folk wanted to EXPORT as much as possible.
The issue for YOU, is that you have to decide what you want to achieve with your PV power.
We have to assume that you have NO special FIT values available ie.. 60c etc..

The sun only shines during the day . . and so, depending upon your domicile arrangements, you will either want to reduce your daylight usage (cost) or maximise your grid-feed.
It is assumed that you want to minimise your COSTS, and so you will need to connect the PV-System to the MOST used phase.
If you wanted to maximise your Grid-Feed, then you would connect to the least-used phase.
In fact, you would likely seek to remove as much consumption as you can from that phase..
You might also consider IF you need three phase, or is it an historical thing.. eg. a 3phase water heater..
eg. It would be a shame to be exporting power at 6c via one phase, when you were consuming power at 40c on another phase..

Anyway for correct advice, you likely need to detail exactly what you have and hope to achieve..

PS.. ( Moved from "Hi" thread..)

One salesman said I need 3 inverters

Be sure to exclude that quote - a demented fool indeed.. 3Kw is NOT a MASSIVE system..
So - back to my last question as to what you have and need..
..
.

[hsvz]

Hi Tracker,

My aim is naturally to try to consume all the pv power as possible since the feedin tariffs are so low. When the 3 phase was installed they balanced the load of all my circuits over the 3 phases. To achieve my aim I can see I may have to unbalance the load (not sure whether this is legal to do or not)
Say on phase A I will put all power point circuits plus use this phase to connect the pv to, Phase B connect all the lighting circuits to, Phase C connect Misc circuits to.

Doing this will achieve maximum usage of the power generated during sun hours with phase B only being used at night time. I have 3 phase due to my air conditioner.

Currently my daily average is 23 kwh so I am thinking a 3kw pv system. With the NSW Gov stuffing up the feedin's I cant ever see me eliminating the power bill, my aim is to reduce it as much as possible.....

Am I thinking down the right path here ???

Thanks
Glenn

[Bthree]

If you have a single three phase meter (not three seperate meters) it makes NO difference which phase you connect your inverter. A meter is just that it meters ALL incoming and outgoing power and the smart meter tells you all, the power distributers would not let you have an advantage would they.

I have a small solar system, three phase meter, and a 3 phase AC and I can assure you the above is the way it works.

The inverter does not need to be 3 phase, you may think about the possibility if you are purchasing a 10KW system but not for 3kw.

[Clemo]

Yes it meters all incoming and all outgoing but he is only offsetting his usage against the load connected to the phase that his PV system is connected to. If you are exporting power on a net connection then your not getting the best advantage from your PV system.

[hsvz]

We dont have smartmeters in NSW like in other states, I have 3 conventional meters and they are talking about installing an outgoing meter.

[Clemo]

Yep, the connection point for a net system will be at the consumers main switch, the meter is only reading whats coming in and whats going out.
If you are producing more than you are using on the phase that the system is connected to then you will export power. You cannot offset usage from a phase that your system is not connected to.
The meter, or the retailer does not do the "netting" its done in your installation.
You would be better off with single phase supply.

[hsvz]

You would be better off with single phase supply.

It's definatley looking that way. The only reason for 3 phase is the air con. I wonder if you are allowed to load up one phase - (apart from the air con of course) and have all breakers feeding off one phase ?

[Tracker]

If you have a single three phase meter.....it makes NO difference which phase you connect your inverter.

I won't disagree, but will seek further advice..... BUT when you think logically...

In SYDNEY, installing a PV system WILL result in replacement of the CONSUMPTION meter, and the fitting of an EXPORT meter. ( either separate meter or extra element in the main meter )
I would have logically thought that each phase will count the units used, and the EXPORT meter (element) will just count the units that exit via whatever phase.
Thus, it could be possible (if not likely), that EXPORT will exceed IMPORT on that phase..
So - the BIG question -- will "THEY" consider the exported power, when they review the IMPORT on the other phases..

The past advice has been... "...with three phase, if you want to maximise export, connect the PV to the least used phase, and, if you want to minimise your consumption, you connect to the MOST used phase.."

Alternatively, does an electronic 3Ph meter measure each phase consumption and just increment a single accumulator for the period.. ie.. ONLY ONE figure for the three phases..

Irrespective, with a humble consumption of 23units, the 3Ph is not very important and again , I suspect that the NEED for 3Ph, no longer exists... Thus, it would be simple to also convert back to 1Ph, and the uncertainties are gone.. We do need to confirm the change in need for 3Ph..
The only likely FUTURE need for 3Ph , would be for a BIG air-conditioner (3Ph).. but, I wonder who would start thinking that way, given the massive electricity price-rises, that we have yet to see..

Is there ANY advantage in having 3phase, these days?

Remember that you can use your own meter installer and as I have mentioned many times, I know one who charges fair rates. ( $300 -- I THINK -- for the two meters )
HE - could be engauged to convert to 1Ph and install the appropriate meters..

IMHO.... ( I forgot to press ""SUBMIT"" ) SO

PS - Just spoke to a Solar-Inspector, who said he saw a 3Ph system only days ago, where the PV was connected to the LEAST used phase.. The result was that MOST of the PV was exported at the 6c whilst the customer was paying 40c for that same power via other phases..
To put it in other words, the 93 register on the meter was almost the same as the total of the GCI.. ie. Clearly proving that most all the generated power was exported..
I think that this proves that it's important to remove the 3Ph meter, so that you have the greatest chance of generating your own power for consumption.. ( UNLESS - there is a glaring need for 3Ph )
..
.

[Tracker]

The only reason for 3 phase is the air con. I wonder if you are allowed to load up one phase - (apart from the air con of course) and have all breakers feeding off one phase ?

OK - So we have a 3Ph RAC.. and we assume that you need that to remain. and .. We still are only looking at 20plus usage..

I think that I would just get it all installed and connected to the MOST used phase and THEN look at moving some circuits to that same Ph, such that you are not exporting any power.

IF - you are at work during the day, then your usage will be at a minimum.. You should then ensure that you connect to the phase with ALL the running appliances eg. Fridges etc...
..
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