“After installation, we have found out the battery will not power the aircon after dark…”
This is a direct quote from the My Efficient Electric Home (MEEH) Facebook group. Tim Forcey suggested it deserved an article. I agree, because there’s a limitation of three-phase battery systems you need to understand before buying.
An MEEH member claimed they bought a FoxESS 41 kWh battery with a 3-phase 15 kW inverter, sold on the promise it would power his entire house through a blackout.
But after installation, the owner discovered the air conditioner shuts off after dark with no solar available to help power it. The installer’s alleged fix? Switch the battery system off and run the aircon on grid power only.
A disclaimer before we go further: everything above comes from one side of the story, posted on Facebook. I haven’t verified the install, seen the quote, or heard from the supplier, who I’m deliberately not naming. There may be facts that change the picture. What follows is the physics and the law that apply to any system sold this way – whatever turns out to be true in this particular case.
Your Options When Installing A Battery
- Whole home backup. When the grid is connected, the battery is powerful enough to power everything in your home that would normally be switched on at any given time. When the grid is not connected, it can still power everything.
- Partial home backup – with every circuit downstream of the battery power sensor. The battery only backs up ‘essential circuits’ when the grid is down. But when the grid is connected, it can ‘see’ all the circuits in the home and will cover self-consumption of every circuit in the home – up to its total max power output (kW – across all phases if you have 3-phase). Note: this latter part is misunderstood by crap installers, many non-solar sparkies, untrained salespeople, and idiot support staff from cheap battery companies, who I see telling consumers that – when the grid is up – batteries can only provide power to circuits that are on the backed up circuits. This is incorrect.
- Partial home backup – with some circuits wired upstream of the battery – so they are invisible to the battery’s power sensor and will never be powered by the battery – with or without the grid. These circuits are forced to use the grid all the time. The most common circuit to treat this way is your EV charging circuit. If you can get free or very cheap electricity from the grid – it is rational to force that energy to come from the grid, not drain your home battery.
- No home backup whatsoever. Some cheap and nasty retailers appear to think battery backup is too hard and now only sell home batteries with no backup whatsoever, so they’ve got one less thing to fuck up.1
The customer in this instance asked for option 1, and claims he was told that – not only was his air conditioner not backed up – but it couldn’t even be powered by his 15 kW battery system with the grid connected.
Let me explain how a battery system ends up in that sorry situation.
The Power Limit Is Per Phase, Not Total
A “15 kW” three-phase inverter does not have 15 kW available on any phase you want it. It has 5 kW available on each of three phases.2.
So a 6+ kW single-phase aircon meets an inverter port that can only provide 5kW on the same phase, and one of them loses3. The inverter trips, or the air conditioner gives up, or both.
For the aircon to work under normal grid-connected conditions, the inverter 4, must have enough “pass-through” current rating to handle the entire house load, and this can be model-specific.
For example, the Solax 3-phase 15 kW G4 will only pass through 32 A, whereas the Solax 15 kW Ultra model will handle 80 A. During a grid outage, neither will support a large 7kW single-phase load, such as an EV charger, floor heating, or a large aircon but the Ultra will work fine if the grid is connected – simply passing through up to 83 A (~19 kW). But even with the Ultra, you won’t be able to use your aircon without the grid, as the inverter simply can’t output more than 5 kW from the battery on a single phase.
So while specifying the Ultra still won’t give you whole-home backup, it makes the installation cheaper, because it avoids the need to divide your switchboard into essential and non-essential circuits.
To honour a “whole house backup” promise from the salesperson, everything has to be wired behind the inverter’s backup port, and the inverter needs to be capable of not just passing through the maximum expected current, but outputting it from the battery alone. For most Australian homes, that requires a really beefy inverter. Sigenergy realised this before anyone else, and that’s one reason their 30 kW, three-phase unit is so popular – it will back up most Aussie homes without worrying about essential circuits.
Proper Design Without A Giant Inverter
A proper design doesn’t put the oversized aircon on the inverter’s backup port – but still puts it where the battery can see it5. Then – while the grid is connected – the battery can still power the aircon by using all three phases to discharge, netting your bill out at your meter6.
But with this design, during a blackout, the aircon is off.
If whole-house backup is non-negotiable, then the designer must specify an inverter that can handle the single-phase loads7 or design a transfer switch system.
What should never happen is a salesperson saying “powers the entire house” about hardware that physically cannot.
None Of This Is Exotic Knowledge.
Per-phase limits are on page two of every datasheet. Any installer who has commissioned a three-phase hybrid knows them cold. If your salesperson is also the installer, there is no excuse for getting this wrong.
If you are dealing with a salesperson who is not an installer, then ask them if they have SAA design accreditation – you don’t need to be an electrician or engineer to get it. If they don’t have it – move on.
Already Been Burned? The Law Is On Your Side
All of this is great to know before you buy. But what if you’ve already been promised whole-home backup and sold a system that physically can’t deliver it?
Simple. Under Australian Consumer Law, what the installer promised you is enforceable. Even verbally.
A salesperson saying “this will power your entire house when the grid goes down” creates an express warranty. It doesn’t need to be in the contract. It doesn’t need to be in writing at all. If the promise helped convince you to buy, it counts. On top of that, if you told them what you wanted the system to do and they sold it to you anyway, the system has to be fit for that purpose.
A system that cannot do the very thing it was sold to do is a major failure, and for a major failure you choose the remedy, not the installer. Your options:
- A refund. Full removal, money back.
- A replacement or modification that delivers the promise. A bigger inverter, a rewire, whatever it takes, at their cost.
What the installer cannot do is shrug and tell you to switch the battery off when you want to use the aircon. That’s asking you to live with the failure, which is precisely what the law says you don’t have to do.
Phase Shift is a weekly opinion column by SolarQuotes founder Finn Peacock. Subscribe to SolarQuotes’ free newsletter to get it emailed to your inbox each week along with our other home electrification coverage.
Footnotes
- Don’t even think about trying to explain to these guys the concept of certain circuits being upstream/downstream of the battery power sensor; it will blow their minds. ↩
- I haven’t verified which inverter or aircon is behind this particular install, so treat the exact numbers as illustrative. But the pattern holds across most budget three-phase hybrids on the Australian market. ↩
- The reason it only happens after dark is that there is no solar behind the meter to reduce the grid draw ↩
- Technically, I should say **series-connected** inverter ↩
- i.e. through the batteries CT ↩
- Say your aircon pulls 8kW on phase one at night. The 3-phase inverter puts about 2.7kW (8kW divided by 3 phases = ~2.7kW) onto each of the three phases to cover it. Phase one still imports 5.3kW from the grid to supply a total 8kW on that phase. Phases two and three export 2.7kW each. Your meter sums all three phases before determining whether you’re importing or exporting. Net result: zero. You pay nothing, the battery covers the lot, and the aircon never knows the difference. ↩
- They also need to consider the inrush current, but that’s a whole other blog post ↩
About Finn Peacock
RSS - Posts
Australian Consumer Law…yes, but some suppliers and manufacturers don’t respond to even threats of that. Sungrow is still advertising and stating on it datasheet that its SBR battery is 100% usable and 100 % depth of discharge, which it isnt unless the consumer gets into the installer configuration and reduce the hidden reserve to zero% and void their warranty. Sungrow and my installer are disinterested in rectifying that.
Australian Consumer Law is not meant to be a mere threat, make the call, get traction on the issue. Do it to them in the only way lawyers know how. The ACCC gets to ream them a new one and you get what was promised at no extra cost to you.
Dodgy retail relies on the premise that taking them to court will cost the plaintiff a lot of money. So they back down and live with the retailers failure.
then take them on
Whole home backup is possible with SIG three phase. Just don’t get talked down by your installer to a budget system. Make sure you get a big SIG battery and a large SIG inverter. My system (48kWh & 30kW) happily runs the ducted air con during grid outage. However, the SIG AI is the real winner in the SIG family.
Good article!
This is an important point to make sure installers understand.
I got four quotes for my system last mid last year. Not one of them had a big enough inverter for my 3 phase house. I went with the one that offered a 15kW Sig system and otherwise seemed most competent. I then got them to up the size to 22kW. If I had realised that a 30kW was available I might have gone with that but the 22kW, at 7.3 per phase has run my reverse cycle heater all winter day and night as well as induction cooktop, oven etc. We haven’t ever thought about changing our power use patterns.
I suppose that if I had let the house get really cold and then tried to start the heating at night it might have struggled given the gadget is rated at 8.4 kW, particularly if I was using something else on the same phase but it’s typically drawing around 800W just to keep the temperature topped up once the temperature is about right.
By the way. We had four power outages over winter and didn’t notice any of them until we got a note from the network.
We also had an over voltage issue when grid voltages were hitting 257V+ . You could do an article on that too. It had me worried when the Sig was shutting down until I checked grid voltages and realised what was going on.
We had the same thing. Our fronius system was going to grid only because of the over voltage issue. This was at night, mostly around 9.00pm.
Essential ended up reducing voltage at the nearest transformer.
They also rang back and said they were returning that afternoon to physically disconnect our solar as the installer had not bothered with an annoying detail, that is, the required approvals. Fun time.
We have a Sig battery coming, due in a couple of weeks.
3 x 10kw modules (27 usable) 3P 15kw inverter, gateway, they say will back up whole home on the 3 phases.
A timely article, and I will ask about limitations etc, but I think with the 4 x splits, positioned at 4 diagonal (X) points of the home, each drawing less than a kw when running, so should be ok.
We only run 2 of them if guests in other diagonal of home, otherwise just our BR is on.
We only need it after about 3 – 4 days of 35c weather (SA), not too often.
Can programme to charge from grid for the 2 EVs overnight at 8c rate.
The AI looks good too, will try both the TOU and AI options.
Les, the price increase to go from 15kw 3p to the next size up is likely hundreds of dollars only. Spend the slight extra. 5kw per phase isn’t much, kettle and toaster in the kitchen on at the same time is almost at 100%. In my house at Breakfast, it’s highly likely that will occur.
I’m stuffed if I know in today’s reality why 15kw 3p inverters are available, only a super basic home can get by, it’s ok to suggest that the grid can pick up the difference but there are electricity plans around that penalise significantly if you draw more than 30wh from grid in peak usage times.the one I’m thinking of gives a $1 rebate for every night you don’t draw, having a 15kw inverter cause you to loose that every day would suck, the extra it would cost could pay for the step increase in 1 year or less
15kW inverter is not likely to prevent most people getting zerohero rebate for no usage for not drawing. A 15kW TP Sig inverter when grid connected will offset up to 15kW of loads irrespective of phases the loads are on thanks to the magic of net metering which applies in Australia which has total power netted across all 3 phases. This would be similar I suspect for just about all semi decent 3 phase battery systems and is not unique to Sig.
So the 5kW per phase limitation for 15kW TP inverter is only limit when isolated from the grid in a blackout. So if seamlessly continuing to run in a blackout with no distribution and no change of behavior or management of loads is high on the priority list, a step up from 15kW is probably advisable. But you will also want to consider the size of your battery, as a 27kWh Sig battery can only support a max load of 13.5kW, and that load will run the battery flat in just 2 hours.
I’ll ask about a mild upgrade, they just phoned to book it in, and the rep will call me back.
Will inquire, even though we’ve been getting by with 2 x 5kw SolarEdge inverters on 2 phases and for 2-3/4 years without any issues.
We only have 3P now from when I had a kiln here 2 decades ago, that needed a 90a supply.
All good, we are fine to 63a apparently.
The price difference between a 15kW vs 30kW hybrid inverter is more like $2k ~ $3k.
For how long in a total outage with tge next day expecting cloud and rain?
That depends on the size of your battery and your panel array, not the size of your inverter.
If you want that sort of a decent backup you need to make that very clear, as just about every installer’s default design will only recommend a battery that gets you through the night, not several days of inclement weather.
I suppose it is also depends on whether you are using that air con system for heating or cooling, if cooling, you wont be running it very hard, or even at all that next day in your scenario, where as if you are heating you may be running it hard if you live in a southern state.
This very situation wouldn’t be a problem with an AC coupled battery would it?
still the same issue. the inverter can only supply “x” current per phase.
so while grid power is available the additional would come from the grid.
and any that the solar array is providing.
in a blackout situation you still have tje limitation of what the battery inverter can provide per phase.
typically 3 phase supplies have the single phase loads spread over the phases to keep them balanced some what this is for grid stability and reliability reasons.
if you care to notice you will be wired to a different grid wire than your neighbour and it rotates as you go along the street a,b,c,a,b,c
It would be worse as you wouldn’t have the support of DC coupled solar as well
If you want your AC system powered from your battery, I think that’s a fine thing to want.
But does it economically stack up?
A bit of back-of-the-envelope cost analysis.
Let’s say it costs $2000 in extra hardware to uprate your inverter to handle the load.
Let’s say you get 1 grid outage per year over the 10 year warranty period.
That’s $200 per outage just to keep your AC running. (And some of those may have been during autumn/spring or when you were out of the house etc.?)
I made some pretty big assumptions, not trying to make a definite statement, just adding some food for thought. Tweak the numbers in your own head.
Again, if you want this capability, you’re the customer and your money is as good as mine (your opinions are probably better)
T, I wasn’t sure this was just about running the AC in a grid outage, I think it would still hold for running it after dark, I might be wrong though. My issue is if I can’t run the 3ph AC off the battery then I just can’t justify the cost as it’s my biggest constant load in both summer and winter.
food for thought while your aircon might be 20kw cooling power its electrical power is only a third of that.
and it only runs the compressor at full power for maybe 10 minutes per hr (once at temp)
(hence why it can be cheaper to never turn it off unless your away for a couple of days)
so it may not use as much as you think.
a proper power monitor is very helpful to calculate the system size you really need.
Yes, this is a good point and one I missed, thanks!
If your AC system shuts down after dark — your battery isn’t fit for purpose. Get a remedy under the Australian Consumer Law.
If your AC system only draws solely from the grid after dark, not touching the battery — I’d say your battery isn’t fit for purpose because a reasonable person would expect it to work in this situation.. ACL.
If your AC system draws from your battery, to its limit, and from the grid after that — it might be arguable, but those arguments can be tested against the ACL.
We don’t really know what the situation was, but definitely I’d expect the battery to be doing **something** in this circumstance.
Hi T,
If your AC system draws from your battery, down to it’s lower state of charge limit, and then from the grid afterward — that’s just as it should be.
The example in the article is just because they put a large ducted aircon on the eps, taking it off will prevent it tripping the inverter.
That will still use power from the battery at night, just not be able to run during a blackout.. they should have advised the customer they needed to get the h3 pro model or a larger h3 smart instead for that size of aircon.
‘Whole house backup’ likely had an asterisk beside it stating you need balanced phases not exceeding 5kW, not that I approve of sales people and installers not making this 100% clear to the customer especially when they are wiring a large ducted system in to it.
it is definitely worth it when the cyclone takes your power out for 6 days in the middle of a Queensland summer… ask me how i know…
I have whole house backup with a single phase FoxESS KH10 with 42,Kwh battery. It easily runs 3 splits. Being 2 of Fujitsu 2.5 cooling (0.65KW ea) and a fujitsu 7.1 kw cooling (2.1KW ) in lounge . So maximum load with all compressors running is only 3.4 KW
Splits are a lot more efficient and much easier to work with a PVES in EPS mode. On hot SEQ summer nights, with all splits running the AC system rarely uses uses over 30% of battery capacity
Yes. It’s a lot easier and more straightforward with single phase.
Yes, in North America you’d only see three-phase power at a commercial or multi-unit residential building, still with a centre-tapped ‘neutral’ line to most of the low power, 110 volt plugs.
Our Canadian house has a 200 amp x 250 volt single phase connection through the meter. And I’ve heard of 400 amp, single-phase services to larger homes that use 100% electric heat in eastern Canada.
Larger appliances are generally rated 208 / 240 volt because an apartment would have 208 volt nominal, and a detached house would be nominal 240 volt. (or in the case of my last house, 253 volts on a sunny day and 230 volts at night)
Would a 3 phase air conditioner avoid this issue?
no. the issue is with larger 3 phase units.
even single phase jas the same issue you are limited by what the inverter can provide
and also by what pass through current it can handle
It does at our house. 15.4kW of inverter is plenty to run the 3 phase ducted air throughout the house (pulling about 8kW total across the 3 phases)
So in years gone by a single phase supply was in rare cases insufficient to meet a houses need. 3 phase is available but like everything with electricity costs more to setup and more in continued payments.
These days with affordable big solar and battery behind the meter, and much more efficient AC solutions the need for 3phase grid power is mostly abated. It should really be rare to need 3 phase any more. I have a 12kw single phase Sig system and I can, should I somehow need to get 12000w from my inverter night or day in addition to the 15400w I can pull from grid… I have 24kwh of battery which is enough to run AC during day for whole house and at night in our bedroom without needing any grid energy for summer. Winter it runs during the day but less so at night. In summer and winter you get natural cool down at night, good for summer, not so much for winter. If I added another 8 or 9kwh battery module it simply wouldn’t be an issue for me on north coast of NSW.
I had a Fronius full backup installed. They only wired it up to power the lights. I’m still trying to get someone to add more circuits to it but everyone is busy doing installs and don’t want a small job 😑 I just want it to cover another circuit or two, not the heavy load ones (I’m on 3-phase).
Hi Dean,
Fronius is excellent because the inverter is wired in parallel with the main supply, so you’ll never have issues with overloads when the grid is present.
Some installers are shy about a 1 hour job when they see it burning half a day’s productivity by the time they’ve rolled the van to your place.
What kind of hot water do you use? You might make the job more substantial for yourself and the electrician by adding a diversion circuit to control a pool pump, plug in EV charger or hot water. The smarts are already built into your Fronius.
I had a SolarEdge backup installed with 30kW of batteries a few months ago, so as long as I manage power consumption I can get through the majority of the day on batteries (I now have 4 free hours of electricity to charge the batteries which helps too).
What I have found post install is that hitting the system hard (when the batteries are charging full rate they cap out around 11.6kW) and having some load on the house the circuit breaker trips around 14.5kW total consumption from the grid… Means I have had to automate the crap out of the charging rates via Home Assistant…
Single phase by the way. What trips is the actual circuit breaker labelled as “Main Switch (Alternative)” as it’s a 50A breaker (grid is 63A, and Inverter is 50A too)… I’m wondering if they have not installed a large enough breaker on the meter to handle my actual consumption when the battery is under charge load and we do anything major in the house (oven on, heater, washing machine etc).
Would you please clarify whether you’re talking about single phase or three phase heat pumps to power the heating/cooling. If single phase please provide your best advice on dealing with three phase heat pumps for the different scenarios you mention.
Hi Nigel,
We’ve got an article coming for you.
I tried explaining 6. in your footnotes to the first subcontractor installer for our current system. I even tried to show him data from the Fronius power meter to explain when he came back. Too complicated. Which explains why he messed up part of the wiring.
When he first set up the back up circuits (option 2 in your article) he managed to add a single phase load, the AC, that was well above the limit per phase limit. Why, because “batteries can only provide power to circuits that are on the backed up circuits”. (Were you quoting him?)
Most distressing, amusing now, and contradicting other things he did, was his explanation that the only way the battery could ever power anything in the house was if this big contactor disconnected the grid. The battery and grid couldn’t both supply the house at the same time.
Some people really should stick to pulling cables for someone else.
Hi Matthew,
I’ve worked with electricians who are effectively German trained engineers, while others literally had “cable monkey” printed on their business card.
The former I could agree to disagree with sometimes but the latter was our go to guy for AlphaESS systems that I couldn’t make peace with.
Different people have different experience & training but you’re right, some need improvement.
Another solution to the issue of powering your AC is to install a three phase AC to spread the load over three lines. They are also more efficient.
Added to my “if only I had known” list.
Very interesting indeed! Do we have any system designers that are proven to know their stuff listed on SolarQuotes?
“No home backup whatsoever. Some cheap and nasty retailers appear to think battery backup is too hard and now only sell home batteries with no backup whatsoever”
Cheap & Nasty is correct if the retailer did not discuss or offer backup.
However, some retailers do the right thing and allow the customer to CHOOSE whether they want to spend extra money on backup.
Regardless of whether backup components are built-in the inverter, or separated into a ‘Backup Gateway’, installing backup power does cost extra time and money.
Money doesn’t grow on trees in customers backyards. Some people rarely experience blackouts and prefer a lower price without backup included.
OR
Some people prefer to spend those extra $ on extra battery capacity or extra solar panels; something that can benefit them daily instead of once in a blue moon.
“If you are dealing with a salesperson who is not an installer, then ask them if they have SAA design accreditation – you don’t need to be an electrician or engineer to get it. If they don’t have it – move on.”
Really?
There’s a Facebook page called ‘Crap Solar’ with hundreds of examples of poorly designed & poorly installed solar systems. And every one of them was signed off by a CEC / SAA accredited designer & installer. Should we tar all installers with the same brush as those numpties?
Just like installers, there are competent & incompetent salespeople.
Even without SAA accreditation, there are plenty of knowledgeable salespeople / consultants within the industry, some with 10+ years of experience, who honestly & accurately advise customers on solar & battery system design. It’s not rocket science.
A $3,000 accreditation course (plus renewal fees) doesn’t stop an installer or salesperson from being dishonest, lazy, selling cheaper poorly designed systems.
Some info here that hopefully helps those intending to run Aircon on batteries.
We recently installed an 18kw single phase Fujitsu ducted system in our double brick house on the the mid north coast NSW-no ceiling insulation (coming ) but blanket under colorbond.To monitor power consumption a Shelley CT monitor was put on the a/c circuit and the main supply.Generally a/c is set between 19 for bedrooms and 21 in living areas via an Airtouch 5 controller.
On cold mornings it starts consuming up to ~1.6 Kw and eventually ramps down to around 750 Watts after about 2-3 hours.In the evenings it rarely uses more than 800 watts.Power factor determined by Shelley.
All in all we’re pretty impressed with the low consumption-a lot of bang for the buck compared to a wood stove system ! Incidentally we don’t have solar or a battery here but we’re looking into it .
In our installation the installer spoke with me on arrival and explained backup. He said ‘we can wire complete blackout’ but…..i want you to think about it. You have around 33kwh if the battery is full. Of course backup power circuits and lights but…..you have two i want you to think about. The spa….does it need to be on backup?. No. Then we have a ducted ac. It draws around 6kw. If you back that up you will have just a few hours. But you do have a split in your main area. That is backed up. Is that enough. The split draws around 1kw.
So we accept we have around 8-10 hours of potential backup. Longer if we conserve power use. Ducted doesnt work but split does.
Last Feb we had a outage. 2 hours at night. The house coped. We coped. It was hot upstairs but not downstairs where we were. We were happy with that. We conserved power to assist.
I think its unrealistic to expect to run ducted AC on battery in a outage. Is it a hours, two or ten ? Thing is you dont know.
Heck yeah Paul, focus should be on lighting (hopefully LED), fridges / freezers, and power points.
I like the options of systems that actually take some seconds to change over, cut power and reset clocks etc, before transfer to battery, as they give a heads up that you should go and turn off anything non essential until you know how long the power might be out.
The systems that switch over before even a clock can reset and you don’t notice you don’t have grid power might let you keep using big draw items without even knowing.
“Then we have a ducted ac. It draws around 6kw” Wow,what size and make of a/c and is it an inverter ? read my post above re our power consumption
Peter, part of the issue with ducted is uncertainty over what it actually requires. There’s often ambiguity over whether it’ll be single or three phase, what it’s rated versus what it will draw on average, and what it uses when on but not needing to do anything because the current house climate is within current parameters.
Yes if you personally go out and select a unit from a shop and get expert advice you can probably get this data, but if you buy a house with one pre-installed, or build a house with a ducted unit, then odds are your builder\real estate agent won’t be able to give you useful specs.
Its 20 yr old no inverter. It caters to our two level 4 bed home. If it was replaced it may draw just 4kwh. Thats not worth it.
Paul,
You’re spot on, I think. All the anecdotes I’ve heard about ducted suggest power hunger and reticulation losses.
Off-grid here, it’s perpetual backup. So I have three splits instead of ducted. After sunset, I run just one, sometimes all night, without the battery falling below 80%. It’s 3.5 kW thermal, so about 1 kW input at full whack. It mostly runs at 500W or less. That’s enough for 72 m² double glazed & well insulated, with HWS heat leakage helping in winter, as it’s indoors. Rather than crank it up on a -2°C night, I light the wood heater. Summer’s a doddle, not least with a little 3.6 kW west-facing array tilted up 40° to grab the last of the setting sun, postponing battery draw
In a week with the flu, the aircon ran 24/7, and the battery stayed above 84%.
Good insulation, small aircon, ample battery, and a BIG array, avoid need for any grid draw or generator start, I’m finding. Match system design & lifestyle for a good fit.
My son got caught this way, 3 phase house power is very rare here, it seems to have become a thing for new housing estates though.
A lot of people dont understand that you need to divide a 3 phase inverter specified “size” by 3 to know how much power it can actually deliver per circuit, and to be frank, 5kw is ridiculously inadequate. Turning on the toaster and the jug at the same time your fridge cycles on, will likely trip out your inverter, which is what was regularly happening to my son and the Installer just kept fobbing him off.
When the battery subsidy came in, my son used the opportunity to upgrade to a decent sized inverter at the same time he upgraded his battery. Obviously using a different installer…
“the owner discovered the air conditioner shuts off after dark with no solar available to help power it”. I’m intrigued with this statement early in Finn’s article. How can the solar help? The inverter can output a max of 5 kW to each phase, whether that comes from the battery or solar or the grid (neglecting pass through as the inverter involved doesn’t appear to have that capability). The a/c apparently requires more that 5 kW, at least part of the time, so it should never have worked… what am I missing?
Inverters can “passthrough” to draw more power from grid when a phase needs more than 5kW (of a 15kW 3-phase inverter). Perhaps that inverter doesn’t support passthrough?
Phase limit (in this case, 5) usually only applicable during blackout or off-grid mode.
What if my big A/C is a 3-phase unit? Does that make a difference?
Hi Glen, you might get away with it if your solar power is 3 phase and the air con is well matched.
depends on how your circuits are wired and what else is on at the time – the first half hour as it gets to temperature is the big power draw period, after that they don’t draw much power.
So might be best that you dont turn on the aircon, the oven and the jug all at once when you get home.!
I have a Solaredge system and whole house backup on one 10kwh battery (capable of delivering 5kW) . When there is a blackout and Solaredge switches over to battery, there is a 3 second delay where we have no power at all. That means my airconditioner turns off and they don’t come back on again when the battery starts supplying energy to the house. Consequently when the battery takes over, none of the airconditioner load is on. Now I could go and turn the aircon on again but I don’t. I treat it as a real blackout and try to only use emergency loads. I thought the 3 second delay was a bit of a pain but it’s not been too bad really.
Hi Kingston,
Fronius also offer an interrupted backup supply, which I explain to people as a big fat unmissable analogue warning signal. It doesn’t matter if you have a new phone and your solar app in on the blink, when the lights go off, you know you have to pull your head in and conserve energy.
I have a quote proposing an A/C coupling of a 15kW 3 phase inverter to the exisiting 10kW Fronius inverter.
The rationale:
“Essentially, the GoodWe system runs in parallel with your existing Fronius inverter:
Your existing Fronius inverter continues to manage solar production
The GoodWe inverter manages battery storage, charging and discharge
Both systems operate alongside each other rather than unnecessarily replacing your existing solar inverter
If your solar system was installed in 2021, it was installed under the previous DC cabling requirements. If we replace the existing Fronius inverter and the existing DC cables do not reach the location of the new GoodWe ESA inverter, we cannot simply extend the existing DC cabling under the old requirements.
Once we alter or extend that cabling, the altered DC wiring is required to comply with the current regulations, which means the DC cabling for the existing array would need to be rewired accordingly”.
Does this sound rational?
What an absurd situation, I can’t believe installers like this exist. I have this exact system, and have partial home backup but full visibility of all circuits which can have their consumption offset by the battery but also supplied by the grid if necessary.
It’s so simple – all hybrid inverters have two output ports, the Emergency Power Supply port (which this poor sod has all his circuits connected to) and the Grid port. All circuits should be connected in parallel with the Grid port in normal operation which will allow all circuit consumption to be fully offset up to the capacity of the inverter, then any additional consumption can be supplied by the grid automatically.
Forget about connecting circuits permanently to the EPS port, simply wire the desired backup circuits to an Automatic Transfer Switch which will switch those circuits over to the EPS port upon loss of grid, avoiding EPS port trips during normal operation like the guy in this story is suffering.
Hi Beau,
To be honest the ATS is a layer of complexity most electricians don’t want a bar of, nor have room in the switchboard for, especially when it’s already built into the inverter.
Many hybrids are now “whole home” capable but the cheaper ones still pose a trap to young players.