Inverter shutting down in summer | Grid voltage rise

Hi, Harvest.
I have solar panels already. However, I’m finding an issue with the size of the inverter. I have 18 x 250 watt panels that should generate 4.5kW. The inverter that was installed has a maximum capacity of 4kW. When I asked the installer, I was told that there would be a slight loss of power and the 4kW inverter will be sufficient. guess what? It isn’t. In summer, on a clear warm day, my system pomps out very close to the 4.5kW. However, the 4kW inverter cannot handle this and shuts down for the rest of the day. Therefore, I lose ALL solar input for that day, and sometimes several in a row. Get an inverter that equals or exceeds you panels output and don’t listen to any rubbish about power loss. The company that installed my system went belly-up during my fight with them to get an upgraded inverter.

Hi Keith

That’a a worry! If you’re having problems with a 4.5 kW panel / 4 kW inverter setup, it suggests a 6.6 kW panel / 5 kW inverter setup would also experience problems. But I haven’t heard of any such problems. Can I ask what brand of inverter you have?

Regards
Erik

Hi @Keith2

Your inverter shouldn’t be shutting down that’s for sure. What’s the brand?

Cheers
Marty

Marty. I’ll get back to you with the brand when I find the paperwork for it. Shouldn’t be too long.

Marty,

It’s a SolarMax P-Serie Inverter (4000P), made in Switzerland.

The instruction manual seems to say it has shut off protection for overloads, but the manual indicates this is more to do with surge suppression (lightning strikes, power surges from the grid) rather than PV panel output being over the capacity of the inverter.

If you can suggest anything that may help, I would appreciate it.

Looking at trying to buy a larger inverter, but so far, the solar companies I’ve contacted will not supply one, without installing a complete new system (PV panels, etc). My PV panels are only 4.5 years old.

Regards,

Keith

That’s a real shame Keith. You’re saying that the company that sold it to you went bankrupt? I know that SolarMax inverter company has also gone under, so that’s a bad combo.

I suspect the shutdown issue might be to do with heat rather that overloading from the PV. You mentioned it happens in summer, does it happen in winter on a clear, sunny day? In fact panels output less power when it’s hot as opposed to cold. Where is your inverter located? What direction does the wall face, and is it in sun or shade? Also, where is your house located?

Marty

Marty,

Lots of questions you raise.

The Mark Group (based in Macquarie Park or Ryde NSW) went belly-up about two years after they installed the system.

My house is Winston Hills, near Parramatta NSW.

The panels only get to output more than 4kW in Summer on a clear day, generally anywhere from 9am onwards. In Spring, Autumn or Winter, the outputs never get close to 4kW output.

In fact, today is partly cloudy @ 1pm and it’s ticking along @ 1500watts.

The inverter is on the Eastern wall (facing the sunrise), but it’s sheltered next to an external water tank, which blocks a lot of the Sun. We have the usual 18" wide eaves about 1.2 metres above this as well.

I have pictures of it getting up to 3990watts @ around 9am, then as soon as it gets to 4000watts, it simply switches off, usually until just before sunset, when it may restart, but too late to do any good as far as power output is concerned.

It will switch on again at first light the next day, but sometime between 9am and 10am, same thing happens. This may go on for a week, until we get a Southerly change or cloudy weather.

I really doubt it’s the heat as the day has hardly warmed up before it switches off. It has never switched off in Spring, Autumn or Winter as the PV output simply cannot get near 4000watts.

I have attached a picture I took of the LED panel on the inverter, which had turned itself off sometime just before 9:22am on 14 Jan 2016. Date & time pics were taken is in the file name attached (yyyy/mm/dd
hhmm). Time is also shown on the pic.

This forum only allows me to attach one pic at a time. I have literally dozens of photos taken over the Summer months from 2014 to 2016. Once The Mark Group went under, I gave up taking any more photos as I have to replace the inverter. That is another frustrating exercise. However, I now have some contacts for inverter suppliers, BUT, if I could just get this inverter to stop switching itself off and just remain at 4000watts, that would be good.

The panels were installed facing East and West as The Mark Group advised that two neighbours trees would block the Northern roof of my house.

I queried this at the time, but they were adamant this East/West placement would give me the 4.5kW I wanted, then they installed a 4kW inverter, which I didn’t realise at the time as the specs were on the side and the PV Array switchbox was right up against it. When I tried to get them to install a larger inverter, that’s when I found that The Mark Group was no longer in business.

Does this clear up your questions, or what happens next?

Thanks & regards,

Keith

I have split this topic off from the below, because it has become an important topic of its own:
Seraphim vs Suntech Panels with Solax Inverters

Thanks @Keith2, yes that clears things up a lot. I think the fact that the inverter is well covered, on the east wall, reduces the likelihood of overheating, as well as what you are saying about the time of day it is occurring.

What you are saying is concerning because I would say that the vast majority of new residential solar installs in Australia, oversize the inverter with panels. There are good reasons to do so, we talk about why in our Guide to Buying Solar here: Oversizing your inverter.

For that reason, I am interested in getting to the bottom of your issues Keith, because I know that generally, oversizing the inverter does not cause problems like what you are describing.

I am not a solar installer or electrician, so hopefully someone with more inverter technical knowledge will be able to wade in here. I’ve had a look at the Solarmax 4000p data sheet, and it looks like the shutdown voltage is 600V. It’s possible that if all 18 panels were run together in a single string, then the system is reaching this limit and shutting down. I’m just guessing here. I guess it’s also possible that there is some limit built into the inverter that shuts it down when it reaches 4kW, but that would be very unusual from my understanding.

Keith, I would recommend getting an electrician with solar experience to take a look. You’ll need an electrician at some stage either way to fix this, I think it’s worth getting them involved before buying a new inverter. Rather than getting a new inverter, they may be able to do some rewiring. Which won’t necessarily be easy, but installing a new inverter might mean getting the system inspected again, and that could complicate the whole matter even further.

Good luck!

Marty,

Thank you for that advice. Really appreciated. Let’s see if anyone else has input to this discussion.

After reading the link to “oversizing your inverter” in your email below, I now get it. However, my SolarMax inverter should still supply 4kW of power @ maximum Summer sunlight, not just “shut down”.

The SolarMax Manual seems to indicate it has protection from power surges and also has over-temperature sensors.

According to the manual, there is supposed to be a cooling fan, but I’ve never heard it work, which, if faulty, could be the reason it cuts out when receiving large outputs from the PV panels, although I do not quite understand how kW = heat transfer, especially @ 9am in summer when this shut-down problem occurs. Although, the fan could be working, but is quite silent.

As you suggest, I’ll be getting in touch with a solar-qualified electrician over the next week or two. I’m a bit busy over the next week.

Thanks again, & regards,

Keith

Hi Guys, sorry I only just came across this discussion.

Keith, oversizing the solar PV is not the problem. I am almost certain it is a grid voltage issue which is causing your inverter to trip-off or shutdown. The Australian standard (AS4777) requires all solar inverters sold in Australia to ramp down (throttling) when the grid voltage rises above 253V and shut off completely above 255V. This is to try to keep the grid voltage from rising too high.
Unfortunately this now a common issue in area’s of high solar penetration (high percentage of houses with solar), but often only an issue in summer when solar generation is at it’s peak.

There’s are some ways to get around this such as by using a device called a ‘voltage optimiser’ which is designed to adjust the voltage in your home to be lower than the grid voltage thus allowing your inverter to still operate with high grid voltage. I would be careful though as some of these do not work correctly or are not certified for use in Australia.

The best path to take (but more difficult) is to contact your local network distributor, which I believe is Ausgrid in your area, and tell them to lower the voltage at your local transformer (called re-tapping). No doubt this is a problem in the whole area and many people are simply unaware. Unfortunately Ausgrid will probably not listen to you unless you can give them evidence of high voltage in your street. Many modern inverters can log the grid voltage and if you have a wifi connection you might be able to get the data. Otherwise you may need a power meter installed or a device such ‘Solar Analytics’ energy meter.

Hope this helps,
Jason

Jason,

Thanks, but what you are saying is way over my knowledge. I have three-phase power coming into my house (due to a 5kW air-con system), but I’ve never heard of “253V grid voltage” before.

Nearby there’s only one other house with solar panels (fifteen houses nearby without) and looking at the number of panels on that house, I’d say thay only have a 3kW system (4kW max.).

I know these neighbours, so I will talk to them about there system first and see if they had any issues during last Summer.

My network distributor is Endeavour Energy. After I talk to the neighbours, I shall discuss this with them and see if what you’re saying is happening.

Thanks for your input, it might be the key to solving this mystery.

Regards,

Keith

HI Keith,

Sorry I might have not been very clear. The grid voltage for single phase and 3 phase supply should be around 240V (per phase) but due to many variations in the electricity network, the voltage can fluctuate anywhere from 215V up to 255V or even higher. The higher grid voltage is what causes solar inverters to shut down as explained in the previous message.

This article will help explain the issue in more detail…
https://www.energynetworks.com.au/news/energy-insider/too-much-solar-blame-voltage-issues

Even without much solar in your area the grid voltage can still rise above 253V on a sunny day due to the ratio of supply (from solar) and low demand. The only way to determine if this is the issue is to somehow to monitor the grid voltage in your area. The display on a solar inverter can often tell you the grid voltage, but it would best to use an energy meter to log the voltage. Maybe one of your neighbours has a way to monitor the grid voltage?

Jason,

Very interesting article in the link below. Some of it was lost to me, but I got the gist of it.

I’ve checked my SolarMax manual and I cannot see anywhere where I can check the Grid voltage.

The troubleshooting guide in the manual does say that if an error message of: “Vac to high” appears, to contact the “grid operator in charge”.

But, I don’t get the error messages, the led screen just goes blank.

It looks like I’ll be discussing this with my “grid operator”, which I’m guessing is “Endeavour Energy” in my case.

I’ll first speak to my neighbours who have solar panels and see if they’re experiencing any issues and go from there.

It does appear that I have a voltage overloading issue as the “transformer on a pole” (mentioned in linked article) is only two houses away from me.

Thanks again and regards,

Keith

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Hi Keith,

Another ‘cheaper’ option to measure the grid voltage is to use a ‘power meter’. Plug it into a power point which is not used by any large appliances (as this will reduce voltage) and it will tell you what the grid voltage and frequency is.
Note the grid voltage can vary greatly throughout the day so take several measurements at different times, especially when you notice the inverter has shutdown.

They are very cheap (i think even bunnings sell them or jaycar electronics)