Sunsynk Inverter more reliable than grid?

[sol4096]

I am looking to get solar panel for my house in the UK. The quotation I am likely to go for is with a 5.5kW Sunsynk inverter, 6kW panels, and 5kWh battery.

In principle I'd like to make use of backup function, to keep the "essential load" going if there is a grip power outage.
This is more of a "why not" case, for piece of mind: power outages have been very rare where I live in the past few years (to be fair, part of me also wonders if there may not be more power outages in the future, due to more renewables which vary more in production, and sad geopolitical events which threaten gas supplies... I might be overthinking though?)

Now the "essential load" is plugged on the "LOAD" port of the inverter:
1) does that mean that it would lose power if the inverter fails? if so presumably I'd have no power on those until I can get the inverter fixed, or an electrician to re-route the rings directly to the main consumer unit / grid, which could take days? Or is it clever enough to automatically get the "essential load" ports on mains in case of failure?
2) how reliable are (Sunsynk) inverters? any view on the risk of inverter failure vs. risk of grid power outage in a zone which have had very few power outages?

Thanks!

 

[houseofancients]

I am looking to get solar panel for my house in the UK. The quotation I am likely to go for is with a 5.5kW Sunsynk inverter, 6kW panels, and 5kWh battery.

In principle I'd like to make use of backup function, to keep the "essential load" going if there is a grip power outage.
This is more of a "why not" case, for piece of mind: power outages have been very rare where I live in the past few years (to be fair, part of me also wonders if there may not be more power outages in the future, due to more renewables which vary more in production, and sad geopolitical events which threaten gas supplies... I might be overthinking though?)

Now the "essential load" is plugged on the "LOAD" port of the inverter:
1) does that mean that it would lose power if the inverter fails? if so presumably I'd have no power on those until I can get the inverter fixed, or an electrician to re-route the rings directly to the main consumer unit / grid, which could take days? Or is it clever enough to automatically get the "essential load" ports on mains in case of failure?
2) how reliable are (Sunsynk) inverters? any view on the risk of inverter failure vs. risk of grid power outage in a zone which have had very few power outages?

Thanks!

1. yes, which is why a transfer switch ( or second inverter ) always is mandatory in my mind.
i hate SPOF's

2. do a search here for deye / sol-ark / sunsynk ( all same platform) and see how many real life failures are recorded, that will give you an idea.
to add sol-ark's and deye are sold in HUGE numbers

also, what you might want to look at is how these bidirectional.inverters actually work.
it might very well be in your case that zero-outing on the line port is a much better idea

 

[sol4096]

thanks @houseofancients.

I didn't know about transfer switch (newbie here ), thanks for the pointer. In this case the inverter would switch automatically, and I don't think I need an automatic backup on the automatic backup if that makes sense. So I guess a simple manual changeover switch (so switch the "essential" rings between the inverter essential load port and the mains) would do the trick, if it doesn't go against an electricity/wiring safety rule?
I imagine that would mean an extra small consumer unit for the essential rings, which should be ok.

I also found Sunsynk's training manual (available in "Documents" on their website) which is useful.
Looking at the diagram I found in there:

I guess the (essential) Load stops getting power if the AC relay at the top right fails (or fails in the wrong "configuration").

I'm not sure what you meant with "zero-outing on the line port"... could you please clarify?

 

[zanydroid]

I'm not sure what you meant with "zero-outing on the line port"... could you please clarify?

I assume since this was mentioned in the same sentence as bidirectional, that zero out is British for zero export. Basically the inverter is able to send power out to the grid in some (most?) configurations. If you connect the inverter via a branch circuit (US terminology) on the consumer unit rather than in the critical path of power coming in from your utility to your consumer unit, then you can chop off the inverter and everything will still work. BUT this requires you to install CT current sensors on the service conductors from power company so that the Deye will only push enough power from your batteries to supply your local loads. It does this by doing math and a control loop to zero the power flow to the grid, or keeping it coming in.

I believe Deye can only operate in bidirectional mode, even if you connect it in the critical path. So you should be permitted to install it this way in most jurisdictions. But I welcome being educated.

I think the suggestion above is to install a bypass. In that case if the inverter goes down then you can skip it without any configuration issue. In this case the inverter strictly adds reliability. Unless you believe the bypass is going to introduce a point of failure. In practice It’s not, the reliability of a burly switch is certainly better than the grid and the inverter.

 

[sol4096]

@zanydroid yes the Deye/Sunsynk is bi-directional, and I *think* what you are describing is the default setup where all the home ring circuits stay on the consumer unit and the grid (e.g. the manual says "Grid [terminal block]: [...] It is both an input and output connection for non-essential load and supply"). The sunsynk inverter does include a CT coil, and the manual even says "The CT coil is one of the most important parts of the Sunsynk Ecco Hybrid Inverter"

However I *think* the inverter does *not* supply any power to the grid (and thus on-grid home load) if it detects a grid outage, e.g. for safety of grid workers (although I didn't see any explicit mention of this in the manual, so I might be guessing/inferring?). My understanding is that when there is a grid outage, only the (essential/backup) Load terminal block on the Inverter will get power. So essential loads have to be plugged directly to that terminal block, and the inverter becomes a single-point-of-failure for those.

So the idea here would be to install a manual changeover switch so the essential/backup load ring(s) are normally plugged to the "LOAD" on the inverter, but should the inverter fail they can be manually switched to the grid.

Maybe clearer with a picture. So the "basic" wiring (as in the sunsynk inverter manual) is:

... and the idea here would be to add the Manual Changeover Switch as show below (that one is me changing the image above, it's *not* in the sunsynk manual):

Hopefully possible and safe?

 

[zanydroid]

Yes, if this topology of hybrid detects grid down it will disconnect the connection to the grid and only power the other AC ports.

The bypass switch should be allowed, it's pretty standard around here. You would need to check what kind of switch you need (EG whether you switch both L and N).

And you probably want to add a way to turn off power to the inverter for servicing (Grid, Battery, and Solar).

 

[houseofancients]

@zanydroid yes the Deye/Sunsynk is bi-directional, and I *think* what you are describing is the default setup where all the home ring circuits stay on the consumer unit and the grid (e.g. the manual says "Grid [terminal block]: [...] It is both an input and output connection for non-essential load and supply"). The sunsynk inverter does include a CT coil, and the manual even says "The CT coil is one of the most important parts of the Sunsynk Ecco Hybrid Inverter"

However I *think* the inverter does *not* supply any power to the grid (and thus on-grid home load) if it detects a grid outage, e.g. for safety of grid workers (although I didn't see any explicit mention of this in the manual, so I might be guessing/inferring?). My understanding is that when there is a grid outage, only the (essential/backup) Load terminal block on the Inverter will get power. So essential loads have to be plugged directly to that terminal block, and the inverter becomes a single-point-of-failure for those.

So the idea here would be to install a manual changeover switch so the essential/backup load ring(s) are normally plugged to the "LOAD" on the inverter, but should the inverter fail they can be manually switched to the grid.

Maybe clearer with a picture. So the "basic" wiring (as in the sunsynk inverter manual) is:
View attachment 141524
... and the idea here would be to add the Manual Changeover Switch as show below (that one is me changing the image above, it's *not* in the sunsynk manual):
View attachment 141523
Hopefully possible and safe?

your second image reflects exactly what my setup is, with the exceptance that i am using an Automatic Transfer switch .
an ATS still allows for manual switch over in case of maintanance or inverter error, but it also allows me to control a power source based on programmatic parameters.
furthermore i found that in my case the CT Coils comming with the inverter not acurate enough and subject to magnetics due to to cramped space.
i have replaced it with an Eastron SDM630 Modbus v2 , which is support by the inverter too, but is much more accurate, fits on a dinrail and is regulatory approved here, where as my inspector did take issues with the 3 ct clamps

 

[solartist]

I also found Sunsynk's training manual (available in "Documents" on their website) which is useful.

Looks like that training manual could be very useful for people (like me!) evaluating whether to choose a Sunsynk inverter/AIO. Any chance you could upload it to this thread as an attachment?

(I tried your link, but it isn't working for me - and unfortunately, neither is the "Documents" page on the Sunsynk website.)

 

[sol4096]

Indeed the link I used earlier doesn't seem to work(?!). Just to confirm, did you:

1. Go to https://www.sunsynk.org/documents
2. Then Browse to Training Manuals folder (at the bottom of the list) -- you should see two Training Manual PDF files

and that doesn't work for you?

 

[solartist]

Indeed the link I used earlier doesn't seem to work(?!). Just to confirm, did you:

1. Go to https://www.sunsynk.org/documents
2. Then Browse to Training Manuals folder (at the bottom of the list) -- you should see two Training Manual PDF files

and that doesn't work for you?

Step 1 results, for me, in just a blank page. Tried on a couple of different browsers & PCs. (I have accessibility issues & corresponding web-browser accommodations, but sometimes web pages are so badly-built that they just don't show anything.)

So, I can't see a "Training Manuals" folder at the bottom of the list because no list or folders are showing up for me - it's literally just a blank page.

 

[SeaGal]

I am looking to get solar panel for my house in the UK. The quotation I am likely to go for is with a 5.5kW Sunsynk inverter, 6kW panels, and 5kWh battery.

If you can afford it, I'd recommend more battery - like 10 to 15kWh would be a better match for 6kWp panels in the UK, IMHO. YMMV.

 

[sol4096]

If you can afford it, I'd recommend more battery - like 10 to 15kWh would be a better match for 6kWp panels in the UK, IMHO. YMMV.

I could afford it, but (basic) consumer seems to be that it actually takes longer to break-even with a battery than without. They also seem at best neutral from a eco-friendly point of view. So I was thinking to be on the lower side for the battery, and use it fully (even if it didn't always quite cover all my overnight usage) rather than get a bigger battery and only use it partially. I was also thinking that I could always add another battery module, whereas I wouldn't remove one that end up not really needing...
But I'm not entirely sure here... if you have feedback on return on investment depending on the battery size I'm interested!

 

[sol4096]

Step 1 results, for me, in just a blank page. Tried on a couple of different browsers & PCs. (I have accessibility issues & corresponding web-browser accommodations, but sometimes web pages are so badly-built that they just don't show anything.)

So, I can't see a "Training Manuals" folder at the bottom of the list because no list or folders are showing up for me - it's literally just a blank page.

Weird. Anyway, sure: see attached.

 

[SeaGal]

I could afford it, but (basic) consumer seems to be that it actually takes longer to break-even with a battery than without. They also seem at best neutral from a eco-friendly point of view. So I was thinking to be on the lower side for the battery, and use it fully (even if it didn't always quite cover all my overnight usage) rather than get a bigger battery and only use it partially. I was also thinking that I could always add another battery module, whereas I wouldn't remove one that end up not really needing...
But I'm not entirely sure here... if you have feedback on return on investment depending on the battery size I'm interested!

It will obviously all depend on your total daily usage amount and pattern of usage (e.g. in day vs. evening), as well as what price you are paying at the moment. We have economy 7 tarrif, so a bit more in day, but much cheaper at night. Payback for our DIY built 15kWh battery is estimated to be about 3 years and we do use it pretty much fully daily, but obviously YMMV.

 

[sol4096]

Now my system is in place, at the moment a 5kWh battery seems right for me. At the moment it gets me to at least 2am, and I've switched to the UK Octopus Flux which is a bit like economy 7 (cheaper from 2am to 5am). I get the battery charged to 20% until 5am, to bridge me until the sun comes up (some days I need a bit less, some days I would need a bit more).

At the moment a 10kWh battery would be a bit wasted for me I think.

Now I'll see how it goes in the winter... the 5kWh probably won't be enough, but then again I'm not sure I'd have enough solar energy to charge a 10kWh then, so who knows...

 

[houseofancients]

Now my system is in place, at the moment a 5kWh battery seems right for me. At the moment it gets me to at least 2am, and I've switched to the UK Octopus Flux which is a bit like economy 7 (cheaper from 2am to 5am). I get the battery charged to 20% until 5am, to bridge me until the sun comes up (some days I need a bit less, some days I would need a bit more).

At the moment a 10kWh battery would be a bit wasted for me I think.

Now I'll see how it goes in the winter... the 5kWh probably won't be enough, but then again I'm not sure I'd have enough solar energy to charge a 10kWh then, so who knows...

are you using the dynamic rates option for octoplus ?

 

[SeaGal]

Now I'll see how it goes in the winter... the 5kWh probably won't be enough, but then again I'm not sure I'd have enough solar energy to charge a 10kWh then, so who knows...

It's all about balancing your usage vs. prices of electricity and investment in PV and battery.... + the law of diminishing returns kicks in the more kWh of battery you invest in.

I agree that in winter, with 6kWp of PV, you won't have enough solar to charge 10kWh of battery, but what worked for us was topping up our 15kWh at the cheap overnight tariff. That, combined with a bit of sun on a good day, meant we used virtually no peak rate electricity over the winter months.

 

[sol4096]

are you using the dynamic rates option for octoplus ?

Yes, Octopus Flux (although only the import part is active at the moment, I'm still waiting for the export to become active. They did say it may take a few weeks, and it is indeed taking a while...).
It felt like Octopus Flux would pretty much always be better as long as you have a battery (even if I may have to charge the battery a bit before the expensive 16:00-19:00 period in winter, we'll see).

 

[houseofancients]

Yes, Octopus Flux (although only the import part is active at the moment, I'm still waiting for the export to become active. They did say it may take a few weeks, and it is indeed taking a while...).
It felt like Octopus Flux would pretty much always be better as long as you have a battery (even if I may have to charge the battery a bit before the expensive 16:00-19:00 period in winter, we'll see).

then you should be able to get the fullest out of it using standard TOU

 

[sol4096]

It's all about balancing your usage vs. prices of electricity and investment in PV and battery.... + the law of diminishing returns kicks in the more kWh of battery you invest in.

I agree that in winter, with 6kWp of PV, you won't have enough solar to charge 10kWh of battery, but what worked for us was topping up our 15kWh at the cheap overnight tariff. That, combined with a bit of sun on a good day, meant we used virtually no peak rate electricity over the winter months.

A quick back-of-the-envelope calculation suggests it isn't obvious I would break even.

At the moment I import about 2kWh overnight on average, probably around 1kWh at normal price (£0.34/kWh) and 1kWh at the lower price (£0.20p/kWh) between 02:00 and 05:00 (when I top-up my battery -- when my Flux export is setup, I'll charge it fully).
Let's assume I would have enough solar energy every day to cover that if I had an extra 5kWh of battery (which has been true every day but one or two in the past few weeks), and let's say I do that for 180 days per year.

In winter, let's say I charge an extra 5kWh of battery at the cheap £0.20p/kWh rate overnight, which saves me from buying the same amount at the normal rate at (£0.34/kWh), i.e. I save about £0.15/kWh for those 90%*5kWh each day, and I do that for 180 days a year.

That gives me a saving of:
saving = (1*0.34+1*0.20)x180 + (5*90%*0.15)*180 = £218.7 / year = £2187 over 10 years.
But a 5kWh battery would be about £2,500, with a warranty of 10 years. It may last longer, but it will also lose capacity over time.
So it doesn't feel like a good investment for me? (and batteries are not great for the environment either)
Does my logic and calculation make sense? have I missed anything here?

Maybe with a cheaper home-made it may be OK, but I'm not sure if we're allowed to use them in the UK, and I don't feel brave enough to do that anyway...

Also my hope is that when I change my car in a few years, electric cars can act as a battery for the home, which would make a bigger dedicated battery largely redundant.