Solar - 8kW Hybrid Inverter w/10kWh (upgraded to 20kWh in Sept. 2022) ESS/battery (not DIY)

[ExpatOilWorker]

39 minutes ago, Crossy said:

 

Good question, and one I thought about in the past. In the end we decided not to and our AVR is currently disconnected.

 

Just how low is "somewhat low", most hybrids are perfectly happy down to 185V or so at which point they disconnect from the grid and continue powering the loads from solar/batteries.

 

My main worry is that the AVR isn't designed with this mode in mind and the control system could become confused and do weird things.

 

Note that I didn't actually test this so what actually happens is unknown and is very likely variable with the type and manufacturer of the AVR.

 

If your supply is always very low you could consider a fixed boost auto-transformer, basically a manual voltage regulator, much lower cost than an AVR and no control system to become upset.

 

Personally, I wouldn't bother doing anything unless it becomes an actual issue.

Currently 167 V, but can at times drop below 160 V.

I already have the AVR, so my only worry is if there is any possibility the AVR and inverter will "fight" each other, possibly cause damage to either unit.

It is reassuring that the inverter simply just disconnect below 180 V and jumps to battery, but that creates a new problem. If the battery runs out, the inverter will switch to grid, potentially damaging pumps and other household equipment with low voltage. 

 

[Crossy]

Ouch!

 

If the inverter never goes into export, then I suspect things will be just fine as it's seen as just another load, but ...

 

I'm pretty sure the Deye can drive an external transfer switch, so you could run the AVR to that, and in the event of low battery the external ATS flips over and you get regulated power.

 

I would check with your solar installer what he recommends, then you have someone to blame if it all goes pear-shaped

 

[Muhendis]

3 hours ago, ExpatOilWorker said:

Currently 167 V, but can at times drop below 160 V.

Are you by any chance on a temporary supply?

If not then I would take those low voltage readings to PEA.

When we were on a temporary/construction supply we had similar problems with low voltage.

It was even worse if anyone decided to do a bit of welding in the village 1km away where our supply came from.

It was this that caused me to go solar.

We had to wait a few years until there was sufficient  customer demand for a transformer to be installed for supplying five houses.

[ExpatOilWorker]

3 hours ago, Muhendis said:

Are you by any chance on a temporary supply?

If not then I would take those low voltage readings to PEA.

When we were on a temporary/construction supply we had similar problems with low voltage.

It was even worse if anyone decided to do a bit of welding in the village 1km away where our supply came from.

It was this that caused me to go solar.

We had to wait a few years until there was sufficient  customer demand for a transformer to be installed for supplying five houses.

Good suggestions, but no and it is complicated. The generators work great and have good voltage, most of the time, but they each have about 50,000 running hours and we have had a few unscheduled shutdowns. 

PEA is the only alternative, but they are not interested is selling more power. PEA run their own generators, but since they by law has to sell at the government rate, they are making a loss on every kWh they produce. 

On top of that, my impedance is 1.25 ohms, which shave off another 5-10 V depending on load.

Solar 🌞 it is.

[Muhendis]

27 minutes ago, ExpatOilWorker said:

PEA run their own generators

Minor and quite possibly irrelevant correction.

Electricity is produced by EGAT. PEA is the provincial distributor and does not produce electricity.

I wasn't aware you were using generators.

How do you get the fuel for them up all those steps?

[Fruit Trader]

29 minutes ago, Muhendis said:

Electricity is produced by EGAT. PEA is the provincial distributor and does not produce electricity.

 

https://temca.pea.co.th/docs/TEMCA_PEA_MG_and_ESS.pdf

[Muhendis]

10 minutes ago, Fruit Trader said:

https://temca.pea.co.th/docs/TEMCA_PEA_MG_and_ESS.pdf

Thanks for that Fruit Trader.

This is new information for me.

It would seem I have been kept in the dark for the past three years.

[Fruit Trader]

28 minutes ago, Muhendis said:

This is new information for me.

 

New info for me also until the AI master heard me ask about PEA generators.

[Peterphuket]

5 hours ago, Muhendis said:

Are you by any chance on a temporary supply?

If not then I would take those low voltage readings to PEA.

When we were on a temporary/construction supply we had similar problems with low voltage.

It was even worse if anyone decided to do a bit of welding in the village 1km away where our supply came from.

It was this that caused me to go solar.

We had to wait a few years until there was sufficient  customer demand for a transformer to be installed for supplying five houses.

Funny, it was for me exactly the same reason to switch to solarcell.

Opposite where I live, across the road, is a car repair shop with a welding machine, and here too the voltage dropped to around 160 volts and also I bought an AVR of 20 KVA which is now needlessly standing.

I don't have any trouble with that anymore, including power failure, which occured on average once a week.

[ExpatOilWorker]

1 hour ago, Muhendis said:

Minor and quite possibly irrelevant correction.

Electricity is produced by EGAT. PEA is the provincial distributor and does not produce electricity.

I wasn't aware you were using generators.

How do you get the fuel for them up all those steps?

They burn through 6.5 million baht/month, but at least we have a 30,000 litre diesel carbon footprint 👣 every day.

 

[Crossy]

Our system is like this highly-simplified diagram.

 

The breaker between the inverter and home loads is usually off (turn it on if we need to charge the batteries from the grid).

 

Home loads are just our on-demand water heaters, keeps the meter moving in the right direction and limits strain on the inverters and batteries. If/when we get an electronic meter I'll shift the heaters to the load side and stuff PEA. 

 

If we lose the inverters then the transfer switch flips over and, after about a second, we get grid supply to the loads.

 

[ExpatOilWorker]

2 hours ago, Crossy said:

Our system is like this highly-simplified diagram.

 

The breaker between the inverter and home loads is usually off (turn it on if we need to charge the batteries from the grid).

 

Home loads are just our on-demand water heaters, keeps the meter moving in the right direction and limits strain on the inverters and batteries. If/when we get an electronic meter I'll shift the heaters to the load side and stuff PEA. 

 

If we lose the inverters then the transfer switch flips over and, after about a second, we get grid supply to the loads.

 

You already had the diesel generator and wiring up comes as second nature to you, but isn't the generator pretty much redundant?

It will have to be a long night, with ur 95 kWh totally drained and the grid down before you really need it. DEFCON 1 or you have a box of candles for the very end?

[Crossy]

No candles other than the orange religious ones, but we do have some oil lamps recovered from MiL's home when she died a few years back, they've been cleaned and polished and now live in the nick-naks cabinet. I'm sure they would actually work 

 

Madam sold the plot which was in a good location, and bought a similar sized plot a bit further from the road. She had enough $$$ left over to build a nice steel and Shera family home for remaining family. Smart cookie that lady (she married me) 🙂

 

We already had the genset of course and it seemed a waste not to use it. In reality it gets run once a month or so for testing and we push the energy into the batteries, I doubt we will ever actually need it in anger (famous last words?).

 

[ExpatOilWorker]

Just came back from Thai Solar System and should get a quotation in a few days.

They outsource the installation to local teams around the country, so it was not possible to iron out the finer details with the actual installation team, but the AVR can stay on the grid side.

@Crossy, does this look like professional work or are there some Somchai red flags?

Ignore the lead-acid batteries, it must be one of their more low budget installations.

 

[Crossy]

35 minutes ago, ExpatOilWorker said:

Just came back from Thai Solar System and should get a quotation in a few days.

They outsource the installation to local teams around the country, so it was not possible to iron out the finer details with the actual installation team, but the AVR can stay on the grid side.

@Crossy, does this look like professional work or are there some Somchai red flags?

Ignore the lead-acid batteries, it must be one of their more low budget installations.

 

 

Looks pretty OK to me.

 

Fuses, breakers, surge suppression, labelled terminals, ATS - Check! 🙂

 

[ExpatOilWorker]

On 3/17/2025 at 8:37 AM, Crossy said:

Ouch!

 

If the inverter never goes into export, then I suspect things will be just fine as it's seen as just another load, but ...

 

I'm pretty sure the Deye can drive an external transfer switch, so you could run the AVR to that, and in the event of low battery the external ATS flips over and you get regulated power.

 

I would check with your solar installer what he recommends, then you have someone to blame if it all goes pear-shaped

 

The sparky is now suggesting to have a CT (current transformer) installed on the export side of the inverter to avoid power feed back.

That sounds like a sensible solution. 

[KhunLA]

17 minutes ago, ExpatOilWorker said:

The sparky is now suggesting to have a CT (current transformer) installed on the export side of the inverter to avoid power feed back.

That sounds like a sensible solution. 

The inverter will actually have that built in, to control exporting.  We do have a cut off switch, that was already on the incoming grid line, before Solar was installed.  We have exporting disabled on the inverter.

[Crossy]

24 minutes ago, ExpatOilWorker said:

The sparky is now suggesting to have a CT (current transformer) installed on the export side of the inverter to avoid power feed back.

That sounds like a sensible solution. 

 

Doing it as drawn will give you ZERO battery backup if the grid is down. Grid off = House off.

 

Is that what you require?

 

[Crossy]

Do it like this.

 

 

"Home Loads" are not battery backed up (but they do use solar energy if the grid is up).

 

'Load" is battery backed up.

 

You can put the AVR at A or B. I would prefer A unless you know it's going to behave having a grid-sync inverter on its output.

 

Ignore the diesel if you don't have one. 

[ExpatOilWorker]

1 hour ago, Crossy said:

 

Doing it as drawn will give you ZERO battery backup if the grid is down. Grid off = House off.

 

Is that what you require?

 

Nope, that is absolutely not the idea.

Isn't the battery connected as per the red circle and the CT just preventing feed back on the export side of the inverter?

 

[ExpatOilWorker]

1 hour ago, Crossy said:

Do it like this.

 

 

"Home Loads" are not battery backed up (but they do use solar energy if the grid is up).

 

'Load" is battery backed up.

 

You can put the AVR at A or B. I would prefer A unless you know it's going to behave having a grid-sync inverter on its output.

 

Ignore the diesel if you don't have one. 

Take away the generator and home load, which is unique to your setup, and with the AVR in the B position isn't that exactly the same at the solar sparky's hand drawing?

You both have the CT in the same position. 

[lom]

1 hour ago, ExpatOilWorker said:

Take away the generator and home load, which is unique to your setup, and with the AVR in the B position isn't that exactly the same at the solar sparky's hand drawing?

You both have the CT in the same position. 

It is correct that you will need a CT to protect from export into the grid through the AVR which most likely won't like power flowing through it in opposite direction to which it normally operates.

Most inverters do have a UPS/EPS output for emergency light and equipment and that is the only active output from battery and PV when grid is not present. The inverters grid connection follows the frequency and voltage of the grid and will become inactive (island mode) when grid isn't present.

 

What brand of inverter did Thai Solar System quote to you? In general I'd say by looking at the picture that this is a very "el cheapo" Thai system. A PV combiner box combines 2 or more strings and contains fuses, breakers, and over voltage protection,  that is the upper part of the box in your picture. I would never mix DC (PV or Batt)  and AC (grid) in the same box! If the installer has to put everything in one box in order to keep the price down or his profit up then I would go somewhere else. Using lead-acid batteries is also a sign of made in Thailand for Thais..

[ExpatOilWorker]

37 minutes ago, lom said:

It is correct that you will need a CT to protect from export into the grid through the AVR which most likely won't like power flowing through it in opposite direction to which it normally operates.

Most inverters do have a UPS/EPS output for emergency light and equipment and that is the only active output from battery and PV when grid is not present. The inverters grid connection follows the frequency and voltage of the grid and will become inactive (island mode) when grid isn't present.

 

What brand of inverter did Thai Solar System quote to you? In general I'd say by looking at the picture that this is a very "el cheapo" Thai system. A PV combiner box combines 2 or more strings and contains fuses, breakers, and over voltage protection,  that is the upper part of the box in your picture. I would never mix DC (PV or Batt)  and AC (grid) in the same box! If the installer has to put everything in one box in order to keep the price down or his profit up then I would go somewhere else. Using lead-acid batteries is also a sign of made in Thailand for Thais..

The plan is never to export, as others have tried and it damaged control boards at the generator. 

Thai Solar System will quote a 10 kW Deye inverter. 

Are you saying the inverter can only support a small load when the grid is down?

That is bad news, as we have frequent power outages and I was planning to run the whole house, around 3,000 W, from the batteries. Is that really not possible?

[lom]

3 hours ago, ExpatOilWorker said:

Are you saying the inverter can only support a small load when the grid is down?

That is bad news, as we have frequent power outages and I was planning to run the whole house, around 3,000 W, from the batteries. Is that really not possible?

It is possible, the EPS output from a Deye inverter can supply your whole house if you want, not only the essential consumers.

It can supply up to the limit of the inverter (in your case 10KW) from PV and/or battery and if you don't have enough power from PV and or battery then it will take the missing part from the grid through Deye's grid connector (grid-assist).

 

You will not even need a CT if you run everything on the EPS output, there is a setting for it:

"Zero Export To Load: Hybrid inverter will only provide power to the backup load connected. The hybrid inverter will neither provide power to the home load nor sell power to grid. The built-in CT will detect power flowing back to the grid and will reduce the power of the inverter only to supply the local load and charge the battery."