Advice needed to choose a solar inverter

[beddhist]

Hi All,

 

This is kind of a follow-up on this old topic:

@Crossy, do you mind updating us what you bought in the end?

 

Our story: we will soon start building our house in Central Thailand. We have a storage container on site and I bought 14 x 325W Jinko panels and installed them on top of it. I have been looking everywhere for a suitable inverter, but every one I looked at didn't quite fit the bill. One of the problems is that you can slice and dice a 17-panel array only two ways: 7x2 and 2x7, unless you have an inverter with two inputs (reasonably common, it seems).

 

A little detail on the panels:

 

ModuleTypeJKM325PP-72        STC NOCT
MaximumPower(Pmax)         325Wp  241Wp
MaximumPowerVoltage(Vmp)  37.6V  35.0V
MaximumPowerCurrent(Imp)  8.66A  6.89A
Open-circuitVoltage(Voc)   46.7V  43.3V
Short-circuitCurrent(Isc)  9.10A  7.40A

 

I guess that makes the PV max. total about 4.5 kW

 

This is my wish list for the inverter:

1. Easy control whether export to grid or not.
2. Batteries optional (I may add them later)
3. Keeps going when the grid goes down during the day.
4. From a reputable manufacturer with a decent warranty
5. PEA approved

 

The only one that seems to tick all the boxes is this one, made in Thailand: Leonics Apollo S-219C ia

Nobody advertises them online and the only useful link seemed to be one to an event where the Leonics MD donated 2 of these, value 400 kB. That's about 5 times what I intended to spend.

 

Any and all advice welcome.

 

Thanks,

Peter.

[sometimewoodworker]

1 hour ago, beddhist said:

• Easy control whether export to grid or not.
• Batteries optional (I may add them later)
• Keeps going when the grid goes down during the day.
• From a reputable manufacturer with a decent warranty
• PEA approved

AFIK the information under is correct 

 

1 ) probably not a problem 

2) some may have that option but it's expensive.

3) only possible if you have batteries, as they require a grid connection for syncing unless you are off grid.

4) Humm you can get a guarantee but will it be worth anything? I don't know

5) why? you are unlikely to get official PEA approval to connect to the grid.

[Crossy]

In the end we didn't do anything, finances changed (had to buy a new car) and the project was shelved.

 

@sometimewoodworker PEA have certainly allowed grid-tie in the past, a number of members have approved systems both as part of the My Solar Roof initiative and independent of it with simple net-metering, so an approved inverter is certainly a possibility. Both PEA and MEA have (or at least had) lists online of approved inverters.

 

Here's a thread on approved grid-tie with net-metering

 

 

Now of course things may have changed, but it's doubtful there's enough connected solar capacity to cause grid stability issues.

 

It does seem odd that we are now getting reports of the PEA not permitting grid tie. What we need are reports from other parts of the country.

 

EDIT

Here's the list dated 12-Dec-2018 https://www.pea.co.th/Portals/0/Document/vspp/PEA_Inverter_list_12-Dec-18.pdf good (ish) news for @beddhist is that the Apollo S219C is on the list.

 

Have a look here for PEA policy on VSPP (Very Small Power Producers) https://www.pea.co.th/เกี่ยวกับเรา/การดำเนินการตามนโยบายรัฐบาล works ok with Google Translate.

 

I've not read all of the above, but since they published a recent list of inverters it's evident that (at least national) PEA policy is alive and reasonably well.

 

[Crossy]

It's worth having a look at these two forms which I got a couple of years back to apply for approval for grid-tie solar.

 

8 ________ _ 4.2 _____ ___ 6 __ FINAL.pdf

2015-Combine Apply to MEA PEA Feb 8(1) (1).pdf

 

May be some pointers within, of course it's all in Thai.

[beddhist]

Thank you both for your input. More reading to do... ????

[beddhist]

We have just spoken with PEA and were told that we must tell them if we install a solar system. Back feeding is not allowed, because it endangers the linesmen.

[BritManToo]

7 minutes ago, beddhist said:

Back feeding is not allowed, because it endangers the linesmen.

Modern grid-tied inverters stop feeding back when the line voltage stops.

PEA are just interested in profits, and will tell you any BS to stop their profits falling.

Your mistake is asking permission.

[Crossy]

12 minutes ago, beddhist said:

Back feeding is not allowed, because it endangers the linesmen.

Did you phone or visit (and talk to the actual engineers)?

 

Any decent (certainly all approved, I'd hazard all domestic level) grid-tie inverter will have island protection which kills the grid connection if the supply fails (so no hazard to the linemen), if you have a hybrid (like the Apollo S219C) it will continue supplying your side of the inverter.

 

So what do you have to do to "tell" them?

 

You should be able to set up the inverter to not export and to dump excess power into the batteries which you can then use at night, not ideal as you use up battery life.

 

PEA do seem to be putting up obstacles to domestic solar, despite the government wanting to harness green energy.

[beddhist]

Ok, so we eliminate point 5 and now where do I start? So much choice!

 

I think I'll make sure that the inverter can play with LiFePO4 batteries and when they have come down far enough we will buy them. Then they make 0 profit from us.

[BritManToo]

22 hours ago, beddhist said:

14 x 325W Jinko panels and installed them on top of it. I have been looking everywhere for a suitable inverter, but every one I looked at didn't quite fit the bill. One of the problems is that you can slice and dice a 17-panel array only two ways: 7x2 and 2x7, unless you have an inverter with two inputs (reasonably common, it seems).

Distributed energy resources is the way to go.

600w grid tie inverters that plug into power sockets (around 5kbht each) .......... now all you need is 7 spare sockets in your house. No batteries required, no special wiring required.

[beddhist]

We visited and had to wait for the responsible person to arrive. He was either the big boss or an engineer.

 

Yes, I know about grid monitoring and that most inverters simply shut down when the grid does. The rest of the world functions like that...

[Crossy]

10 minutes ago, beddhist said:

Ok, so we eliminate point 5 and now where do I start?

Assuming you still want a hybrid rather than pure off-grid then the Infinisolar in my linked thread is still a good fit (and can definitely be set to not export and work with LiFePO4 batteries).

[beddhist]

Indeed, that one is on my radar. However, I'm a bit wary importing one, as I don't know how much excise I will be charged.

 

Thanks to all.

Peter.

[beddhist]

I'm still researching my options, but I have a technical question:

 

From the panel specs:

Max power voltage Vmp 37.6V

Max power current Imp 8.66A

Open circuit voltage  46.7V

Max system voltage 1000VDC

Max fuse rating 20A

 

If I put 7 in series Voc is 326.9V, well within the system limit for the panels. I need an inverter that can handle this voltage.

However, if my choice of inverter stops me from doing that (many inverters have a Voc of 145V) I will have to wire 7 in parallel.

Imp will be 66.2A. Does that mean that every panel will require its own fuse? It will also require very thick cables.

 

Thanks again,

Peter.

[beddhist]

Taking into consideration my 7x2 array I have come up with a modified feature list:

 

1. Easy control whether export to grid or not.
2. Batteries optional (I may add them later)
3. Keeps going when the grid goes down during the day.
4. From a reputable manufacturer with a decent warranty
5. PEA approved
6. Voc > 327V

 

After combing the net for the last 10 days I have found three that seem to fit the bill:

 

MPP Hybrid V2

But it's only 3kW, so we need two of them

 

Easun IGrid SV II

and again, we would have to use 2 of them

 

and

 

Must PH1000 series

This looks like a perfect fit.

 

The only problem: I can't find any vendors in Thailand so far. However, Must Power have been quick to reply to my queries and offered to buy direct from them. I have also emailed OffGridThailand, who claim to be official resellers.

 

Cheers,

Peter.

[shaemus]

On 1/5/2019 at 7:11 PM, beddhist said:

I'm still researching my options, but I have a technical question:

 

From the panel specs:

Max power voltage Vmp 37.6V

Max power current Imp 8.66A

Open circuit voltage  46.7V

Max system voltage 1000VDC

Max fuse rating 20A

 

If I put 7 in series Voc is 326.9V, well within the system limit for the panels. I need an inverter that can handle this voltage.

However, if my choice of inverter stops me from doing that (many inverters have a Voc of 145V) I will have to wire 7 in parallel.

Imp will be 66.2A. Does that mean that every panel will require its own fuse? It will also require very thick cables.

 

Thanks again,

Peter.

Hi Mate,

 

I am a qualified electrician and ex solar installer & designer In Australia.

 

When wiring your panels in series the amps don't add up as well just the voltage. In Parallel its the opposite 

 

the specs of your inverter will tell you the maximum voltage allowable per mppt. Generally the manufacturers have some software that allows you to design your system.

 

There are quite a few solar shops popping up now so getting cable and dc isolators isn't so much of a drama.

 

the cabling for solar (rooftop) it normally a tinned copper very fine flex. it can be bought in pre teminated lengths or on the drum. normally 4mm, then 6 then 10mm.

 

As i am sure you are well aware the design need to take into account azziumth and pitch. these are quite important factors in determining the output % from your panels.

 

thanks 

 

Shaemus

 

 

 

 

[beddhist]

Thanks for the pointers, @shaemus. I know the basics, that's why I wanted to avoid a low-V configuration, which would have forced me to high A and thick cables.

 

In the end I ordered 2 Easun iGrid SV II 3 kW inverters. They are now in Customs. They do everything I wanted (I hope), except I may have to install batteries to run them in parallel. Easun aren't saying that, but MPP sell an identical one and they make that very clear. The operators manuals are identical to the last full stop. I think they are made by Voltronics.

 

I haven't seen any solar shops in our area, nor any rooftop installations. I think Central T is quite backward technologically, except there is excellent fibre internet, just not to our place (yet). If all else fails, all of what I need now is available online.

 

Regards,

Peter.

[shaemus]

1 hour ago, beddhist said:

Thanks for the pointers, @shaemus. I know the basics, that's why I wanted to avoid a low-V configuration, which would have forced me to high A and thick cables.

 

In the end I ordered 2 Easun iGrid SV II 3 kW inverters. They are now in Customs. They do everything I wanted (I hope), except I may have to install batteries to run them in parallel. Easun aren't saying that, but MPP sell an identical one and they make that very clear. The operators manuals are identical to the last full stop. I think they are made by Voltronics.

 

I haven't seen any solar shops in our area, nor any rooftop installations. I think Central T is quite backward technologically, except there is excellent fibre internet, just not to our place (yet). If all else fails, all of what I need now is available online.

 

Regards,

Peter.

You need to ensure that your string voltage is within the limits of the inverter! and i would aim to the higher end.

 

the info i found on your inverter was not detailed and didn't show the max input A and only has 1 MPPT. which means you will have to parallel up the strings before the inverter.

 

I am not sure who is going to install your System. But i will warn you that They will need to be a proficient electrician or you will need to be a VERY competent D.I.Y.er 

 

i would suggest that you buy your self a solar marshalling Junction box, from aliexpress to save your self a load of hassles with a multi string array you should really be able to isolate each string before it is paralleled down .

 

there are plenty of solar items available on Lazada :https://www.lazada.co.th/catalog/?q=solar+cable&_keyori=ss&from=input&spm=a2o4m.searchlist.search.go.561a3a3cnYrlPJ

 

you can't get away from the fire risk and also different the water proofing issue of penetrating your roof, you should really have a very good look if you haven;t allready at the bad installs. Also the wind loading of your roof need to be considered. i am not sure where you live but you dont really want your roof ripped of either by a poorly positioned array install or exacerbate the problems with a poor roof 

 

if you want to PM me and have a chat please do.

 

 

 

 

[beddhist]

17 hours ago, shaemus said:

You need to ensure that your string voltage is within the limits of the inverter! and i would aim to the higher end.

That's exactly what I was aiming for and why there was a very limited choice, limited as in zero in Thailand.

 

17 hours ago, shaemus said:

the info i found on your inverter was not detailed and didn't show the max input A and only has 1 MPPT. which means you will have to parallel up the strings before the inverter.

The details are here: http://www.easunpower.com/content/?991.html

I had to order two inverters to handle the 4.5 kW from the panels, so two strings it is.

 

17 hours ago, shaemus said:

I am not sure who is going to install your System. But i will warn you that They will need to be a proficient electrician or you will need to be a VERY competent D.I.Y.er 

I am and the panels have been up for a few weeks:

 

I have wired 1.5 houses. Does that qualify?

 

17 hours ago, shaemus said:

i would suggest that you buy your self a solar marshalling Junction box, from aliexpress to save your self a load of hassles with a multi string array you should really be able to isolate each string before it is paralleled down .

Hmm, neither Google nor Ali can find this, but Ali offers me lots of junction boxes for low-powered panels. Anyway, it looks like I won't need to join the strings.

 

17 hours ago, shaemus said:

you can't get away from the fire risk and also different the water proofing issue of penetrating your roof, you

Fire from...? Luckily, I don't have to worry about the roof or wind. 5 cm square section pipes bolted on with 10 mm bolts should hold.

 

I will have to learn about how to attach it to a roof later, when the system is expanded.

 

17 hours ago, shaemus said:

if you want to PM me and have a chat please do.

Thank you, very kind. But if we talk here then others can learn, too. ????

 

Regards,

Peter.

[beddhist]

Update for anyone thinking of importing inverters: duty and tax on the total value (incl. freight) came to 23.4%, plus 400B payable up front to Transpeed for processing, plus 1084B for EMS Bkk to the nearest PO. No home delivery for 25kg parcels.

 

There is one thing worrying me, though: lightning. Do I need a lightning rod and how do I go about installing it? I know nothing about it, other than that it needs to be tall, thick and well grounded.

[Crossy]

A big tall rod, probably not (although it does look very open and flat), plenty of surge suppression most definitely on both the DC and AC sides. Does the manual for the inverter tell you anything useful?

 

Have a look at ginboy2's thread I linked to earlier, several photos of his installation showing the general arrangement of breakers and suppression.

 

By the way, please make sure that container is solidly grounded, we've had several site workers killed over the years when container site offices became live.

[beddhist]

Update: the post did deliver the boxes today, despite what they told us on the phone. I have installed the parallel communication circuit board and have struck the first case of the manual not quite describing what I have got. Fiddly, but not difficult in the end.

 

Yes, our site and until the horizon our area is flat. There are currently no trees on our 2 ha, so if lightning is looking for a way to ground it will be either our car port roof or the frames of the solar panels. I'm worried if it hits the panel frames it will go right through and fry everything. Hence me thinking about a lightning rod.

 

That must have been an awful experience with these accidents. The CU has a proper grounding connection and RCBO. The container is welded to the rebar of the columns on which it sits. Is that sufficient, or does the cement insulate it too much from the soil?

[Crossy]

10 hours ago, beddhist said:

The container is welded to the rebar of the columns on which it sits. Is that sufficient, or does the cement insulate it too much from the soil?

That will actually be a very good ground (https://en.wikipedia.org/wiki/Ufer_ground) our house roof steel is actually a better ground than the 2.5m rod I put in to comply with the local regs 

 

With a large open area lightning is indeed a worry (and it doesnt always hit the highest point). You could put in some steel scaffolding tubes with decent grounds at the bottom and Franklin rods (pointy bits) on the top but there's no warranty implied or inferred.

 

 

 

[beddhist]

Very interesting read about the Ufer grounding. Funny thing is, when we went with our builder to buy some electrical stuff I showed him the latest requirements. He just shrugged and bought a 1m copper rod instead.

 

Perhaps I just wait until we get Tot to put up the aerial for wireless internet. It's taller that a 2 storey building. I'll connect the pole to ground.

 

I had another read of ginboy2's topic and noticed that there are 2 different surge protectors used. Where and what do I buy for the DC side?

 

Thanks again! ????

[shaemus]

On 2/5/2019 at 8:51 PM, beddhist said:

Update for anyone thinking of importing inverters: duty and tax on the total value (incl. freight) came to 23.4%, plus 400B payable up front to Transpeed for processing, plus 1084B for EMS Bkk to the nearest PO. No home delivery for 25kg parcels.

 

There is one thing worrying me, though: lightning. Do I need a lightning rod and how do I go about installing it? I know nothing about it, other than that it needs to be tall, thick and well grounded.

you can buy earthing clips that fit underneath the panels. then from there all the metal should be bonded together (6mm) copper cable with lugs then from there to your main earth point. i would be sticking in the largest earth rod you can find .

 

If you have a global house shop near you, they have an extensive range of Lightning rods etc

 

SPD 's  (surge protection devices) are becoming more common, In the 18th edition in the UK they are now mandatory. There is plenty available in thailand you can buy specific lightning protection SPD and there are a few types, class i, class ii, 

 

I was going to do you a design for your system but the Inverter wasn't listed in my Software  ( PV SOL) and the info was poor that i found on the model so i am not sure exactly where you inverter is designed to be used, Does it have CE markings?

 

If you haven't purchased your consumer unit yet for your Container, i would recommend a Siemens metal clad unit. you can buy them empty, or full of CB's either with a DP main swithch or an RCD. You can also buy RCBO's (single pole) you need to leave room for your solar feed as well.

 

Good luck with your Inverter

[beddhist]

It turns out that EMS did deliver to our home. My wife was too pessimistic.

 

Thanks again for all the tips, Shaemus.

 

The panels are directly bolted onto galvanised steel using stainless bolts. Is that sufficient earthing? I guess the weak point in that earth connection will be how the frame is bolted onto the container (painted).

 

I can't find CE marks in the manual, in fact nothing at all about any conformity. Must be aimed at the Asian market...

 

Wiring the panels should be straight forward, 7 in series per inverter. The interesting part will be to splice it into the mains feed, 20m of trenching away on a power pole. I'm still not sure whether we do have to run separate cables in separate ducts underground. That would be 4 ducts.

 

The manual says that the inverter must be wall mounted on a non-flammable surface. The installs I have seen so far were usually mounted onto chip board, which is obviously the easiest to work with. Is this a no-no?

 

Kind regards,

Peter.