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Solar power, can it be done DIY?


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1 minute ago, Crossy said:

 

Yeah, they go under the panel, you need one per panel ???? 

 

If you have space it's cheaper to add more panels.

So something like the Micro Inverters (one per panel) but without the converting DC -> AC part ????

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1 minute ago, MJCM said:

So something like the Micro Inverters (one per panel) but without the converting DC -> AC part ????

 

Yeah, they are a sort of local MPPT.

 

I have zero experience of the beasts so can't really comment on just how well they work.

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On 8/6/2022 at 12:43 PM, Crossy said:

With a 50m gap you can safely run the remote stuff as a TT island with just a local ground rod and no N-E bond.

 

Definitely tie all your structure to the rod, our inverters etc are actually connected to the structure, there is a rod too (also connected to the structural steel) but in reality the structure is already a better ground than the rod.

 

Nice meaty surge arrestors at least 40/80kA preferably 60/100kA and don't forget the DC side if you have string inverters (micro inverters I wouldn't bother with DC arrestors).

 

I have been trawling AliExpress and can find loads of 20KA-40KA DC surge arrestors and some 30KA-60KA but nothing bigger. Do you have any links from earlier purchases to some of the "meatier" ones?

 

Many of the surge arrestors come with different rated voltages 500V/600V/800V/1000V, normally at the same price. Is this one of those situations where bigger is better, or should I buy a smaller one?

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3 minutes ago, Sophon said:

I have been trawling AliExpress and can find loads of 20KA-40KA DC surge arrestors and some 30KA-60KA but nothing bigger. Do you have any links from earlier purchases to some of the "meatier" ones?

 

Many of the surge arrestors come with different rated voltages 500V/600V/800V/1000V, normally at the same price. Is this one of those situations where bigger is better, or should I buy a smaller one?

You don't need them.

I've been running for 2+ years now without problems or surge protection.

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15 minutes ago, Sophon said:

Many of the surge arrestors come with different rated voltages 500V/600V/800V/1000V, normally at the same price. Is this one of those situations where bigger is better, or should I buy a smaller one?

 

You match your DC suppressor voltage to the system voltage. I would go for a suppressor of system maximum voltage +15 to +30%.

 

AC suppressors should be 275V working.

 

Surge suppression is one of those things you don't need, until you do!

 

With a hybrid inverter worth 45k Baht I'm happy spending a few k on surge suppression. And ours have definitely triggered to the point that they wore enough for the inverter to complain about earth leakage.

 

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28 minutes ago, Crossy said:

 

You match your DC suppressor voltage to the system voltage. I would go for a suppressor of system maximum voltage +15 to +30%.

 

AC suppressors should be 275V working.

 

Surge suppression is one of those things you don't need, until you do!

 

With a hybrid inverter worth 45k Baht I'm happy spending a few k on surge suppression. And ours have definitely triggered to the point that they wore enough for the inverter to complain about earth leakage.

 

That makes it even harder to find a suitable suppressor. 95% of what I find on AliExpress is rated for 500V plus. With my two strings of six panels the voltage will be in the 230V region. I did find this suppressor:

image.png.273281229a184270591d14dfc1f19be0.png

 

But that is rated for 250V, which would be below your recommended plus 15-30% range. And as most, it's only 20-40KA.

 

How effective (or not) would a 500V rated suppressor be in protecting your solar panels running at around 230V? Would it not be worth it to install it?

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What's the maximum solar input voltage of your inverter?? Just go over that (there will be internal protection anyway), I expect the 500V unit would do a fine job. 20-40kA would be fine on the panel inputs, it's not like you have massive cable runs picking up the crud.

 

The 15-30% is just a guideline so you don't go too low. MOVs do wear, the trigger voltage gets a little lower each time they fire, so starting too low just means that you'll replace them sooner. 

 

We have 1000V units on our 600V inputs as the 800V units were out of stock.

 

It's always worth installing suppression.

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16 hours ago, Crossy said:

What's the maximum solar input voltage of your inverter?? Just go over that (there will be internal protection anyway), I expect the 500V unit would do a fine job. 20-40kA would be fine on the panel inputs, it's not like you have massive cable runs picking up the crud.

 

The 15-30% is just a guideline so you don't go too low. MOVs do wear, the trigger voltage gets a little lower each time they fire, so starting too low just means that you'll replace them sooner. 

 

We have 1000V units on our 600V inputs as the 800V units were out of stock.

 

It's always worth installing suppression.

I don't actually have an inverter yet, but the most likely candidates I have been looking at have a max. PV array Voc of 500VDC.

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1 minute ago, Sophon said:

I don't actually have an inverter yet, but the most likely candidates I have been looking at have a max. PV array Voc of 500VDC.

 

I'd go with the 800V unit then.

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Any thoughts on this supposedly Hybrid on-grid inverter:

image.png.9a5c32b505c7afbfdce7c51dd830ba35.png

 

The product description specifically claims that the inverter can export to the grid. I still think that I will probably start out with an off-grid hybrid inverter, but for the price it's tempting.

 

I know the sellers history is questionable, only on Lazada for four months and only a few sales (none of this item). But the same seller has also been on Shopee for 20 months, the description of the inverter is just better on the Lazada link. There are also other sellers on Shopee of the same inverter but under a different brand, such as this one:
image.png.210fac8dcddc2a3aa991d27ae7e0b2d4.png

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2 hours ago, Sophon said:

Any thoughts on this supposedly Hybrid on-grid inverter:

image.png.9a5c32b505c7afbfdce7c51dd830ba35.png

 

The product description specifically claims that the inverter can export to the grid. I still think that I will probably start out with an off-grid hybrid inverter, but for the price it's tempting.

 

I know the sellers history is questionable, only on Lazada for four months and only a few sales (none of this item). But the same seller has also been on Shopee for 20 months, the description of the inverter is just better on the Lazada link. There are also other sellers on Shopee of the same inverter but under a different brand, such as this one:
image.png.210fac8dcddc2a3aa991d27ae7e0b2d4.png

Here is a nice deal from same company

 

Pink

easun.jpg

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17 hours ago, Crossy said:

That it has a CT suggests that it can export at least some energy. Could be a good buy at the price.

 

Even though it claims to be an hybrid on-grid (actually off/on-grid) inverter, it doesn't seem to have to load split into essential/non-essential. I can only see one set of out-put ports:

 

image.png.7788889b5277c628f38648e8236095fa.png

 

So it would essentially be wired up like an hybrid off-grid inverter, which is good for me.

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A question for those who already have solar panels.

 

On days like we have had this week, where it is overcast and raining the whole day, do you get any production at all from your panels? If you do, how much compared to the maximum capacity of your panels? 

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43 minutes ago, Sophon said:

A question for those who already have solar panels.

 

On days like we have had this week, where it is overcast and raining the whole day, do you get any production at all from your panels? If you do, how much compared to the maximum capacity of your panels? 

Yep, my small scale system still seems to be able to produce something on 'bad' days like you have described, which is better than nothing.

 

My system comprising 4 x 415W half-cut monos should in theory should be capable of producing 1.6kWh under ideal (laboratory) conditions,.  However, because of potential efficiency losses I'm lucky to get 75% of the potential output, or 1.2kWh, even on a good sunny day.  Under reasonably good sunshine days I would normally hope to achieve approximately 7 units per day.

 

This month, almost every day, it has been overcast for most of the day, with occasional heavy downpours and thunder.  The monthly output graph below shows that the system has been averaging about 5.5 units per day, which is about 75% of normal production on a good month.

Monthly.jpg.ffa54cda4470921de1d9b06ad27e9961.jpg

 

The worse day this month was the on 1st as shown in the above graph when it was very overcast all day, and we had a very heavy downpour and thunder storm which lasted several hours as can be seen by the big dip in the production graph below.  Total production that day was only 2.7kW which as mentioned is still better than nought.

01_08.jpg.998abea0f79fe59c1ce52bfa19e31028.jpg

 

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So, the seller was nice enough to email me the manual for the Powland hybrid inverter and it definitely does export to the grid:

image.png.4d1f1e930293a6fe492f27ac4949dc1a.png

 

This is what the manual says about the Inverters different modes:

Quote

Working mode
AC:(default)

AC will provide power to the loads as the first
priority, solar charging the battery. When solar energy is
insufficient, AC and solar energy charge the battery at the
same time. When AC is unavailable, it will be powered by
solar energy or batteries.

 

Solar:

Solar energy provides power to the loads as the
first priority. When the solar energy is sufficient, the extra
energy will charges the battery. When solar energy is
insufficient for load, batteries and solar will supply power
the loads at the same time. When solar energy and
batteries are insufficient or solar energy is unavailable,
AC power to the loads and charge the battery at the
same time.

 

Battery:

Battery provides power to the loads as the first
priority. AC provides power to the loads when battery
voltage drop to low-level warning voltage or setting point,
and the AC power will charge the battery. When
the battery is fully charged, battery provides power to the
loads again.


AC+PV:

Solar energy provides power to the loads as the
first priority. If solar energy is not sufficient to power all
loads, AC energy will supply power to the loads at the
same time.

AC mode (default):

In this mode it sounds like the PVs and battery are only used as a back-up system, and the grid is used day to day to power your load. This would provide very little in the way of savings on your PEA bill.

 

Solar mode:
Sounds like the mode to be in, and it all sounds fine until the last paragraph:
"When solar energy and batteries are insufficient or solar energy is unavailable,
AC power to the loads and charge the battery at the same time."

 

If this is to be taken litterally, then at night or when it's raining your load will be powered by the grid, and the grid will also charge your batteries (if not full). That is not what I would want.

 

In the absence of solar, what I would want is for the load to be powered by the batteries for as long as they hold sufficient charge, and only when the batteries are expended would I want the grid to power my load. And I would also not want the grid to charge the batteries, that would result in them being full when the sun comes up, and there would be nowhere for excess energy from the PV panels to be stored. 

 

Battery mode:
No mention of PV panels in this mode, and I don't really understand the point of this mode.

 

AC+PV mode:

No mention of batteries in this mode. According to the manual, this is the mode you have to be in, if you want to export excess energy to the grid. Sounds like a mode for a system without batteries, where you use the grid for storage. I understand from what I have read that in a utility company authorized system with export to the grid, you will not have power when the grid is down even if your PV panels are producing energy, so maybe it makes sense not to have batteries.

 

Are these modes (especially the Solar mode) normal? The Solar mode doesn't make much sense to me, but maybe something has been lost in translation.

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1 hour ago, Sophon said:

If this is to be taken litterally, then at night or when it's raining your load will be powered by the grid, and the grid will also charge your batteries (if not full). That is not what I would want.

 

Yeah, that's how I would read it too, but it does follow "When solar energy and batteries are insufficient" - zero solar is also "insufficient". Does it allow you to set the maximum grid charge current (set to the minimum)?

 

It might be worth asking the seller if he knows how it behaves at night.

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32 minutes ago, Crossy said:

 

Yeah, that's how I would read it too, but it does follow "When solar energy and batteries are insufficient" - zero solar is also "insufficient". Does it allow you to set the maximum grid charge current (set to the minimum)?

 

It might be worth asking the seller if he knows how it behaves at night.

Yes, it does but I don't see how that would help:
 

Quote

Charge current
Total Charge:
(default 60A)setting range is 10A to 90A,
the increment or decrement is 10A per click.
Note:Total Charge=Solar Charging Current+Utility Charging current

 

AC Charge:
( default 30A)setting range is 0A to 60A,
the increment or decrement is 10A per click.
Note: when the AC charging current is set to ‘0A’,if PV,battery and Utility exsist at the same time ,the PV will only charge the battery and the load is powered by
utility and the grid-tie function is not available.

So, if I set the grid charging max. to 0A to prevent PEA from filling up my battery, then my load will be powered by grid power.

 

From reading the description of the different modes, I get the impression that they are going for maximum supply security rather than autonomy and cost savings.

 

I will try to ask the seller, but the English ability of Lazada sellers can be a bit hit and miss and I doubt that the autotranslate will help.

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57 minutes ago, Crossy said:

You could try the manufacturer, many of the Chinese makers actually have pretty good support.

 

Yeah, I already asked the seller by email and just 7 minutes later I received this reply:
 

Quote

Don't worry my dear, these two setting options of the product can solve the problem

image.png.65c81f63cbf4130ea775d025da58b0e8.png

 

image.png.e7b4ce801a65f90aa77e8786a80b5cba.png

 

These settings were not in the user manual they sent me, so there must be a second set-up manuel as well. I have asked them to send me that one too.

 

I am pretty sure that I have been communicating with someone in China, and I must say that I am very impressed. They really seem to know what they are talking about and reply very quickly. 

 

I am very tempted to go for this inverter.

 

Update: Just 10 minutes after sending my second email, I received the user manual with the additional settings.

Edited by Sophon
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So what do you guys use to isolate your system from the grid, so you can work safely without having to have the wires pulled at the meter?

 

I could use a MCB, but then I would have the same problem if the MCB developed a fault, so I would like something bulletproof. The old fashioned Chang knife switch would do the job, but I wouldn't mind something a little less medieval looking.

 

Edit: The knife switch or whatever would be followed by a MCB, so it's not essential to have overcurrent protection in the device.

Edited by Sophon
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9 minutes ago, Sophon said:

So what do you guys use to isolate your system from the grid, so you can work safely without having to have the wires pulled at the meter?

 

I could use a MCB, but then I would have the same problem if the MCB developed a fault, so I would like something bulletproof. The old fashioned Chang knife switch would do the job, but I wouldn't mind something a little less medieval looking.

 

Edit: The knife switch or whatever would be followed by a MCB, so it's not essential to have overcurrent protection in the device.

Inverter settings will take care of export/import to/from grid.  Just need to pay attention, if export to the grid.   I also have a breaker between the meter and house.  Of course there's the grid supply breaker on the 'breaker box/panel' in the house.

Edited by KhunLA
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46 minutes ago, KhunLA said:

Inverter settings will take care of export/import to/from grid.  Just need to pay attention, if export to the grid.   I also have a breaker between the meter and house.  Of course there's the grid supply breaker on the 'breaker box/panel' in the house.

Yes, I understand that but there is always a point where the power from PEA is first connected to your system. If we take my not yet finished plans for my solar installation:

image.png.69835a974aa8e8c643ec2a738e5c4910.png

 

There is a MCB breaker on the incoming line from PEA (small blue box). If for instance the surge protector for the grid input blows, I can turn that breaker off to change to a new surge protection device. But if the incoming MCB breaker develops a fault, there is no way to change that breaker without having to work with live wires (other than getting the PEA to pull the wires at the meter). And there is nothing I can do in the inverter settings to change that.  

 

That's why I want to move the MCB to the main box, and install a bulletproof isolation switch at the small box at the power pole. Something like the good old Chang knife switch:
image.png.4f4dde55a2e123b5df8beb433e8f6a5e.png

 

But I am open to better suggestions.

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8 hours ago, Sophon said:

Anything I am missing?

 

I reckon you're good to go, hopefully I've not missed the fatal flaw.

 

It always takes me a few minutes to interpret these "graphical" diagrams, I can interpret an ISO standard drawing quickly but the graphics suffer from "too much information" which confuses my aging and pre-programmed brain.

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5 hours ago, Crossy said:

 

I reckon you're good to go, hopefully I've not missed the fatal flaw.

 

It always takes me a few minutes to interpret these "graphical" diagrams, I can interpret an ISO standard drawing quickly but the graphics suffer from "too much information" which confuses my aging and pre-programmed brain.

Because I don't have your knowledge about electrics, I am the opposite. In order for me to visualize how things should be put together, i need to map out the exact connections. Putting pen to paper (or electrons to display) also helps me think through what equipment I will need and where problems may arise.

 

Producing the diagram also gives me confidence that I have thought about everything, and that I will actually be able to do this myself. I think my biggest challenge will not come when putting everything together, but if/when something suddenly goes wrong six months down the road.

 

Thank you for taking the time to review my plans.

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When it says this in the specifications for an inverter;

image.png.f04b95e1a82ee6d752e6402a6eb395ef.png

 

does that mean that the inverter can operate at 110% of rated capacity for reasonable periods? So a 5.5kW inverter could operate at 6kW during, for instance a 15 minutes shower, when both pump and shower heater is on?

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54 minutes ago, Sophon said:

When it says this in the specifications for an inverter;

image.png.f04b95e1a82ee6d752e6402a6eb395ef.png

 

does that mean that the inverter can operate at 110% of rated capacity for reasonable periods? So a 5.5kW inverter could operate at 6kW during, for instance a 15 minutes shower, when both pump and shower heater is on?

 

Sort of.

 

The spec. you show says that if you run your inverter between 110% and 150% full load it will shut down after 10 seconds. Exceed 150% full load and it shuts down after 5 seconds. The idea being that it can support brief overloads such as motor stating surges.

 

What happens between 100% and 110% is indeterminate, it may or may not shut down after 10 seconds, this "gap" is to ensure that it WILL run at 100% indefinitely regardless of manufacturing tolerances.

 

Your 5.5kW unit running at 6kW is running at 109% and is in the "unknown" area, it may run ok, it may shut down after 10 seconds or 10 minutes (more likely on overheat).

 

It is generally accepted as "unwise" to design your system to run the inverter at maximum power regularly or for extended periods anyway.

 

If you actually have the above loading pattern you need a bigger inverter or a gas water heater.

 

 

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