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Solar power, can it be done DIY?


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15 minutes ago, MJCM said:

Is that John Holmes talking ????

 

I assume you also remember the delightful Mary Millington ???? 

 

John died in 1988, he was only 43, probably got an erection and died of lack of blood to the brain!

 

We are both showing our age!!

 

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With what I have so far learned, i am thinking that the hybrid on-grid system is probably not worth the extra cost, so I am now leaning towards going for a 5 kW hybrid off-grid inverter. If it turns out to be insufficient, especially if i later install a 7 kW wall charger for the EV, I can add a second inverter (I know not all inverter models can do this).

 

Still a little confused though, as Crossy states this about the hybrid off-grid system in his pinned topic:

Quote

Like the simple off-grid system this unit still has the issue that the maximum load can never be greater then the inverter maximum output.

But I am pretty sure that I have read a post from Crossy in a separate topic, where he mentions a model of hybrid off-grid inverter that is able to top up from the grid to deliver more than the inverters rated capacity (and BritManToo saying that his Chinese model can do the same).

 

So some hybrid off-grid inverters do have the ability to top up from the grid???

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9 hours ago, Sophon said:

But I am pretty sure that I have read a post from Crossy in a separate topic, where he mentions a model of hybrid off-grid inverter that is able to top up from the grid to deliver more than the inverters rated capacity

 

Many if not all off-grid hybrids can top-up the solar by using grid energy.

BUT

I'm not aware of an off-grid hybrid that can go over rated capacity when topping up from the grid (we are entering the realm of the on-grid hybrid here), of course they may or even probably do exist. Many have a "bypass" facility but this completely bypasses the inverter so no energy is taken from the solar or batteries.

 

In order to avoid future issues I would bite the bullet and get enough inverters to parallel for your prospective load now. One never knows if the same model will be available when you need to expand, or, for that matter, even if one is available will it be compatible with your older version.

 

In reality, I'd be tempted to go on-grid hybrid and adjust your house wiring to split off your "essential loads", it's not such a major task. When you get your EV just add another on-grid hybrid or even a pure grid-tie if you are only going to charge during the day.

 

An on-grid hybrid plus a grid-tie is what we have and they play remarkably well together, even charging the batteries from their combined outputs which is something I didn't expect as there's no comms between them.

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5 hours ago, Crossy said:

 

Many if not all off-grid hybrids can top-up the solar by using grid energy.

BUT

I'm not aware of an off-grid hybrid that can go over rated capacity when topping up from the grid (we are entering the realm of the on-grid hybrid here), of course they may or even probably do exist. Many have a "bypass" facility but this completely bypasses the inverter so no energy is taken from the solar or batteries.

 

In order to avoid future issues I would bite the bullet and get enough inverters to parallel for your prospective load now. One never knows if the same model will be available when you need to expand, or, for that matter, even if one is available will it be compatible with your older version.

 

In reality, I'd be tempted to go on-grid hybrid and adjust your house wiring to split off your "essential loads", it's not such a major task. When you get your EV just add another on-grid hybrid or even a pure grid-tie if you are only going to charge during the day.

 

An on-grid hybrid plus a grid-tie is what we have and they play remarkably well together, even charging the batteries from their combined outputs which is something I didn't expect as there's no comms between them.

Thanks for your comments and suggestions Crossy.

 

Our incoming supply goes from the PEA pole to a pole at the corner of our land (where the solar panels would be located). It then goes underground for 50+ meters and enters the house through the wall downstairs:

DSCI1104.thumb.JPG.c3d6d67e5e5ec92e3622e7303ddd4e05.JPG

 

From there it goes through the floor of the living space upstairs into a cavity wall of one of the upstairs bathrooms into the ceiling space. Making that whole in the wire mesh reinforced concrete floor was a major task even back when the cavity wall was not there yet. It then comes down to the consumer unit embedded in the AAC wall:

DSCI0936.thumb.JPG.71d63b0465df5da6399a250af1dac5d2.JPG

 

Splitting the load into essential and non-essential, would require me to run a second buried cable to the house (in itself an added cost of THB 20k+). I would also have to drill extra holes in the downstairs wall, the floor between downstairs and upstairs, embed the extra cables and a second C.U. in the wall . After that I would have to have the wall upstairs and the ceiling downstairs re-plastered and the downstairs wall re-tiled. That is in addition to the actual re-wiring work, which would require me to extend at least some of the existing cables. Having to split the load would be an absolute deal-breaker for me.

 

I have some questions about grounding that I would like your input on, but I think I will post those in a separate post.

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From reading posts in the electrical forum over the years, I have learned that having more than one ground can in certain situations be extremely dangerous. 

 

As mentioned, my solar panels will be ground mounted close to where the incoming supply enters our land, which is about 50 m (as the crow flies) from the house and where the existing ground rod connected to the consumer unit is located. At the moment I don't have a supply isolation breaker (other than the main RCBO in the C.U), nor do I have any surge protection, so the only way to cut the supply is to have PEA pull the cable from the meter. This is an oversight I now plan to fix, so I will put an incoming breaker where the PEA cable is today crimped onto my cable running to the house and after that I will add a MOV (I think it's called?) surge protection unit. These will be in a small box on the pole we had erected to receive our incoming supply from the PEA pole, which is on the other side of the soi.
 

DSCI0414.thumb.JPG.9133a3a130b21b351e8784bbc7302b6f.JPG

 

the new box will be here, where the workers plugged in their equipment during the construction of the house (looks safe, doesn't it?).
DSCI0747.thumb.JPG.acd610f743b4691bcfb346efd0f6d462.JPG

 

The panels will be located a few meters away from this pole, and the inverter and battery etc. will be under the panels protected from the elements with some walls (but semi open for ventilation).

 

The Inverter, as well as the surge protection I plan to add, will both need to be grounded, and as the existing ground rod is 50 m away it would not be very practical to run cables to it if it can be avoided. So would adding a second ground rod next to the panel location create a dangerous situation?

 

I have also read about people using the house roof construction as a UFER ground, so would the 6 m x 4 m metal structure with six concrete footers I will build be a suitable ground and would you connect the inverter/surge protection to the structure as well as the second ground rod? All that is, of course, assuming that the answer to my first question is, that a second ground rod 50 m from the existing one will be OK. 

 

DSCI0412.JPG

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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).

 

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7 hours ago, Crossy said:

 

<snipped>

In order to avoid future issues I would bite the bullet and get enough inverters to parallel for your prospective load now. One never knows if the same model will be available when you need to expand, or, for that matter, even if one is available will it be compatible with your older version.
<snipped>

I have snipped your post to highlight the relevant (to this post) part.

 

Yeah, it's always difficult weighing up options when you are not sure what the future brings.

 

I could do as you suggest, and buy two 5 kW hybrid off-grid inverters, so that i know they would be compatible. The down-side being that I may in reality only need one, so having wasted the cost of the second one.

 

Alternatively, I could buy just one and hope that I can find a compatible unit (or the same model if not to much time has passed), if it turns out that one unit is insufficient. Of course, the risk being that I can not find a compatible unit, and have to buy two new ones, wasting the investment in the original one.

 

The second option do have the benefit of giving me added flexibility. Assuming the first 5 kW hybrid Off-grid inverter lasts me a year or two, and during that time I decide that I need to change to a hybrid on-grid inverter, I would have wasted less money than if going for two inverters right away.

 

Of course, since splitting my load is a deal-breaker the latter option of switching to on-grid would only work, if I can find an acceptable solution to the essential/non-essential load connections. Have you seen my question about connecting both output ports from a hybrid on-grid inverter to a manual switch-over switch, such as is normally used to switch between grid and generator? Could that work? It would give me the option to:

  • Have the switch default on "essential load", and manually switch to "non-essential when I need more than the inverter can handle (when charging EV via wall charger), or
  • have the switch default on "non-essential load", and manually switch to "essential" when power goes out.

If i can find an acceptable option to the load problem with an hybrid on-grid inverter, I think that I will probably initially go with a cheap Chinese hybrid off-grid inverter like the model BritManToo uses. That way I can learn from my own real life experience, without having wasted too much on equipment that it may turn out doesn't deliver what I need. 

 

Thank you for your patience in answering my questions. I know some of them must sound basic (or even down-right stupid) to you.

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21 minutes ago, 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.

 

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

 

Sounds good that I can use a local ground rod, that will make my life easier.

 

I will have string inverter(s). With 12 panels, I believe I would connect them as two strings each with six panels in series, and the two strings then connected in parallel?

 

I am sorry, you lost me with the "and don't forget the D side", is "D" a specific type of arrestor or what did you mean by that?

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6 minutes ago, Sophon said:

Have you seen my question about connecting both output ports from a hybrid on-grid inverter to a manual switch-over switch, such as is normally used to switch between grid and generator? Could that work? It would give me the option to:

 

Yeah, you could do that, it might be wise to do anyway with your off-grid hybrids so you can bypass the inverters if something goes wrong.

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Just now, Sophon said:

I am sorry, you lost me with the "and don't forget the D side", is "D" a specific type of arrestor or what did you mean by that?

 

It means my "C" key is erratic, should read "DC" ???? 

 

But the DC side needs DC arrestors and DC rated breakers. Please don't be tempted to use AC breakers on the DC lines.

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3 minutes ago, Crossy said:

 

It means my "C" key is erratic, should read "DC" ???? 

 

But the DC side needs DC arrestors and DC rated breakers. Please don't be tempted to use AC breakers on the DC lines.

Yeah, I was aware of that. It seems that DC breakers and wiring in general is a little more expensive than AC equipment, but it will not be a major cost so not that important. 

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1 hour ago, Sophon said:

Yeah, I was aware of that. It seems that DC breakers and wiring in general is a little more expensive than AC equipment, but it will not be a major cost so not that important. 

All the same price if you buy from China (through Lazada or Shopee dealers).

No special wires required, the wire doesn't care if it's AC or DC passing through it.

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Stupid question.

 

Are normal MCB's directional? In most wiring diagrammes I have seen they have input at the top of the MCB and output at the bottom like e.g. this one:

image.png.ef561dacd8dfda57c5d9ff68b6e151ae.png

Sometimes it would make for easier wiring to have the input on bottom, and when talking about the MCB for battery storage the energy can flow either way depending on the circumstances.

 

I would have thought that MCB's are bi-directional, and can be wired up either way, but as we have already established my electrical knowledge is limited.

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DC MCBs (like you show in your diagram) are often polarity (+/-) and direction (line/load) sensitive, it's all to do with the special arc-suppression/quenching arrangements needed for DC that AC units don't require.

 

AC MCBs tend not to bother with polarity or direction, but be aware RCDs and RCBOs are direction sensitive. 

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11 minutes ago, Crossy said:

DC MCBs (like you show in your diagram) are often polarity (+/-) and direction (line/load) sensitive, it's all to do with the special arc-suppression/quenching arrangements needed for DC that AC units don't require.

 

AC MCBs tend not to bother with polarity or direction, but be aware RCDs and RCBOs are direction sensitive. 

So that means that I can wire up an AC MCB either way, but what about the MCB for the battery storage? Does that mean that there are special MCB's specifically for the battery storage?

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Just now, Sophon said:

So that means that I can wire up an AC MCB either way, but what about the MCB for the battery storage? Does that mean that there are special MCB's specifically for the battery storage?

 

This is a very good question of course as the current can flow in either direction.

 

You need to find a DC MCB that's not directional, there are plenty around. Generally if it doesn't actually say line/load it's good in either direction. In the past I've found far more DC MCBs that are polarity sensitive than I have that are direction sensitive.

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22 hours ago, Crossy said:

 

Yeah, you could do that, it might be wise to do anyway with your off-grid hybrids so you can bypass the inverters if something goes wrong.

Hi again Crossy.

 

In my reply to using a changeover switch for changing between essential/non-essential load in a hybrid on-grid system, you suggested maybe using one to bypass the inverter also in a hybrid off-grid system. Did you mean something like this:

Solar.jpg.c9660ba5494c7620b8b746bf6a687a01.jpg

 

Any glaring mistakes in my diagram? I haven't yet added surge protection on the DC side, as I don't really know where it would be needed?

 

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11 minutes ago, Sophon said:

Did you mean something like this:

 

Yeah, that would work.

 

Your DC surge suppressors go between the panel MCB and the inverter (close to the inverter, it's this you want to protect), if you have very long cables between the panels and inverter it might be wise to double up on the suppressors at the panel end of the run too, probably not needed but ... There's no need to suppress the battery lines.

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23 minutes ago, Crossy said:

 

Yeah, that would work.

 

Your DC surge suppressors go between the panel MCB and the inverter (close to the inverter, it's this you want to protect), if you have very long cables between the panels and inverter it might be wise to double up on the suppressors at the panel end of the run too, probably not needed but ... There's no need to suppress the battery lines.

Thanks. 

 

Stupid question alert! I assume that I can use the same ground bus bar for both the AC and DC (surge suppressors) side?

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Just now, Sophon said:

Thanks. 

 

Stupid question alert! I assume that I can use the same ground bus bar for both the AC and DC (surge suppressors) side?

 

Yup, no problem there ???? 

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52 minutes ago, Crossy said:

 

This is a very good question of course as the current can flow in either direction.

 

You need to find a DC MCB that's not directional, there are plenty around. Generally if it doesn't actually say line/load it's good in either direction. In the past I've found far more DC MCBs that are polarity sensitive than I have that are direction sensitive.

This is where I feel completely lost, i.e. when trying to figure out if equipment meets my requirements or not.

 

How do I know if these two examples of DC MCB's can be used for my battery storage, what is it in the description that gives it away? There are wiring diagrams on the MCB's themselves, but I don't know enough to understand them.
 

Example 1:
image.png.8ea39a88ff5563c130cfc4c5aa4baede.png

 

There are a couple of questions about polarity in the Q&A, but the translation makes them incomprehensible:
image.png.22522accd84221866a7669d71fc501de.png

 

Example 2:

image.png.b0d107f49e840a05dea01c4c8655f8fb.png

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OK, let's take the easy one first.

 

The second unit (with the red handle) is clearly marked + and - on the little diagram, it doesn't seem to be line/load marked. OK for battery.

 

The Tomzn one also has + and - markings but they appear to differ at the top and bottom of the little drawing. Need to investigate just what this means.

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2 minutes ago, Crossy said:

OK, let's take the easy one first.

 

The second unit (with the red handle) is clearly marked + and - on the little diagram, it doesn't seem to be line/load marked. OK for battery.

 

The Tomzn one also has + and - markings but they appear to differ at the top and bottom of the little drawing. Need to investigate just what this means.

Thank you again Crossy.

I will let you get back to enjoying your week-end.

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On 8/1/2022 at 4:08 PM, Sophon said:

10 kWh of battery storage, more would be better but would come at a cost.

What type of cost for descent batteries.

 

I would need a much bigger system.  Our bills are around 8,000 baht a month.

 

Next house we're planning on building in Hua Hin.  I'm going solar for sure.

 

Definitely going to have it done by professional company.

 

I'm having trouble replacing a plug.  I'll have to pM you.  

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1 hour ago, 007 RED said:

@Sophon, As @Crossy has pointed out above, it is wise to have an appropriate breakers and surge suppressors located either side and as close to your inverter as practically possible.  As has been mentioned, it is extremely important to only use a DC breaker on the DC side of the inverter and an AC breaker on the AC side of the inverter.  Big flashes and magic smoke are likely to occur if you use an AC breaker on the DC side of the inverter.

 

The breakers enable you to isolate the inverter from DC and AC supplies, so that you can carry out any maintenance on the panels or remove the inverter if necessary.  The surge suppressors are there to protect your investment (inverter) in the event of a surge arising from a nearby lightening strike or problems with you local PEA supply.

 

The photo below which I provided in an earlier post shows my small scale set up with the Sofar inverter in the centre. 

1103023929_20210926_105915x.jpg.edc3bfdf0502ca0c0ad8b641201e37fc.jpg

 

The cables coming down from the top left of the picture are the DC +/- feeds from solar panels which are mounted directly above on the roof of the car port.  These cables are connected to the DC breaker and and surge suppressor which are housed in my home made 'safety box' (small empty consumer unit box).  From the DC breaker the +/- cables are then connected to the respective input DC sockets on the inverter. 

 

The large black plug and cable coming out the bottom right of the inverter is the AC cable which is feeding power generated by the inverter to my house consumer unit.  This cable is initially connected to the AC breaker and suppressor, again in a home made 'safety box' before being connected to the consumer unit in the house.

 

FYI.... Both 'safety boxes' and the inverter have separate earth cables which are connected to the metalwork of the car port.  The metalwork inside the main supports of the car port are buried quite deep " meters plus) into the ground, but I have also connected a 2 meter earth rod buried in the soil to the car port metalwork.  'Belt and braces' approach.

 

Thank you.

 

One thing I am a little hazy about, are the actual connections on the DC side. From your picture it looks like there are special plugs for plugging into the inverter, rather than the "shove the cable into a hole and tighten a screw" that I am used to on the AC side. The same is probably true for the battery connections, and I have already seen that it's the case when connecting the solar panels.  

 

I am also not clear on what cable sizes I need for a 5 kW system, one of the sellers of inverters on Lazada quoted 4 sq.mm. but is that enough for a sustained energy flow of up to 5 kW? FWIW the finished cables that Global sell does seem to be mostly 4 sq.mm.
image.png.bfebfa8d8683752f1ee4ba58155ea43f.png

 

And, as I have not presently any surge suppressors, what kind of cable sizes do they require? They need to be able to divert large amounts of energy, but obviously only for a very short time.

 

Hopefully, these are things that will become clear with further research. 

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