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Monbat 180ah 12v Agm Batteries


Chris-R

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Just now, cvzyl said:

Yes, but the relative humidity increases so although the air contains more moisture the humidity is higher and condensation happens easier.

I assume that's because at the lower temperature the same amount of water potentially becomes a bigger problem. Mmmmh. Never thought of it that way.

Setting the AC to "Dry" mode might help with that. Still, I think there are solutions to the problem that doesn't involve a big heavy refrigeration unit.

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Yes, as the temperature decreases the ability of air to "absorb" water is reduced, therefore the same quantity of moisture in air represents a higher relative humidity. Up to the point where condensation starts to take place. If you cool the air further then the air remains at 100% relative humidity and water continues to condensate. If you then heat up the air again the relative humidity will drop as the amount of moisture remains the same but the air's ability to absorb it is higher.
Heating up the air slightly should be an effective way to avoid condensation. I think @Mike suggested installing the inverter inside a cabinet could help to increase the temperature inside the cabinet and avoid condensation in that way. Not sure an AC will be the right direction.

For interest, here on the West Coast relative atmospheric humidity peaks >90% almost daily with the average daily humidity around 60-70%.

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Hi Mike

Did you replace the fans with original replacements or with local fans. What was the problem with the original ones and after the replacement, did the same happened again or was the problems solved? I am getting very worried about all the negative talks! Maybe I should start investing in Imeon spares !!

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Hi Chris

I think the fan failure is due to humidity issues. I have seen an Aussie video of an install where the Imeon was in an enclosure so that it runs hotter. Bloem does not strike me as a place which has humidity issues (excluding the last couple of weeks :D). Nevertheless carrying some spares would make sense. I have spare fuses, cable, circuit breakers but not fans. I think you have just prompted me to get two spare fans.

 

 

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Chris

Just something I was wondering about. Lightning?

I did not notice any lightning arrestors on the pic of your panels posted a few weeks ago. I also noticed on a pic recently where there was earth cables fitted to just about every piece of ducting or equipment on the panel.

What is the correct way to do. We've got lots of lightning around here and our power normally goes off even if the thunder storm is still in the middle of the Karroo! We have never had a direct strike in our vicinity, but one never knows. I am going to fit the panels on the IBR roof of my shed +/- 4m from the ground. Any advice?

Thks 

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On 24/11/2016 at 8:43 AM, Chris Rossouw said:

Chris

Just something I was wondering about. Lightning?

I did not notice any lightning arrestors on the pic of your panels posted a few weeks ago. I also noticed on a pic recently where there was earth cables fitted to just about every piece of ducting or equipment on the panel.

Hi Chris each panel is earth with a earthing clip and those cables go to a surge arrestor in the combiner box. From there it is buried with the insulation removed for several metres and then connected to a earthing rod also buried.

20160131_075744.jpg

As I have said before nothing is going to help with a direct strike. Virge has ably demonstrated this. Surge protection can help with inductive current flow from a close strike - that tingling feeling in your hair and extremities when there is a close strike. Lightning was one of the considerations when I decided to mount my panels on the ground. We live in a valley surrounded by dolerite (ysterklip) and lightning strikes all around us but very rarely on the yard. Those antenna that one sees in Gauteng near thatch roofs may be an extra insurance against lightning.

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  • 4 weeks later...
Quote

hi Chris

The earth clips you mention above, where did you get hold of it? I was planning to use the copper strip with holes, pop rivet it to each panel a few times, going right around the outer edge of the array of panels, combine the two arrays with a earth wire going to the combiner box and surge arrestor and the to a proper ground pen.

Will this also be ok? Could you perhaps share a pic of the clips you talking about?

Thanks

 

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Hi Chris

https://solar.rubiconsa.com/mounting-systems/solar-mounting-structures/araymond-grounding-glips-220492000.html

Rubicon here in PE The were R15 excl. in June 2015. They are easy to use as they expose the insulation as they clip on to the cable. I think in the event of a direct strike the frame that the panels are on will carry more current than the earth wire. A direct strike is game over as far as I am concerned. I have a lighting antenna on the roof of the house and a large tree to the south of my panels. I am hoping that the tree will take a direct strike. I think the best bet is to make sure your insurance is adequate. 

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Is it then viable to earth the frame properly? I have never had any direct strikes, but a lot of lightning in the surrounded area. Also have quite a few large trees from about 10metres away from the panels. I think I will mount an antenna also in the nearby area. Looking at your combiner box pic, looks like the cables is coming in from the panels to the surge protector and back to the earth peg. Is that correct?

Last question: Is this earth connected to the earth in the DB or is this totally separate?

Sorry for all the questions, but I want to try and do it best I can!

Thanks Chris

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Hi Chris2, my opinion:

1) Lightning conductors must be as short as possible to offer a low impedance path. (not only low resistance but also a low reactance) This implies installing an additional earth electrode near your array.

2)  So now the question is do you interconnect the two earthing systems?

3) The answer is Yes.  If you have cables running between the earthing systems then you must interconnect the earth systems together.

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Hi Chris

4 hours ago, Chris Rossouw said:

Is it then viable to earth the frame properly? I have never had any direct strikes, but a lot of lightning in the surrounded area. Also have quite a few large trees from about 10metres away from the panels. I think I will mount an antenna also in the nearby area. Looking at your combiner box pic, looks like the cables is coming in from the panels to the surge protector and back to the earth peg. Is that correct?

Last question: Is this earth connected to the earth in the DB or is this totally separate?

Sorry for all the questions, but I want to try and do it best I can!

Thanks Chris

Jip thats correct

Separate earth. DB earth is near gennie room so the two earths are more than 200m apart. Do not want a ground voltage gradient if there is a lightning strike. Normally I would connect all earth mats and pegs to prevent voltage gradient but loathed to run a lightning conductor through/round the house.

Addition: Unless we have a dry thunderstorm my panel frames are very well grounded - bolted to a concrete slab and the rain pools on the slab about 2mm deep.

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59 minutes ago, Carl said:

2)  So now the question is do you interconnect the two earthing systems?

My only concern with this is that if your other earth is the one that comes with the supply on your TN-S connection (ie it's at the transformer down the street), you now officially changed it to a TN-C-S (PME) setup. Not that I see any problem with that from my limited knowledge, I just wonder what the regulations say.

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The TN-S and TN-C-S earthing systems relate to the way the Source of Energy is supplied to your premises. (point of Supply) 

T - means the the transformer neutral source is directly grounded.

N - The exposed conductive parts of the consumer's electrical installation are connected direct to the source earth, which, in the case of an a.c. system, is usually the transformer neutral point.

S - The neutral and protective functions on the incoming supply and in the consumer's electrical installation are provided by separate conductors.

C-S - The neutral and protective functions on the incoming supply are combined in a single conductor and in the consumer's electrical installation are serviced by separate conductors.

In Cape Town all of the supplies that i have seen so far is TN-C-S system as this saves the council from having to run an extra conductor. The council however requires you to install an earth electrode at your premises although this is not prescribed by SANS 10142. This would provide some protection should you lose your neutral supply. The physical earth / soil would then be your return path for neutral currents.

So interconnecting your earthing systems (lightning protection for your PV array and your Council supply earth) has nothing to do with your supply earthing system.

What i was trying to point out is that independent earthing systems are fine if you have no cables running between the systems. Once you install cables between the systems then you should interconnect the earthing systems. The lighting current will predominantly flow through the low impedance path to ground and your earth interconnection cable will only provide a path for a much smaller current that will provide an equipotential platform for your cables. 

This is my understanding and i think we should debate this further to get to some earthing rules.

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1 hour ago, Carl said:

In Cape Town all of the supplies that i have seen so far is TN-C-S system as this saves the council from having to run an extra conductor.

I have a TN-S at home, which is technically Cape Town. Transformer is right across the street though :-)

Come to think of it, maybe I should check again. I know where the connection point is on the back of the house, maybe I missed the cable that goes to my local earth electrode.

From many forum posts I dug up with Google, it seems the rest of the world is moving to a TN-C-S (PME) system, that is essentially a TN-S system but with multiple earths (PME, protective multiple earth). If you have an extra earth electrode at the premises, you essentially have PME. My issue isn't that I think there is a problem. My issue is I wish I understood better why you'd use one and not the other, pitfalls, caveats... that sort of stuff :-)

1 hour ago, Carl said:

So interconnecting your earthing systems (lightning protection for your PV array and your Council supply earth) has nothing to do with your supply earthing system.

Understood, my worry was always that connecting the two gives lightening two paths (and almost like the original quantum mechanics experiment, it always takes both!), one of them into the DB board where it might otherwise not have gone if I didn't provide the path. Additionally, these days they expect you to also earth that small metal bracket on which your satellite TV dish sits, but only to a local spike, no interconnection. I would expect that the rules for the solar panel FRAMES are the same.

So my gut feeling is to interconnect if its stuff that you will regularly touch, that is close to mains wiring and therefore at risk of rising to live potential, etc. If its an aluminium frame on the roof, or a steel bracket up on the wall, and the act of earthing is to tell lightening "go THAT way" I would think you shouldn't interconnect.

This is my gut feeling.

I think the kind of inverter in use also plays a role. The isolated inverters -- those with boost stages and low-voltage PV inputs -- with those you probably don't want to interconnect. With the high-voltage non-isolated models, your PV panels are potentially at live potential: A break down in the inverter switch gear could cause that. So here it would make sense to me to interconnect the PV panel earth to the one in the DB board.

I think this comes back to what you said about the need arising when you have cables running between the systems, just perhaps more subtle: If there is a path from L potential to the frame, then you also want a path from the frame to the same E :-)

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