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beachman
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# Posted: 13 Jun 2014 10:30
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What about grounding a solar system? I am about to set up a more robust system with a PV away from the cabin and since we have some pretty good lightning storms, I plan to have a ground near the pv. I also will wire the cabin and have a ground there for the system - but I hear you have to tie both grounds together for some reason - equalization of a major strike or something like that. Anybody have thoughts on this?
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MtnDon
Member
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# Posted: 13 Jun 2014 12:02
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Distance from PV to CC and the other stuff??
What's the system voltage?
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beachman
Member
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# Posted: 13 Jun 2014 16:37
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Don, I have a 240 watt panel that I will run about 40 ft of 12AWG to a Morningstar charge controller, then on to a bank of 2 6volt deep cycle batteries (Trojan) in parallel to produce 12 volts, then to a 1000 watt inverter, to a distribution box to outlets and a couple of lights. I am concerned about the panel being exposed to potential lightning strikes being on the shore of a lake. The cabin system should be grounded for safety as well. I have a special lightning breaker to put in between the panel and the batteries. I think I can use the ground near the panel for the cabin and get away with one.
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MtnDon
Member
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# Posted: 13 Jun 2014 18:36
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Two good references for the topic
One at NAWS
and another
The best surge protector / lightning arrestor is the one from Midnite Solar. It has an LED that indicates if it is working properly. The others only let you know they have failed when the system electronics get fried.
With the PV panel close enough to the CC and other stuff you should run a ground wire along with the positive and negative from PV to CC. That ground would be connected to a ground buss at the cabin. The buss would be grounded to a pair of ground rods, usually 8 foot copper clad steel. Separate the rods by 8 feet minimum and connect to the ground buss with a continuous wire from buss to the first and then on to the second rod. Not 2 separate wires.
Your inverter may or may not have an internal bond (AC neutral connected to ground). That will have to be checked before making any bonds in the AC servoce panel, if you use one.
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beachman
Member
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# Posted: 13 Jun 2014 21:08
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OK Thanks. I think I follow you here. It seems to make sense and the use of a bus is a good idea. One thing I was planning is the use of a ground plate near the pv. The ground is rocky and driving a pole of sufficient length would not be possible. if I did get a strike, the distance to the plate would be shorter - and away from the cabin. Then I was going to run a ground wire from this plate to the cabin instead of having a ground at the cabin.
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MtnDon
Member
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# Posted: 13 Jun 2014 22:09
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Ground rods can be driven at an angle too; don't have to be straight down. More important than straight down 8 feet is to hopefully have the grounding rod in moist earth. If you are thinking of a steel plate, they rust and the rust doesn't conduct electricity as well. A stainless steel plate might be better if you can't do copper.
Two separated ground rods are recommended.
One advantage of a buss is that any one item can be removed for service without interrupting the ground path as can happen when wires are connected serially from one thing to another.
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beachman
Member
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# Posted: 16 Jun 2014 09:26
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Here is my proposed system. Anything anybody might recommend or warn against?
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MtnDon
Member
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# Posted: 16 Jun 2014 09:49
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Maybe just the fault of the drawing detail, but a lightning arrestor has three wires. One connected to positive, one to negative and one to the ground wire.
Batteries; two six volt would be in series not parallel as labeled.
The inverter size is not listed, nor the distance between it and the batteries. Twelve gauge wire does seem light, but then there is a 20 amp fuse listed so maybe that is just a small inverter. 20 amps on 12 volts should have the distance no more than 4 1/2 feet and even that will have 3% voltage drop. I'd use heavier gauge wire myself; like at least 8 gauge and keep the line drop as close to 1% as possible.
Can't comment on the 12 gauge for the PV as distance, amps, volts are unknown.
Fuses. Add fuses in the + from PV to CC and CC to batteries. Also a fuse for the 12 vdc water pump.
Small buss bars at the batteries can also make those connections tidier as well as make it possible to add remove connections for devices without disturbing the others. Just a thought I find useful.
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ILFE
Member
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# Posted: 16 Jun 2014 11:11 - Edited by: ILFE
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beachman,
Here are two schematics of the new Kid MPPT Controller by Midnite Solar, as PDF files. One shows a parallel PV array; the other in series. They show proper order of fuses, wiring for the lightening / surge protector, batteries, etc.
I have one of my array schematics attached as well. I have no lightening protection currently attached to it. As soon as my Kid controller arrives this month, I will be replacing the ProStar 30m with it.
Hope this helps,
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MtnDon
Member
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# Posted: 16 Jun 2014 12:31
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Quoting: ILFE no lightening protection
Just an opinion, but the lightning protection should be installed first thing. I have personal knowledge of 2 different systems being struck by lightning and all the electronics getting fried. Only the PV panels remained functional. One had no protection and the other had a brand that had been unknowingly struck before and rendered inoperative. That is why I do heartily recommend the Midnite Solar aresstors / surge protectors for the reason mentioned before, the LED.
For certain there are many unprotected systems that never get struck; some folks can be luckier than others.
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ILFE
Member
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# Posted: 16 Jun 2014 15:57 - Edited by: ILFE
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MtnDon,
I am not sure if it matters really, geographically speaking. But, I live in Cambodia. We get tons of rain every year - and brother, I mean TONS. But, the numbers of lightening / electrical storms we experience only rarely happen. (No, I am not discounting the fact that it only takes one strike to completely trash an entire solar system.)
But, one also has to take in consideration what most people can afford, especially in this country. Most Khmers (who even can afford a solar system) only have the funds to pay for a fairly simple, small output system to be installed on their homes. I'm pretty certain that lightening protection is quite low on the priority list, here in the Kingdom, especially for poor rice farmers.
From the time I began looking for a local company to provide the parts we needed to construct our system, until now - eight months later, I have yet to find a local company that even offers lightening / surge protection devices in stock.
Now, my personal opinion. For me, it isn't a very high priority. Especially for a small system like ours, I really don't see it being necessary. Not to mention, is there any guarantee, whatsoever, that adding lightening protection even be able to do its job and protect your system from a bolt? Not on your life. I too, have personally seen what lightening can do to people, property, farm animals, homes, and even amateur radio equipment - which was well protected. I have yet to see a device on this planet that I feel would truly protect any solar array from a lightening strike.
For me, high priority is to get the power generated where it is needed.
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beachman
Member
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# Posted: 16 Jun 2014 17:43
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Thanks to you both. Yes, series would be correct. Each schematic seems to show a common ground so my plans should be OK. I agree about the lightning arrester and I plan to get this installed as well as the grounding prior to hooking up the panels. I'm thinking about the ground rods going in at an angle - might try this. The place is quite rocky and an electrician told me to use the grounding panel and to put it down 2 ft. I see where the breakers in the Kidd schematics isolate the system so it can be shut down. Obviously I am no electrician and YouTube gives enough info to be dangerous. I will likely get a professional opinion before I go live. My place is so remote that I have had to learn all of this myself over time. Thanks so much for your comments.
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creeky
Member
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# Posted: 16 Jun 2014 19:59
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beachman. your electrician is correct. plate grounding is code acceptable. 2 ft by code. the plates are galvanized metal. given these factors, you wouldn't expect there's much chance of them rusting.
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