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sm paul
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# Posted: 14 Feb 2011 20:35
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I am going to be doing a major upgrade of my pv system this spring.
I have already bought 3- 120 watt panels , 6- 210 amp hour 6 volt batteries , a xantrax 3000 watt modified sine wave inverter with 2 15 amp breakers and a 30 amp mppt charge controller.
I will be putting the batteries and electronics inside of a vented rubbermaid yard storage unit, with the panels being mounted on a framework built directly over the top of the box.
I will be using 12 gauge extension cords to my camper and to my well pump.
My question is.. What are the must have safety features that should be incorporated into my system.
I'd appreciate any advice that I can get. Thanks
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MtnDon
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# Posted: 14 Feb 2011 21:42
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1. Do not put any electronics in the same box, cupboard, etc as the batteries. The batteries belong by themselves. No fuses, breakers or switches that could be ignition sources should be near the batteries. Electronics may contain relays that can spark and acid fumes are not good for them.
2. You've missed or not mentioned grounding the system. DC and AC sides separate. The PV modules should all have their frames connected, special non corroding stainless steel clips/mounts should be used. That in turn should be connected to any metal support framing and/or poles and then to a ground buss. All the DC equipment should be connected to the ground buss as well. Then the buss connected to the ground rod with a single wire. At one point the battery negative should be connected to the ground buss; this is called a bond. The caveat here centers around the square wave inverter. Does it have AC power outlets built in? If it does it may have internal bonding already. And it may not. There should only be one bond in the entire DC side of the system and it should not be inside a piece of equipment that at some point could be removed from the system. If the inverter does not have outlets built in then more than likely, but not guaranteed, there is no internal bond. That's up to you to check (owners manual, wiring diagram).
The AC side gets grounded just like a grid connected house.
3. Lightning protection, in the form of an arrestor that connects to a ground. DC and AC sides separate.
4. A suitably sized DC breaker or Dc fuse for the battery positive to inverter wire.
5. DC breaker or disconnect between PV modules and charge controller.
6. DC breaker or disconnect between charge controller and batteries.
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MtnDon
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# Posted: 14 Feb 2011 21:44
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The lightning arrestor protects against lightning induced power spikes being transmitted through the DC wiring. It senses and clamps off routing the high voltage spike to the ground. A lightning strike to the frames would be directed to ground via the grounding wires, to the rod.
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sm paul
Member
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# Posted: 14 Feb 2011 22:03 - Edited by: sm paul
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There are two breaker protected ac outlets on the inverter but I noticed there is a grounding screw on the back. sooo.. I guess I would have to hook that up to a grounding rod?? Then another grounding rod hooked up to the negative on the DC side.
I have all of the inline fuses.
I was planning on making the framework out of green treated 2x material. Will this work?
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MtnDon
Member
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# Posted: 14 Feb 2011 22:47 - Edited by: MtnDon
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That could be an AC ground? Or maybe not? Impossible to say without a wiring diagram or markings on the case. There is no telling what the manufacturer has done without that or without contacting the manufacturer.
Wood will work, but PT wood should not come in contact with aluminum. The aluminum will be corroded by the pressure treatment chemicals. Stainless steel fasteners are best, hot dipped galvanized are also safe with PT wood.
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