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Here's a drawing of my simple set-up; remember that this is in a small cabin that will be used for 6-8 days at a time, about 4 times a year.

Notice that I start with two 195-watt, 13amp panels but will eventually expand to four: the charge controller and the inverter are sized to handle that. My question on this thread is switching and fusing. I am a putter-arounder sort of guy and hate to spend a lot of money on off-the-shelf stuff for the 4kw system designs NOB: for example, this is my PV combiner box w/ #6 from the panels and #4 to the charge controller:

A simple exterior box with a grounding buss cut in half and a cover plate and for about $10 I've got it.
I do not want to buy a Midnite Solar or Xantrex DC disconnect for $200+.
1: I'm thinking of using in-line maxi fuses for fuses #1 and #2: any issues or recommendations for these?
2: Is a disconnect or switch between the panels and CC really necessary; and if so, what do you use (remember, this will eventually carry about 60 amps if I stay at 12v). I can get switches from the auto supply stores cheaper, by a long shot, than from solar supply sources.
3: For the "Circuit Breaker" in the drawing, I'm thinking of using a Perko switch and a 150amp fuse that sits on the battery terminal that is often used in marine applications (I am using 2/0 wires for battery connects and to the inverter). Suggestions here will be appreciated as I only know A/C and am uncomfortable with D/C. Note: All 2/0 runs will be under 5' - fer sure.
4: Grounding has really got me confused: can I use the grounding buss in the A/C panel for the inverter and the CC? In other words, can I have one grounding rod that everything, the PVs, the CC, the inverter, the load center is all tied to? If so, I'm thinking of putting a grounding buss on my make-up board, a 4'X4' piece of plywood, bond that to the load center buss and have one run to the ufer ground. By the way, per Bob and a few others, I am not bonding the neutral buss to the ground buss in the load center.
5: I do not quite understand this drawing: the perko switch and the fuse in #3 above takes care of the breaker in the positive run; but what is the shunt doing? It looks like it's just a pass-thru to me and the negative and grounding busses are bonded together. Why is the hair on the back of my neck standing up?

Since none of the experts seem to be replying, I'll give you my two cents worth. I don't claim to be an expert, however I did design and install my 7.2 kw system in our off-grid house in Loreto and a year later, it is working perfectly.
First of all, I like you diagram. A nice simple design for a low power system. I don't see anything wrong with you home made combiner box, however why don't you just run the panels in series and forget "combining" them. I assume you are using an MPPT charge controller, so it will just manage the higher voltage to the best advantage depending on the battery needs. This also sends less amperage through the wires to the CC.
Not sure why you want to use any fuses in the system, breakers are actually pretty cheap and they then serve as disconnects as well. You don't really need disconnects, however they are a good idea especially if you ever have to troubleshoot or service the system. You do want to be able to disconnect the PV array from the CC and also between the battery bank and the inverter.The Perko switch and fuse would work, but again, breakers are not that expensive (Perko switchs are not cheap as I recall). Keep in mind that you need to use DC breakers on DC circuits, they are different from household AC breakers.
As far as I know, using the ground buss in the AC panel is fine for all the system grounds, someone else might know otherwise. Most inverters specify that you bond neutral and ground together at some point (and only one point) in the system, I used the AC panel for mine with no issues, don't know why this would not be OK, again, some one else might know otherwise. Hope this helps and good luck.

Originally Posted by Santiago

4: Grounding has really got me confused: can I use the grounding buss in the A/C panel for the inverter and the CC? In other words, can I have one grounding rod that everything, the PVs, the CC, the inverter, the load center is all tied to? If so, I'm thinking of putting a grounding buss on my make-up board, a 4'X4' piece of plywood, bond that to the load center buss and have one run to the ufer ground. By the way, per Bob and a few others, I am not bonding the neutral buss to the ground buss in the load center.

I'm glad N.Campion answered, I sat down three times to write but got distracted.

Here's my two cents on grounding:


You will get many different answers on grounding. This is how my system is set up:

I have all the system grounds (green wire) from every component (charge controller, inverter, breaker boxes, etc. etc. bonded together to a buss in the main breaker panel. In the main panel I bonded the system ground buss to the neutral buss. This is the only place it should be bonded.

From the system ground buss I ran #4 wire out to the ground rods. If the soil is dry (most of Baja), you'll need to sink at least two rods, preferably more. Try to place at lease one of them in a place that gets watered regularly, that will help with conductivity.

The battery negative IS NOT tied to system ground, or the ground rod, it floats. I was told by several experts that grounding the batteries invites lightning strikes.

My panels are also floating and not tied to system ground (green wire from the frame), for the same reason as above. Only the combiner box is. Positive and negative from the panels run through the combiner box to the charge controller, then directly to the batteries. Once again, the batteries float, the negative does not tie back to the ground rod.

Now your generator. You need to make sure that the generator DOES NOT have neutral and ground bonded in the generator. If it is, you must find where they are connected, and disconnect it. Having the ground and neutral tied together at the generator will set up a ground loop that will cause the windings to heat up and cause premature failure of the generator.

Hope this helps

Thanks guys,
I've posted this on Northern Arizona's board and have gotten some good advise. Yes, it is a small system but I still want everything to be safe for people and equipment. I am truely amazed at the difference of opinion an many of these issues - I figured this would all be agreed on procedures but not even close. Many ways to skin a cat, but then, I like kitties.[IMG]http://[/IMG]

The wind-sun board is an excellent source. It's saved me many times. Also try: http://outbackpower.com/forum/ Even though it's specific to Outback products, there is still a lot of useful information.

The Midnight Solar website also has a new bulletin board:

http://midnightsolar.com/ , again specific to their products, but still has useful info.

That cat is too cool....

Originally Posted by wessongroup

That cat is too cool....

That IS a cool cat

Must say a thank you to all of you folks who put up all this "real time" information on solar.. it is a wealth of useful knowledge which can be used .....

Grounding is one of those funny subjects when it comes to electrical wiring. There is more than one camp of ideas on how it should be done ranging from personal safety to equipment integrity. Most homes down here are not grounded and the reality is that if they are wired correctly they rarely present any problems. If that were not true I think you would be seeing daily reports of electrocutions down here based on the way they love to jerry-rig their power tools.

Just saying...

Jim
Nice drawings. One of the things that pops out at me is the size of the battery bank. 1000 amp hours seems a little large for the system you have proposed. You could save some money, and your battery bank will charge much quicker, by using less batteries. 2-13 amp panels is only 2.6% of your banks capacity and even when you expand to 4-13 amp panels you will be just at 5.2%. Most battery manufactuers recommend that your array amps be 10% of the amp hour capacity of your bank. Are you going to have some pretty heavy night time loads that you will need 1000 amp hours? Even in my house where I have 2 refrigerators, freezer, television, computers, etc. I only use a max of 300 amp hours over night. Here is a link to Trojans battery maintaince site. Lots of good info there on charging and maintaining batteries.
http://www.trojanbattery.com/Tech-Su...intenance.aspx
Hope this helps,
Larry

Good point Larry. My guess is that he would never be able to equalize that battery bank. Besides, you can never have too many panels...

I forgot to add that I agree completely with ncampion, go with breakers. If one pops you just flip the switch and you are going again. When you run out of fuses you are going to bypass it and then you are un protected.
Ron, you are right, it is going to be hard to maintain that large a bank with the initial panels and still might struggle when he adds the extra solar. Those 195 watt stc (standard test conditions) panels are actually in the real world only 168 watts and a little over 11 amps each. Here is a web site that lists most panels and what they put out in the field.
List of Eligible SB1 Guidelines Compliant Photovoltaic Modules - Go Solar California
It always amazes me how much there is to know about batteries and solar and how little I actually know. Every where I look I learn something new.
Larry

Ain't that the truth brother. But it surely has been interesting along the way. There is no exact, one size fits all setup. Learning to work with the variables based on energy needs, budget and even wind is a real learning process...

There's soooooo much to learn. I often panic when I read posts about how someone else did their solar, oh...geez did I do that correctly? I can't tell you how often I've gone back over my system, again and again, to be sure it's put together correctly. So far so good.....

It is truly amazing how many ways there are to do the same thing. I like Jim's combiner box, and how he cut a ground bus in half. I did basically the same thing when I made mine but I used 2 pieces of copper and drilled and tapped them so I could attach the wires from the panels. His way is much simpler, quicker and probably cheaper. Next time.
Larry

When I first started out an old, off-grid veteran friend in Australia gave me some pointers when first designing my system. Once I started putting it all together and having expressed a fear or two as to whether I had "done it right", he assured me that if after a couple of years you still have the lights on, you probably did it right...

Jim
I'm guessing you must be back from the Bay by now. How did your system work out for you? Any suprises? When I came by that day everything looked like it was fine. Just curious.
Larry