Solar Panels Pointing in Different Directions on Same String

Solarman · November 2014

Hello, I'm new to the forum

Anyone have experience with solar arrays tied into the same string but facing different directions? I've done exactly this for now as an experiment.

My set up goes like this:

Panels are 12volt Mono, 520 watt, about 30amp Total Array

320 watt array pointing south, 200 watt array pointing west. Blue sky MPPT 30amp controller, 4 x 250 AH 6volt Golf Cart Batteries, wired series/parallel to make 12 volt at 450AH Capacity. 1,000 watt pure sign 12V eliminator inverter.

All panels lead to a common buss bar( used as a combiner) and in turn run to the controller or 300 watt grid tie, whatever I prefer at the time via circuit breakers, but not both at once.

I am in an urban area and not off grid, just was always interested in experimenting with a solar setup such as this.

I've read that you will take down the system with a set up like this, but to be honest, I have not noticed it yet. There is a abundance of Sun on the west side, especially in the afternoon, All Seasons, so I am experimenting with a setup as above. If I had to guess, there would be more, or almost more hours of sun on the west side than the south side.

With this setup in late Oct, (almost Nov) I've managed to put in 1kwh a day on a sunny day in my house. I do not see any hint of the system being taken down from the different directions the panels are facing. Im sure in the summer months, I will be over the 3x my array of 1.5kwhs. I'm thinking I will get close to 2 kwh in the summer months.

I'm in the GTA Toronto Ontario area.

Thanks for an input you may have.

Cariboocoot · November 2014

Re: Solar Panels Pointing in Different Directions on Same String

Welcome to the forum.

Here's what you haven't encountered yet, thankfully: the bypass diodes have not burned out as a result of having to carry the current generated by the unshaded panels through the shaded ones.

With differing amounts of light on the same panels the current output will differ. Not a problem for parallel connections because the current is added in parallel, so whatever a lower producing string can contribute it will at the same Voltage level.

Put the panels is series, however, and the lower producing ones become a 'choke' in the circuit, causing current to flow through the bypass diodes instead of the panel segments. Although it is true that is why the diodes are there, they are meant to make up for occasional, brief encounters of partial shading on a panel. They are not meant to take a daily beating of Isc for half the hours of sunlight. Okay, it's not quite that extreme but it does mean that they are more likely to fail than they would if they weren't having to do this service.

Some panels have rather low current bypass diodes in them for the Isc potential. Some have multiple diodes in parallel to make up the current difference. Either of these types are more likely to fail than single diodes of above Isc current rating.

Now if what you really mean is the 320 Watt array and the 200 Watt array are in parallel on the controller (which I suspect) then the only power loss will come from the Voltage difference between the two arrays. The total output will be less than ideal, but greater than either array individually.

A couple of other things about your post trouble me. First, the Blue Sky controller; not really that good and it may be more of a power loss than a mismatched array under some circumstances. Second, and more important, "300 watt grid tie": there is no way such a set-up would be legal, and it is doubtful that it is safe.

You have in essence 520 Watts of panel. Yielding only 1 kW hour per day shows a pretty sizable loss in the neighbourhood of 500 Watt hours from what might be expected. Much depends on how the power potential is realized/utilized of course.

Solarman · November 2014

Re: Solar Panels Pointing in Different Directions on Same String

Thanks for your reply Caraboo

The panels are not at a perfect angle perpendicular to the sun by any means. They are just in position on 2 separate shed roof tops tilted at about 15 degrees in my yard. The 320 is 15 degrees pointed south, and the 200 is 15 degrees pointed west, but still in the south, (sun soaked) (back yard) I know the angles because I build the sheds. And I know its by far, the wrong angle for this time of year and not perfect even for the summer months.

There is absolutely no hard shading on the panels whatsoever on the panels throughout entire day. I've checked the voltage on both arrays throughout the day separately and they register the same or very close to 20.5 volts. With the breakers on, they drop to about 17volts. I'm still wondering why that is, (resistance in the breaker maybe?) or is the controller doing that?

The Controller is not the best of course, but it was what I could afford. I used more array on purpose for the winter months and cloudy rainy days, where I can still charge the bank up appropriately. If in the summer I find its too much for the controller to handle, I can "pull the plug on some of the PV if need be. This is all still up in the air sort of speak, but as it stands, the most amps I've put in at this time of year in the sun is close to 23.

I've read that getting 3 x your array is ideal and about the best you can expect. Is this incorrect? Are you saying I wont pull 1,560watts in the good months? And if I do, that's not ideal? Just want your opinion.

As far as the grid tie goes "its illegal" well, so is going 10 km over the speed limit, jay walking, double ended male cords, smoking near gasoline pumps. Its probably illegal because there is no UL stamp on the unit. Just because its illegal, does not mean its not safe. It means its not approved by anyone other than me.

Cariboocoot · November 2014

Re: Solar Panels Pointing in Different Directions on Same String

With the panels disconnected the Voltage on them is Voc: 20-ish is normal. Connect them to a load and the Voltage drops, which is also normal. 17 Volts would be around where the Vmp ought to be. Nothing wrong there at all.

What are the specs on an individual panel?
It sure sounds like you have them all in parallel, not series connections facing different ways.

Note that your getting Watts and Watt hours mixed up. Watts is a rate, Watt hours is a quantity. if your 520 Watts of array could produce full power for 5 hours that would be 2600 Watt hours. Don't expect this. Normally they would put out an average of about 77% of their nameplate rating so if it could all be captured it would be (520 * 0.77 * 5) 2kW hours. Shorted up the hours, lose Watt hours. Decrease insolation (poor panel angle), lose Watt hours. Be unable to realize full potential (charging batteries which gives a diminishing return as they come up), lose Watt hours. A battery-based system with all the power stored in, removed from batteries is about 25% less efficient than a grid-tie system.

As for this statement "Just because its illegal, does not mean its not safe" that is backwards. Things are illegal because they are not safe. Those unapproved pieces of equipment could go up in flames and burn your house down. How happy would you be then? Especially after the insurance company spots the wiring and stamps your claim "disapproved". Even legal equipment if installed improperly can cause a fire. This is not some toy to play with: it's electricity. It can kill you in more ways than one.

Solarman · November 2014

Re: Solar Panels Pointing in Different Directions on Same String

Specs on the panels are:
8x 40 watt panels, 2.29 short circuit, 21.5 open circuit, 17.1v
2x 100 watt panels, 5.9 short, 21.5 open circuit 17.1v

looking in the manuals, nothing there, that's what I can remember, panels on rooftop, obviously, cant read that now, if you need more, let me know.

Unapproved, is the key word in your statement. I agree totally with your statement. I would not be covered under my house insurance if they were to prove (key word "prove") in the investigation it was that piece that caused the fire, spark that started the fire, whatever. I agree 100%. But lets look at other scenarios...

You burn a 15amp fuse out in your house and all you can find under your work bench is a 20amp, so you say for now, it will be ok. When I get to the hardware store, I'll get a 15. Days pass, you forget to get the fuse, but it all works good.

What I just did was illegal. I put a 20amp/120v fuse into a circuit that the 14awg wire is only rated for 15amps at 120v. The circuit gets overloaded because someone plugged too many heaters into the outlet in the dead of winter, and the fuse does not blow until the wires start to melt and possibly cause a fire. Innocent mistake right? Wrong, Its a stupid mistake, but only by folks who don't know any better. But it was still illegal.

Here's another scenario...Its illegal to use 2 wires on any electrical screw terminal, (switch, receptacle etc.) But yet ive seen this all the time and corrected it. Its code to make a pig tale with murettes to join the wires the proper way. Again, if the insurance company found this to be the start of the destruction of my dwelling, and PROVE it, I would not be covered.

I'm not a licensed electrician, but I do know how to be safe, and just because a piece of equipment does not have a stamp of approval on it, does not make It unsafe. It just makes it, unapproved.

Illegal is a harsh word, but I don know exactly what you are saying.

.

solar_dave · November 2014

Re: Solar Panels Pointing in Different Directions on Same String

The problem is that an illegal setup is enough for them to say no, now you will have to fight them for a payout. Your lawyer vs insurance company lawyers, what do you think might happen there? They drag you out in court for 5 years, you still pay your mortgage and have no place to live. They argue the illegal devices or wiring show your intent to not be code compliant and that is probably enough to keep you from getting paid in any case.

The easy thing for the insurance company to do is make you prove you are safe while having unapproved install. Hard to do when it is mostly all ashes.

BTW I saw some illegal wiring last week in a house my buddy just bought. A 220 split phase line running to a junction box (well not even a electrical junction box, just some random metal box with no cover) buried in the wall, connections just twisted and taped. A 220 outlet connected with 12 gauge wire then two 110 outlets connected to that junction box with 14 gauge wire. I am so glad we opened up that wall and looked at what was happening in there. At that point we ripped out all the stupid and fixed all the outlets with #12 wire and GFIs run to a sub panel in his garage. He then sat and pulled every device out of the walls in every room looking for more stupid. Found one more where the hot water heater had a 15 amp DPST toggle switch to it. The connection to the switch was made with automotive type crimp connector eyelets, several of them melted along with the switch quite chard along its full length. Ripped all that out and replaced with the proper wire nuts.

Talk about a fire waiting to happen. The previous owner was quite handy you see and his neighbors all knew about some of his antics.

Cariboocoot · November 2014

Re: Solar Panels Pointing in Different Directions on Same String

solar_dave's comments about the legality are spot on. So many of us have seen illegal and unsafe wiring that was nevertheless working and hadn't burned the place down, but we are left wondering why and knowing it would only be a matter of time before luck ran out. It's scary. As for those not certified inverters - I wouldn't trust them as far as I could kick them with my bad leg. Everything around them may be perfectly okay, but what's inside you don't know about. It doesn't take much arcing to start a fire, and with 120 Volts you can get a good arc sustained. Amazing how many inflammable materials are inside too.

Your panel specs indicate they are perfectly compatible in a parallel wiring scenario. Example:

Two 100 Watts in series makes 34.2 Vmp.
Two of the 40 Watts in series makes 34.2 Vmp.
You can then parallel the strings without any worries; the current available will simply add up.

Note that if you tried to put one of the 100 Watt panels in series with one of the 40 Watts you would be limiting the current to the lower value of 2.29 Amps effectively reducing the power from the 100 Watt to the same 40 Watts.

Solarman · November 2014

Re: Solar Panels Pointing in Different Directions on Same String

You saw the same thing I saw a few years back. Except there was no box at all. Wires taped together with murettes inside the wall stuffed into the insulation that my brother was renovating. This was 220 running a clothes dryer. Now that was scary to see. My bro could not believe what he was seeing. Of course, he started ripping out all the wireing and checking for more stupid. Don't recall if he found more.

Yes, my system is wired in parallel, and its a 12volt system.

Thanks for all your comments, everyone that is.

stmar · November 2014

Re: Solar Panels Pointing in Different Directions on Same String

I am thinking of an additional array facing more SW than South as my current array, to catch more late afternoon rays. But I will put the additional array on a separate controller/circuit. Luckily I have wiring in place from a wind turbine that I eliminated.

zoneblue · November 2014

Re: Solar Panels Pointing in Different Directions on Same String

Legal,illegal? The question is how do the costs, benefits, risks and oppurtunities compare. On the one side a no name inverter, with very real safety hazard potential, and the aforementioned devastating insurance liability. On the other side is what, a few saved cents here and there (and thats assuming the system is well designed, in fact most solar systems are a net cost), and the learning experience / hobby value.

Even I, whose middle name is Rebel, can see that for the average household, this is a no brainer. But no one can make that decision for you and your family but you. Here with an off grid system, which was installed by someone with an old and lapsed wiring board cert, in a building with minimal insurance and little structure value, using 100% UL listed gear... thats a balance closer to something im comfortable with. And when we build the house, we will certainly get our installation signed off by a registered sparky, even if we do the work ourselves.

Solar Panels Pointing in Different Directions on Same String

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