Panel Mount Setup

[jasonhc73]

Does it matter which four points I use to mount my panels to the crossbars?

I took out my cad program and setup these models...
My roof is less than 5° tilt, so basically flat.

(I bought 12, and did a really dumb thing, I forgot I only have room for 8)
77x39 panels, so these models are close enough to scale.


Horizontal vs Vertical.



double crossbars VS single crossbars


Mid vs edge.



Does it matter?

 

[Maast]

Heh, never thought of using legos as a model...

FWIW I'll be using a unirac setup for my panels in landscape orientation and tilted an additional 20 degrees from the roofs angle. My reasoning is to keep the panels as low profile as I can because of the occasional windstorms we get, and if the wind grabs a 80 inch panel thats sticking into the air thats a heck of a lot of leverage on the racking and roof mounts and I can see it snapping a panel or opening up leaks in my roof.

 

[HRTKD]

Jason, what orientation and brackets did you end up using?

 

[jasonhc73]

Jason, what orientation and brackets did you end up using?

I am 90% complete, still can't find that round2it, to put the other 6 up on the roof. I have them leaning on the wall, they are working and giving me about 80% of they could if on the roof.

Presently 2 columns of 3 rows. 6 on the roof, 6 on the ground.

Will eventually be, 2 columns of 5 rows horizontal, and a 3rd column of 2 vertical, the right edge in this picture.

 

[jasonhc73]

99.9% Complete. That Round2It was by far the hardest one to find.
12 x 72cell panels, 295w each rated.
2 strings of ~80 V, ~18amps
10 awg PV wire from the panels to the MPP-Solar LV 5048s.
3.5 kWp, usually about 2 kW produced
~ 14 kWh of LiFePO4 junk batteries. Enough to run my house for way more than 7 hours that I demand from them. And enough to charge my Chevy Bolt EV exclusivly.

The 0.1% left to do is to put the PV lines in conduit, I doubt I will though. The PV line I used is outdoor rated and UV protected.


The triple pulley used to hoist them up;

The "ladder sled" scrap wood and harbor freight ball bearing rollers;

The first output installed on the roof;

5:30 PM Early Fall, and 100% behind a shadow from a tree two houses down.

My other system is grid-tied on the sloped part of the roof, installed by the pros, IN ONE DAY!

I was a front-page article in my local newspaper about how people in Kansas are getting screwed by the power company with their "demand tarrif".

 

[HRTKD]

Nice job on the ladder sled.

From what I've read here, wire in conduit is a no-no unless you're sized the wire knowing it would go in conduit. Something about the amount of heat generated.

 

[jasonhc73]

Nice job on the ladder sled.

From what I've read here, wire in conduit is a no-no unless you're sized the wire knowing it would go in conduit. Something about the amount of heat generated.

Interesting idea, 18 amps heating up a conduit. I wonder where these ideas originate.

Every single "installed to code" installation is in conduit from the panels to the inverter. My plan, if I do put it in conduit, is to have a conduit large enough for the connector to fit through also. This would leave a great deal of space if I installed new ends after running through the conduit. My only rationale for the conduit is just to have more protection of the wire. But I do have running alongside the base of the house and it's out of the way of everything.

 

[HRTKD]

Interesting idea, 18 amps heating up a conduit. I wonder where these ideas originate.

Hey, I read it on the Internet!

 

[the_uglydog]

We're down at 14*N latitude so it gets very hot. Our panels are 3 stories up so they can get the sun all day so the wire runs are quite long. We used solar wire from the panels to the combiner boxes that are exposed to the outside, then standard wire from the boxes to the charge controllers inside conduits. We went one size up on the wire size and used a conduit a bit larger than needed. We left both ends of the conduit open, the lower end inside the power room, but the other end inverted to create a weatherhead next to the combiner box. The air circulates through them rather like a chimney and there doesn't seem to be any effect on the wires, voltage drop or temperature inside the conduit. That's about it. the dog

 

[jasonhc73]

I just did the rewiring today.
2 strings of 6. 1 string 6S on input1 of inverter 1, 1 string 6S on input1 on inverter 2.

I guess the next step might be to get some conduit for the four lines going into my garage.

It took about two total hours. I had to lift and reinstall 7 of the 12 panels. Going from parallel lines to serial made everything so much more simple.

If you have the option, I hope you max out your Solar Charge Controller VOC limit. When I checked the VOC, these 12 very used panels, formerly utility grade panels, put out 250.4V and 249.5V VOC. It is really neat to see these things support the load with such low amps.

Tomorrow I'll be able to really see how much lower amps my setup produces. Normally they were pushing 144V and 18 Amps. At 4:00 PM (The last day of February), they were only pulling 0.5 amps at 240ish Volts, but my batteries are charged and this thing is probably just sitting idle.

 

[jasonhc73]

I ran into "Over Voltage" at the MPPT with strings of six of these panels. Now I am three strings of four. Five is the max with these panels, but I only have twelve, and two won't turn the MPPT on.

 

[jasonhc73]

Adding ten more panels.
Canadian Solar 144 half cell panels, 40x80, 340 watt.

This time ground mount.
~$500 in aluminum extruded, the same kind I used on my cargo trailer.

Here is my "ground mount";
Wood, screws, and strong ties - ~$185 at Home Depot.

3 -4x4x12
2 -2x8x16
5 -2x4x12
10 strong ties
4 carriage bolts washers and nuts
100 pack of #9 x 1/1/2 screws
4 80lb bags of quickreet

38° angle, set up to hold 10 panels. 2x5 portrait.



Sketchup Attached.

 

[Sanwizard]

Any updates on your build? How are things working out?

 

[jasonhc73]

Any updates on your build? How are things working out?

I just got the base things that hold everything to the ground.

Instead of digging holes and using concrete, I am using earth anchors aka giant screws. I just screw them into the dirt, and then bolt the 4x4s to the screws.

I am using one right now for my dual axis tracker, it's working nicely.

Amazon.com

 

[jasonhc73]

Home Depot trip... $207 later.

I decided on 24" "rafters" instead of 48".
9 - 2x4x12 rafters
4 - 2x6x8 cross beams
2 - 4x4x8 posts (7'5" will be used)
2 - 4x4x6 posts (4'10" will be used)
all ground contact treated wood.


Just in case you were wondering... just one 4x4x8 piece of iron was $240.

I started with a 38° setup, and then decided to go a summer bias and changed it to 23°.
My latitude is 38° North, with a summer bias, I'll get more energy for the air conditioner months. We have natural gas for the winter, the electricity demand is 1/3 of the air conditioner.

I am using the earth screws instead of the concrete and hole method.

Last night my dual-axis tracker had gusts of nearly 40 mph and wobbled but held strong, that's with just one 4x4 post attached to the earth screw. This fixed mount system is

The top of the panel at the peak is the same height as the panels on my utility room.
The sidewalk is where the wall of the house is.
The white thing in the grass is my irrigation line, just so I know I'm not killing it.

I am attaching real PV racking to all the 2x4s. I imagine it's possible to just skip that step and just bolt everything to the 2x4s.
I used these rails on my cargo trailer build and really like them.





Here is what my 10 additional panels will be adding to;

Attached is the SketchUp drawing.

 

[Sanwizard]

Looks great! If you end up needing something sturdier, check out Grainger supply. They have the exact same ground mount components as Snap-n-rack at MUCH less expense, and their ground mount kits dont even include the 1.25 inch schedule 40 pipe.
I paid a bit over $400 for my parts without the pipe.

The reason I bring this up is if you need a permit, or an Insurance policy on the house, there are some wind and load standards you may need to meet in your area. Things like depth and width of veritcal mount posts becomes important

 

[jasonhc73]

Finally a under 90°F day.

Main base cut and attached.



I added a diagonal brace N/S. This made an enormous difference in the rigidity.

I thought about adding diagonals to the E/W beams also, but it is very sturdy and rigid E/W.

 

[jasonhc73]

Wood part complete.





Next, take apart the dual-axis tracker, then install the panel racks, and finally the panels.

 

[HRTKD]

Are you ditching your dual axis tracker?

 

[jasonhc73]

Are you ditching your dual axis tracker?

Not really.

I have 12 panels on the flat part of the roof.

I will take two panels from there so I can have two strings of 5 up there. Right now it is two strings, of 4, one is 4s, and the other is 4s2p. I like 5S better. I had it at 6S when I first connected it, but it kept hitting the VOC limit in the early am.

The other reason I have to move the tracker is that it hits the panel mount in the late evening.

When all is complete, I'll have 4 strings of 5 on my 2 MPP-Solar LV6548's.

The two panels on the dual-axis tracker are on grid-tied microinverters, I just plug it into the wall outlet.