Suggestions on routing cables for basic installation

[crashintoty]

I'm planning a simple cheap 4 panel installation on the roof of my 20 ft x 20 ft detached garage - 4 x 305w, 54v panels. I'm in Seattle, Washington (latitude 47.6600° N). Attached is a detached garage similar in size to mine - mine actually has a lower pitched roof and no doors or windows except the car garage door itself (hence the X's). The markings show what I have in mind so far, which is basically that I think the panels should go in the southeast corner (to squeeze out as much sun as possible before my neighbor's house starts shading that roof, west to east). There are gutters on the south end of my garage roof. That box to the right of the garage is my neighbor's detached garage (but it butts up directly to my garage). Due to space issues, my family and I use the left side (north) inside of our garage as storage, park one car in front of the left side of the garage and park the other car inside the garage on the right (south). Because of this, the most abundant space for the charge controller, inverter, battery, etc. along the right side of the east/back wall (inside) - about 7 ft W x 3 ft D.

Looking at this and considering the limitations list above, what's the best way to route the necessary cables and meet bare minimum code or best practice for an installation like this (i.e., PV cut off switch, etc.)?

Also, can I simply attached the panels to the roof using two 12 gauge unistrut/superstrut channels or is the mounting/racking more involved than that (i.e., I need to create a new forum post for this question)?


detached-garage-design-for-sale-pa - mod.jpg

[SunEagle]

I guess I am confused with the word "cheap". A 1200watt solar / battery system is not cheap but if you really want to build it then you may need to meet all local code requirements since the garages are butted next to each other and a fire in your garage could damage your neighbors. Depending on what loads you want to run I would have looked into getting grid power to it instead of using solar and batteries.

You did not mention a battery voltage so for worse case I can say with a 12V system you will need an 80amp MPPT type CC.

I would keep all of the equipment located in the corner of the garage that the panels are on so the wire lengths are as short as possible. You could probably run the wires from the roof into the garage from the East side but it will need to be weather proof.

Since it is an off grid system you will need to know what your local codes are concerning disconnect switches and grounding.

[Ampster]

I'm planning a simple cheap 4 panel installation on the roof of my 20 ft x 20 ft detached garage - 4 x 305w, 54v panels............
Also, can I simply attached the panels to the roof using two 12 gauge unistrut/superstrut channels or is the mounting/racking more involved than that (i.e., I need to create a new forum post for this question)?

Assuming you are going to pull a building permit, you will probably need engineering drawings for the panel mounting. The easiest way to get them is to go to UniRac or Iron Ridge and do a plan that will include the engineering calculations. It is worth using their rails because then you have the engineering details for free. I would find a local supplier or you can order online but shipping rails can be expensive and it might be easier to find a local supplier. I highly recommend the mounting brackets that include flashing so you won't have any issues with leaks. There is also a convenient junction box that also works as a way to get your conduit through the roof into the attic. You can route the conduit from there to the wall where you are going to mount your inverter. As mentioned by @SunEagle, you may want to check your local building department of the Authority Having Jurisdiction (AHJ) to see what their specific requirements are. There are too many to list but they include labels on the conduit and exterior, type of conduit and other usual electrical code requirements.

[crashintoty]

shhhhhhhhhhhhhhhhhhhhucks! I didn't factor code and requirements being this big of a task. Good point about a fire hazard and my neighbor's garage being so close, I didn't even think about that.

Thanks for the info!

[SunEagle]

shhhhhhhhhhhhhhhhhhhhucks! I didn't factor code and requirements being this big of a task. Good point about a fire hazard and my neighbor's garage being so close, I didn't even think about that.

Thanks for the info!

If your system was smaller and totally away from your neighbors garage I would think you only needed to follow the NEC for your state to be in compliance. But that system is pretty big and could be considered a fire hazard by others.

[littleharbor]

Sure looks like a lot of shading going on here. From the angle of the shadow it looks like mid morning. If this continues throughout theday you may not be too impressed with your system's production.

[SunEagle]

Sure looks like a lot of shading going on here. From the angle of the shadow it looks like mid morning. If this continues throughout theday you may not be too impressed with your system's production.

I believe that picture is just an example of a detached garage but not the one the OP owns. I agree that the neighbors garage roof may produce unwanted shadows onto the OP's panels but it is hard to say exactly what will happen.

[crashintoty]

I believe that picture is just an example of a detached garage but not the one the OP owns. I agree that the neighbors garage roof may produce unwanted shadows onto the OP's panels but it is hard to say exactly what will happen.

Yes, that picture is an example, not my actual garage. And the neighbor's garage roof is flat and doesn't shade my roof at all. But his actual house does start to shade my roof when late afternoon hits. Might not be as big of a deal in the summer time, as the sun is higher in the sky.

[crashintoty]

But that system is pretty big and could be considered a fire hazard by others.

Really, this is considered big?!!! This is the small version of the small version of my full plan (that's not a typo). This 4 x 305 watt panel setup (1.22 kWh) is just for me to DIY/tinker with solar. I was then going to graduate to covering the whole garage roof with 10 panels (3.05 kWh) if this is as fun as I think it's going to be. Then the real/final version (hopefully this is equal to or greater than 3.05 kWh DIY garage installation - 3.05 kWh just happens to be the max recorded energy consumption... summer time with AC, I'm assuming) was to have solar professionally installed on my main house roof (not sure what I am going to do with the DIY garage roof installation at that point).

[HarryC]

Are you getting any engineering drawings for the panel mounts? They will advise the best way to attach the panels. They might tell you which hooks are needed and how to clamp the panel onto the rail so that there is some ventilation.They might suggest a weather proof seal. Unistrut can be used and its quite cheap. Cable tidies such as Twist locks might come in handy for attaching cables underneath the solar panel.

[SunEagle]

Really, this is considered big?!!! This is the small version of the small version of my full plan (that's not a typo). This 4 x 305 watt panel setup (1.22 kWh) is just for me to DIY/tinker with solar. I was then going to graduate to covering the whole garage roof with 10 panels (3.05 kWh) if this is as fun as I think it's going to be. Then the real/final version (hopefully this is equal to or greater than 3.05 kWh DIY garage installation - 3.05 kWh just happens to be the max recorded energy consumption... summer time with AC, I'm assuming) was to have solar professionally installed on my main house roof (not sure what I am going to do with the DIY garage roof installation at that point).

Well I guess I felt it was a big installation since mine is only about 340watts and still in the process of being permanently installed. It was originally going to used in my RV but since I moved I decided to use it on my small shed until I can get grid power over to it. I rarely use the power from the batteries except to run an LED light in the shed. It is over kill for that one light but again it was something I put together about 5 years ago before I really understood the cost of a solar/battery system and how little it can provide me what I need for tools and things.

After spending about $2500 on my system I found I could have done better with the panel wattage, batteries and CC and paid about $1000 less. Still it was just a DIY tinker system like yours but portable so not as complicated concerning permits.