This kit enables one person to install a solar panel onto a low level slate roof, it can also be used on other types of roof. The kit also includes moulds to make the rubber gaskets and bushings along with tools to place the parts just in case a person is not able to climb or stand on the roof.
NOTE: this instructable is heavily reliant on 3d printed parts you will either need your own printer or have access to a service.
Quick guide / Index
1. Make a jig that helps mark the positions of the bolt holes to be cut.
2. (Optional ways to make the positioning jig)
3. Survey the area on the roof inside and out, make sure prospective holes can go clean through with no obstruction.
4. Screw or affix the jig in place and mark out the holes with chalk
5. Buy special diamond coated drill bits.
6. 3D Print the Cable vent and Its Ancillary Components
7. Make rubber parts using the included 3D printable moulds
8. How to use rubber parts
9. Setting up the cable vent
10. Cut holes and place panel
11. Rafter mounts
Step 1: 3D Print a Jig
The first step is to download and print a simple jig that helps locate
and position the mounting bolts on your solar panel. The holes that you will cut into your roof need to line up precisely with the holes on your solar panel and in most cases you will not be able to see through the roof to do this! You now need to 3D print the jig and can download this part here, it is a part that lets you use readily available wooden dowel rods as a frame. Dowel rods can be found at any DIY hardware store and will slide into the 3D printed part. This frame will be positioned on the underside of the roof where you can easily and accurately mark out the hole positions by drawing a circle of chalk around the pegs. The 3D printed part needs to be printed out four times and is designed to be used with 11mm diameter dowel rods although you can modify this by using FreeCAD if you want to use a different size rod. In the image, the pegs that look like legs on the green component are 8mm dowel rods and are guides that you will need to align up with the holes on the back side of the solar panel (these pegs are the same diameter as pencils). Once the pegs have been aligned the wooden rods should be screwed or glued in place and once set will be used to draw marking circles onto the surface of your roof.
1. 3D Print four identical dowel holders
2. Insert and secure the pegs
3. loosely insert the dowel rods
4. position the pegs on the loose frame into the bolt holes on the reverse of the solar panel
5. Tighten up the jig by screwing or gluing the dowel rods in the best position
Step 2: Alternative DIY Version of the Jig
This frame is also fairly easy to make without 3D printing. Some may prefer to improvise if they have plenty of spare scrap laying about. This jig can be made easily and it doesn't need to be particularly strong as you can see in the illustration image. This frame can be improvised and made from a variety of materials like plastic UPVC tubes / Cardboard or anything. Simply position some pegs into your solar panel’s bolt holes and mark their positions onto the frame or measure them.
Step 3: Positioning and Layout
Before you can place the jig and commit to marking a hole you will need to survey the area inside and outside to make sure the approximate locations are safe and able to support the hole. You will need to make sure nothing is going to obstruct the hole like a wooden beam or nail causing unnecessary extra work and you will need to make sure the hole does not fall onto the side of an overlapping slate because the hole will have the potential to cause leaks if not prepared properly. You need to have visual access to both sides of the roof.
A powerful magnet with some blue-tack can be placed onto the outside of the roof with a pole to help you roughly identify an ideal position for your prospective hole. This also helps ensure that there will be no obstacle or problem. Use a tape measure to gauge your top and bottom solar panel limits.
A compass waved about on the inside of the roof can easily identify the location of the magnet. As you can see here in the image there is a wooden beam obstructing the potential hole and I will need to move my jig up or down to avoid this. This technique can be reversed by placing a magnet on the inside and waving a compass over the exposed outside roof whichever is easier.
Step 4: Placement of Jig
Once you have created your jig and worked out roughly where the best place to put it will be, all you need to do is place it inside your roof at your desired location up against the roof surface and mark the positions of the pegs with a chalk. Remove the jig and put it to one side once you have made four marks.
You could hold the jig by hand while marking it out but this can become awkward one handed. It is better to screw it onto a rafter or clamp it into place leaving both hands free for marking.
Step 5: Buy Specialist Drill Bits
The best type of drill bit to use is a diamond coated hole cutter and although that sounds expensive or difficult to find it is quite the opposite. The example image is from eBay to highlight the expectation of price and familiarise you with what the tool looks like.
My particular build uses one 12mm hole cutter to accommodate a M10 70MM bolt for the attachment of the solar panel and one 40MM cutter to mount the cable vent outlet which will be used to feed the solar panel cables inside the building.
These hole cutters can quickly and cleanly cut through several layers
of slate or tile at once without shattering the material. I would recommend that you position the holes in a way that is away from any side edge of the slate / tile especially on the outside of the roof as it is important for the rubber seal to have a nice flat clear surface to lay upon.
Step 6: 3D Print the Cable Vent and Its Ancillary Components
The cable vent is a three part 3D print with an additional two parts that are used for placement and making a gasket from a mould. Download it all here.
The first thing to do after printing is to paint this part to protect it from the elements as it will be exposed on the roof for years, also paint a marker onto the threaded bottom which will indicate where the cable gap on the outside is. The the next step is to feed the MC4 cables in through the top (outside bit) down through the shaft then out past the thread. Glue the lid in place with epoxy glue making sure the gap is open at the front of the lid. The cables will feel quite stiff and you may need to clamp the lid closed while the glue dries.
The Cable vent part is designed to remain partially open with its open side facing down the slope of the roof so that water flows down and past the vent. The lid will need to be glued in place with epoxy glue after the cables have been fed through. This whole part fits into a 40mm hole cut into the middle of the solar panel's footprint. All parts including the silicone mould can be printed right away.
1. Print and test fit the 3D parts.
2. Paint a mark on the bottom of the threaded vent end to indicate the orientation of the top vent.
3. Spray paint the parts to protect them from the weather.
4. Feed the solar panel cables into the main part of the vent.
5. Glue the lid onto the cable vent.
6. (LATER) Place the silicone washer over the threaded vent so that the washer will be outside on the roof.
7. (LATER) Put the vent into the hole using the hook while placing the panel later.
Step 7: Make Rubber Parts
Before you go ahead and cut the holes you will need to have all the parts ready so that you are not waiting for parts while you have holes in your roof.
3D print the washer seal mould and four bushing block moulds. Download it all here.
The rubber parts can be made easily by filling the 3d printed plastic moulds with any silicone, it is also possible to use window sealant, also known as Silicone Caulking. This silicone rubber has a 25+year outdoor life and can be found in many hardware stores. Alternatively RTV silicone, the type used for moulding models will also work. You will need to pour / inject or paste the silicone into the mould then carefully scrape any excess over the top of the mould.
1. Download and print the parts
2. Pour in your chosen silicone remembering to also make the gasket washer for the cable vent
3. Once cured break off plastic 3d print and remove rubber parts
4. (LATER) Place rubber parts on the vent and over the bolts with the provided tools
Step 8: How to Use Rubber Parts
These rubber bushings will suspend the panel above the slate while forming a weatherproof seal around the hole. These bushings protect the slate from momentary force from things like wind or debris. This rubber suspension will cushion the panel allowing a slight play without exerting stress on the slates or panel.
The bolts pull the panel down from under the slates and the rubber bushings cause a spring like tension that keeps the bolts tight against the rafters. The cross section illustration helps visualize how this works.
Most panels come with bolt holes underneath the panel and there are several ways to attach panels by bolting them onto frames that can be permanently fixed to the rafters using sheet metal, these expose access to the panel bolts to potential thieves. This is usually not an issue on a high roof but on lower roofs like sheds this could be exploited.
Use the hook to put the silicone bushings onto the protruding bolts
Step 9: Setting Up the Cable Vent
Before any hole cutting is done you need to be ready with this 3D printed part and you should have already practised
playing with the hook, learn how to attach and detach the hook from the vent shaft.
1. The vent in the hole will hold your panel on the roof prior to bolting
2. It feeds the cables through the roof and into the solar charge controller
3. It prevents rain and water from leaking into your roof
IMPORTANT: Make sure you have put on the moulded washer gasket as soon as you can before placing the part on the roof and make sure it doesn't fall off, if you forget to do this it will be a pain to pull it apart and re-do.
The placement hook will fit on the end of a long dowel or pole and you will use it like a robot arm (unless you can climb on the roof and do it by hand)
At this point the cable vent should already be attached to the solar panel via its cables and the lid on the vent should be glued firmly in place.
Make sure the MC4 cables are strong enough to hold the whole panel. Make sure the MC4 cable connectors will not move through the shaft of the cable vent once they are in place.
Step 10: CUT HOLES AND PLACE PANEL
Drilling the holes out is a fairly quick and easy process and the diamond tipped cutters wont crack the slate. I would recommend that you use a fairly hefty power drill that uses a mains voltage rather than a cordless. Carefully align up the diamond bit to the chalk circles that you drew around the legs of the jig frame earlier.
When the holes have been cut you can balance the panel on the roof while you insert the cable vent using the hook.
Once the panel is on the roof you can use the hook to place the vent into the hole. The vent will have wire protruding from its threaded bottom and you will need to carefully guide the wire into the hole first then the vent using the hook. You will need to unhook and reattach several times. Once the cable vent has fallen into the hole you will need to go Inside under the roof and find the cable vent's screw threaded end.
The vent assembly will temporarily hold the panel in place by its cables while you leave.
Under the roof make sure the position of the cable vent is facing downwards, this can be done by noting the position of a mark that you should have made during painting the part, this is important to prevent water entering the roof. Place the 3D printed nut onto the thread of the vent and lightly tighten the 3D printed part by hand keeping it tight but not so tight that you could have difficulty adjusting it later.
The Cable Vent should sit under the solar panel in the middle of its footprint and will have a 20mm clearance.
There are two ways to approach the bolting configuration, you can either have the bolts facing down out of the panel ready to go into the slate or protruding up out from under the slate ready for the panel to be balanced on top. Whichever way around you do this make sure you stick the rubber bushings over the bolts first before placing the panel down. You can use the hook tool to place the bushings. Make sure you use a long enough dowel rod or pole.
1. Drill the bolt holes.
2. Place the panel on the roof and hold with one hand while you use the hook to insert the cable and vent.
3. Go inside under the roof and screw on the cable vent's nut.
4. Using the bushings hook, apply the silicone rubber blocks over the bolts.
5. Go back to the panel outside and position the panel by hand over the bolts.
Step 11: Rafter Mounts
There are four rafter mounts to 3D print. Download here
Each 3D printed mount will slide over a bolt and you will need to pull down by hand on the print to set the tension before marking the screw holes with a pencil for drilling or self tapping.
As you pull on the mount point you will feel the rubber bushing compress like a spring. Try to feel for a lightly repelling counter force, you will be able to tighten this up later using the bolts if needed. Make sure you don't use to much force because you could buckle the rubber bushings, if the bushings buckle they may not sit flat on the slate and could leak.
The 3D printed mount points are fairly universal, there are two versions a long one and a short one. Also included is the FreeCAD file and STEP file so you could modify it. The length on the long one is about 20cm so that allows for some tolerance play.
Step 12: Using CAD to Modify the Files
The CAD program I used was FreeCAD 0.17 . There is also a (STEP) file included which is an interchangeable format that will allow you to edit or modify in any CAD program. FreeCAD is free software and open source.