Guide to electrical solar panel self-install
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17-08-2022 10:11am#1
Ive mostly lurked on this forum for information on PV solar panels installations. There is some fantastic information here, so I wanted to try and do my bit giving back some information by outlining how we did our own solar PV install. We were building a new block garden shed, and decided to look into installing solar panels on the roof. We had a family friend who was a RECI electrician and could help where needed.
Specification
Solartricity.ie has an online designer, where you can specify the number of panels that you need, and it will output a Bill Of Materials (BOM) for you to purchase. You can then purchase the materials from them, and they will deliver it all on a pallet within a day or two. For our installation, we wanted 6 panels as it was the most that could be installed on the south facing side of the roof of the new shed that was being built. Some highlights of the final BOM was:
- 6 x 360w panels (2160w in total)
- Solis Mini 2Kw 4G inverter
- “K2” mounting system for slated roof
- Overall cost of kit: 2247e
All parts were included, bar the following:
- 50m 3 core 4mm2 armored AC cable
- This ran from the consumer unit in the house to the inverter in the shed.
- Cost: 170e
- 4” conduit to bury the armoured cable in the garden
- Trunking and clips for cables, for running the AC cable up the shed and house wall.
- Aluminum paneling to place the trunking/cables behind on the shed wall.
Approx overall cost of materials: ~2500e
Return on investment
I used the Irish Government's SEAI online calculator to find out how much money we would save.
https://www.seai.ie/tools/solar-electricity-calculator/
So it looks like we would break even after roughly 7 years, and save 341e every year after that. Note that this was calculated before Putin decided to invade Europe, so the savings are better now due to the increased cost of energy.
To be honest, doing a self-install does not save as much as you would expect compared to getting a professional to do the install due to the very generous grants available. These grants are only available if the installer is a SEAI registered installer, not just a RECI electrician. However, there is still a saving to be made, and I was looking for a project to do, so this looked like an interesting one to learn from.
Installation of the panels
The roof was to be done using bangor clay tiles, as shown below:
https://lh3.googleusercontent.com/eR1vJ0tauPMx6DIHASpRnc5CuBUW_1ZlWL5UE7q21V6NzWDB771wVm35Nwqsf2yJpDeNZ7zFkmROKHLanzKFh8lWKpO50I5bpqXKC4AHtxMZvtJPeXhBTLTa0crcmvwAzuk4-LraxJfSBEkBofsM8VcThese are pretty thick in size, so solartricity were emailed who recommended their flashing kit for cable entry and “K2 Roof Fastner for flat tile, 15cm”.
The overall kit with these fasteners was ordered. The roofer finished installing the roof tiles. We left the scaffold up for easy access to the roof. Solartricity provided an installation PDF guide for the overall system.
This was used to mount the brackets for the mounting rails. Each mount point was marked on a tile and the tile removed using a long flat head screwdriver. The roofer was asked to order a few spare tiles for breakages. Thankfully it was possible to remove all the tiles needed without breaking any.
The guide specifies that the hook is screwed into the timber plant, which is in turn screwed into the rafter. I asked our roofer about this. He said that he could see no need why this was suggested, as it should be better to screw the hook directly into the rafter. As the shed was not in a high-wind load area, we went with this approach.
Shims were cut to ensure that the hooks cleared the tiles correctly, as shown from the instruction manual below:
The panels were mounted to the rails using their clamping system, shown below:
The installed panels are shown below.
Each panel has a female and a male “MC4” connector on a tail. This allows for them to be easily connected in series.
Female connector
Male connector
A long tail was added to the first and last panel with enough DC cable to bring it through the attic for connecting to the inverter. These two connectors were carefully crimped with a proper crimping tool. I bought a couple of spare MC4 connectors off amazon.
An earth had to be run from each panel. This was trickier to install, as there was no obvious connector on the panels, nor was the method described in the manual. As a result, outdoor earthing clamps were purchased from Screwfix and mounted to the aluminum frame of each panel.
A loop was made to each panel in series.
For entry of the cables into the roof, a notch had to be cut in one tile with a junior angle grinder with a diamond blade. This allowed the flashing to be installed.
Flashing for cable entry through the roof
Notch cut in tile for the flashing
The installed cut tile, flashing, and the entry of the three cables is shown below:
A small hole had to be made in the breathable moisture membrane below the cable entry flashing. All cables were secured with cable ties below the panels to keep them away from the elements as much as possible.
Next, onto the installation of the inverter.
Post edited by SchrodingersCat on19
Comments
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Installation of the Inverter
The inverter was mounted to a gable end of the shed in the attic. The following wiring diagram was used:
The specification requires that a firefighter safety switch is installed as close as possible to the entry point of the DC cables into the attic. This disconnects the panels from the house if there is a power cut, for example, if the emergency services disconnect your power from the grid. However, if the inverter is within 1.5m of the entry point, the switch is not required, as the inverter does the same job. This was outlined in the manual, and this was the case in our situation. A photo of the completed installation is shown below:
The DC isolator was wired as follows:
Two tails were added to the DC isolators output and were terminated with male and female MC4 DC connector. These were crimped with a proper tool and inserted into the inverter, as shown by the “DC1” pair of connectors below.
For the Grid (AC) connection on the inverter, a tail was made using the supplied connector and 4mm sq AC cable. This fed into the AC isolator. The AC isolator was wired as follows:
We also connected the earth from the panels into the earth on the AC isolator.
All cables were clipped to the wall to secure them in place. Cable glands were used where appropriate.
Next, we needed to connect the AC isolator to the consumer unit. We had our main consumer unit located in the house. We had a secondary consumer unit located in the shed. The standard method to perform this installation is to connect it to the main consumer unit in the home. It would be more convenient, and save on cabling costs, if we were to connect it to the consumer unit in the shed. Researching this, there were installations described online that did this. But to play it safe, we decided to connect it to the main consumer unit in the house using its own dedicated cable.
We purchased a 50m drum of 4mm sq. cable to do this.
This was run alongside the previous cable from the house to the sheds consumer unit. The gable wall was chased from the attic to the floor. Two 25mm (white) conduits were fitted.
Both cables were put into 25mm conduit and ran down the gable wall, as shown below:
A hole was made under the surface of the floor, leading outside. Four inch ducting was buried under the garden from the shed to the house in which the cables ran. In addition, a separate two inch duct was buried for ethernet.
Shown below is the exit hole from the shed, the four inch ducting, and the two inch ducting for the ethernet cables.
The four inch ducting is shown below
The cable was run up the side of the house with 25mm conduit, into the attic under the eves, and over to the consumer unit.
Next, was the wiring to the consumer unit in the house.
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Wiring to the consumer unit
Note: Please note that the following is provided for reference only. Dont do anything that you are unsure about. Use a qualified professional where appropriate.
The manual indicated that the wiring to the consumer unit was as follows:
Note, a second AC isolator was not indicated in the manual. However, we wished to have one both at the consumer unit side and the shed side for ease of access.
The AC isolator and the consumer unit is shown below:
The internal wiring of the AC isolator is shown below
The bottom AC tail was run into the consumer unit to the RCBO. The following RCBO was purchased from screwfix:
It was wired into the consumer unit as follows:
While we were at it, we wired in an Eastron SDM230 power meter on the main live feed after the main fuse/breaker. Note, this is a "nice to have" and not necessary for the installation.
This would allow us to read the total power usage of the house, or any power that was going back to the grid.
The two modbus wires of the energy meter were wired to raspberry pi using a modbus to usb adapter. A small python script would read the meter every minute and upload the results to a free online service called “Blynk”. This allows you to monitor the power usage and graphs remotely on your phone.
Finally, warning stickers were placed where appropriate, as described in the manual. One is shown below.
You need a RECI electrician to sign off on the installation, both before it is performed (look up “NC6” documentation) and a commissioning cert after. See here for details: https://www.esbnetworks.ie/new-connections/generator-connections-group/micro-generators-
The inverter came with a wifi stick that allows it to upload its generation stats to the cloud. You can configure it using its app. A sample daily graph is shown below:
And that's it!
Overall it was an interesting project. The biggest difficulty I would imagine is getting access to your roof to perform the installation. I would highly recommend solartricity as their documentation and after sales service was great.
Post edited by SchrodingersCat on24 -
very impressive and thanks for the guide.
one thing i noticed was the day time unit rate for electricity you used with the SEAI online calculator was 0.195 cents. Surely its much higher than that? and if so it would bring down the pay back period.
i'm trying to convince the folks to install something similar. this is what i'm getting when i plug in their details.
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