Discoveries, Solar Technology News

Installing PV on a new home

We begin a typical home Solar PV Installation. For a new home being built it is good practice to meet with the builder and the site manager and supervisor. Familiarize yourself with the rules and regulations pertaining to the building site. Work with the builders, plumbers and electricians and not against them, it makes the job work out much better.

First step is safety, for a high roof with a steep pitch we used climbing gear and erected scaffolding, provided by the builder. The aluminium frames were bolted to galvanized steel roof trusses and all the bolts had waterproofing installed and then the special roof tiles. We were able to tie our safety harness to the aluminium frames due to the strength of the rails.

Like a tiler we started in the middle of the roof and worked out towards the sides as we had an even number of tiles in each row. We found that the rafters were not quite straight and lined the PV panels up with the tile lines as that is what the eye will see. Spacers and clamps and the sub frame for the PV Panels were manufactured and supplied by a local company in KZN.

Under the tiles near the bottom the builder installed a sealed enclosure with 2 x 32mm pipes going into the ceiling. We drilled our holes for the glands at the bottom of the enclosure to avoid any moisture or water entering the enclosure or the roof. All string cables were cable tied to the sub structure and kept off the roof and out of the way of water. The PV Panels are quite heavy and the system that we used to secure them does not have a slot to move the bracket or slide the bracket so our measurements had to be extremely accurate. We cut PV pipes and used them to measure from the edge of the roof to the bottom of the PV panels ensuring that the PV panels were parallel and that the gaps were even.

via fuses and then onto a DC busbar on the left hand side of the panel. All cables for the strings were 6mm. The cables from the Busbar to the Surge arrestor were 25mm2, the surge arrestor was connected to earth via an earth spike using 16mm2 cable and also to the the Distribution Board earth using 2.5mm2 cable encouraging lightning to take the path to the earth spike. The roof structure and frames are all earthed to the earth spike via 16mm2 cable by the electrician. A DC isolator was installed in the combiner box and connected to another DC Isolator in the Inverter room. 25mm2 cables were used to connect the DC Combiner Isolator to the DC Isolator in the Inverter room.

The DC Isolators x 3 were connected to the respective Victron MPPT’s, if the PV supply needed to be isolated in the inverter room the isolators were within arms reach. MPPT’s were connected to a DC busbar through Victron fuses using 50mm2 cable due to the voltage being reduced from 130vDC to 48Vdc which meant an increase in current and potential volt drops. All the DC cables connecting to the DC Busbars were cut to the same length to avoid harmonics etc. The Victron Inverter was also connected to the DC busbars via a fuse as was the Freedom Won 10/7 Kwhr Battery.

Final tidying up and commissioning to be added, trunking is not closed yet, DC cables need to be tidied up, Colour Control mounted, labels installed etc. We left space above and below the MPPT for air flow, but still managed to hide the 25mm and 50mm DC cables in trunking.

Now let  us look at the Controls.

The final solution commissioned and up and running. All cables and devices labelled.