Kevin's off grid system in Marlborough

Now that all is installed I thought you might like so see the installation that you helped put together.

The 85W PV panel is on the main house roof, facing southeast that happens to be just above the small loft space over the garage – the power cables from the panel to the battery are less than 1.5m long so its quite efficient on the charge cycle. The heating panel is high on the garage roof facing southwest. This means the plumbing has a long run along the entire length of the garage roof but it provides minimum shadow so the panel gets the best illumination throughout the day. It also means that the manifold snuggles at the edge of the ridge tiles to minimise the panel profile – I have a constraint on planning that means the tubes must be no more than 80mm above the roof line which I just achieve by running the frame in the gully of the roof tiles. It’s a difficult installation to maintain the profile since all the nuts and bolts are incredibly difficult to get at – I had to get a low profile ratchet and lost most of my knuckles – still its there now. The water feeds also run in the gully of the tiles in the gaps left under the ridge tiles – all in all it’s a neat installation that is not at all obvious to the quick glance.

All controls are in the small loft over the garage extension with the plumbing running along the underside of the ridge and then into the main loft space to meet the cold-water header tank. There are three main controls on the system; on the left is a 10A battery charger controller, in the centre is the pump differential controller and on the right a 300W inverter. There are two fuses next to the charge controller; one for the inverter and one for the pump controller that also supplies a 20W/12V spot light so that I can read the displays. The start-up current of the inverter is more than 10A so I have a relay to switch the current directly from the battery – the coil current coming from the charge controller. The inverter provides 230V power for the downstairs lights and switches in automatically when available. The charge controller switches off the inverter if the battery gets to less than 30% charge.

The Laing pump is exceptional – I’ve had to restrict it and turn it to fixed voltage operation to slow down the flow rate – you can see it hanging from the plumping in the ridge of the roof. The system is direct exchange so the pump takes from the cold feed to the hot water tank and hot water from the panels flow back to the top of the tank. Sensors are half way down the tank and in the sensor tube of the manifold. The hot water storage tank is on the ground floor so the run is long. It has taken a little time to optimise differences and flow rates but today – a sunny September day – the top of the tank hit 59.5ºC with a centre temperature of 50ºC so I guess its working OK! At 9:30 Ts read 26.5ºC, I took the pictures at around 10:30.

The 12V system seems to work fine and a system with a shorter run should be very efficient.