July 2017, I was contracted to carry out a solar hybrid installation for a domestic facility in Lagos, Nigeria. I visited the facility to carry out an energy audit to come up with a suitable system for my client. Initial audit resulted in peak load of 3.6kw, i was able to convince my client that with some energy saving tips we could reduce his load to 2.6kw and only place 1.9kw load on the system comprising of lighting, 13amp sockets(PC, Phone, Fans etc.), a Fridge-Freezer etc. Pumping machine, toasters, pressing irons etc. was not connected to the solar hybrid system.
Given the forecasted consumption pattern and sun movement, we designed and installed a 2.4kWp PV system, 5kva Inverter and a 9.6kWh battery bank at 50% DOD.
When connecting the load, we noticed that the electrical engineer who carried out the wiring design and installation of the house had carried adopted a ring circuit design for some of the 13amp sockets connecting critical equipment. This is detrimental to our efforts to secure the solar hybrid system because the 13amp socket in the kitchen which was intended for the fridge-freezer was connected to another 13amp socket which was intended for the toaster. In a scenario where there is a power cut and the solar hybrid system automatically comes online it will have to cater for the toaster load as well as other loads which will eventually tell on the system as a toaster load was never intended on the system. The solution for us was to disconnect the ring and connect the 13amps socket directly.
In electricity supply design, a ring circuit is an electrical wiring technique developed and primarily used in the United Kingdom (and some common wealth countries like Nigeria etc.). This design enables the use of smaller-diameter wire (2.5mm) than would be used in a radial circuit of equivalent total current. The reduced diameter conductors in the flexible cords connecting an appliance to the plug intended for use with sockets on a ring circuit are individually protected by a fuse in the plug. Its advantages over radial circuits are therefore reduced quantity of copper used, and greater flexibility of appliances and equipment that can be connected. The primary reason Nigerian electricians have adopted this technique is to use less wire in the wiring of facilities to maximize profit. While this is good for them it is very detrimental to a solar system installation.
If you are installing a solar or inverter system at a brown field site please do carryout due diligence; if you have the opportunity of connecting with the wiring team to get their guidance on how they wired the facility, that’s good if not study the wiring design and make the disconnections and reconnections where you deem fit.
N.B-Sustainable Standards Africa is a social impact organization focused on the achievement of the No. 9 goal of the Sustainable Development Goal’s which is Industrialization, Innovation and Infrastructure with precise attention to Waste, Water and Energy to enable productive and competitive manufacturing in Africa.