we are planning to install solar panels in few years but as we are renovating our plumbing system now, we will install a new unvented indirect cylinder. If we install a cylinder with dual coil (solar ready) whats the best way to connect it without the solar system installed yet? When installing the cylinder with a solar system, the top one is for the boiler and the bottom one is for solar input but till we install the solar panels, is it better to connect both coil to the boiler (in parallel or serial?) or just the bottom coil to the boiler?