Yes, I think the confusion has arisen because the normal Solartwin system that Emord has will not need the coil (unless they too are heating mains-pressure water). As I understand it, the Solartwin system was designed from the ground up with simplicity in mind. No need for antifreeze, hence no need for separation of the solar water and the rest of the water, hence lower cost and less complication. The solar PV-powered pump is a nice touch. The stronger the sun, the faster the pump runs, and therefore the faster the flow rate through the collectors.vtsnowedin wrote:Yes there is nothing "wrong" with the zig zag line it is just how they depict a coil inside a tank that's contents are isolated from mixing with the contents of the tank and can be at a separate pressure. I merely pointed it out as the written description of the system did not agree with the drawing.Tarrel wrote:Nothing wrong with the zig zag line. Water under mains pressure would normally feed into the combi-boiler and be heated instantaneously as it flows through to the taps. The system as shown is merely pre-heating the water before it enters the combi-boiler so the boiler has less work to do, if any.
Even if your solar collectors could work at your mains pressure you might want to maintain the separation as it would guard against a leak in your system leading to a major loss of metered/billed mains water. Here in Vermont solar thermal panels usually have non toxic antifreeze in them and that of course needs to be kept isolated from your consumable water supply.
IIRC, the Solartwin is a British system. Not sure if its antifreeze-free design would stand up to the lower temps typical of a New England winter?