He had an airlock in the plumbing ** – fluid circulating properly. This is how hot it gets in partial sun! Wow. Plus that is with only 2/3 of the tubes installed. I’m thinking my load discharge of hydronic radiators will not be big enough.
** This is a short video that explains the principle of evacuated tube solar hot water. We created a little experiment to show how water can be heated for domestic hot water or for heating a swimming pool.