Solar Hot Water

I say it started in 2010, but the seed had been sown many years before. When exactly I can’t remember, but I do remember watching a eco program on the BBC hosted by Dick Strawbridge (, where they used evaporated tubes to heat hot water. Some years later and a Ebay purchase, I had solar hot water kit comprising of:

1 x 210 Liter twin coil storage tank

2 x 20 tube evaporated tube arrays

1 x Pump

1 x Expansion tank

1 x Control unit and related sensors

Just needed to add a load of 15mm copper pipe and high temperature insulation.

Stage 1 – Tank Replacement

The additional water storage capacity of the new tank is quite evident when the two are stood next to each other. It can be seen here that the new tank has the 22mm central heating coil, and the micro bore solar coil at the bottom.

The first jobs is to swap the tanks and return a hot water supply to the house:

Stage 2 – Install Manifolds and Frames

Safety first, good job I have a tree in the front garden:

Frame and manifold roof install:

Stage 3 – Controller and Electrics

There is a main control unit located in the loft and a remote control panel which I located in airing cupboard. There are three temperature sensors (roof, bottom of tank and top of tank).

Stage 4 – Plumbing

The majority of the plumbing is 15mm copper, with the odd bit of 22mm. All joints are compression, solder joints could well fail under the high temperatures coming off the solar array. All insulation is also high temperature.

Once all connected up, just filling with water/antifreeze mix.

Stage 5 – Tube Install

Until this point the tubes were kept out of the sun, the copper bulbs soon heat up. Small addition of heat transfuse compound and the tubes slot in.

Stage 6 – Solar Heated Hot Water

The system monitors the three temperature probes. When the roof is 8 degrees higher than the bottom of the tank, the pump turned on. When this difference drops to 4 degrees the pump turns off. This repeats eventually heating the whole tank.

I’ve generally found this system generates all my hot water needs from April till October. Even outside of this period it’s always pre heating the bottom of the tank up, reducing the energy required from other sources.

Next – First Steps into Solar PV