Boll%@!s

All was going so well, and then I broke the Topsflo solar circulator! Nothing to be done about it, but come up with a plan B for the time being. I tried to repair it, but an 8mm copper tube insert and a podge of silicon rubber wasn't going to do it. Leaking like a sieve, no flow through the calorifier and game over for the day. Which was a shame...the solar collector, once filled with water, was getting hot enough to burn my hand on it.

A quick Google, and I can find a replacement pump, but not much change from £60 and about 2 weeks to ship one in from the USA. In the mean time...no hot water.

But...hiding in the polytunnel I have the Wilo Gold circulator which was my first pump I'd used on my wood-fired system. Mains powered, and consuming 35W on it's slowest speed, I'd replaced it with the Topsflo as that only needed 15W at 12vDC and could be battery-powered off grid. As we have power to the shed, this isn't so much of a problem now. Yes, a power overhead but not a complete stumbling block. I removed my short lengths of 15mm copper in the pump line (so I can refit a replacement Topsflo if and when I can find one) and began to fettle the suitable pipework to take the 22mm pump flanges. I ran shy on materials so I need to get a few bits in the morning.

On the upside, I have modified the Maplin Temperature Controlled Switch kit to work as a differential controller using a pair of LM335Z sensors as my inputs. In order to drive a mains-powered pump, I've added a 2A round pin socket (with the plug on the pump cable) and fitted a higher-powered relay. All seems to work just fine and bench tests show excellent results.

So, the collector works, the calorifier is a known quantity, and all I need to do is hook up the pump and get it running. The secondary circuit (cold supply to the tank and hot out to the tap) should be reasonably straightforward. I could have done without the hassle, but as it turned out, the 3m length of tube I'd bought on Friday wasn't enough anyhow, so no major hassle. I'll just be a few days behind on my hot water plans, but that's not the end of the world.

One minor consolation....the Wilo pump I bought on ebay about 4 years ago, for something like £40, now costs about £200 new! If nothing else, I've reused and recycled an expensive surplus item.