Temperature sensors
The day after I mounted the temperature sensors on the panels, we had a big storm. Had this happened after we had put the glazing on, this would not have been a problem. In reality, despite the sensors being encased in a large blob of silicone, the water managed to do some impressive capillary action where the wires enter the silicone, shorting out 5 of the sensors. One of the sensors inside the tank also failed, though this was more expected. 12/18 still working!
Water tanks
The original setup made use of an old blue plastic water tank, which acted as a heat store (unpressurised) through which passed a couple of copper coils carrying the water to be heated.
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| System diagram - with heat exchanger. |
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| Old blue tank with heat exchanger coils. |
While the heat exchanger method was giving decent enough results, after a few days of sitting at 70-80°C, it became clear that the surface of the plastic was not responding well to the hot water, so we bought a new superior quality (allegedly!) tank to replace it.
This tank had the advantage of having a screw top, hopefully allowing us to seal the tank. This would allow us to run the tank under pressure with direct connections to the water supply, dispensing with the heat exchanger coils. The larger tank will also run cooler, meaning lower heat losses and thus better efficiency.
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| System diagram - without heat exchanger. |
In a separate issue, it was found that the pressure loss caused by all the additional pipework meant that there was no longer enough pressure for the washing machine's liking (it's a bit fussy!). So we raised the height of the water tower supplying the pressure by another 5 feet.
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| Newly raised water tower. |
Anyway, yesterday we sealed the top of the tank, screwing the top on tight with silicone applied to the screw thread. After giving it a few hours to cure, I opened the valve from the water tower. The tank ballooned out slightly as expected, then the top just popped off! Inspection revealed no cracks or tears anywhere; the lid had apparently just stretched enough for the screw threads to pass over one another.
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| Recalcitrant lid (with air release valve and sensor leads), having just popped off. |
So, take 2: this morning we strung a bunch of jubilee clips together around the edge of the lid, with the hope of holding the screw threads in a meshing position. This seems to hold okay, but the way the tank bulges makes me nervous about its future longevity.
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| Bulging lid. The rest of the tank looks similarly bloated. |
I think we'll revert to the heat exchanger plan (assuming we can get the kinks out of the copper pipe).
Tank stand
A stand which was adequate for the 600l tank was not sufficiently strong for the new 1200l tank, with a couple of dodgy welds breaking. Fortunately we spotted one of the legs beginning to bend in time to avert a complete collapse, and the stand was then beefed up considerably with an extra central support and some proper diagonals made of some nice new chunky angle iron to stop it flexing.
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| Beefed up tank stand with new 1200l tank. |
These problems partly stem from the way people are taught to learn parrot-fashion and the general low standard of education here - the guys have an idea what a structure should look like, but often without really understanding why you need to put a particular strut in a particular place. Hence you will end up with something which looks similar to a strong structure, without necessarily having the function of one.
