Dave and his father-in-law have been busy the last few days....
Dave will hopefully talk us through the details of what he's done when he gets time, but in the meantime I am taking the liberty of posting up a few pics Dave has sent me of his work in progress.
The panel is a 20 tube evacuated tube panel supplied by Declan McDonald (Eco Systems Direct). The tubes are the big ones (58mm diameter X 1.8m length) and the panel is a quality make/model & MCS accredited. Dave is fitting the panel to his car port roof using an A-frame that came with the panel. The panel used is exactly the same as that used both by fellow 'solar co-opers' George Row in Derry/L'Derry, and Dermot Leonard in Galway.
Dave is wisely taking the 'small steps' approach and retaining his existing standard household tank in the meantime. He may decide to replace it with a solar tank at some stage in the future, but he will play that by ear. Keeping the existing tank can greatly simplify the task of getting a solar hot water system up and running, minimises disruption to the household, and it also keeps the costs down.
To retain his existing tank, Dave is using a plate heat exchanger (PHE) which is expected to work just like the willis solasyphon, albeit significantly less expensive than the willis solasyphon (£50ish for the PHE versus £200ish for the solasyphon). The PHE is exactly the same model used by Dermot Leonard (Galway) and Wookey (GB).
Great work and well done! Please keep the pics coming!
Thanks for posting the pics Cye as i still cant work it out and hopefully you,ll put the rest i sent you as well. So quick progress update-started putting the tubes in yesterday morning (10th july) and by the time i'd half of them in (10) it was heating the water,now it was light drizzle when i started but did clear up but was still overcast so i was surprised/impressed/happy all at the same time.It was still churning out hot water at half 6 when i left for training. I had the tank sensor near the bottom of the tank but after talking with Cye i've moved it to the point where my PHE t's in above the tank ala Willis solasyphon so i'll hadda see how this works. Was up just before 8 this morning and its making hot water and pump is on,i think i,ve hit the jackpot with location as its in a position to heat water all day long!!!! I just need to finish my lagging and tidy the wires up and thats it sorted....well apart from sorting a heat dump next.
the above is the wall on the far side of the hot press. below the red expansion vessel (EV) and to the right slightly is a tiny 12v 6w hot water pump, pumping on the cool side of the loop (from the plate heat exchanger back out to the panel) - This is good practice to maximize the life of the pump as it has the pump running cooler on average than had it been plumbed on the hot side of the solar loop.
The EV is what pressurizes the system & the feed pipe for this is teed into the cold side of the loop - This helps keep heat away from the EV in normal use. The pipe from the tee to the EV goes downwards then up in order to minimise 'single pipe thermosyphoning', again keeping heat away from the EV in normal use. Also note that the EV is plumbed with the shrader valve (car tyre valve) on the base, meaning that the air half of the EV is below the water half of the EV, and this again tends to keep the warmest fluid away from the rubber diaphragm membrane of the EV. The care Dave has taken plumbing the EV means that he was able to avoid the extra expense of using a solar rated EV and instead can use the standard red 'central heating' type of EV.
The pipes to and from the panel pass through the wall into the hot press on the left hand side of this pic, as does one of the white sensor cables for the 12v differential temperature controller. The controller is the wee black box on the floor and is a DIY hack of the Velleman 12v thermostat kit, converting it into a differential temperature controller.
You can also see a garden sprayer in this pic which Dave has used to pressurise the system at the initial commissioning. This is connected into the filling loop of the EV. I believe Dave may have used a Zilmet EV which was purchased with an Altecnic Robokit, latter being a kit of fittings including 3bar pressure relief valve (PRV), filling loop with check valve, pressure guage, etc/
All Dave's plumbing follows best practice for small DIY systems, i.e., using 10mm copper piper with any elbow joins done using 15mm elbows with the 10mm adaptors (this allows a bigger bore for the sharp turn of the pipe thereby minimising resistance to flow and less work on the pump.
pic of Dave's heat dump... (think Dave was seeing a lot of very hot water the last week and was keen to get a heat dump arrangement in place)
this is a 'run-off' type of heat dump, i.e., akin the running the hot tap when the tank get's too hot.
it's about the simplest form of heat dump one can fit, and it's not particularly wasteful of water if the system is sized correctly, as it's really only there to dump heat (hot water) in exceptional circumstances.
it is a solenoid valve where the pipe on the left hand side of the white solenoid valve is tee'd/branched into the hot water pipe feeding the hot tap at the kitchen sink. the outlet of the solenoid valve Dave has fed through the external wall of the house so it dumps safely outside. The pipe protruding outside the house, not shown here, will either be be safely curved inwards to allow the boiling water to trickle safely down the wall or will be fed to a drain, either way there will be no risk of spraying passers by with hot water.
the black cable carrying the 12v control power to the solenoid is also fed through the outside wall to the solenoid.
the solenoid is a 24v washing machine hot water solenoid valve, fit for 90c. Whilst 24v spec, it operates just fine on 12v (i've been using the same model myself for years with no issues)
the valve is triggered by a pipe/tank stat fitted to the base of Dave's hot water tank. this is because Dave's setup (plate heat exchanger / solasyphon) heats the tank from the top down, so we want to trigger the dump when the whole tank has reach max temp. (with a normal solar tank, we would fit the heat dump stat at the top of the tank. )
the solenoid is fitted on the ground floor rather than the first floor bathroom because the spec of the solenoid requires a minimum head (water pressure) to function (0.3 bar i.e., 3m from memory), so we provide some additional pressure by installing the solenoid as low down in the house as possible.
(Health and safety note: If the house has thermostatic mixing valves (TMVs - scald prevention devices) on all hot water taps and showers, or if there is a whole house TMV fitted at the cylinder, then it may be safe to set the dump temperature to possibly 75-80c, otherwise one should set the dump stat to 60c.)