norm
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"Work is the curse of the drinking classes" - Oscar Wilde
Posts: 18
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Post by norm on Apr 30, 2011 13:49:10 GMT -5
The starting point.
S1. Auxiliary feed/expansion tank already in roof space. It is not used for anything else, but needed cleaning out and re-plumbing to mains.
S2. "Solar" type domestic hot water cylinder (about 180 litre) was fitted about 3 years ago when the heating system was updated.
S3. The unreliable electricity heated shower was replaced with a pump and thermostat mixer type. Full advantage can be taken of solar heated water for showering.
S4. When the old windows were replaced, one of the double glazed units was saved to act as front window for a solar collector.
S5. There is only a relatively small area of roof which is both south facing and conveniently located for plumbing.
There are a few design features.
D1. Cheap and cheerful design initially.
D2. Plumbing and control unit to be such that the volume of water in the solar collector is equal to the volume of the indirect heating coil in the DHW cylinder. One litre.
D3. The control unit to be differential temperature activated, and activated for a time which allows the entire heated volume of water in the collector to be transferred to the DHW cylinder coil.
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norm
New Member
"Work is the curse of the drinking classes" - Oscar Wilde
Posts: 18
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Post by norm on Apr 30, 2011 13:54:58 GMT -5
The proposed plumbing details are attached below. Notes: 1. The levels shown are approximately to scale. It should be possible to arrange for continuously rising pipe between the cylinder coil and the solar panel. 2. The inverted U at the highest point acts both as an air bleed and as steam/pressure relief. 3. There is no one-way valve. I will include one if there is evidence of water flow in the loop when the pump is off. I don't really want to have one in case it interferes with the effective pump pressure or causes problems when draining the system. Attachments:
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norm
New Member
"Work is the curse of the drinking classes" - Oscar Wilde
Posts: 18
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Post by norm on Apr 30, 2011 13:59:06 GMT -5
The circuit of the proposed controller is below. Notes: 1. It is based on a DIY thermostat available from Maplin. www.maplin.co.uk/thermostat-kit-316982. Two similar thermistors are needed to perform the differential temperature function. Any approximately matched pair would do fine. The ones that I use are both about 100K at room temperature. 3. The capacitor SOT sets the time for which the pump remains operating after being triggered by the temperature difference. Its value will be chosen (see D3 above) by trial and error when the complete system is up and running. 4. The circuit was built on the board supplied by Maplin. Many of the kit components are used. The board needed several modifications on the print side. It would probably have been easier to build the circuit on strip board. Attachments:
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norm
New Member
"Work is the curse of the drinking classes" - Oscar Wilde
Posts: 18
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Post by norm on Apr 30, 2011 14:00:41 GMT -5
Photograph of the controller unit is below. Attachments:
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norm
New Member
"Work is the curse of the drinking classes" - Oscar Wilde
Posts: 18
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Post by norm on Apr 30, 2011 14:05:07 GMT -5
The proposed solar panel is detailed below. 1. The overall size is set by the double glaze unit 1.96m X 0.84m 2. Collector will be 10mm copper pipe snakeing over the surface of a 1.5mm thick aluminium sheet. Detail below. Attachments:
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norm
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"Work is the curse of the drinking classes" - Oscar Wilde
Posts: 18
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Post by norm on Apr 30, 2011 14:09:22 GMT -5
More detail 1. Some detail of bending the pipe is shown below. Note the jam jars, screwed down to decking, used as pattern. Also bending spring at "recent" bend. Attachments:
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norm
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"Work is the curse of the drinking classes" - Oscar Wilde
Posts: 18
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Post by norm on Apr 30, 2011 14:12:26 GMT -5
Total length of copper pipe is about 20m. This length contains one litre of water. When the panel is constructed, and is being tested at ground level, visitors will be welcome. Thank you Cye for the advice so far. I'm sure I will be asking for more very soon. Attachments:
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Post by cye on Apr 30, 2011 14:45:36 GMT -5
Norm, This is great and thanks for sharing details of your installation.
Your plumbing circuit design is very nice, and I especially like the clever multi-purpose vent pipe up at the panel which serves both as an automatic air bleed and pressure release. Should work a treat provided the levels are as shown and there is at least a few inches of fluid in the vertical section of the vent pipe, otherwise air could perhaps get drawn into the fluid.
Thanks also for sharing your pump controller circuit design - Copying this design should be in the reach of us mortals with minimal electronics expertise, and I particularly like the fact that it's broadly based on a £6 project kit available from Maplins.
Keep up the good work!
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norm
New Member
"Work is the curse of the drinking classes" - Oscar Wilde
Posts: 18
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Post by norm on Jun 2, 2011 2:09:27 GMT -5
The surface etching of the aluminium sheet so that matt black paint will adhere. Done using sodium hydroxide (caustic soda) soluion. "Buster" brand kitchen drain/plug hole clearer does the trick. Works for aluminium only. Aluminium sheet (about 1.5 sq metre) outside on ground close to drain. spray some water on it then about 5 or 6 capfulls of "Buster". Brush over surface several times. The reaction gives off hydrogen gas - the "Buster" contains some sort of perfume which stinks. Rubber boots are a good idea also have a hose or bucket of water close by. After 20 or 30 minutes of reaction, hose all away. Photo shows reaction in process, the drain cleaner bottles and detail of the reaction. Attachments:
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norm
New Member
"Work is the curse of the drinking classes" - Oscar Wilde
Posts: 18
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Post by norm on Jul 3, 2011 16:38:49 GMT -5
It's only a month since. Here's what has been done. Aluminium sheet painted with matt black stove type paint. PVC insulating tape placed on sheet along track of copper pipe. Copper pipe secured to sheet with nylon cable ties. Thermistors positioned at top and at about half-way down the sheet. In close contact with the copper pipe. Gaps between pipe and sheet filled with a roof/gutter repair compound. Copper pipe painted with the stove paint. Quickly tested today using car windscreen washer pump and bin of water. Photo is below. The 12V battery is hidden inside the garage. Hope to get longer to experiment tomorrow. Attachments:
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Post by cye on Jul 3, 2011 16:56:03 GMT -5
Norm, looks very well put together. if you need a hand lifting it up onto your roof give me a shout.
what's the roof repair material made of by the way? regards, cye
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norm
New Member
"Work is the curse of the drinking classes" - Oscar Wilde
Posts: 18
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Post by norm on Jul 4, 2011 14:01:37 GMT -5
Cye - pic of the tube of sealer is below. It was being sold at Lidl a month or so ago. It is still a bit flexible even after having been in the sun. I will post about it if it gives problems. Attachments:
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norm
New Member
"Work is the curse of the drinking classes" - Oscar Wilde
Posts: 18
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Post by norm on Jul 4, 2011 14:07:17 GMT -5
Another sunny day and put the double glaze unit in front of the panel. No attempt (yet) to encase the whole unit. Photo is below. Guess its value is in reducing direct heat loss to the surrounding air. Wonder if a single glaze unit would be as effective. A single glaze unit would reflect, and absorb, less of the incident solar energy. Attachments:
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norm
New Member
"Work is the curse of the drinking classes" - Oscar Wilde
Posts: 18
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Post by norm on Jul 4, 2011 14:19:42 GMT -5
Noted the approximate temperatures of the water at the top and bottom of the heat accumulator. Weather was sunny with occasional light cloud. The panel faces near south. The solar panel delivered its heated water to the top of the bin. It was replaced by cooler water pumped from the bottom of the bin. The volume of water in the bin was 24 litres and the volume of the pipe on the solar panel was 1 litre. In the 4 hour period 10:15 to 14:15 the average temperaure went from 22C to about 52C. See the pic below. Guess that the 52C represents equilibrium of heat gain and heat loss. This may be improved when connected to a real DHW cylinder with its much larger volume. And when the solar panel has a draught excluding frame. Attachments:
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Post by cye on Jul 4, 2011 16:24:53 GMT -5
as you suggest, you will get better energy capture efficiency with the bigger tank as efficiency is highest when panel temperature (closely tied to tank base temp) is closest to ambient air temp. bigger tank should provide colder water to the panel for longer.
sealed collector box will help too. several people have suggested that single glazed is as good as DG. Attenuation of the light energy proportional to glass thickness. Try the DG first. You can always split the DG unit with a stanley knife and use the toughened panes for two panels later!
all looks good so far and thanks for posting up the details.
your sealant is for fireplaces as well so i presume high temp rated?
best regards
cye
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