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Installation Guide for a Solar Panel Direct Connection to a Vented system    **click here for notes on the alternative 'Indirect' Layout

or HERE for details of heating Swimming Pools

Having been through this process personally, I offer the following description of the stages in fitting your own Evacuated Tube Solar Panel. This is intended as a guide to support an installation into a standard UK 'Vented' plumbing system. These systems are characterised by a cold water storage tank in the loft of the dwelling which supplies water to a hot tank, typically located in an airing cupboard.

 

nb. Properties with a Combi Boiler will not normally be suited to this method

Direct ConnectionGeneral Principles:

Cold water is taken from the base of the hot water storage tank and pumped up to the Solar Collector. The heated water is returned at the top of the storage tank.

As the water in the collector is the actual water you will be bathing in, it cannot contain any antifreeze, so a suitable electronic controller is used to protect the collector from potential frost damage. This operates by briefly circulating the water to prevent freezing. This has only very minimal energy usage.

Stages:

Mount Solar Collector Panel in position

1/ Assemble Solar panel frame. (approx 20 minutes, Instructions provided)

The tubes are not fitted at this stage so the assembled frame is easily manoeuvred into position on the roof.

2/ Mount the frame to its selected location. The ideal site is between South East and South West and the top of the frame at least 20 degrees higher than the base.

roof strap

The panel is secured using suitable 'roof ties' at each corner. These are right angle strips of perforated galvanised steel that screw into the rafter, either through the roof tile or slid flat between an upper and lower tile. A single stainless steel bolt (supplied) fixes the tie to the frame at each corner.

3/ Make a 25mm hole in the roof for the pipe work to pass through. A single hole will suffice for both feed and return pipes. This is later weatherproofed with lead or mastic flashing. Alternatively, the pipe can be laid between two tiles and will fit snugly if a shallow groove is cut in the tiles to accommodate the pipe.

Make Plumbing Connections

4/ Turn off mains water at stopcock and open ground floor taps. Drain down the hot tank by the drain valve fitted to the base of the cold supply. For speed, some plumbers prefer to siphon the contents out from the top 'hot outlet pipe'

5/ Cut the pipes and fit 22mm compression Tee fittings to both the inlet and outlet pipes to the hot tank. Place gate-valves on both connections to allow future isolation of all new pipe work.

Base connection-supply to panel

Photo above shows the tank's cold supply teed off to a gate-valve. The pump is connected to the black rubber hose on the RHS. The green hose is the tank drain point described in 4/

hot return from panel

The top of the Hot Water Tank, with connection and valve. Heated water from the panel re-enters the tank here, ready for use.

6/ Run pipe work from the new connections to the collector manifold, noting that cool water feed goes to the end without the temperature probe socket. Fit an auto air vent at the outlet (hotter) end of the collector, to trap any air bubbles that form. This prevents air locks forming.

7/ Fit a check valve (one way valve) to the hot return pipe as it joins the tee at the top of the tank. This is to prevent the water circulating in reverse by thermal siphoning at night.

Note: In my own installation I have found that coiled 10mm 'Plumbeasy' plastic pipe used with brass compression fittings and plastic pipe-inserts makes the plumbing task very easy. The temperatures involved in the direct connection method are much cooler than 'indirect' and have been well within the stated ratings of the pipe work. I have not seen any water circulation temps above 85 C even in mid summer as this method is always taking the cooler water from the base of the hot tank. However, I would not recommend using the push fit plumbing fittings.

New Experience 2011:....Whilst I have had no problems using the plastic pipe, I have now seen other installations where a pump failure has allowed a prolonged boil in the panel and the steam has caused the plastic pipe to break down and form a blockage. For that reason, for peace of mind I would now recommend using 10mm copper pipe for the pipework, especially adjacent to the panel on both flow and return.

Fit the Pump and Controller

8/ The best position for the pump is close to the Tee connection on the cool supply side of the circuit. Connection can be made using automotive water hose and jubilee clips.

9/ The controller can be sited to suit yourself where it is visible and has a mains supply for the 12Volt adaptor. The power runs from this control box to the 12Volt pump.

10/ Run the Collector Temperature Probe to the port provided at the RHS of the manifold. Insert it 100mm into the port. Use of thermal paste is not necessary.

11/ Fit the other temperature probe to the base of the hot tank, 125mm to the side and above the cold inlet point. Using a stanley knife, cut a 75mm square of insulation foam out, place the probe against the metal of the tank and replace the insulation to make a snug fit. (see photo above)

Commissioning

12/ When all plumbing is complete, disconnect the pipe to the top gate-valve and open the bottom gate-valve. Allow water to circulate through the circuit and out of the newly loosened pipe. If necessary, switch the pump on to push the water round and bleed the air from the system. Reconnect the pipe to the top gate-valve and open the valve.

13/ Check thoroughly for leaks and power the pump again, to confirm that the water is circulating freely.

14/ Warm the collector temp. probe to confirm the controller and pump are switching in and out correctly. The circuit will trip in when the collector probe is 6 C hotter than the tank probe. The green LED will light and the pump will start.

15/ When checks are complete, fit the heat pipes into the frame and manifold, using the thermal paste provided. This is left to the final stage of the installation as the pipes will create heat as soon as they are exposed to sunlight.    ( process as described in the instruction document provided with the panel)

16/ Wait for bright sunshine and adjust the water flow rate as desired using one of the gate-valves. Slowing the rate increases the temperature of the water entering the hot tank. By way of example, my system is set at about half a turn from closed to provide hotter water.

17/ Insulate all pipe work, keeping the feed and return pipes from touching directly, and weather-seal building at pipe entry point(s).

18/ Once installed, the system should not require any regular maintenance beyond a periodic check that the pump is operating smoothly and that your water is getting hot.

nb. If the pump failed to operate during a sunny day you might expect to hear a knocking sound as the water in the panel turned to steam. This would need urgent attention or temporary covering of the solar panel to shut out the sun's energy. However, by using the Direct method, the maximum pressure within the system is controlled by the head of water from the loft header tank, so the risk of a pressure build up is avoided..

As the pump is the only item with moving parts and is relatively inexpensive, a spare pump is certainly a good investment.

Controlling Overheating

If you have two or more panels, a small hot tank and strong sunshine, there may be a risk of the water in your tank becoming hotter than you want it. This will be most apparent if you are away from home and using no hot water, so the tank will start the day full of hot.

There are several methods of managing this: The simplest method is to shade the panels from the sun when you are away, or manually run the hot water to waste.

Alternatively, you can fit a heat-dump circuit, so that the heated water is diverted round through a towel rail or even an old radiator, mounted in the loft, when the heat is not required in the tank. This might be manually switched or tripped automatically by the Controller at a given maximum tank temperature.

Another solution is to have the Controller start the central heating pump circulating (without starting the boiler), so that any excess heat is extracted through the boiler heat-coil in the Hot Tank and sent round your central heating system. With many thanks to Tim, you can see how this can be done using one of our standard 12V controllers and a couple of relays into your central heating three port valve- click here for the circuit diagram-

**Please don't try this if you have any doubts about your electrical competence, these are mains voltages with all the associated risks**

Problem Solving

"My pump starts running unexpectedly during the night "

Take a look at the temperatures that the controller is seeing - it is unlikely to be a controller fault! Is it showing a positive heat differential between tank and panel? Yes? -That's why it told the pump to run, it thinks there is heat to be harvested.

The pump trips in whenever heat is detected in the panel, relative to the temperature recorded at the base of the water storage tank. If the probe is placed too close to the base, or too close to the point of cold water entry, then drawing hot water off for your bath means cold water flows in to replace it. Mains water is cold! This creates a differential between panel (still warm from the earlier sun) and tank, so the pump trips in.

As the flow can then stir up the stratified water in the tank, the water being pumped round may actually be warmer than the very bottom level, so the pump may then stay on if the probe is very low on the tank.

Solution: Moving the Tank Bottom Probe upwards avoids this happening . The best place is usually about 100mm diagonally above the cold water entry point.

The second possible cause of this behaviour can be an unintended thermal circulation in the circuit, where hot water is able to rise from the top outlet, up to the panel and back down to the base of the tank as it cools. This reverse flow only happens when the pump is switched off but the impact is to heat the panel and thereby trip the pump. As previously, the flow can then stir up the stratified water in the tank, so the water being pumped round may be warmer than the bottom level, so the pump may stay on if the probe is very low on the tank.

Solution: Fit a one way check valve into the circuit so that flow can only occur when the pump is running. These are spring loaded and prevent thermal circulation in either direction, needing the pressure created by the pump to open.

 

**click here for notes on the alternative Indirect Layout

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