Retro-fit Solar Geyser installation manual

This solar geyser installation manual is intended to give you the sufficient knowledge to design and install a retro-fit solar gesyer system. It is recommended that you read the entire solar geyser installation manual before attempting any of the procedures within.

1: Solar Frame Assembly:

1.1 Handling:

The evacuated tubes are made from glass and though they can handle quite a bit of impact they can break. When unpacking, ensure that the bottom of the tube is a shiny silver colour. If it is white it indicates the tube has been broken and it has lost its vacuum.

We recommend that the tubes are left in the box until they need to be inserted into the manifold. If left uncovered in the sun the copper heat transfer tip can reach temperatures of up to 250 degrees, which may cause burn wounds.

The DAKO power evacuated tube solar hot water collectors are supplied as follows:

  • Box containing evacuated tubes.
  • Box containing collector manifold and frame(including reflectors).
  • Box containing tube mounting clips, thermal paste, rubber end pieces and reflector fastening screws. Figure 2 and figure 3.

1.1 Frame assembly:

Figure 1 shows the unassembled frame parts for a solar hot water collector. At the top of the picture is the manifold, left and right are the 2 down bars, bottom is the crossbar, and left and right of the crossbar are the 2 rubber end piece inserts.

Figure 1Unassembled Frame













Each down bar has a number of holes in and two sets of bolt slots. One set of bolt slots are further apart from each other (these are the manifold mountings). The other set of bolt slots are closer together and are for the crossbar mounting.

The frame kit is supplied with a bolt and bracket system for the fastening of the manifold and the crossbar to the down bar.

Bolts

Bolts













Bolting the cross bar to the down bar is shown in Figure 4.

Figure 4Bolting cross bar to the down bar











Figure 5 shows how the manifold is mounted to the down bars.

Figure 5Manifold mounted to the down bar














2. solar hot water collector Placement:

Evacuated tube solar hot water collectors are much less sensitive to placement than flat panel solar hot water collectors but there are still a few basic rules.

  • In the Southern Hemisphere the optimal position for the solar hot water collector is Solar North. Solar North is relatively close to magnetic north. Solar North is the ideal position, but the evacuated tubes solar hot water collector can face anywhere from NE to NW without any considerable loss in performance.
  • The evacuated tube solar hot water collector contains heat pipes inside to do the heat transfer. Because of this function, the solar hot water collector needs to be at a minimum horizontal angle of 18 degrees. Since roof angles are normally between 22 degrees and 45 degrees the collector can be mounted flush on the roof. If however the collector needs to be mounted on a flat roof, a stand giving the collector a minimum tilt of 18 degrees is required.

Other things to take into account are:

  • Trees or other buildings that could cast shade on the collector.
  • How far will the solar hot water collector be from the geyser(long pipe runs cause loss in heat)

3. Roof Mounting and Waterproofing:

3.1 General

More often than not the solar hot water collectors are mounted on the roof, there are many different types of roofs and so there are many different ways to mount the solar hot water collectors. In windy place take extra care to secure the collector.

3.2 Mounting options

On cement tile roofs one can use tin metal strips to fasten the solar hot water collector. Simply slide the strips under the roof tiles and fasten them to the roof trusses. On most roofs however it might be the most secure if you bolt the collector through the roof to a cross beam on the inside.

Once the mounting position has been determined and the method of fastening is decided upon, it is probably easiest if you were to first drill the holes where the copper piping is to come through and connect to the manifold.

Figure 6 shows an example of the copper pipe coming through the roof and connecting to the manifold. Remember to always waterproof these holes afterwards.

Figure 6Copper pipe coming through the roof
















3.3 Pipe connections and Temperature Sensor

Due to the extremely high temperatures reached by the solar hot water collector (+- 250 degrees) the pipe connections close to the manifold must be copper piping and compression fitting. On the one side of the manifold there is a temperature sensor hole. This hole is where the solar controllerís temperature sensor must be inserted. Slide the sensor into the solar manifold so that it penetrates about 300mm. Drill a separate hole through the roof for the sensor wire.

3.4 Air vent valve

This valve needs to be connected to the manifold pipe connection. Trapped air will drastically decrease the performance of the system, thus it is important to bleed all the air out of the system on commissioning.

4. Plumbing in the Roof

4.1 Draining the Geyser

Close the main supply valve to the geyser, switch off the electrics and then drain the geyser. Preferably use a piece of pipe connected to the drain cock that leads outside as often drip trays are poorly installed.

4.2.1 Specialized valve Fitment (for horizontal geysers)

Specialized valve Fitment


















This is a valve specially designed to help in the conversion of standard electrical geysers to solar geysers. Once the geyser has been drained remove the drain cock and fit it to the end of the conversion valve. This conversion valve connects to the cold inlet of the geyser and has a 0.5 m length of copper pipe that sticks into the geyser.

Some geysers have a plastic insert in the cold inlet; this insert needs to be removed in order to connect the conversion valve. Some older geysers have a spreader situated about 100mm in from the cold inlet. For these geysers a hole needs to be drilled through the spreader to allow the insertion of the conversion valve.

4.2.2 Plumbing of vertical geysers

Plumbing of the geyser if it is vertical is easier than that of a horizontal geyser. In fact it is preferred if the geyser is vertical as there is less surface area for the loss of heat. When plumbing in the vertical geyser, a Banjo valve (see figure 7) is essential. The Banjo valve is installed on the outlet on top of the geyser; this then allows this outlet to be used for hot water feed to the house and the pressure release. The hole on the side of the geyser will then be used as the hot water return from the solar hot water collector. The drain cock will then be used as the cold water inlet to the geyser and as the feed from the geyser to the solar hot water collector manifold.

Figure 7Banjo Valve

Schematic installation diagram - vertical


















4.3 Solar Loop Piping

The solar hot water collector can reach extremely high temperatures and therefore copper piping and compression fittings need to be used for these connections. It is also advised to install ball valves in the loop in order, to and from the solar hot water collector, in case maintenance work needs to be done on this section of the system. This allows you to do the maintenance on pipes, the manifold or the circulation pump without having to drain the geyser every time.

4.4 Solar Loop Insulation

Insulating the solar loop drastically influences the thermal performance of the solar system. It is essential that you insulate the loop with high quality pipe insulation, as the water in the solar loop can reach temperatures in excess of 140 degrees, and lesser grade pipe insulation may not handle these temperatures.

4.5 Circulation Pump Installation

The circulation pump needs to pump from the cold water port of the geyser through the manifold and return into the geyser in the hot water port. Please ensure that the pump is installed the right way around, the arrow on the pump indicates the pumping direction. Most of the pumps require the drive shaft to be mounted horizontally; pumps mounted vertically will eventually overheat.

4.6 Re-pressurizing the System

After the geyser plumbing, solar loop plumbing and manifold are all finished you can then turn on the main supply valve. Inspect the system thoroughly for any water leaks (especially the compression fittings).

5. Controller and Electrical Installations

5.1 Controller positioning

The solar control box can be mounted anywhere but ideally the closer to the geyser the better (shorter cable runs). The remote display unit (SR868C6) can be mounted where the customer will have easy access. Please consult client on this topic. Power can be obtained from any plug circuit or mains in the house.

Please consult the controller manual for more information.

5.2 Temperature Sensors and Wiring

The temperature sensor gets inserted into the manifold as explained before, but the other temperature sensor must be inserted into the geyser so as to measure the temperature inside the geyser. Since the element is now going to be controlled by the control box, the geysers thermostat can be removed. The second sensor is then slid into the old thermostat pocket. Twin flex cable can be used to extend the temperature sensor cables if need be. Please consult solar controller manual for more information regarding required wire diameter.

5.3 Circulation Pump Wiring

The solar controller has a 220V ac live and neutral output to the circulation pump. Suitable 220V ac 0.5A cable must be used in order to make the connection between the controller and the circulation pump.

6. System Commissioning

6.1 General

Before switching on the power please double check all connections. Also insure that all maintenance valves are fully opened. Insure that all the air in the system has been released as trapped air will drastically affect the heat transfer. System commissioning mostly involves the solar controller so please consult the controller manual and familiarize yourself with all its functions and settings.

6.2 Circulation Pump Test

Ensure that there is water in the system before activating the pump!
The solar controller has a pump override function to switch on the pump. Activate this function and then feel the pump for vibration to make sure it is working. The pump has 3 speed settings, for most single collector installations the lowest speed can be used. During commissioning it might be good to select the fastest speed in order to pump out any trapped air.

6.3 Electrical Heating Test

Ensure that there is water in the geyser before activating the element!
Activate the solar controllers override function to switch on the electrical heating element. You should hear the relay latching. Leave the element on for a while to insure that the temperature in the geyser is increasing. The controller will automatically switch off the electrical element when the default temperature is reached (set on the controller).

6.4 Temperature Sensor Test

On the remote display unit the temperature readings are visible. Determine the temperatures of the different sensor (consult controller manual) and make sure the values make sense.

6.5 Inserting the Evacuated Tubes

If everything is functioning correctly and there are no leaks in the pipe line the evacuated tubes may be inserted. The thermal transfer tips of the evacuated tubes need to be covered with thermal paste to improve the thermal coupling with the manifold. The paste is also used to stop the copper from self-welding, which will make it very difficult for removal of the tubes at a later stage if need be. The thermal paste should be applied very evenly and lightly, too much thermal paste will cause increased thermal resistance (Figure 8).

Figure 8SInserting the Evacuated Tubes














Before inserting the tubes apply some petroleum jelly in order to aid the insertion process.

8. Cleaning

Before leaving clean the glass tubes with a suitable glass cleaner, this will ensure that maximum solar energy will hit the absorber surface.