Solar Hot Water System Installation Guide
ECOSOLAR Solar Hot Water Heating Installation Guide Energy Conscious Design Limited / EcoSolar 15B Saturn Place, Albany, Auckland, Postal PO Box 81049 • Whenuapai • Auckland • New Zealand Phone 09 442 0996 • Fax 09 442 0997 E info@ecosolar.co.nz • Web. www.ecosolar.co.
Table of Contents Thank You 1 Selling the benefits of SWH 1 System types 16 Mains pressure system 16 Low pressure system 17 Connection to an existing hot water cylinder, Selecting the most appropriate system 2 with no solar system connections Types of system 2 system connections Basics of system sizing 4 System operation and control 4 Caution - issues 9 17 Connection to a hot water cylinder, with solar 17 Solar water heating system types and schematics 18 Direct or open loop systems
Collectors inclined across roof pitch 36 Maximising the benefit from solar hot Water 37 System Control Basic wiring and programming of the ESR21 controller 52 Initial wiring 53 Programming 53 37 System control overview 37 Controller user guides 57 Pumped systems 40 System control using EcoSolar ESR21 solar Temperature sensor installation 40 controller and One Shot backup heating Variable speed drives 40 controller 57 System control using EcoSolar ESR21 solar Over heating 41 Cylinder
S O L A R H O T W A T E R I N S T A L A L T I O N G U I D E Thank you Thank you for choosing an EcoSolar hot water system. You may look forward to many years of monetary savings as well as knowing that you are helping provide a sustainable future for generations to come.
supplied to the hot water cylinder. The efficiency of a system is often overstated or misinterpreted, two of the most common overstated efficiency levels are outlined below; • 97% efficiency – we have heard salespersons promoting that a system is 97% efficient. This level of efficiency is only for the absorber within the collector i.e.
Figure 1 Thermosyphon system Figure 2 Indirect pumped drainback system EcoSolar Energy Conscious Design Limited 3
Figure 3. EcoSolar 12Volt UVR61 controller Basics of system sizing As a rule of thumb solar hot water systems are often sized on the basis of 1m2 of collector area per 50 to 75 litres of water storage or per person. For instance, based upon 75litres of water storage per person a two person house hold should be able to comfortably utilise an existing 135 or 180 litre cylinder.
adequately managed to maximise energy savings and to ensure that excess heat is not provided to the cylinder increasing the risk of overheating. There are numerous methods of providing backup heating 1. electric elements in the cylinder 2. boiler or other heat source heating the water in the cylinder 3. wetback 4. an instantaneous water heater with the solar system acting as a preheater 5.
Figure 4 “One Shot” Backup heating controller, allows manual control of the backup heating. The heating is manually turned on and will be automatically turned off, maximising the savings from the solar system Timeclock – the electric elements or boiler are switched on at a predetermined time towards the end of the day, once the cylinder has been heated by the sun, and only in the event that the water is not up to the desired temperature.
system and automatically switches the wetback pump on only when there is heat available in the wetback. Solar water heating as a preheater In most cases a solar system installed in either a commercial or higher specification domestic system will have to act as a preheater.
Figure 6.
In summary the solar water heating system must be promoted with the correct level of savings else, it is unlikely that the customer will be satisfied with the system. The type of system is key to the reliability of the system and the sizing and control of the system are key to the performance of the system and energy savings achieved. Caution There are several issues that you should be aware of and manage prior to installing a solar hot water system.
be confirmed and the valve replaced if there is any doubt over its operation and correct function. The function of this valve shall be regularly checked and be appropriately maintained. The tempering valve must be suitable for the high temperatures experienced in solar systems • damage to system components. Some components installed in conventional hot water systems are not compatible with the high temperatures experienced in solar hot water systems.
drain the contents of the tank to solve the problem. If the glycol is replaced, it should be drained from the system, contained and disposed of in a suitable manner. Another commonly found problem is that of incorrectly sized expansion vessels. Any thermal expansion of the antifreeze mixture is taken up within the expansion vessel, this vessel is often undersized and the excess expansion results in discharge from the pressure relief valve.
close after the water has warmed up, this results in excess water usage. The valves are susceptible to damage and go out of calibration if exposed to high temperatures. Increased reliability can be obtained if the frost valves are installed on a 300mm length of uninsulated copper tube with a heat trap, thereby limiting the heat from the valve. These valves are useful as a back up to the controller frost protection and also on thermosyphon systems where no controllers are installed.
Cylinders There are many options for hot water cylinders. Low pressure Low pressure copper cylinders offer a good resilience to high water temperatures as experienced in solar water heating systems and are historically proven for most areas. There are several areas in New Zealand that suffer from poor water quality and this can result in a significantly reduced life expectancy. Many households now insist on higher water pressures and this limits the number of low pressure cylinders being installed.
operate as a direct (open loop) system, that is, the water contained within the cylinder that is drawn off at the taps is also the water that circulates through the solar collector. Most existing cylinders do not have an internal heat exchanger and therefore if a solar system is being retrofitted on to an existing cylinder, the solar heating system will generally need to operate as a direct system, that is unless an external or retrofit heat exchanger is installed.
Thermosyphon systems Thermosyphon systems do not have pumps and operate on the principle of warm water rising from the solar collector into the hot water cylinder. Thermosyphon systems can either have the cylinder close coupled to the collectors or have a remote mounted cylinder. The systems with horizontal cylinders, such as the case with close coupled systems, have reduced efficiency due to thermal mixing within the cylinder.
System Types There are two overall types of thermal hot water systems; • Direct System • Indirect System In a direct system the hot water that is heated as it passes through the solar collector is supplied to the taps. An indirect system has a heat exchanger, generally within the hot water cylinder which transfers heat between the liquid being heated in the solar collector and the hot water that is drawn off at the taps.
• open vented, a vent pipe will extend from the cylinder through the roof and terminate some distance above the roof with an open end. • valve vented, a thermal / pressure and / or pressure relief valves will be installed to relief any excess pressure or heat from the cylinder. Low Pressure Systems Low pressure hot water cylinders are generally fabricated from copper, insulated and have a specification stamped on the cladding over the insulation providing details of pressure rating etc.
Symbols TEMPERATURE, PRESSURE, VACUUM RELIEF VALVE PRESSURE REDUCING VALVE AS REQUIRED CIRCULATING PUMP TEMPERING VALVE NON RETURN VALVE STRAINER ISOLATING VALVE PRESSURE RELIEF VALVE TO TUNDISH Solar water heating system types and schematics Direct or open loop systems Many direct systems are the retrofitting of a solar system on to an existing hot water cylinder as shown in Figure 8 and 8.
Figure 8 above shows an open loop solar hot water installation retrofitted on to a cylinder with only bottom entry fittings, no bottom dispersion plate. This installation uses the 4 way inlet fitting.
Figure 9 Mains pressure open loop solar hot water installation, using side entry connections and retrofit 4-way connection.
Indirect or closed loop systems Many indirect or closed loop systems have historically been systems using a Propylene Glycol and corrosion inhibitor, however these system are becoming less favourable as the deficiencies of Propylene glycol are becoming understood. An indirect Glycol based system is shown in Figure 10 below. These systems are resilient to frost however they have a higher installed cost than direct systems, can be exposed to overheating and have increased levels of maintenance.
Figure10 Closed loop glycol based system with single pump and heat exchanger in the DHW cylinder.
Indirect drainback system Drainback systems are often seen to be the most flexible and reliable system and are becoming more commonly installed in NZ. As well as the conventional drainback system as shown in Figure 11 below, options are available to retrofit a drainback system on to an existing cylinder or a cylinder without an internal heat exchange coil, see Figure 12.
Figure 11 Closed loop drainback system with single pump and heat exchanger in the DHW cylinder.
Figure 12 Retrofit indirect drainback system with twin pumps.
Thermosyphon systems Thermosyphon systems do not have pumps and operate on the principle of warm water rising from the solar collector into the hot water cylinder. Thermosyphon solar heating systems can be either direct or indirect systems depending upon site requirements. There are several forms of thermosyphon system as follows; Close coupled The cylinder is mounted directly above the collectors on the roof.
General Installation Pipework All pipework shall be copper and completed in a neat and economical layout, using long radius bends and minimising the use of fittings to ensure that the resistance to flow rate through the pipework is minimised. Pipework shall run straight and true, at a constant grade and parallel to adjacent surfaces. Pipework joints shall be located a minimum of 75mm from walls, beams and floors.
• The pump shall be installed in the flow to the solar collector pipework, i.e. colder pipework. • A non return valve shall be installed about 0.5m from the hot water cylinder on the hot return to the cylinder to eliminate back circulation, (thermosiphon action using warm water from the hot water cylinder to heat the solar collector) Roof penetrations There will invariably be a requirement for both pipes and electrical cables to penetrate the roof.
Solar collector location NOTE The solar collector is to be installed with the vent holes at the bottom or with the new slot vents on the side. The vents shall not be orientated to allow moisture ingress. Orientation The solar collector should be orientated to geographic north for optimum solar gain. Geographic north is between 17 and 24degrees west of magnetic north as shown by a compass. See table below.
Location Geographic north is (X) degrees west of magnetic north, as shown by a compass Latitude (X for locations in NZ are shown below) Cape Reinga 17 34 Kaitia 17.5 35 Whangerei 18 36 Auckland 18.5 37 Hamilton 19 38 Taupo 19.5 39 Palmerston North 20 40 Wellington and Nelson 20.5 41 Kaikoura 21.
Solar collector mounting The collector fixings shall be mad in accordance with the NZBC, G12, AS2 or shall be specifically designed by a structural engineer. The details below are generic, however specific design is required in high / extreme wind zone areas, such as above a height of 8m above ground level.
Figure 14 Fixing method to corrugated iron and long run, pan or deep trough roofing.
Tiled roofing For tiled roofs, install the kitset collector fixings. This kitset consists of 4 lengths of predrilled galvanised strap, 2 lengths of channel, 4 angle brackets and various fixings. The 4 angle brackets are secured in to the channel and temporarily bolted in to the top and bottom of the collector. The collector is then sited in the required location and the positions of the channel marked out on the roof. The collector is then unbolted from the angle brackets.
Figure 15 Fixing method to tiled roofing EcoSolar Energy Conscious Design Limited 34
Flat roof or to increase or decrease collector inclination from roof pitch The concept for increasing the collector pitch off of a pitched roof is shown below. The pitch required shall be stated when ordering the fixing kits from EcoSolar.
Collector inclined across roof pitch This type of installation requires specific design for the design of the collector mounting frame, however the concept is similar to that shown in Figure 16 above. Figure 17 presents a potential system. Please contact us for details.
Maximising the benefit from solar hot water Following these recommendations will further enhance the benefit from your solar hot water system.
The monitoring of the water temperature in the top of the cylinder is a beneficial feature as it allows the user to more closely manage the water temperature in the cylinder, being more informed about how much hot water is available and whether the backup heating should be initiated, see section below on “Existing hot water cylinder heating source”. This controller is installed in cylinders that must have their maximum temperature limited, such as lined steel mains pressure cylinders.
Figure 19 EcoSolar UVR61R3 controller • Ecosolar “OneShot”, this backup heating controller is installed with the above controllers. The user is able to manually turn on the backup heating and the controller will automatically turn the heating off once the water is up to temperature. The user can choose if the heating should only be turned on once, i.e. it will turn off once the water is up to temperature and will not turn on again if the water temperature drops, or to have the backup heating on continually.
Pumped Systems In addition to the control requirements of the thermosyphon systems, pumped solar systems also need a differential temperature controller to only turn on the circulating pump when there is heat to be recovered from the collector, i.e. when the water temperature in the collector is warmer than that of the water in the bottom of the cylinder. Figure 20.
The pumps are installed and set to the high speed (3 on Grundfos) setting. The pump will then always start on the high speed thereby providing the maximum torque to start the pump.
the water pressure and the temperature, for the water to boil and lead to cavitation which can damage the pump. Expansion vessels Expansion vessels will have maximum temperatures that should not be exceeded, this can often be managed with correct location of the expansion vessel. The sizing of expansion vessels is critical for the reliability of the system. Propylene Glycol Heat leads to the premature break down of propylene glycol in to various acids.
Figure 21 Latest generation EcoSolar controller is able to automatically control a solar system to prioritise heat to several heating demands and then dump excess heat so to avoid system overheating.
A heat dump may be an external heat exchanger, such as a fin and tube located under the South facing eaves or shaded under the solar collectors, hot water passes through the heat exchanger transferring the heat to the surrounding air. Another option, especially suited when a hydronic underfloor heating system is being installed, is to install a circuit in an outdoor area, such as under a patio area. The excess heat is then provided to the underfloor heating system which directs it to the heat dump circuit.
Figure 23. Low pressure drainback system with header tank. Mains pressure drainback with receiver – these systems are uncommon in New Zealand but offer many more advantages than conventional closed loop circuits with propylene glycol whilst costing about the same to install. The closed loop is charged with water so that the receiver is a maximum of about two thirds full of water. Provided the system is installed properly the system should operate as follows.
Figure 24. Mains pressure drainback system using a closed loop system Mains pressure hot water drainback system using a heatstore cylinder – see figure 25 below, these systems are becoming more common as again they offer significant advantages over closed loop systems. The cost of installing these systems is much lower than a conventional closed loop system using glycol and therefore these systems are often being installed with an instantaneous gas heater to boost the water temperature upon demand.
Figure 25. Mains pressure hot water drainback system using a heatstore cylinder Reliability As a solar water heating system returns savings over an extended period of time and is generally not located in an readily accessible position, the system needs to be installed and operate with minimum intervention from either the owner or the installer. We all have a duty to ensure the systems we specify or install are fit for purpose and will provide maximum savings for the client.
The first and most popular method is for the occupants to monitor the temperature within the hot water cylinder, using the controller, to ensure there is sufficient hot water for their requirements. The temperature below which additional hot water is required will vary from household to household and the occupants will determine this temperature over time.
to achieve. Another option, although having a greater capital cost, is to install a preheating solar system, these options will be discussed in greater detail in a future article. For maximum savings when installing solar on to gas heated cylinders a solenoid valve is installed on the main gas burner line to hold off the main burner, the solenoid is then initiated by a timer. This will also be the subject of another future article.
Periodic Maintenance To ensure correct system operation and to retain the system and component Warranty, the system must be maintained in accordance with the recommended levels of maintenance. Please also refer to the operation and maintenance manual and check lists for further information.
• Replace cylinder sacrificial anodes • Clean out strainers • Check pump and differential controller Glazing maintenance The glazing will require periodic cleaning, ensure you have a suitable standing area, that will not become wet during cleaning or if it does, will not endanger. Clean during cool times of the day so the glass is not hot. Hose off, clean with a brush using simple green or similar and rinse off again. During the life of the collector, the glazing may be damaged and require replacement.
• Guarantees • Code of Compliance and • Other relevant certificates and information Structural Structural has not been dealt with in this document and it has been assumed that the building has been designed to NZS3604 or equivalent. It is the installer’s responsibility to ensure that the necessary structural assessments have been made.
Initial wiring • • • • • • • • • The reverse of the front plate has a wiring diagram, however remember that when the front cover is flipped over, this diagram is shown as the opposite to the connections on the back plate. The temperature sensor with the pink cable is sensor number 1 and shall be installed in the immersion socket on the top of the solar collector. The cable to this sensor may need to be extended, this shall be done using 0.75mm2 2 core Trurip cable as supplied.
1. With the screen displaying the sensor T1 temperature, use the right hand arrow to scroll through, 4 presses of right hand arrow, from the T1 screen, until the words ENTERPar are shown on the screen. 2. Now press the down arrow, to enter and start programming the parameters, CODE32 appears on the screen, if 32 isn’t shown press the down arrow, now the right hand arrow to change the number to 32, then press the up arrow to select the code number. 3.
temperature as recommended by the cylinder manufacturer, in many cases for mains pressure steel lined cylinders this is 65 to 70OC. The max temperature is always greater than the max temperature. If when reducing the max temperature it will not reduce any further, it is probably because the max temperature needs to be reduced first. 6.
13. Now press the right hand arrow, once CODE32 is displayed press the right hand arrow and then press the up arrow. Then press the left hand arrow until T1 is displayed on the screen. Now press the right hand arrow 5 times, ENTER men is displayed on the screen. Press the down arrow Engl should be displayed, this is the language for the programming.
20. Now press the right hand arrow 21. F Check is displayed, this needs to be turned on, press the down arrow, press the right hand arrow and press the up arrow to select. 22. Now press the right hand arrow HQC is displayed, this is the heat counter, i.e adds up the heat absorbed from the solar system, if it is to be initiated refer to the manual.
controller turns on the pump to circulate water from the cylinder to the collector to raise the collector temperature. The Solar Controller also has the capability to data log the heat being recovered from the collector, this requires the optional flow meter to be installed. The Solar Controller has four buttons of quadrant appearance located to the left of the LCD display.
Please note that the above will limit but not prevent Legionella from establishing its self in the hot water cylinder. The shower head is most at risk most pipework is also a risk area. All the pipework should be regularly flushed to limit the establishment of Legionella this is the case on all hot water systems, more so where tempering valves are installed as the water downstream of the tempering valve only reaches 45OC which is an optimum temperature for Legionella growth.
turns on the pump to circulate water from the cylinder to the collector to raise the collector temperature. The Solar Controller also has the capability to data log and download to a PC, temperatures around the system, solar radiation and the heat being recovered from the collector, these require the optional sensors and flow meter to be installed, together with a USB interface. The Solar Controller has four buttons of quadrant appearance located to the left of the LCD display.
button on the EcoSolar “One Shot” controller. This controller will heat the water and automatically turn off the heating once the water is up to temperature, the user will not need to turn it off. The override switch on the “One Shot” controller turns on and keeps on the electric elements. Under normal use the boost operation should suffice, however, if there is significant hot water usage the user may want to consider using the over-ride button.
