Ecosolar Solar Hot Water System User manual

Solar Hot Water System Installation Guide

 EcoSolar Energy Conscious Design Limited
E C O S O L A R
Solar Hot Water Heating Installation Guide
 Energy Conscious Design Limited / EcoSolar
15 Saturn Place, Albany, Auckland,
Postal PO ox 81049 • Whenuapai • Auckland • New Zealand
Phone [phone] • Fax [phone]
E [e-mail] • Web. www.ecosolar.co.nz
Revision Date 29 May 2009

 EcoSolar Energy Conscious Design Limited
Table of Contents
Thank You
Selling the benefits of SWH
Selecting the most appropriate
system 2
Types of system 2
Basics of system sizing 4
System operation and control 4
Caution - issues 9
Building consent and Code Compliance 9
Heat Rejection 9
System Temperatures 9
Freeze Protection 0
Water quality
Collectors 2
Cylinders 3
Low pressure 3
Medium pressure systems 3
Mains pressure 3
Cylinders with/without heat exchangers 3
Cylinder capacity 4
Horizontal versus vertical cylinders 4
Pumped/thermosyphon
systems 4
Pumped systems 4
Thermosyphon systems 5
System types 6
Mains pressure system 6
Low pressure system 7
Connection to an existing hot water cylinder,
with no solar system connections 7
Connection to a hot water cylinder, with solar
system connections 7
Solar water heating system
types and schematics 8
Direct or open loop systems 8
Indirect or closed loop systems 2
Indirect drainback system 23
Thermosyphon systems 26
General Installation 27
Pipework 27
Roof Penetrations 28
Relief Valve 28
Safe Tray 28
Controller 28
Solar Collector Location 29
Orientation 29
Shadows 29
Inclination 29
Solar Collector Mounting 3
Corrugated / iron sheet roofing 3
Tiled roofing 33
Flat roof or to increase or decrease collector
inclination from roof pitch 35

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Collectors inclined across roof pitch 36
Maximising the benefit from
solar hot Water 37
System Control 37
System control overview 37
Pumped systems 40
Temperature sensor installation 40
Variable speed drives 40
Over heating 4
Cylinders 4
Collectors 4
Valves 4
Pumps 4
Expansion vessels 42
Propylene glycol 42
System design and over
heating 42
Heat dumping 42
Drainback 44
Reliability 47
Existing hot water cylinder
heating Source 47
Legionella 49
Safety 50
Periodic Maintenance 50
Glazing maintenance 5
System handover 5
Structural 52
Basic wiring and programming
of the ESR2 controller 52
Initial wiring 53
Programming 53
Controller user guides 57
System control using EcoSolar ESR2 solar
controller and One Shot backup heating
controller 57
System control using EcoSolar ESR2 solar
controller and One Shot backup heating
controller 59

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
 EcoSolar Energy Conscious Design Limited
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.
Please ensure you read these instructions carefully and complete the installation to these guidelines,
the New Zealand uilding Code, AS/NZS3500 and The Code of Practice (COP) for Manufacture
and Installation of Solar Water Heating Systems in New Zealand, this COP is available for download
from www.solarindustries.org.nz.
Where there is a conflicting requirement, either within this or, between documents, suitable
professional guidance should be sought.
This guide is not intended to be exhaustive and there are many types of system and variations there
of, that are not intended to be covered here. For instance, there are systems that incorporate a
second hot water cylinder acting as a preheater and it is possible to incorporate a wetback system for
heating water in winter and the solar system for heating water in summer.
Prior to proceeding with the installation the installer should discuss the requirements with the end
user to ensure an appropriate system is installed. The EcoSolar check sheets should be completed,
guidance sought and complied with where required, and the installer should understand the type of
system most suited to the particular installation.
Selling the benefits of solar water heating
Selling the system and in particular informing the customer what they can expect from the solar
water heating system and selecting the right system for a particular client are key to the success of the
installation. If the system and its benefits are over inflated by the person selling the system to the
customer, then the customer will have unrealistic expectations and is unlikely to be satisfied with the
installation.
A correctly designed, installed and maintained solar water heating system will provide effective
savings on the energy consumption of a household, of around 70% of the electricity consumed for
water heating. As a rule of thumb delivering around 90% of the hot water in Summer, 50 to 75% in
Spring and Autumn and 25 to 40% in Winter.
There are many levels of efficiency being promoted to customers however, the bottom line is that a
correctly designed, installed and operated system will have an annual efficiency in the order of 30 to
40%, this is the percentage of the solar gain that the sun delivers compared to the amount of heat

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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. the absorber within a collector,
which historically was a matt black high temperature paint is often now a selective coating which is
able to receive high levels of solar gain and only reflects back a very low percentage.
•70% efficiency – this level of efficiency is often the peak collector efficiency and will certainly
not be delivered and maintained in practice. This collector efficiency reduces as the water is heated
above the ambient (outside) temperature.
Selecting the most appropriate system
Selecting the right system for a customer can be split into three;
•Type of system – the type of system is key to ensure system reliability and is dependent upon
the climatic conditions of the site and how the customer will use the system.
•Size of system – this is key to the performance of the system and delivering acceptable energy
savings
•System operation and control – there are several levels of system operation and control, the
selection of these is dependent upon how much the customer is willing or able to manually intervene
and control the system.
Type of system
The types of solar hot water system include, thermosyphon systems, pumped systems, drainback
systems, indirect and direct systems. Each of these systems has advantages and disadvantages that
should be understood so that by the most appropriate system is recommended to the customer. For
instance a remote site without reliable power could have a thermosyphon system installed, see Figure
1 below, which requires no power but will probably have a lower efficiency and may require
increased maintenance, alternatively a pumped drainback system could be installed, see Figure 2
below, that would potentially utilise a 12Volt controller (see Figure 3) and pump, the system would
be more efficient, would address the issues of freezing and overheating but may be more expensive
to install than a thermosyphon system.
A batch with an intermittent hot water demand or a house with a variable hot water demand would
probably have a drainback system installed, as this system is able to manage overheating in a fail-safe
manner

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Figure 1 Thermosyphon system
Figure 2 Indirect pumped drainback system

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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. In many cases solar collectors are able to be retrofitted on to an existing cylinder and
providing the issues associated with frost protection, backup heating, excessive temperatures and
volume of water storage are effectively managed, can provide the most cost effective solution with
very favourable returns for the consumer. Such retrofitted systems should be installed such that they
can be extended and the cylinder replaced with a larger one once hot water usage increases i.e. the
couple start a family. A four person household would require a larger system with a 300 litre hot
water cylinder and multiple collectors.
The sizing of solar water heating systems for conventional housing is fairly well known
however, sizing of commercial or larger scale multiple residential sites requires extensive engineering.
The engineering of such systems would require computer simulation of hot water loads and solar
gain to refine the system design. Energy Conscious Design have completed many engineering,
feasibility reports and system designs for high rise multi tenancy dwellings, hotels, retirement villages,
offices, schools, as well as other commercial applications and swimming pools. This engineering
utilises computer software, this together with our historical experience are able to determine if solar is
suitable and deliver well engineered designs for each application.
System operation and control
System operation and control was discussed in previous articles last year. The solar water heating
system will operate automatically by recovering heat from the solar collector to the hot water
cylinder. However, all solar water heating systems need a backup heating system, this needs to be

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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. a boosting cylinder with the solar system acting as a preheater
The first two options highlighted above are usually controlled through a time clock or manual
intervention by the customer, these options are commonly used in domestic systems and will not
suffice in the commercial environment where the solar water heating system has to act as a preheater
as highlighted in items 4 and 5 above.
Electric elements or boiler heated cylinder
These are by far the most common methods of providing backup water heating but its use is rarely
optimised. Solar cylinders often have multiple electric elements, one at the bottom to be used for
Legionella control and one in the upper half of the cylinder for boosting the water temperature. The
use of the electric elements, the boiler or other heat source should be minimised and ideally should
only be switched on at the end of the day if the sun was unable to heat the water to the desired
temperature. There are several methods of controlling the backup heating system.
User intervention – i.e. the customer determines if the water is up to temperature, modern
controllers, such as the one shown above in Figure 3, display the water temperature in the cylinder, if
below a predetermined temperature, the customer manually switches the element or boiler on and
switches it off once the water is up to temperature. Historically. this has been a manual process for
instance using the main element isolator and the problem has been that the customer forgets to turn
the element off thereby leading to increased energy usage. The installation of the EcoSolar “One
shot” controller makes this control method much more user friendly and eliminates the problem of
the electric element being left on. The “One Shot” controller as shown below in Figure 4 allows the
customer to press a button to switch on the backup heating and once the water is up to temperature
the heating is automatically switched off.

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Figure 4 “One Shot” ackup 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
Timecloc – 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. The modern solar controller as shown in Figure 3 above, is able to
determine cylinder temperatures and turn the electric elements or boiler on if required.
Wetbac
Combined solar and wetback heated installations are becoming increasingly common. The solar
system heats the cylinder in the normal way either as a direct or indirect circuit and the wetback
heating is provided directly in an open vented cylinder, or via a heat exchanger in a valve vented
cylinder.
If the wetback is some distance from the cylinder and unable to operate as a thermosyphon system,
the water is able to be pumped between the wetback and cylinder. Some solar controllers, such as the
one shown in Figure 3 above, are able to not only control the solar system, but are also able to
control the wetback circulating pump. The solar controller monitors the temperatures in the wetback

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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. A solar preheated system ensures that there is hot water on demand,
the temperature of the hot water drawn off at the taps is not dependent upon the amount of solar
gain available, in this type of system the customers see a seamless supply of hot water delivered to the
points of use.
The solar preheated water can be supplied to the following boosting systems,
1. an instantaneous gas water heater as shown in Figure 5 below. If the water being heated by the
solar system is up to temperature, the bypass valve in the hot water supply diverts the water around
the instantaneous gas heater, if the water is not up to temperature the bypass valve directs the water
through the instantaneous heater to be heated.
Figure 5. Direct solar water heating system being used as a preheater to an instantaneous gas heater
2. a backup heated cylinder as shown in Figure 6 below. The solar heated water is supplied
from the preheat cylinder to the boosting cylinder as its cold water supply. The boosting cylinder
may be heated by electric elements, gas boiler or another heat source. Figure 6 below shows an
EcoSolar drainback system operating as a solar preheating system with a boiler heated booster
cylinder.

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Figure 6. EcoSolar drainback solar preheat system c/w boiler heated booster cylinder

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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.
Building consent and Code Compliance
You will be required to submit a building consent for the installation of a solar hot water system. An
owner occupier can undertake some of the installation however, in order for the building consent
application to be signed off and a Code of Compliance Certificate granted, a registered plumber will
need to check, complete the installation including connecting in to the existing hot water system or
potable water reticulation and sign off the installation.
Heat Rejection
All solar hot water systems must have a method of discharging heat in event of a control or power
failure. Without a suitably sized method of rejecting heat, in the event of a thermostat or control
system failure or excessive heat being supplied by the solar collector, the hot water cylinder could
explode causing serious injury / death and or damage. There have been many such cases and the
results can and often have been, catastrophic. It is therefore imperative that adequate heat rejection
be maintained.
As a general rule, each 1m
2
of solar collector should have at least 1.5kW of heat rejection capacity, if
in any doubt please consult a suitably qualified and competent Engineer. These systems of relief must
not have isolation valves installed between the heat source and the relief discharge point. Also take
precautions to prevent the hot water discharge from causing damage to building elements or scalding
persons. These discharge points must not be long enough to allow freezing and therefore allowing
pipe blockages to occur. This requires a tundish or air gap to be present at the discharge point of the
relief valve and the relief valve piped away safely. The relief may be hot and therefore the relief drain
from a solar water heating system shall be of copper, not of plastic.
System Temperatures
Solar systems are able to heat the water to very high temperatures this leads to the following
concerns,
•temperature of water delivered from taps. A tempering valve must be installed to limit the
water temperature delivered at the taps. If there is already one installed, its correct operation should

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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. Of
particular concern are;
•mains pressure hot water cylinders which, unless manufactured specifically for use in high
temperature systems, have a recommended temperature limit. In many cases this will be between
70
O
C to 80
O
C. The specification of the installed cylinder should be checked and a temperature
limitation device installed to limit the temperature within the cylinder to within acceptable limits. The
solar controller has this function and should be programmed to suit.
•Pipework. All hot water pipework upstream of the tempering valve should be completed in
copper. Please be aware that many other alternatives have unacceptable temperature limitations and
are not suitable for the high temperatures associated with solar hot water systems.
Frost Protection
Many areas of New Zealand are prone to collectors freezing and subsequent damage, including areas
which are not renowned for heavy frosts or pipes freezing. y their very nature solar collectors are
good at absorbing heat, they are also good at absorbing coolth. The collector temperature is raised
mainly by thermal radiation from the sun, in the same way its temperature is lowered at night by the
cold night sky. A night sky can, especially on a cold clear night, freeze the water within the solar
collector even if the ambient temperatures are above 0
O
C.
The water in the collector generally freezes within the pipe risers, the smaller copper tubes that run
the length of the collector, see Figure 2 below. Once the water in the collector freezes, it generally
results in the riser splitting and a subsequent leak once the ice has thawed. This split in the pipework
can generally be repaired by removing the absorber from the collector and brazing.
Antifreeze
A reliable system of frost protection, indirect systems circulate water with predetermined
concentrations of a suitable Propylene Glycol antifreeze through the collectors and through a heat
exchanger to transfer heat to the hot water cylinder.
eing a chemical, the handling and use of Propylene Glycol should be strictly in accordance with the
manufacturer’s recommendations. The Propylene Glycol should also contain:
•a dye to help identify leaks and system failure. If a customer observes dye in the hot water
from the cylinder they should suspect a leak in the solar system and immediately contact their local
EcoSolar solar installer for guidance.
•a corrosion inhibitor to prevent corrosion in systems containing dissimilar metals.
The PH of the Propylene Glycol mixture should be periodically tested and the mixture replaced as
necessary usually every year. The discharge of Propylene Glycol should be contained and not left to
enter the environment or rainwater tanks. If Propylene Glycol does enter a rainwater tank used for
drinking water, it will have an adverse effect upon the taste of the water and it may be necessary to

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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. To ensure
effective long term system performance the expansion vessel should be suitably sized, most systems
will have an expansion vessel installed with a volume of 18 to 35 litres or more.
NOTE Do not use Ethylene Glycol, as used in vehicle coolant systems, in solar systems as it is toxic,
use only proprietary Propylene Glycol as recommended by the solar water heating supplier.
Drainbac
Indirect and direct drainback systems can be designed to be the most reliable and appropriate solar
water heating system. The systems incorporate a solar controller which only turns the pump on when
there is heat available to be recovered from the collector. When the pump is off, i.e. there is no heat
to be recovered from the solar collector, the solar collectors are empty. When the controller detects a
greater temperature in the collector, it starts the pump, forcing water up in to the collector and
circulates it through to the cylinder. During times of cold weather the pump will not be operating,
therefore there will be no water in the collector and thus, providing the water level is suitable, no risk
of the collector freezing. This system effectively manages the risks of freezing and overheating.
Controller
The EcoSolar solar controllers have functions to start the pump and allow warm water to enter the
collector when low temperatures are recorded by its sensor in the collector, thereby reducing the risk
of the water in the collector freezing. The controller monitors the water temperature in the collector
using a sensor located in the solar collector. For effective control this sensor should be installed
within a dry pocket with heat transfer paste and adequately insulated from the ambient temperatures.
Under normal conditions the controller uses this temperature sensor to determine when the collector
is warmer than the bottom of the cylinder and turns the pump on and off to recover this heat.
If the collector temperature sensor detects that the water temperature within the collector has fallen
below a predetermined temperature, the controller will turn on the pump for a short period of time
to circulate some warm water from the cylinder to the collector to increase the collector temperature
and prevent it from freezing. This is not a fully reliable method of frost control as it relies upon
power being available to the controller and pump, so in the event of a power failure there will be no
frost protection. The accuracy of the temperature sensors also needs to be monitored during
maintenance to ensure they are recording an accurate water temperature.
Frost Valves
These mechanical valves open, when they are subjected to low temperatures, discharging water from
the collector which is replaced by water from the cylinder. This relies upon the correct flow patterns
through the system and collector and water being supplied to the collector being warm. These valves
should be installed at the top and bottom of collectors on direct heating systems. Please note this is
not a fully reliable method of freeze protection, are prone to going out of calibration and are slow to

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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.
Figure 7 Mechanical frost valves
Frost valves rely upon the warm water in the cylinder heating the collectors, this therefore results in
cooling of the hot water cylinder and thus increased energy consumption.
Water Quality
Water that contains a high percentage of foreign matter, is of poor or unacceptable quality or
contains low chlorine concentrations can lead to blockages, corrosion or premature failure of the
systems. Such failures are out of acceptable limits and are not covered by the warranty. Systems
operating under such conditions should have their periodic maintenance increased to suit.
Collectors
For reference the collector specifications are available from the EcoSolar website.

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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.
Medium pressure
Medium pressure copper cylinders offer a good resilience to high water temperatures as experienced
in solar water heating systems and offer increased resilience to poor quality water than low pressure
cylinders. Medium pressure cylinders provide a good reliable cylinder at a lower price than mains
pressure cylinders whilst offering increased water pressures over low pressure cylinders. In many case
a good compromise. However, again many households now insist on higher water pressures and this
limits the number of medium pressure cylinders being installed.
The low and medium pressure cylinders often offer a reduction in water usage, which is becoming
increasingly important.
Mains pressure
There are now more and more options available for purchasers of mains pressure cylinders, including
steel lined and stainless steel cylinders.
Lined steel cylinders are often the lower cost option for mains pressure cylinders however care
should be taken in their selection for solar water heating systems as many have a relatively low
maximum recommended storage temperature. Temperature limitations of between 70 to 85
O
C are
common. Care should be taken in moving steel cylinders as the internal lining can easily be damaged,
which then exposes the steel cylinder to the stored water.
Stainless steel cylinders, especially duplex stainless steel cylinders appear to have a good resilience to
poor water quality and to the higher water temperatures experienced in solar water heating systems.
However their quality and thus life expectancy is very dependent upon the quality and cleanliness of
the manufacturing process.
Cylinders with / without heat exchangers
Cylinders can be fabricated with or without internal heat exchangers and there are several
configurations available. Unless a heat exchanger is installed, the solar water heating system will

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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.
If a new cylinder is being specified it is cost effective to manufacture it with a heat exchanger and
these cylinders are available from several manufacturers in New Zealand.
Cylinder capacity
Domestic solar heated cylinders are generally sized on the basis of 75litres of water storage per
occupant. This commonly results in the installed cylinder being of a greater capacity than would
otherwise be installed. This results in several issues;
•Space allocation and structural loading for the cylinder, although many cylinder manufactures
can produce cylinders to suit the space available
•Existing cylinder storage capacity is often only suitable for two to three people and therefore
retrofit solar systems, where the solar system utilises the existing hot water cylinder, are only suitable
for smaller households. Retrofit systems will be covered in more detail in a future article.
Horizontal versus vertical cylinders
Vertical cylinders are invariably more efficient than horizontal cylinders. However, site limitations
may dictate that a horizontal cylinder be installed.
Most thermosyphon systems are designed as a close coupled package of collector and storage
container with the storage container invariably horizontal for aesthetic reasons as it will be installed
on a roof where a horizontal cylinder blends in better than a vertical cylinder would.
Pumped / Thermosyphon systems
Solar systems can utilise two forms of circulation system;
Pumped systems
These rely upon a small circulating pump to circulate water between the collectors and the hot water
cylinder. These pumps are usually mains operated and are initiated by a controller that only turns the
pump on when the collector is warmer than the bottom of the hot water cylinder. These pumps are
very quiet offering no noise disturbance and only draw between 50 and 100 Watts.
We can also offer 12 volt pumps and controllers which are coupled to a photovoltaic cell of
approximately up to approximately 20 to 30 Watts depending upon system characteristics. These
systems offer increased reliability on sites susceptible to mains power failure. These systems are often
installed in remote sites where thermosyphon systems cannot be suitably installed.

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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.

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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.
This system has the advantage that a suitable antifreeze mixture can be used in place of water in the
solar collector thus limiting the potential of the collector freezing.
All direct and indirect heating solar systems shall incorporate additional suitable relief valves on the
solar circuit such to ensure adequate relief of heat or pressure. These will be in addition to other relief
valves on the cylinder or in the system. Direct systems will usually have pressure relief valves
installed, no isolation valves shall be installed between the cylinder and collectors or relief valve.
Indirect systems will usually have pressure relief valves installed which will be suitably rated for the
installed expansion vessel, if installed. If the system installed is a drainback system there will be an
overflow from the system.
If the hot water cylinder is valve vented, the existing relief valves should be checked for correct
operation and adequate sizing. This needs to be completed by a competent and trained plumber. If
the relief valves sizing or function is in doubt then it should be replaced with a correctly sized relief
valve. The open vent should be checked to ensure that it is not blocked and not becoming blocked.
Mains Pressure Systems
If a high pressure system is installed, it is important to determine the material the hot water cylinder
is made from and to obtain guidance from the manufacturer as to the cylinder’s maximum allowable
temperature. Many high pressure cylinders have a vitreous or glass internal surface that is damaged at
the high temperatures, as experienced in solar hot water heating systems. It is important to limit the
storage temperature within these recommended limits, this can be done by programming the solar
controller and installing three sensors, the third sensor being at the top of the cylinder. At EcoSolar
we tend to specify duplex grade stainless steel cylinders, due to their resilience to temperatures and
pressures and have found them to be a reliable option.
The solar system may have a pressure reducing valve on the inlet to the cylinder and will be vented in
one of two ways either;