ISO/TR 12596:1995

Solar heating - Swimming-pool heating systems - Dimensions, design and installation guidelines

Gives recommendations for the design, installation and commissioning of solar heating systems for swimming pools, using direct circulation of pool water to the solar collectors. Does not include electrical safety requirements and does not deal with the pool filtration systems.

Chauffage solaire — Systèmes de chauffage pour piscines — Dimensions, conception et guide pour l'installation

General Information

• Status: Withdrawn
• Publication Date: 06-Dec-1995
• Withdrawal Date: 06-Dec-1995
• ICS: 27.160 - Solar energy engineering
• ICS: 97.100.99 - Heaters using other sources of energy
• ICS: 97.220.10 - Sports facilities
• Technical Committee: ISO/TC 180/SC 4 - Systems - Thermal performance, reliability and durability
• Drafting Committee: ISO/TC 180/SC 4 - Systems - Thermal performance, reliability and durability
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 07-Jan-2005
• Completion Date: 13-Dec-2025

Relations

• Corrected By: ISO/TR 12596:1995/Cor 1:1996 - Solar heating - Swimming-pool heating systems - Dimensions, design and installation guidelines - Technical Corrigendum 1
• Effective Date: 06-Jun-2022
• Parent: ISO/TR 12596:1995/Cor 1:1996 - Solar heating - Swimming-pool heating systems - Dimensions, design and installation guidelines - Technical Corrigendum 1
• Effective Date: 15-Apr-2008

Standards Content (Sample)

ISO
TECHNICAL
REPORT TR 12596
First edition
1995-12-15
- Swimming-pool heating
Solar heating
- Dimensions, design and
Systems
installation guidelines
- Systemes de chauffage pour piscines -
Chauffage solaire
Dimensions, conception et guide pour I’installation
Reference number
lSO/TR 12596: 1995(E)
Contents
Page
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.
Scope . . . . .
. . . . . . . . . . . . . . . . . . . . . . . .*.
Definitions
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Solar collectors
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
System hydraulics
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Controls and instrumentation
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pipework
. . . . . . . . . . . .~.
System design
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*.*.
Commissioning
Annexes
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A Calculation of pool heating load
. . . . . . . . . . . . . . . . . . . . .*.
B Pool covers
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C Bibliography
0 ISO 1995
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronie or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-l 211 Geneve 20 l Switzerland
.land
Printed in Switzer
ii
0 ISO ISO/TR 12596:1995(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide
federation of national Standards bodies (ISO member bodies). The work
of preparing International Standards is normally carried out through ISO
technical committees. Esch member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. ISO
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
The main task of technical committees is to prepare International Stan-
dards, but in exceptional circumstances a technical committee may pro-
pose the publication of a Technical Report of one of the following types:
- type 1, when the required support cannot be obtained for the publica-
tion of an International Standard, despite repeated efforts;
- type 2, when the subject is still under technical development or where
for any other reason there is the future but not immediate possibility
of an agreement on an International Standard;
- type 3, when a technical committee has collected data of a different
kind from that which is normally published as an International Standard
(“state of the art”, for example).
Technical Reports of types 1 and 2 are subject to review within three years
of publication, to decide whether they tan be transformed into Inter-
national Standards. Technical Reports of type 3 do not necessarily have to
be reviewed until the data they provide are considered to be no longer
valid or useful.
ISOnR 12596, which is a Technical Report of type 2, was prepared by
Technical Committee ISOnC 180, Solar energy, Subcommittee SC 4,
Systems - Thermal Performance, reliability and durability.
This document is being issued in the type 2 Technical Report series of
publications (according to subclause G.4.2.2 of part 1 of the lSO/IEC Di-
rectives, 1992), as a “prospective Standard for provisional application” in
the field of solar heating Systems for swimming pools because there is
an urgent need for guidance on how Standards in this field should be used
to meet an identified need.
This document is not to be regarded as an “International Standard”. lt is
proposed for provisional application so that information and experience of
its use in practice may be gathered. Comments on the content of this
document should be sent to the ISO Central Secretariat.

A review of this type 2 Technical Report will be carried out not later than
two years after its publication with the Options of: extension for another
two years; conversion into an International Standard; or withdrawal.
Annexes A, B and C of this Technical Report are for information only.

TECHNICAL REPORT 0 60
- Swimming-pool heating Systems -
Solar heating
Dimensions, design and installation guidelines
2.2.3 collector, unglazed: Collector in which the
1 Scope
absorber is directly exposed to the environment.
This Technical Report gives recommendations for the
The rear surface may or may not be insulated.
design, installation and commissioning of solar heat-
ing Systems for swimming pools, using direct circu-
2.2.4 collector, plastic Strip: Collector System in
lation of pool water to the solar collectors. The report
which extruded plastic Strip embodying fluid passages
does not include electrical safety requirements and
is arranged to act as an absorber, on a roof or other
does not deal with the pool filtration Systems to which
base.
a solar heating System is often connected. Annexes
A and B are included dealing with calculation of heat-
The Strip is typically about 50 mm to 150 mm in width
ing load and information concerning pool covers.
and made of flexible elastomeric or plastic material.
The material in this Technical Report is applicable to
all sizes of pools, both domestic and public, that are
2.2.5 collector, plastic Panel: Unglazed collector in
heated by solar energy, either alone or in conjunction
which the absorber is made of rigid plastic sheet em-
with a conventional heating System.
bodying numerous closely spaced passages for fluid.
NOTE 1 Many of the recommendations in this Technical
2.2.6 collector, plastic piping: Collector System in
Report have been adopted from BS 6785 and AS 3634.
which plastic piping is arranged to act as an absorber
on a roof or other base.
An example of such piping is black polyethylene agri-
2 Definitions
cultural piping.
For the purposes of this Technical Report, the follow-
2.3 differential temperature controller: Device
ing definitions apply.
that detects a specified differente between two
temperatures, and controls Pumps and other electrical
2.1 absorber: Device within a solar collector for ab-
devices in accordance with this temperature differ-
sorbing radiant energy and transferring this energy as
ence.
heat into a fluid.
2.4 direct System: Solar heating System in which
2.2 collector: Device designed to absorb solar radi-
the heated water that will be circulated to the pool
ation and transfer the thermal energy so gained to a
Passes through the collectors.
fluid passing through it.
2.5 drain-down System: Direct solar heating sys-
2.2.1 collector, flat plate: Nonconcentrating collec-
tem in which the water tan be drained from the col-
tor in which the absorbing surface is essentially
lectors to prevent freezing.
planar.
2.6 indirect System: System in which a fluid other
Z.Z.2 collector, glazed: Collector in which the ab-
than pool water Passes through the solar collectors.
sorber is covered by a translucent glazing material.
0 ISO
lSO/TR 12596:1995( E)
2.7 reverse return: Arrangement of collector mani- For public pools the Situation is not necessarily the
folding so that all flow paths through the collector Same as for private pools, since their temperature re-
module offer approximately the same resistance to quirements may be different, and year-round oper-
ation of open-air Pools is common in warmer climates.
flow.
There has been substantial use of both glazed and
unglazed collectors in solar heating Systems installed
3 Solar collectors
on large public and commercial pools. The main fea-
tures of the various collector types are outlined in 3.2
3.1 Types
and 3.3.
Solar collector types commonly used for pool heating
vary considerably from those used for providing do- 3.2 Unglazed collectors
mestic hot water. The differentes arise due to the
relatively low temperatures required of swimming
3.2.1 Plastic (or elastomeric) Panel collectors
po01 heating. Also, swimming-pool water is normally
more corrosive than domestic potable water. These collectors usually consist of a sheet containing
closely spaced passages for fluid, with the top and
The use of unglazed, uninsulated collectors for pool
bottom header pipes integrally attached, normally by
heating is now very widespread in the domestic pool
welding. An example is shown in figure 1. Materials
field and has been successfully implemented in large
used for plastic Panel collectors include polyolefins
public pools. The reason is that conventional flat plate
(polyethylene, polypropylene, etc.), acrylic and
collectors have glazing and insulation to reduce heat
polycarbonate.
losses from the collector. Much of collector design for
domestic hot water heaters is devoted to reducing
3.2.2 Plastic (or elastomeric) Strip collectors
heat losses rather than maximizing heat gain. The
losses are essentially proportional to the differente in
These collectors consist of an extruded Strip (of width
temperature between the collector fluid and the am-
around 50 mm to 150 mm), with a number of fluid
bient temperature. Since the collector fluid in a pool
passages moulded into the Strip. The Strips are gen-
heating application is usually much cooler than in a
erally tut to length and connected to header pipes.
domestic hot water application, the potential losses
An example is shown in figure2. Materials used in-
are proportionately less. Hence the tost of glazing and
clude ethylene propylene diene (EPDM) rubbers and
insulation must be offset by a small reduction of
polyvinyl chloride (PVC).
losses at swimming pool temperatures. The perform-
ante of glazed collectors may be lower than the per-
Strip collectors are designed to be laid on existing
formante of unglazed collectors when the pool
roofs or other supports, and their flexibility allows
temperature is close to air temperature, because the them to follow roof contours and curve around ob-
glazing reduces the solar input to the collector. stacles.
Figure 1 - Example of a plastic/elastomeric Panel collector

ISO/TR 12596: 1995(E)
nfifi
ExampLes of Cross-section
Joining web -
Figure 2 -
Plastic Strip collector
3.2.3 Plastic pipe collectors
3.4 Materials
Materials in contact with po01 water should neither
These collectors consist of an arrangement of plastic
contaminate the water nor become corroded under
piping supported on an existing roof or other base.
normal Service conditions. Special precautions should
The piping may be arranged in parallel lengths be-
be observed with respect to the choice of materials
tween headers, similar to Strip collectors, with appro-
priate flow balancing. Alternatively the piping may be in contact with pool water, as this water may contain
arranged in a spiral, however with this arrangement it chlorides or other corrosive minerals. All metals ex-
is difficult to achieve both a satisfactory flow and cept some chrome-nicke1 steels should be avoided for
sufficient thermal contact with the roof. Careful de- these Parts of the System. lt is important to recognize
that not all grades of stainless steel will resist corro-
sign consideration must be given to this style of sys-
sion in these applications; grade 316 is recom-
tem due to the need to avoid airlocks and the limited
heat gain due to Stagnation in long runs of Pipe. Con- mended.
sequently, for a given heat output, such a spiral ar-
Iron and carbon steel are unsuitable for the fluid
rangement requires a roof area larger than other
passages in direct Systems because rapid corrosion
arrangements and may have hydraulic difficulties.
may occur, resulting in the failure of the passages and
rust-staining of the pool Walls and fittings.
All components exposed to solar radiation should be
resistant to ultraviolet radiation. This is especially im-
portant for plastics.
3.3 Glazed collectors
Materials such as EPDM which are able to withstand
freezing without darnage are preferable for all frost-
These collectors have been developed primarily for
exposure Parts.
domestic water heating. The thermal Performance of
glazed and unglazed collector Systems for pool heat-
ing is similar in Summer, but glazed Systems offer
superior Performance in Winter and accordingly glazed
3.5 Collector location
collectors may offer a higher annual solar fraction for
applications that operate all year. However, the higher
tost of glazed collectors may make them less tost 3.5.1 General
effective than unglazed collectors and the higher
temperatures achieved may have detrimental effects In Order to reduce heat losses and pumping power
on System design and component selection (see requirements, collectors should be located so that
. . pipe runs are as short as possible.
6 1)
0 ISO
lSQ/TR 12596:1995(E)
nature of the roof upon which the collectors are to be
3.5.2 Orientation
mounted. An example of the effect of non-ideal
Whenever possible, collectors should face towards
orientation and inclination is given in figure 3, in terms
the equator. The range of collector orientations that
of the collector area required for a given roof orien-
give output similar to a collector facing the equator
tation and inclination compared with that required for
will depend on the location, the local climate and the
ideal orientation and inclination.
time of year the heating is required. The collector
NOTE 3 The example given in figure3 is for Melbourne,
orientation is not significant if the inclination angle is
Australia, latitude 38”S, and is based on the useable solar
less than latitude IO”. Even at high latitudes this re-
energy received over a 12-month period. lt is included as
quirement is acceptable for open pools, since such
an indication only of the effect of non-ideal installation con-
pools are typically only operated in Summer.
ditions and should not be used as the basis of calculations
in other locations. Similar Charts for other locations or other
NOTE 2 Greater deviation from the meridian is allowable
collector types tan be determined from an hourly perform-
in the westerly direction due to the generally higher ambient
ante evaluation over the required heating season.
temperatures in the afternoon.
3.53 Inclination 3.5.4 Shading
The Optimum collector inclination depends on the cli-
Collectors should be located so as to be clear of
mate, location and the time of year that heating is re-
shade for at least 3 h either side of solar noon at any
quired.
time throughout the pool-heating season.
For primarily Summer heating, the collector should be
3.5.5 Site exposure
inclined at an angle not exceeding the latitude angle
of the installation site (recommended value: latitude
Unglazed collectors are particularly subject to heat
-
IO’). For primarily Winter heating, the collector
losses due to wind. Accordingly, for windy sites,
should be inclined at an angle greater than the latitude
consideration should be given to the use of increased
angle by up to 20”.
collector area or the Provision of Windbreaks.
Windbreaks will also assist in reducing heat losses
For Systems installed in domestic pools, the incli-
nation (and orientation) will often be dictated by the from the pool surface.
; 60
t
f -F 50
aJ
is
; 40
E
aJ
: h 30
-
.-
p 20
.-
-
c
.-
& 10
t
u
aJ
-
-
196% 1
u 0
90 75 60 45 30 15 0 15 30 45 60 75 90
West North East
CoLLector orientation, degrees from north
DATA:
Optimum orientation N - W Pool temperature 24 “C
Optimum inclination 20 “C Heating season November - March
Figure 3 - Relative collector output as a function of orientation and inclination (for southern hemisphere)

ISO/TR 12596: 1995(E)
0 ISO
due to its dependence on the amount of Shelter pro-
3.6 Collector dimensions
vided around the pool.
Different design philosophies exist and are described
3.6.1 General
briefly in 3.6.2 and 3.6.3. Procedures for the evalu-
ation of the thermal Performance of glazed and
The amount of collector area required is one of the
unglazed solar pool-heating collectors are defined in
most fundamental aspects of the design of a solar
ISO 9806-1 and ISO 9806-3 respectively.
pool-heating System. Collector performante charac-
teristics will normally be available from the collector
3.6.2 Pools without auxiliary heating
supplier, and the extent to which a rigorous calcu-
(stand-alone Systems)
lation of collector area is needed will depend on the
operational requirements of the pool, including such
Where auxiliary heating is not provided, the pool
matters as the following:
temperature will vary depending upon the local
weather conditions and the amount of wind Shelter
a) whether a requirement exists for a specified
provided. The pool temperature is essentially the
temperature to be maintained; this may be the
equilibrium temperature reached when total pool heat
case in a public po01 used for sporting purposes,
losses are balanced by heat gain due to solar radiation
or when a varying temperature rise is acceptable,
incident on the pool. The addition of collectors to a
such as in a private pool and in most ( lpen-air
stand-alone System will lead to an increased but still
public pools;
varying equilibrium temperature. The main objective
is to extend the swimming season into spring and
swimming season will be al or part
whether the
b)
autumn.
of the year;
In these cases, accurate collector dimensions are of-
whether there is a conventional heating System
ten not essential and design guidelines, dependent
to Supplement the solar heat delivery to the pool;
on the climatic region concerned, may be satisfactory.
Because the temperature of private pools is normally
whether the purchaser wishes to have an indi-
in the region for which collector energy output is ap-
cation of the likely Performance of the System in
proximately the same for all collector types, the col-
regard to temperature and extension of the
lector area does not depend greatly on the type of the
swimming season.
collector. lt is acceptable to treat all unglazed collec-
tors as being equivalent for the purpose of choosing
t-actors that need to be considered include:
collector area in these applications.
Location - local climate
As a guide, the following collector areas will generally
provide a satisfactory result:
- shading of the roof or pool
Site-specific
Private pools: 80 % to 100 % of pool area
conditions
- roof slope and orientation
Public pools: 40 % to 70 % of pool area
- colour of pool
For both private and public pools, the collector area
- wind protection
may be reduced by 30 % to 40 % if a pool cover is
- roof material
installed (and used). The reason for the larger specific
- roof colour
area for private pools is the higher surface area-to-
volume ratio and hence higher relative heat loss for
small pools.
System con- - collector type
figuration
As an alternative to the use of a simple estimation
- plumbing arrangement
based on pool area, the pool heat load and collector
In some cases a detailed calculation of pool-heating area needed for a certain equilibrium temperature may
load and collector output will be necessary, while in be calculated using a suitable Computer program. The
others a simple estimation will be adequate. A pro- heat load for a given equilibrium temperature tan be
calculated (annex A), and the solar System output for
cedure for calculating the heat requirement for pools
the same temperature derived from the collector
is given in annex A. Caution should be exercised
manufacturer’s data and climate data for the site. The
when applying these methods for the calculation of
two results tan be compared and then an iterative
heat losses from outdoor pools, as wind Speed has a
procedure used to alter the temperature until the pool
significant effect; however, it is not easy to quantify
0 ISO
lSO/TR 12596: 1995CE)
load is equal to the output from a given collector sys- building Codes to obtain an estimate of the wind loads
tem. This will give the equilibrium temperature and that n ay be encountered.
tan be repeated for all months of interest. Similarly,
the effect of different collector areas on equilibrium
temperature tan also be evaluated.
38 . ntercon nection of unglazed col lectors
3.6.3 Pools with auxiliary heating
3.8.1 Parallel connection
A common design approach is to calculate the collec-
tor area necessaty to provide all the heat required in Collectors may be connected in parallel, in series or
the month for which the requirement is lowest, usu- in a combination of series and parallel units to form
ally in midsummer. lt tan then be assumed that the an array. The optimal configuration depends on the
solar System will rarely produce heat that is Surplus
geometry of available area for collector mounting as
to requirements. For other months, the conventional
well as on the hydraulic characteristics of the collector
auxiliary heater may be used to maintain a specified
modules. The objectives are to achieve a low parasitic
temperature. The heating load for this month may be
energy for pumping, usually only 1 % to 2 % of col-
known from energy bills for an existing heater, or lector heat output, and a uniform heat production by
calculated as outlined in annex A. all modules.
For outdoor pools this approach may result in a small
The starting Point for array optimization is the high-
collector area, primarily because of the direct solar
irradiance temperature rise, usually 5 K through each
gain by the pool itself. In such cases, it is generally
series-connected collector group. This value leads to
feasible to install a greater area of collector, to provide
a specific flowrate requirement of 110 I/(h g m*) to
higher solar contribution to season load, even though
140 I/(h . m*) [0,03 kg/(s . m*) to 0,04 kg/(s g m*)]. If
more heat is generated in midsummer than is
a separate pump is used for the collector array (see
necessary to maintain the specified temperature.
4.3), the above recommendation is the basis for the
hydraulic layout. However, the use of an existing pool
filter pump for the collector array as discussed in 4.2
3.7 Mountings
may result in a higher specific flowrate, since the re-
The method of mounting solar collectors has to be
quired rate of turnover of the pool water for filtration
considered carefully, taking into account the consid-
purposes must be maintained.
erable forces caused by wind lift to which collectors
The efficiency of thermal solar collectors decreases
may be subjected. Manufacturers’ recommendations
with increasing operating temperature, particularly for
regarding mounting Systems should be followed. If
unglazed collectors. lt is therefore important that the
mountings are to be fastened to other building struc-
flowrate through the collectors is sufficiently high to
tures, special attention should be paid to the design
ensure efficient Operation. However, flowrates higher
of the mountings and the load that they may place on
than those specified above will produce little extra
the building structure. Mountings should not be liable
benefit and will incur higher pumping energy require-
to torrode, Cause rainwater leaks or work loose be-
ments.
Cause of wind Vibration. Consideration should also be
given to the likelihood of vandalism and the means
Generally the collector modules should be connected
of preventing it, especially if glazed collectors are
in parallel, as shown in figure4 a). The use of series
used.
connection is not recommended, as this may increase
Provision should be made to ensure adequate drain- the pumping power requirement and also Cause the
downstream collectors to operate at higher, less ef-
age either under or over the collectors. Collectors
ficient temperatures. Parallel connection, in which the
should also be arranged to avoid trapping rainwater
water returns to the pool after passing through one
or accumulating debris between the collector and the
collector, avoids these Problems.
roof. This is particularly important in the case of low-
slope unpainted metal deck roofs. For these roof
However, if the recommended specific flowrate
Systems, collectors should be run across the ribs
would lead to laminar flow in the modules in the case
rather than along the channels, even though this con-
of all-parallel connection, then several modules should
figuration may result in lower thermal output.
be connected in series to insure turbulent flow in all
Where collectors are to be mounted on conventional modules (figure 5). Select the number of series-
building structures, reference should be made to local connected modules to be as low as possible.

TopooL I t From POOL
a) Parallel connection
---------------
---__--___----_<
,-----m--------_
---------------.
.---------------
---------------.
.---------------
---------------<
.---------------
-----s---------<
.--------------e
---------------.
.---------------
----------m--m-.
.---------------
------m--m-----<
.---------------
---------------<
.---------------
--_-______-____.
.---------------
---__--_-______.
.------------a-m
---------m-m--v.
.---------------
----------*meee<
.---------------
--------mmmmme-<
.---------------
---------m--w--<
,---------------
---------------<
---------------
-u 1
I
l
Frompool
lopool
b) Series connection hotrecommended)
Figure 4 - Parallel and series connection of Panel collectors

J
r-
I
I
From po01 lopool
a) ALL-paraLLeL arrangement
1 1
From POOL To po01
b) Parallel-series arrangement
Figure 5 - All-parallel and parallel-series arrangement of Panel collectors

0 ISO
ISO/TR 12596: 1995(E)
anced and the temperature rise measured near solar
In large arrays, an additional reason for connecting
noon on a clear day is approximately the Same for all
some modules in series is the requirement that the
collector groups. A qualitative criterion is that the
pressure drop in the header pipe not exceed IO % of
largest temperature rise in the array should be at most
the pressure drop through a module in Order to obtain
twice the smallest rise observed. This may be
uniform flow through the parallel-connected collec-
achieved by the layout of the plumbing (reverse re-
tors. Therefcre the number of modules that may be
turn) or the use of balancing valves.
connected in parallel as shown in figure 4a) is limited.
3.82 Interconnection of collector groups Balancing valves may be used to obtain uniform spe-
cific flow distribution when site requirements make it
The collector groups should be arranged in parallel in
impractical to balance the flow with simple plumbing
such a way that the length of the flow and return
arrangements, e.g. when the pressure drop in the
paths is approximately the same for each collector
pipework at nominal flowrate is significant compared
Panel, so that flow will be evenly distributed. to the pressure drop through the collector array. If
Figure 5 a) illustrates the recommended arrangement,
required, balancing valves should be installed in the
with the flow line entering the parallel row at one end
flow line returning water from each group of collec-
and the return line being taken from the far end.
tors to the common po01 connection. Upon com-
missioning [see 8.2 e)] the balancing valves should
Connection of the flow and return lines to the same
be adjusted to give uniform specific flow through the
Panel at one end of a parallel row will Cause those
collectors.
Panels at the near end to short-circuit the flow, while
those at the far end will receive less flow and suffer
Groups of collectors at different heights should be
a reduction in Performance. Such an arrangement
connected so that they all receive water from the
should only be used where the pressure drop in the
lowest Point in the System and return it to the highest
headers is very much less than that in the fluid pass-
Point. Figure6 illustrates a System arranged in this
ages across the Panels.
way. If the return lines do not come from a common
height, flow through the Panels may be uneven,
The flow paths to and from the po01 should be de-
causing a reduction in performante.
signed so that the flow through all passages is bal-
Ir Topool
From '
po01
Figure 6 - Recommended plumbing arrangements for collector Panels at different elevations

0 ISO
4.2 Use of existing po01 filter pump
3.9 Connections
Connections between collectors, and between col-
A Standard po01 filter pump may be used to circulate
lectors and piping, should be made of a suitable flex-
po01 water through the collectors of small Systems
ible material to accommodate variations in alignment
(maximum 100 m* collector area) provided the fol-
at installation, and movement due to thermal expan-
lowing conditions are met:
sion in Service. The material of the connections should
the required rate of turnover of the po01 water for
be no less durable than that of the piping, under the d
conditions of use. filtration purposes is maintained;
The arrangement of Strip collectors will be largely
b) the filter is capable of functioning satisfactorily
governed by the nature of the roof or other structure
under the increased pressure that will result from
upon which they are installed. Interconnection of
the addition of the collector circuit;
Strips may be either by a grid layout, or by a loop-
return arrangement between two adjacent headers.
the pump has sufficient capacity to handle the
Cl
In all cases, a maximum length of Strip of 15 m is
static head and frictional losses introduced by the
recommended.
addition of the collector circuit;
the collector array is located no more than 6 m
d)
3.10 Preventions of airlocks
above the po01 level.
Flow blockage or nonuniform flow in large arrays is
Typical arrangements using an existing pump are
commonly caused by airlocks. To avoid this Problem,
shown in figures 7 and 8. With these configurations
pipework should be installed so that air will naturally
it may be difficult to adjust the flowrate through the
rise to a suitable air-bleed device. Air-bleed devices
collectors to the required level, as the flowrate de-
should be located downstream of the collectors.
pends on Variation of pressure drop in the filter. Per-
iodic adjustments may be needed.
4 System hydraulics
4.1 Pump capacity
4.3 Use of separate pump
Under normal circumstances the solar System will
operate as a closed System, that is, with all com-
A separate pump is necessary in the following cases:
ponents filled with water and no free water surfaces.
In this case the static height is of no importante,
a) small Systems of less than 100 m* collector area
since the static heights of the supply and return lines
if the collector array is located more than 6 m
are in balance and the head required to raise the wa-
above the po01 water level;
ter to the top of the supply riser is balanced by the
head regained as the water flows down the return leg.
b) small Systems if the required rate of turnover of
Only the frictional losses need be taken into consid-
the po01 water for filtration purposes cannot be
eration in sizing the pump for normal running con-
maintained during collector Operation using the
ditions. This is not so at start-up if the System has
po01 filter pump alone;
partially or fully drained down. Until the System has
completely filled with water, a static head will exist.
c) small Systems if the po01 filter pump is not able
Thus while the pump may be sized for the normal
to fill the collector array and establish the required
operating conditions, it must also have sufficient ca-
flowrate through it;
pacity to lift water to the highest Point in the System,
albeit at a rate lower than the design flowrate.
d) all large Systems (more than 100 m* collector
area).
lt is also important to ascertain that an overpressure
is established in the whole collector array when the
If a separate pump is used, and the solar circuit is
pump is operated. Otherwise the air-bleed device at
the output of the collector array may allow air to con- separate from the filtration circuit, the pump should
tinuously enter the System. The necessary over- either be located below the level of the po01 water,
pressure condition tan be achieved by using a or be self-priming. If a separate pump is used, and the
solar circuit feed line is connected to the filtration cir-
balancing valve in the po01 flow line so that the col-
cuit downstream from the filter pump, the solar pump
lector output line is filled with water when the po01
will not normally need to be self-priming.
filtration pump is running (solar pump not running).
Solar collector
Sensor
1 ABalancing
I
Poolwatertem-
I
I/ Ivalve
perature Sensor T
Q r\l
I
Check
Filter
valve valve
Filtration
pump
Heated water
to pool
Figure 7 - Use of existing pump, Single-valve arrangement
Solarcollector
r
Sensor
L Solar delivery
line
Isolatio n
vahes
B
--------- ----
I l
I
I r
Poolwatertem-
Filter
,
Filtration
pump
Heatedwater
to pool
NOTE
- A motorized three-way valve may be used in place of the two control valves shown.
Figure 8 - Use of existing pump, two-valve arrangement (collector array located at or below po01 level)
flooded suction may need frost
NOTE 4 Pumps with
5 Controls and instrumentation
protection.
us-
A typical arrangement of a small collector System
ing a separate pump connected to the filtration circuit
5.1 General
is shown in figure 9. Figure 10 describes the case of
a large System (more than 100 m* collector area).
The control System should be automatic in Operation
and should circulate water through the collectors only
In the case of a large System, draining the whole col-
when heat tan be gained. The Operation of the solar
lector array each time the solar input is interrupted
circuit should not interfere with the run-on time re-
may Cause Problems at restart due to:
quired for removal of residual heat from any fossil-
fuelled po01 heater. The use of manual Operation, or
airlocks in some Parts of the collector array;
d
time switches as typically used to control the oper-
ation of the po01 filter, will not provide Optimum per-
may be carried away to the po01
b) air bubbles
formante.
po01 cover;
disturb swi mmers or darnage the
Circulation of water to the collectors may be either
c) pressure pulses may be created in the collector
by the filter pump or by a separate pump. The filter
array when the pump Starts and darnage the col-
pump would, in the absence of a solar heating sys-
Iector.
tem, normally operate at times when there may be
no solar heat gain. If the filter pump is to be used, the
Hence, the installation of two automatic valves in the
control System should be able to override any time
return and flow lines of large collector arrays is rec-
switch that would otherwise prevent the filter pump
ommended (see figure 10). These valves and the solar
pump should be controlled in the following sequence: from operating (see also 7.4). The control System
should not adversely affect the Operation of other po01
the control Signal from the pump control unit should
equipment, including filters, chlorinators or auxiliary
be transmitted to the valves and the end contact of
heating System. The filtration period should not be
one of the valves used to control the pump. In this
compressed by the Operation of the solar pool-heating
way the proper sequence is ensured and the collector
System.
array is maintained filled with water.
Solar collector
r
Sensor
Solar deL
line
r
Pool water tem-
perature Sensor
Check valves
Filter
i
Heated water
to POOL
separate hydraulic System appl icable to small Systems (maximum 100 m*
Figure 9- Use of
collector area)
Sensor
Solar delivery
line
.-
I
I
1 Solar
I pump
I
Pool watertem- T
I
peraturesensor
I
Valves to keep collector filled with water
Q I
----
End contact control for s -0lar pump
Check
Filter
valve
Filtration
Pump
Heated water
to po01
Figure 10 - Use of separate pump and hydraulic System applicable to large Systems (more than 100 1112
collector area)
In the context of pool heating, a net benefit is
5.2 Differential temperature controllers
achieved when the value of the energy collected ex-
ceeds the energy expended in circulating water to the
52.1 Two-Sensor Systems
collectors. The temperature differential at which the
controller turns the System off should therefore take
In Systems using two Sensors, one Sensor detects the
account of pump energy consumption. lt is also de-
po01 water temperature and the other Sensor detects
sirable to minimize frequent starting and stopping of
the collector temperature. The pool temperature sen-
the pump.
sor should be located in the pool recirculation line
ahead of the solar circuit. The collector Sensor should
be located on a section of collector remote from a
fluid passage or on a piece of solar absorber material
5.2.2 Four-Sensor Systems
near the collector array but not thermally connected
to the hydraulic circuit. For an isolated hot Sensor, it
A System using four Sensors offers several control
is recommended that the temperature differente at
advantages. In such a System, the Start differential
which circulation in the solar circuit Starts should not
Sensors are located in the pool water and on a section
exceed 6 K. The temperature differente at which it is
of the solar collector plate near the collector array but
stopped should not exceed 3 K. The large tempera-
not thermally connected to the hydraulic circuit. The
ture differentials generated by this sensor-mounting
stop differential Sensors are located in the solar col-
arrangement tan be detected by Standard quality dif-
lector inlet and outlet pipes.
ferential temperature Sensors. Collector temperature
Sensors located in the collector outlet pipe are not Circulation Starts when the solar collector plate attains
recommended, as this mounting arrangement relies a suitable overtemperature relative to the pool water.
After a short time in Operation, control of circulation
on the detection of very small temperature rises
is taken over by the stop differential Sensors. Circu-
which will require an accurate Iow-drift detector.
0 ISO
lSO/TR 12596:1995(E)
as this water may contain chlorides (either from sea
lation continues until the temperature differente be-
water or from direct salt addition) or other corrosive
tween collector outlet and inlet has fallen to the set
minerals. All metals except some chrome-nicke1
stop differential.
steels should be avoided for those Parts of the sys-
The stop differential should be set to a value at which
tem. All components exposed to solar radiation (col-
the energy being collected is significantly greater than
lectors, piping, etc.) must be resistant to ultraviolet
the energy needed to maintain circulation. The Start
radiation. This is especially important for plastics;
differential should be set to the lowest possible value
EPDM rubbers have been found to give satisfactory
at which the stop differential is able to take control.
Performance.
5.2.3 Temperature sensing in large Systems All pipework must be able to withstand the Stagnation
temperatures that may be generated in the collectors.
A temperature Sensor located in the outlet of a large
The Stagnation temperature of unglazed collectors is
System may Cause errors at start-up due to nonuni-
generally less than 50 “C; however, glazed collectors
formity in the array heating under no-flow conditions.
tan resch temperatures of around 110 “C to 150 “C
Also, large arrays are often built with several different
for sealed types and 75 “C to 90 “C for types with
collector sections. To avoid incorrect control oper-
significant Ventilation. PVC piping will not withstand
ations in such Systems, a small recirculating pump
temperatures above 60 “C and should not be used in
may be used to mix the water in the collector array(s)
such situations.
so that reliable temperature reading tan be obtained
for start-up control. Alternatively, the two-Sensor ar-
PVC pipework should not be used in glazed collector
rangement (52.1) could be used.
Systems, or where temperatures greater than 60 “C
may be experienced. Black high density polyethylene
(HDPE) pipe may be generally suitable. However, both
5.3 Photovoltaic controllers
PVC and HDPE pipe must have their working press-
Photovoltaic controllers which sense solar radiation
Ures de-rated for Operation at high temperatures.
may be used to control the Operation of the solar cir-
Materials such as EPDM which are able to withstand
cuit. However, it should be noted that such a means
freezing of water in the passageways are preferable
of control is less effective than a differential tem-
perature controller, because it may turn the pump on for all frost-exposed Parts.
during times of high radiation and cold windy con-
ditions when an unglazed collector may not function
satisfactorily. Intelligent controllers may make use of
temperature and radiation Sensors. Photovoltaic sen-
6.2 Installation
sors should be located in a Position that receives the
same level of solar radiation as the collector array at
Pipework should be installed in accordance with rel-
all times during the operating season.
evant local plumbing Codes. Plastics pipework should
be supported by Clips or hangers at intervals not ex-
5.4 System monitoring
ceeding those shown in table 1.
For large public pools it is generally desirable to pro-
The supports should permit expansion movement
vide a means of monitoring the solar heating System,
without imposing undue strain on pipework, valves
so that the Operators have some feedback on the so-
or fittings. Care must be taken to allow for thermal
lar Operation. This should include a flowmeter to indi-
expansion of plastics pipes, which is significantly
cate the flow through the collectors, and a means of
greater than that of topper. Additionally, the expan-
measuring the temperature of the pool water and the
sion of HPDE pipe is more than twice that of PVC
heated water from the collectors. Temperature indi-
Pipe. For PVC Pipe, the Provision for expansion should
cation may be derived from the Sensors in the control
allow for the tem
...