ISO/TR 12596:1995

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)

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ISO/TR 12596:1995(E)
Contents
Page
1
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.
Scope . . . . .
1
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Definitions
2
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Solar collectors
10
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
System hydraulics
12
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Controls and instrumentation
14
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Pipework
15
. . . . . . . . . . . .~.
System design
17
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*.*.
Commissioning
Annexes
19
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A Calculation of pool heating load
24
. . . . . . . . . . . . . . . . . . . . .*.
B Pool covers
25
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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

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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.

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ISO/TR 12596:1995(E) 0 ISO
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.

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ISO/TR 12596:1995(E)
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.
1

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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

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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)

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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
6
f -F 50
aJ
is
; 40
E
aJ
: h 30
-
0
.-
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)

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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
5

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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.

---------------------- Page: 10 ----------------------
ISO/TR 12596:1995(E)
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
1
Frompool
lopool
b) Series connection hotrecommended)
Figure 4 - Parallel and series connection of Panel collectors

---------------------- Page: 11 ----------------------
ISO/TR 12596:1995(E)
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

---------------------- Page: 12 ----------------------
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
heade
...