FINAL DRAFT UGANDA 
STANDARD  
  FDUS 860
First Edition
2009-mm-dd
 
 
Reference numbe r
FDUS 860: 2009
 © UNBS 2009 
  
Standard practice for non-operational exposure and inspection 
of a solar collector 
 FDUS 860: 2009 
ii © UNBS 2009 – All rights reserved
 Compliance with this standard does not, of itself confer immunity from legal obligations 
A Uganda Standard does not purport to include all necessary provisions of a contract. Users are 
responsible for its correct application  
© UNBS 2007  
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permission from UNBS. 
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The Executive Director 
Uganda National Bureau of Standards 
P.O. Box 6329 
Kampala  
Uganda 
Tel: 256 414 505 995 
Fax: 256 414 286 123 
E-mail: unbs@infocom.co.ug
Web: www.unbs.go.ug  
 FDUS 860:2009 
© UNBS 2009 – All rights reserved  iii
 Foreword 
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry  of Tourism, Trade and 
Industry established under Cap 327, of the Laws of Uganda.  UNBS is mandated to co-ordinate the 
elaboration of standards and is  
(a) a member of International Organisation for Standardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex A limentarius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT/SPS Agr eements of the World Trade Organisation (WTO). 
The work of preparing Uganda Standards is carried out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a gi ven field or area and consists of representatives of 
consumers, traders, academician s, manufacturers, governme nt and other stakeholders. 
Draft Uganda Standards adopted by the Technical Committ ee are widely circulated to stakeholders and the 
general public for comments. The committee reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council.  
Committee membership 
The following organisations were represented on su bcommittee on Solar Energy, SC 3 under the Energy 
management standards Technical Committee, UNBS/ TC 13 in the development of this standard: 
• Battery Masters (U) Limited 
• Equator-sun (U) Limited 
• Incafex Solar Systems 
• Makerere University 
• Renewable Energy Department, Minist ry of Energy and Mineral Development 
• Solar Masters 
• Sonnerkraft Solar Systems 
• Uganda Institute of Professional Engineers 
• Uganda National Bureau of Standards 
• Uganda National Plumbers Association 
• Ultratec (U) Limited 
 
 FINAL DRAFT UGANDA STANDARD FDUS 860: 2009
 
© UNBS 2009 – All rights reserved  1
 Standard practice for non operational exposure and inspection 
of a solar collector 
1 Scope 
1.1 This practice defines the procedure to expose a so lar thermal collector to an outdoor or simulated 
outdoor environment in a non-operational model. The proc edure provides for periodic inspections and a post-
exposure disassembly and inspection of the collector. 
1.2 This standard does not purport to address all of the sa fety concerns, if any, associated with its use. It is 
the responsibility of the user of this standard to  establish appropriate safety and health practices and 
determine the applicability of regulatory limitations prior to use. 
2 Normative references 
The following referenced documents are indispensable for the application of this document. For dated 
references, only the edition cited applies. For undated references, the latest edition of the referenced 
document (including any amendments) applies. 
FDUS 854-2, Thermal solar systems and components — Solar collectors — Test methods 
FDUS ISO 9488, Solar energy — Vocabulary  
ISO 9845-1, S olar energy — Reference solar spectral irradiance at the ground at different receiving conditions 
— Part 1: Direct normal and hemispherical solar irradiance for air mass 1.5 
3 Significance and use  
3.1 Exposure in a non-operational mode provides fo r conditioning and assessment of the physical 
appearance of a solar collector resulting from moderate ly severe solar irradiati on, ambient temperature, and 
effects of moisture on the vari ous materials or construction. 
3.2 This practice describes actual ex posure conditions that have a high probability of occurring sometime 
during the installation of a solar collector, or during operation, or malfunction of a solar energy system. 
3.3 This practice shall be considered to be a limited aging test in that it does not address those aging 
effects resulting from fluid-to-collector interfaces. 
3.4 This practice applies to all so lar thermal colle ctor types. 
4 Test specimen   
The exposure specimen shall consist of a complete collector. The collector specimens may be equipped with 
self-contained, self-actuated protective devices. FDUS 860: 2009 
2 © UNBS 2009 – All rights reserved
 5 Collector mounting  
5.1 The exposure specimen shall consist of a complete air or liquid solar collector undergoing the non 
operational mode exposure. Cap (not seal) all inlet, out let, and vent ports not normally exposed to rain.  
5.2 Locate the exposure rack such that it is clear of obstruction that may cause shadows or non-uniform 
reflections on the collector.  
5.3 During exposure, mount the collector to the expos ure rack in accordance with the manufacturer’s 
instructions. When specific exposure mounting instructio ns are not provided, mount the collector to permit air 
movement on all sides and edges. Cover the collecto r for protection from the weather elements until the 
exposure period commences. 
6 Non operational mode exposure  
6.1 Mount the collector securely to an adjustable rack , prepare for non operational mode, and expose at the 
conditions in 6.1.1 – 6.1.3. 
6.1.1 A minimum of 30 days during which, for each day, the cumulative minimum radiant exposure, 
measured in the plane of the collector, shall be 17 000 kJ/m2.day (1500 Btu/ft2.day). Minimum conditions do 
not need to be met for 30 consecutive days. 
6.1.2 In the case of simulated solar radiation: 
a) For solar simulation, one solar exposure day is defined as the exposure for 5 h to a minimum solar 
irradiance of 950 W/m2 (300 Btu/ft2.h) and not to exceed 1150 W/m2 (365 Btu/ft2.h) at an ambient 
temperature characteristic of outdoor  exposure [nominal range from 15 °C to 35 °C (70 °F to 95 oF)]. 
Simulator exposure is to be followed by setting the collector outdoors overnight in accordance with 
5.2. 
b) The simulated solar spectrum shall generally c onform to the Air Mass 1.5 global distribution as 
described in ISO 9845-1. 
6.1.3  The energy distribution in the 0.3 µm to 0.4 µm ra nge shall not deviate more than ± 25 % from the Air 
Mass 1.5 spectrum as measured in 0.05 μm bands. The energy distribution from 0.4 µm to 2.5 μ m shall not 
deviate by more than ± 15 % from the Air Mass 1.5 spectrum as measured in 0.10- μm bands. 
6.1.4  A minimum continuous period of 1h exposure at a solar irradiance greater than 950 W/m2 (300 Btu/h-
ft2). This condition must be experienced in the exposure  day in order to qualify the exposure time as part of 
the 30 h requirement. Once the minimum 1-h exposure period is met, all exposure time (including the 1-h 
period) above the minimum solar irradiance and ambient temperature requirement during the same exposure 
day may be included in the 30-h requirement. 
6.1.5  A minimum of 30 h accumulated radiant exposure with a solar irradiance not less than 950 W/m2 (300 
Btu/h.ft2) concurrent with an ambient temperature of at least 25 °C (80 °F). Measure the solar irradiance in the 
plane of the collector aperture with a pyranometer. The av erage air velocity at the te st station, measured at a 
height corresponding to the mid-height of the collector, should be less than 4.5 m/s (10 mph). Record air 
velocity as part of the test data. 
6.1.6 The nonoperational mode exposure is only conclude d after the requirements of 6.1.1 and 6.1.4 have 
been met. Exposure times under 6.1.1 and 6.1.4 shall be accumulated independently during the same exposure period, as opposed to sequentially meeting the requirements of one section and then the other. 
6.2 The thermal shock/water spray penetration test is inte nded to induce the thermal stresses that will occur 
when rain impinges on a heated collector in order to det ermine the penetration of rain into the collector and 
the effect of such penetration or moisture condensation, if any, on collector performance. FDUS 860: 2009 
© UNBS 2009 – All rights reserved  3
 6.2.1 Perform the test three times during the nonoperational mode exposure period; once during the first 10 
days of the exposure period as defined in 6.1.1, and once each during the second and third 10 days of the 
exposure period . 
6.2.2  In carrying out pre-test exposure, conduct the spray test after at least 1 h of radiant exposure with a 
minimum solar irradiance of 850 W/m2 (270 Btu/ft2-h) measured in the plane of the collector. 
6.2.3 The test apparatus shall consist of three or more spray heads mounted in a water supply rack as 
shown in Figure 1 and Figure 2. Spray heads shall be constructed in accordance with Figure 1 and Figure 2. 
The water pressure for all tests shall be maintained at 35 kPa at each spray head. This pressure will provide 
about 0.3 m/h of rain at the water flow of 190 L/h per nozzle. The supply water temperature shall not exceed 
30 °C.  
6.2.4 Position the spray apparatus to direct a downward spra y from a distance of 1.0 m at an angle of 45° ± 
5° with the collector cover plate surface, as illustrat ed in Figure 3. Direct t he spray onto the cover plate 
surface and the top and side edges of the collector whic h have been exposed as described in 6.2. Adjust the 
water pressure at each spray head to 35 kPa. Maintain the water spray for 15 min per test period. Observe 
and record occurrence of water penetration into the collect or interior. Perform the test three times as specified 
in 6.2.1. 
 
 
 
Item mm 
A 710 
B 1400 
C 55 
D 230 
E 75 
Figure 1 – Rain-test spray-head piping 
FDUS 860: 2009 
4 © UNBS 2009 – All rights reserved
 
 
 
 
 
 
 
Item mm Item mm 
A 31.0 N 0.80 
B 11.0 P 14.61 
C 14.0  14.63 
D 14.63 Q 11.51 
 14.73  11.53 
E 0.40 R 6.35 
F  S 0.80 
G 1.52 T 2.79 
H 5.0 U 2.49 
J 18.3 V 16.0 
K 3.97 W 1.52 
L 6.35   
M 2.38   
Figure 2 – Rain test spray head FDUS 860: 2009 
© UNBS 2009 – All rights reserved  5
 6.3 Clean the outermost surface of the collector cover,  including any reflectors, every 30 days during the 
exposure period, or more frequently if visual inspec tion indicates dirt buildup. Use the manufacturer's 
recommended cleaning procedure if available. Perform cleaning and rinsing such that no visible residue 
remains on the surface. Do not clean the collector while  it is hot. Take care to avoid scratching plastic 
materials. Note and report the cleaning frequency (clause 9). 
6.4 During the period of nonoperational exposure, inspec t the collector once per week, preferably in the 
morning to detect condensation. Note any observed change or degradation. Do not replace or repair 
components of the collector once the exposure sequence has commenced. 
6.5 As required, adjust the rack to a tilt angle or orient ation, or both, that will maintain the incident solar 
irradiance levels specified in 6.1. 
7 Post-exposure cleaning 
After completion of the exposure periods outlined in Cl ause 6, clean the exterior collector cover surface and 
any exterior reflective surfaces in accordance with 6. 3. Make a final visual inspection of the collector. Report 
any changes or degradation observed. 
 
 
 
 
 
NOTE X as required to develop coverage at top back edge A. 
Figure 3 – Test arrangement for thermal shock/rain spray test FDUS 860: 2009 
6 © UNBS 2009 – All rights reserved
 8 Other properties 
As an option, document other specific material propertie s of the solar collector components, such as coating 
absorptance, cover transmittance, insulation, thermal c onductivity, etc., for evaluation and comparison with 
pre-exposure values using samples taken from the exposed collector. 
9 Report 
9.1 Data reporting 
The data in 9.1.1-9.1.4 shall be m easured, recorded, and reported daily. 
9.1.1 Thirty days accumulated radiant exposure 
The total daily solar radiant exposure shall be obtained from continuously measured values (analog recorder, 
integrator, or data acquisition sampling at least every minute). The total daily solar radiant exposure and the 
maximum and minimum daily ambient temperature shall be reported for each day with the corresponding 
date. 
9.1.2 Thirty hours accumulated radiant exposure 
The solar irradiance shall be continuously measured (analog recorder, integrator, or data acquisition sampling 
at least every minute). The ambient temperature shall be sa mpled at least every 15 min. Actual values of solar 
irradiance and ambient temperature above the minimu m requirement of 6.2 sha ll be reported. The date and 
time of occurrence for each useful period shall be recorded. 
9.1.3 Average wind velocity 
The average wind velocity should be measured and recorded during each exposure period meeting the 30-h requirement (see 6.1.4). 
9.1.4 Cover cleaning date 
The date of each cover cleaning as required in 6.3 shall be recorded. 
9.2 Premature exposure termination 
The time and reason for any premature ex posure termination shall be recorded. 
9.3 Materials and subcomponents 
Observed changes in materials or configuration and t he presence of water condensation or other changes 
noted during inspections described in Clauses 6 or 7 shall be recorded. The date of observation shall also be recorded. 
9.4 Collector disassembly and inspection 
The collector shall be disassembled and a detailed inspection performed and recorded. The visual inspection 
should not reveal any impairment of function or evid ence of degradation which could be expected, in normal 
service, to progress to the point of causing failure or  significant impairment of function during the collector 
design life. Typical examples of deterioration are shown in Table 1.  
 
 FDUS 860: 2009 
© UNBS 2009 – All rights reserved  7
 Table 1 – Collector disassembly and final inspection  
 
Materials Description of deterioration 
Cover: cracking, crazing, scratchin g, buckling or severe clouding. 
Absorber: -  severe deformation * of the absorber, 
-  severe deformation * of the fluid flow passages, 
-  loss of bonding between fluid flow passages and absorber plate, 
-  leakage from fluid flow passages or connections, 
-  loss of mounting integrity, and 
-  severe corrosion * or other deterioration caused by chemical action  
-  (corrosive fluxes, vola tiles from collector materi als, salt spray, etc) 
Absorptive coatings: - checking , cracking, blistering, or flaking of the absorber coating  
Collector enclosure - cracking or warping of the collector enclosure materials 
Reflective surfaces - cracking, craxing or delamination of reflective surfaces 
Insulation -  swelling of other detrimental c hanges in the collector insulation that    
   adversely affect collector performance 
-   water retained in the insulation 
Gaskets, cauling and sealants - cracking, loss of elasticity, or loss of adhesion 
Hoses - leakage or damage to hoses inside the collector enclosure or leakage  
  from mechanical connections 
* Deformation or corrosion shall be considered severe if it impairs  the function of the collector or there is evidence that it wi ll 
progress under operating conditions and lead to impairment of function . 
 
9.5 Collector description 
The collector characteristics specified in FDUS 854-2  plus any self-contained protection devices shall be 
recorded. 
10 Precision and bias 
10.1  The solar irradiance measurement accuracy shall be equivalent to or exceed the requirements for a 
WMO Class 2 pyranometer. 
10.2  Ambient temperature measurement accuracy shall be at least ± 2 °C (3.6 °F). 
10.3  Wind and relative humidity measurement accuracy shall be at least ± 10 %. 
10.4  The radiant exposure time shall be determined with an accuracy of at least ± 5 %. 
 FDUS 860: 2009 
© UNBS 2009 – All rights reserved  8
 Certification marking 
Products that conform to Uganda standards may be  marked with Uganda National Bureau of Standards 
(UNBS) Certification Mark shown in the figure below.  
The use of the UNBS Certification Mark is gove rned by the Standards Act, and the Regulations made 
thereunder. This mark can be used only by those licens ed under the certification mark scheme operated by 
the Uganda National Bureau of Standards and in co njunction with the relevant Uganda Standard. The 
presence of this mark on a product or in relation to a product is an assurance that the goods comply with the 
requirements of that standard under a system of supervision, control and  testing in accordance with the 
certification mark scheme of the Uganda National  Bureau of Standards. UNBS marked products are 
continually checked by UNBS for conformity to that standard.  
Further particulars of the terms and conditions of  licensing may be obtained from the Director, Uganda 
National Bureau of Standards.  
 
 FDUS 860: 2009 
 
ICS 27-160 
Price based on 13 pages 
© UNBS 2009 – All rights reserved