FINAL DRAFT UGANDA 
STANDARD  FDUS 856
First Edition
2009-mm-dd
 
Reference numbe  
r
FDUS 856: 2009
 © UNBS 2009 
  
Standard method for on-site inspection and verification of 
operation of solar hot water systems 
 FDUS 856: 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  2009  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilised in any 
form or by any means, electronic or mechanical, in cluding photocopying and microfilm, without prior written 
permission from UNBS. 
Requests for permission to reproduce this document should be addressed to 
The Executive Director 
Uganda National Bureau of Standards 
P.O. Box 6329 
Kampala  
Uganda 
Tel: 256 41 505995 
Fax: 256 41 4286 123 
E-mail: unbs@infocom.co.ug 
Web: www.unbs.go.ug FDUS
© UNBS 2009 – All rights reserved  iii
  856: 2009 
Contents Page 
Foreword………………………………………………………………………………………………..…………iv 
1  Scope .....................................................................................................................................................1  
2 Normative references ............................................................................................................................1  
3 Terms and definitions ...........................................................................................................................2  
4 Summary of guide .................................................................................................................................2  
5 Significance and use .............................................................................................................................5  
6 Procedure ...............................................................................................................................................5  
6.1 Preparation .............................................................................................................................................5  
6.2 General inspection ............................................................................................................................... .5 
7 Test level A — Visual inspection .........................................................................................................7  
7.1 Procedure ...............................................................................................................................................7  
7.2 Interpretation and report of results .....................................................................................................7  
8 Test level B — Estimation of flow rates ..............................................................................................7  
8.1 Procedure ...............................................................................................................................................7  
8.2 Instrumentation .....................................................................................................................................8  
8.3 Interpretation and Report of Results ...................................................................................................9  
9 Test level C — Measure radiation and temperature changes ...........................................................9  
9.1 Procedure ...............................................................................................................................................9  
9.2 Instrumentation .....................................................................................................................................9  
9.3 Interpretation and report of results .....................................................................................................9  
10 Freeze protection ............................................................................................................................... ..10 
10.1 Test level A — Visual inspection .......................................................................................................10  
10.1.1  Procedure ............................................................................................................................... ..............10  
10.1.2  Interpretation and report of results ...................................................................................................10  
10.2 Test level B ............................................................................................................................... ............10  
10.2.1  Procedure ............................................................................................................................... ..............10  
10.2.2  Instrumentation ............................................................................................................................... ....10  
10.2.3  Interpretation and report of results ...................................................................................................10  
11 Controller ............................................................................................................................... ..............10  
11.1 Test level A (visual) .............................................................................................................................10  
11.1.1  Procedure ............................................................................................................................... ..............10  
11.1.2  Interpretation and report of results ...................................................................................................11  
11.2 Test level B ............................................................................................................................... ............11  
11.2.1  Procedure ............................................................................................................................... ..............11  
11.2.2  Instrumentation ............................................................................................................................... ....11  
11.2.3  Interpretation and report of results ...................................................................................................11  
11.3 Test level C ............................................................................................................................... ............11  
11.3.1  Procedure ............................................................................................................................... ..............11  
11.3.2  Instrumentation ............................................................................................................................... ....12  
11.3.3  Interpretation and report of results ...................................................................................................12  
Annex A (informative) Rationale…………………………………………………………….………………………13  
 FDUS 856: 2009 
iv © UNBS 2009 – All rights reserved
 Foreword 
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry  of Tourism, Trade and 
Industry established under Cap 323, 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 856: 2009
 
© UNBS 2009– All rights reserved 1
 Standard method for on-site inspection and verification of 
operation of solar hot water systems 
1  Scope 
1.1 This guide covers procedures and test methods for conducting an on-site inspection and acceptance 
test of an installed hot water system using flat plate, concentrating-type collectors or tank absorber systems. 
1.2 It is intended as a simple and economical acceptance te st to be performed by the system installer or an 
independent tester to verify that critical components of  the system are functioning and to acquire baseline data 
reflecting overall short term system heat output. 
1.3 This guide is not intended to generate accurate measurements of system performance (see ISO 9459 
or FDUS 854 for a laboratory test) or thermal efficiency. 
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are 
for information only. 
1.5 This standard does not purport to address all of the safety 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 fo r the application of this Uganda Standard. For dated 
references, only the edition cited applies. For undated references, the latest edition of the referenced 
document (including any amendments) applies. 
FDUS 853:2009, Code of practice for solar water heating syst ems – Design, installation, testing, repair and 
maintenance  
FDUS 854-1, Thermal solar systems and components — Solar collectors — General requirements 
FDUS 854-2, Thermal solar systems and components — So lar collectors — Part 2: Test methods  
FDUS 860:2009, Standard practice for non-operational exposure and inspection of a solar collector  
ISO 9459-1,  Solar heating — Domestic water heating systems — Part 1: Performance rating procedure using 
indoor test methods  
ISO 9459-2, Solar heating — Domestic water heating systems — Part 2: Outdoor test methods for system 
performance characterization and yearly performance prediction of solar-only systems  
ISO 9459-5, Solar heating — Domestic water heating systems — Part 5: System performance 
characterization by means of whole-system tests and computer simulation 
ISO 9806-1, Test methods for solar collectors — Part 1:  Thermal performance of glazed liquid heating 
collectors including pressure drop  FDUS
2 © UNBS 2009 – All rights reserved
  856: 2009 
ISO 9806-2, Test methods for solar collectors — Pa rt 2: Qualification test procedures  
ISO 9806-3, Test methods for solar collectors — Part 3: Thermal performance of unglazed liquid heating 
collectors (sensible heat transfer only) including pressure drop 
3 Terms and definitions 
For purposes of this Uganda Standard, the terms an d definitions given in FDUS ISO 9488 shall apply. 
4 Summary of guide 
4.1 This guide recommends inspection procedures an d test for: general syst em inspection, collector 
efficiency, freeze protection, and controller and pump/blower operation. 
Verification of satisfactory operation of these components indicates that the system is functioning.  Tests are 
designed to take minimum time in preparation, testing and restoration of the system. They may use relatively 
inexpensive, non-intrusive instrumentation which system  installers can reasonably be expected to have on 
hand. 
4.2 Recommended tests for each component or subsystem fall into categories according to the level of 
complexity and cost (see note below). 
a) Category A - the most rudimentary tests, such as visual inspection; 
b) Category B - tests that requir e minimal instrumentation and skill; 
NOTE 1 Category B tests should include Category A tests as prerequisite, etc. 
c) Category C - tests that require  most expensive or sophisticated instrumentation or more time to 
perform; and 
d) Selection of the appropriate test is at the discr etion of the tester and purchaser, who should be aware 
of the tradeoffs between cost and accuracy at each le vel of testing. The tester should make these 
clearly known to the purchaser of the system who may wish to assume the costs of more 
sophisticated testing. Preferably there should be a par t of the installation cont ract between the tester 
and purchaser spelling out test spec ifics (for example, Category A, B or C for each subtest). 
4.3 Instrumentation includes sensors to monito r some or all of the following conditions: 
a) total incident solar radiation (i n the plane of the collector array); 
b) outdoor ambient temperature; 
c) internal building temperature near storage system; 
d) collector loop flow rate and temperatures;  
e) storage temperature; and 
f) each system should be instrumented to the prac tical level required for calculation (see FDUS 854). 
Some sites may need additional instrumentation as a result of their unique requirements. Figure 1 
shows a typical closed loop system with the instrumentation required for the various tests. 
 FDUS 856: 2009 
© UNBS 2009 – All rights reserved  3
 
 
Figure 1 — Closed loop system – One tank 
3.4 The various types of available instrumentation are listed in Tables  1-4. Approximate /accuracy and 
application information are given. Most of the necessa ry instruments are presently used in conventional 
heating and air conditioning work except the pyranometer or solar radiation fl ux-measuring instruments. 
Table 1 — Solar radiation probes 
Type of Sensor Accuracy Type of output Special comments 
Pyranometer 1 % - 3 % of 
instantaneous value Analog electrical millivolt 
output, may need amplifier Mounting point must be unshaded; some models increase error increase error by tilting 
Integrating pyranometer 5 % of integrated value Mechanical totalizer and 
analog electrical on some models Some models provide instantaneous reading 
Photovoltaic solar cell ± 5 % of instantaneous value Analogue Drift or degradation over long 
periods 
 
 FDUS
4 © UNBS 2009 – All rights reserved
  856: 2009 
Table 2 — Thermal sensors 
Type of sensor Accuracy Convenience Type of output Special comments 
Bimetallic High; 1 % or less 
of full scale Good, when 
installed correctly Visual Not reliable for 
differential temperatures, time lag present; clip on type available 
Bulb type thermometer High Difficult to read 
because of small scale Visual Very fragile 
Digital thermometer Depends on type of probe(s), typically 0.5 
oC 
(1oF) Excellent, one indicator can serve several locations (probes) Visual (digital) Probes typically cost 
$50 
Thermocouple Fair, 1 oC (2 oF) Excellent when 
coupled with indicator Analog (electrical) Not reliable for 
measuring temperature difference; requires special wire for installation 
Resistance temperature detectors (HTD) High  0.25 oC 
(0.5 oF) or better Excellent when coupled with indicator Analog (electrical) Especially suited for 
measuring temperature differences 
Thermistors Good, 0.5 oC   
(1 oF) Excellent when coupled with indicator Analog (electrical) Not available in proper 
housing; can be damaged 
Tapes Fair, 1 oC – 3 oC   
(2 oF - 5 oF) 
steps Excellent, reusable Visual inexpensive 
 
Table 3 — Liquid flow sensors and indicators 
Type of Sensor Accuracy Convenience Type of output 
Pressure gauges Strictly a flow indicator low Visual 
Float type Fair, + 5 % full scale accuracy Moderate Visual 
 
Table 4 — Air flow meters 
Type of Sensor Accuracy Type of Output Special Comments 
Hot wire anemometer Moderate, 2 % of full scale; reca libration 
necessary Analog (electrical) Some models easily damaged by 
debris and improper handling; must be properly located in order to determine mean flow 
Urbine Good, 1 % of flow Analog (electri cal) Must be properly located in order 
to determine mean flow 
Pilot tube Fair, 1 % to 5 % Visual or analog 
(electrical) Standard for measuring duct velocities 
 
 FDUS 856: 2009 
© UNBS 2009 – All rights reserved  5
 5 Significance and use 
5.1 This guide is intended for on-site assessment of in-service operation by short term measurement of 
appropriate system functions under representative operating conditions. 
5.2 Primary application is for residential systems an d medium-size multi-family units or commercial 
buildings. Use of back-up conventional solar water h eating system is assumed to augment solar heating. 
5.3 This guide is intended for use by suppliers, instal lers, consultants and homeowners in evaluating onsite 
operation of an installed system. Emphasis is placed on  simplified measurements that do not require special 
skills, intrusive instrumentation, system modification or interruption of service to the purchaser. 
5.4 The purpose of this guide is to verify that the system  is functioning. Copies of all data and reports shall 
be submitted by the testing group to the owner or his or her designated agent. 
5.5 Data and reports from these procedures and tests may be used to compare the system performance 
over time, but should not be used to com pare different systems or installations. 
5.6 Testing is for a newly installed system and also for periodic checking. 
6 Procedure 
6.1 Preparation 
6.1.1 Install and operate components and controls in accordance with manufacturer's instructions. 
6.1.2 Use temporary portable instrumentation or any permanent instruments installed for continuous 
monitoring to evaluate system  performance as long as accuracy is ± 2 % of full scale and  reproducibility is ≥ 5 
% and instrumentation is installed properly in accordance with manufac turer's instruction. 
6.1.3 Operate the system in a normal and satisfacto ry manner for several days before the on-site 
performance test. Operate the entire system at a nearly steady-state condition for at least a 2 h period before 
testing. Conduct tests for collector effe ctiveness under clear, sunny conditions. 
6.2 General inspection 
6.2.1 The ability to perform as intended for the specif ied period of time defines system durability and 
reliability. System performance depends on the proper  operation of each of the subsystems. The manual 
containing drawings, specifications, and engineering data shall serve as a benchmark for the inspection. 
6.2.2 The following components should be inspected for proper installation (see FDUS 853) and operation 
to check for any malfunctions, leaks or improper adjustments. 
a) collectors and connections; 
b) controls and sensors; 
c) insulation; 
d) interconnections — mechanical and electrical; 
e) pumps and motors; 
f) valves and fittings; 
g) storage containers and media; FDUS
6 © UNBS 2009 – All rights reserved
  856: 2009 
h) heat exchangers; 
i) dampers and ducting; 
j) air or liquid systems leaks; 
k) interrelated support systems, in cluding other air handlers, chille rs, heaters, or heat pumps; and 
l) fans and air handlers. 
6.2.3 Most of the failures reported have been in the collector subsystem and connections and controls with 
considerably fewer failures reported for valves and pump subsystems. There has been a high incidence of 
improper system operation due to contro ls improperly connected or adjusted. 
6.2.4 A visual inspection should be made of all connections (see FDUS 853) to check for evidence of leaks 
or potential future corrosion due to improper use of materials (see FDUS 853), improper joining of dissimilar 
metals (US 853), or improper fluids  (see FDUS 853). A pressure chec k on liquid systems should be done to 
see if it meets manufacturer's recommendations. 
6.2.5 Check pumps for noise (most pumps are very quiet). Noisy fluid flow almost always indicates a bad 
pump, cavitation or air in the system and is symptomati c of further problems. In an open or drainback system 
noisy fluid flow will occur if there is water loss due to leakage. If a pump problem is suspected, one way to 
determine if the pump is seized or has other electrical problems is to touch the assembly to see if it is hotter than the fluid circulating through it. Also any bur ning, odours may indicate electrical problems. 
6.3 Collector operation and effectiv eness (see FDUS 854 for other tests). Table 5 gives the typical 
operating ranges of the test parameters for various collector system configurations. 
Table 5 — Parameters of solar hot water systems 
System type Flow rate, 
cm3/m2.S 
(gal/min.ft2) Temperature 
Rise, On, oC 
(oF) Temperature 
Rise, On, oC 
(oF) Specific 
Heat W-
s/g.oC 
(Btu/lb-oF) Density, g/cm3 
(lb/gal) Solar Radiation, 
Minimum, W/m2 
(Btu/h.ft2) 
Flat Plate : 
Draindown 
Drainback 
Closed loop 
thermosyphon  
7-27 (0.01-0.04) 
7-27 (0.01-0.04) 
7-27 (0.01-0.04) 
……..  
5-11 (10-20) 
5-11 (10-20) 
5-11 (10-20) 
……..  
0.5-3 (1-5) 
0.5-3 (1-5) 
0.5-3 (1-5) 
……  
4.2 (1.0) 
4.2 (1.0) 
3.35 (0.8) 
4.2 (1.0)  
1 (825 – 8.33) 
1 (825 – 8.33) 
1 (825 – 8.33) 
1 (825 – 8.33)  
630 (200) 
630 (200) 
630 (200) 
630 (200) 
Air 
 
Tank Absorber 25 LJm ?-s(5 
fts/min-ft2) 
14 (0.02) 11-22 (20-40) 
 
…….. 
……….. 0.5-11 (1-20) 
 
…….. 
………. 0.8 (0.2) 
 
4.2 (1.0) 0.005 (0.29) 
 
1 (825 – 8.33) 630 (200) 
 
630 (200) 
Concentrating 
Type : 
Parabolic trough 
Evacuated tube  
 
14 (0.02) 
 
7 (0.01)  
 
5-11 (10-20) 
 
17-22 (30-40)  
 
0.5-3 (1-5) 
 
0.5-3 (1-5) 
  
 
3.35 (0.8) 
 
3.35 (0.8)  
 
1 (825 – 8.33) 
 
1 (825 – 8.33)  
 
630 (200) 
 
630 (200) 
 
 FDUS 856: 2009 
© UNBS 2009 – All rights reserved  7
 7 Test level A — Visual inspection 
7.1 Procedure 
Turn on system; observe the pump or blower comes on with sunshine available. Temperature on return line 
from collector should be slightly warmer (about 5 °C) than the supply line to the collector. This can be determined by feel or by temperature gauges (see Table 2) if installed. The return temperature should also 
show a gradual increase during daylight hours (will fluctuate depending on water usage). 
7.2 Interpretation and report of results 
If temperature rise is unreasonable (too little or too much — see 7.1) check pump or blower for proper 
operation and fluid level in system. 
8 Test level B — Esti mation of flow rates 
8.1 Procedure 
8.1.1 In the indirect system, record total head (discharge pressure-suction pressure), and establish flow rate 
using intersection of system curve with blower curv e provided by manufacturer (see Figure 2 correct for 
antifreeze percentage). 
 
Figure 2 — Pump and system curves (closed loop) 
 FDUS
8 © UNBS 2009 – All rights reserved
  856: 2009 
8.1.2 In the direct or open system me asure discharge pressure with drain valve and makeup valve closed. 
Then open makeup valve, turn on pump and adjust the drain valve until the pressure is the same as in 8.1.1 
(see Figure 3 for operating point). 
 
Figure 3 — Pump and system curves (open loop) 
8.2 Instrumentation 
Pressure gauge (see Figure 4 and Table 3), a stopwatch, and a container may be needed for this test. 
 
Figure 4 — Pressure gauge 
 FDUS 856: 2009 
© UNBS 2009 – All rights reserved  9
 8.3 Interpretation and Report of Results 
The system should be providing 7 cm3/m2s to 27 cm3/m2s of collector or as specified in operating manual. 
9 Test level C — Measure radi ation and temperature changes 
9.1 Procedure 
Measure radiation ( q) with pyranometer. To get steady state, re ad every 15 min until two consecutive values 
are the same within 5 %. Record readings, once at st eady state, every 15 min for 2 h. Measure collector inlet 
(Tin) and outlet temperatures ( Tout) every 15 min for 2 h (may need to close off makeup water and backup 
heater for duration of test). Use flow rates from Test  Level B or use flowmeters for fluid flow rate ( Q). 
9.2 Instrumentation 
9.2.1 Use pyranometer or solar cell (see Table 1). 
9.2.2 Use a thermometer or another device in accordance with Table 2. Pr obes or strap-on sensors should 
be at collector inlet and outlet as close to collectors as possible. 
9.2.3 Use flowmeters or data from Level B test (see Table 3 or Table 4). 
9.3 Interpretation and report of results 
9.3.1 Efficiency of the collecting system can be calculated by the following equation (Note 3): 
N = Q × d × 120 (min) × Sh × (Tout – Tin)/q × A × 2 (h)           (1) 
SI: 
N = Q × d × Sh × (Tout – Tin)/q × A                (2) 
where 
N  collector efficiency, 
Q  collector fluid flow rate, cm3/s (gal/min), 
d  density of collector fluid, g/cm3(lb/gal), [water = 8.33 at 68 °F, 8.25 at 120 °F (1 g/cm3)], 
Sh  specific heat of collector fluid,  Btu/lb × °F (water = 4.2 W.s/g°C), 
q   total solar radiation, W/m2 (Btu/h × ft2), 
A  area of collector, m2 (ft2), 
Tout  average collector fluid temperature variant at collector outlet, °C (°F), and 
Tin  average collector fluid temperature variant at collector inlet, °C (°F). 
NOTE For tank absorber measure increase in tank temperature over 2 h (gal × d × Sh × (Tout – Tin). 
9.3.2 Efficiencies should be greater than 30 %. If flow rate or temperature rise is too low, efficiency should 
be low (look for system defects). A plot of efficiency versus ( Tout – Tin/q) can be compared to FDUS 854-2. FDUS
10 © UNBS 2009 – All rights reserved
  856: 2009 
10 Freeze protection 
10.1 Test level A — Visual inspection 
10.1.1 Procedure 
10.1.1.1 For indirect or air system, make sure that  system cannot thermosyphon through the heat 
exchanger when the outside temperature is below 0 °C (f or example, presence of check valve or damper). 
10.1.1.2 In drainback or draindown syst ems check location or sensors a nd valves pertaining to freeze 
protection. Make sure all outside collector array piping is sloped for proper drainage. 
10.1.1.3 For evacuated tube collectors consult manufactu rer's instructions regarding freeze protection 
devices. 
10.1.1.4 For tank absorber and thermosyphon systems secure for freezing season. 
10.1.2 Interpretation and report of results 
If elements are not there for freeze protection s add them or make appropriate corrections.  
10.2 Test level B 
10.2.1 Procedure 
9.2.1.1 If antifreeze is used in a closed system, check, wi th hydrometer, that mixt ure contains the correct 
percentage of antifreeze. 
10.2.1.2 If an open system, turnoff power and make sure system  drains down or back. Also verify that the 
system will drain when temperature is be low 5 °C, test freeze protection by di recting stream of cold gas from a 
CO 2 or compressed air cartridge or sensor. 
10.2.2 Instrumentation 
Hydrometer and thermometer 
10.2.3 Interpretation and report of results 
Add correct antifreeze if needed, adjust sensor control so that valve opens at or near 5 °C or replace if 
nonadjustable snap switch. Make sure sensor is  attached at correct location and is secure. 
11 Controller 
11.1 Test level A (visual) 
11.1.1 Procedure 
Locate attachment points for all sensors. Collector sensors should be screwed or bolted directly to the 
collector absorber plate or immediately outside the hous ing on or in the collector inlet and outlet pipes. Tank 
sensors must be attached to wall or tank or on collector supply pipe immediately adjacent to tank (differential 
control sensor should be near bottom of tank). Sensor s should be insulated from external environment to 
correctly read intended temperatures. Trace sensors back to  controllers, where possible, to make sure wire is 
insulated, in good shape, and is tagged plus routed to correct location on controller. Inspection should be 
made of all splices especially where short sensor wires attach to long wires going to the controller. Corroded FDUS 856: 2009 
© UNBS 2009 – All rights reserved  11
 splices will give wrong readings. Turn on controller, make sure there is power to the control board and that 
electronics are functioning properly. 
11.1.2 Interpretation and report of results 
Correct any deficiencies in the sensor locations or condition. 
11.2 Test level B 
11.2.1 Procedure 
Controller should be matched with appropriate sensor, eit her 3K, 10K, or 30K. Perform a resistance check on 
sensors. A reading of zero ohms indicates a short and a reading of infinite ohms indicates an open sensor or open snap switch in series (consult manufacturer's in structions before using ohmmeter). Typical correct 
thermistor sensor resistances are:  
Temperature 3K Sensor  
Ω 10K Sensor 
Ω 30K Sensor 
Ω 
0oC (32 oF) 10 000 32 600 97 890 
25oC (77 oF) 3 000 10 000 30 000 
93oC (200 oF) 250 830 2 480 
 
11.2.2 Instrumentation 
Ohmmeter 
11.2.3 Interpretation and report of results 
Correct wiring by locating reasons for shorts or open wires. Make sure resistances comply with the table above  or with manufacturer's data  
NOTE Nominal 1000- Ω or 2000- Ω resistance temperature detectors (RTD ) or other sensors will have similar 
calibration points. 
11.3 Test level C 
11.3.1  Procedure 
11.3.1.1 With differential controller in Auto or equivalent position check that the pum p starts if temperature 
at collector is 5 °C to 22 °C hotter than storage (s ee note below). Also confir m that pump shuts off when 
collector outlet temperature for liquid systems is 0.5 °C to 3 °C more than storage temperature of 0.5 °C to 11 
°C for air systems. This can be done by checking te mperature readings during typical collection day or by 
using a test box furnished by manufacturer. 
NOTE Proportional controller or other c ontroller features should be checked in accordance with the manufacturer's 
instructions. 
11.3.1.2 If the pump fails to start check c ontinuity of pump power line input. If okay, next check a-c input to 
controller (240 V a-c) with controller ON. If the ac in put voltage is correct, but the a-c output voltage (to pump) 
is not, replace the controller. If the a-c input and out put voltages are correct, and the pump does not run, then 
the pump or wiring to it are faulty. FDUS
12 © UNBS 2009 – All rights reserved
  856: 2009 
11.3.2 Instrumentation 
Voltmeter and temperature readouts (either in controller or in line) 
11.3.3 Interpretation and report of results 
Either repair or replace faulty components. Adjust, if feasible, controller so that pump turns on and off at 
correct temperature intervals 8 °C to 22 °C (15 °F to  40 °F) ON, 0.5 °C to 3 °C (1 °F to 5 °F) OFF. 
NOTE ON-OFF temperature settings should be within manufacturers' specification. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 FDUS 856: 2009 
© UNBS 2009 – All rights reserved  13
 Annex A 
(informative)  
 
Rationale 
A.1  On-site performance measurements and acceptance criteria are required after system installation to 
ensure that the system is operating as advertised or  as specified. Short-term determination of system 
performance can be used to certify operation. Ongo ing evaluation or checks on system operation may be 
needed to make certain that the system is operating properly and remains adjusted for best performance. 
A.2   Demonstration programs have shown that poor system performance can sometimes be attributed to 
errors in installation or non-functioning components or subsystems. 
Because solar water heating systems have backup from conventional heaters, there is no obvious and 
immediate sign of problems or failure to function—hot water will be de livered to the tap in any case. 
A.3   More sophisticated tests and measurements of long -term thermal performance and efficiency may be 
needed. Given the current state of the art, such test s would be costly and time consuming to perform and 
would entail disruption of service and invasion or modification of the system. The inspection procedures and 
tests in this guide have been selected because of their potential for economy and simplicity. 
A.4   Although designed as an acceptance test, the procedure may be repeated at a future date, or at 
regular intervals, to verify acceptable system operati on and to compare overall short-term system heat output 
to the baseline figures established at the time of installation.  
 
 
 FDUS 856: 2009 
© UNBS 2009– All rights reserved 
 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 856: 2009 
 
ICS 27.160 
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