Bureau of Energy Efficiency
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Schedule 23
Standards and Labelling of Solar Water Heaters
1. SCOPE
This schedule specifies the energy-labelling requirement for Solar Water Heaters
(SWH) imported or sold in India for water heating and similar use. The schedule covers
all types of thermosyphon based solar water heaters up to 500Liters storage capacity.
For this schedule, the star rating shall be based on efficiency of the system averaged
over the day-test period (��
������̅̅̅̅̅) as per ‘IS 16368:2015 Test procedure for thermosyphon
type domestic solar hot water heating systems;
This schedule does not apply to SWHs where:
• Concentrating collectors are used
• Heat transfer fluid changes phase
• Water temperature is ≥100℃
• Unglazed flat-plate collectors are used
2. NORMATIVE REFERENCES
This schedule shall be read in conjunction with the following standards with all
amendments, for the purpose of star labelling
Number Standard
1. IS 16368:2015 Test procedure for thermosyphon type domestic solar hot
water heating systems
2. IS 12933 part-1:2003 Solar Flat Plate Collector- specifications; Part 1
Requirements
3. IS 12933 part-2:2003 Solar Flat Plate Collector- specifications; Part 2
Components
4. IS 12933 part-3:2003 Solar Flat Plate Collector- specifications; Part 3
Measuring Instruments
5. IS 12933 part-5:2003 Solar Flat Plate Collector- specifications; Part 5 Test
Methods
6.
IS 16544: 2015 All Glass Evacuated Solar Water Heating System
7.
IS 16543: 2016 All Glass Evacuated Solar Collector Tubes – Specification
3. TERMINOLOGY
For this schedule, the following definitions shall apply. However, in case of dispute,
the definitions given in ‘IS/ISO 9488:1999 Solar Energy- Vocabulary’ can be referred.
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3.1. Solar Water Heater (SWH)
The system normally consisting of a collector and a container which may be integral,
close coupled or remote, and which heats water by means of radiant energy from
the sun. It is normal for solar water heaters to be either fitted with or connected to
a supplementary heating source.
3.2. Solar Collector
Device designed to absorb solar radiation and to transfer the thermal energy so
produced to a fluid passing through it.
3.2.1. Flat Plate Collector (FPC)
Non-concentrating solar collector in which the absorbing surface is essentially planar.
3.2.2. Evacuated Collector
Collector in which the space between the absorber and the cover is evacuated.
3.2.3. Evacuated Tube Collector (ETC)
Evacuated collector employing transparent tubing (usually glass) with an evacuated
space between the tube wall and the absorber.
3.2.4. Concentrating Collector
Solar Collector that uses reflectors, lenses or other optical elements to redirect and
concentrate the solar radiation passing through an aperture onto an absorber.
3.3. Storage tank
The storage tank is a thermal store for the energy transferred from the collector. It
is a container used for storing the thermal energy. The heat transfer fluid and the
accessories such as heat exchangers, flow switching devices, valves and baffles
which are firmly fixed to the thermal storage container are considered part of the
storage device.
4. TESTING GUIDELINES AND REQUIREMENTS
The schedule is only limited to thermosyphon based solar water heaters. Hence the
testing methodology mentioned in ‘IS 16368:2015 Test procedure for thermosyphon
type domestic solar hot water heating systems’ must be followed to determine the
maximum efficiency of the system.
4.1. Standard Rating conditions
Solar hot water systems must be tested for its thermal performance as per the
clause 7.0 of IS 16368:2015 Test procedure for thermosyphon type domestic solar
hot water heating systems.
4.1.1. Test report
The results of test shall be reported in the prescribed format as given in Annexure B
of this schedule
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Only BIS recognized lab/NABL/ILAC/APAC accredited lab test reports are acceptable.
4.2. Tolerance limit
There is no negative tolerance for star rating band; the system efficiency ��
������̅̅̅̅̅
products tested must be at par or better than the star rating band threshold. System
efficiency of the SWH system will be rounded off to nearest two decimal places as
per IS 2:1960.
5. RATING PLAN / LABELLING PLAN
Star rating will be given based on system efficiency ��
������̅̅̅̅̅. Mathematically expressed
in equation (1) , (2), (3), (4) at standards test conditions mentioned in the clause
9.6.5 of IS16368:2015, reproduced in clause 5.1 below:
…(4)
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where
Ac = Gross area of solar collector, in m
2
Aa = Absorber area of solar collector, in m
2
As = Outside surface area of storage tank, in m
2
Ap = Total outside area of connecting pipes, in m
2
F' = Collector efficiency factor
GT = Solar irradiance on the inclined plane of the solar collector, in W/m
2
(MC)S = Thermal capacitance of the water in the storage tank only, in J/K
t = time, in s
TS = Temperature of water in storage tank, in
o
C
Ta = Ambient air temperature, in
o
C
TSfd = Final storage tank water temperature at the end of the day-test, in
o
C
TSid = Initial storage tank water temperature at the start of the day-test, in
o
C
Ūsys,d = Average overall heat loss coefficient of the system during day-test, in W/m
2
K
UL = Overall heat loss coefficient of solar collector, in W/m
2
K
Up = Overall heat loss coefficient of piping, in W/m
2
K
US = Overall heat loss coefficient of storage tank, in W/m
2
K
ɳ͞
sys,o = Maximum efficiency of the system averaged over the day-test period
ɳ͞
sys = Efficiency of the solar hot water system averaged over the day-test period
(τα)eff = Effective transmittance-absorptance product of the solar collector for solar
radiation
5.1 Standards test conditions as mentioned in the clause 9.6.5 of IS16368:2015 is
as reproduced below:
i. Average storage temperature = 50
o
C
ii. Average ambient air temperature during test period = 25
o
C
iii. Average of total solar radiation incident on the plane of solar collector
= 700 W/m
2
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The star rating levels are given in Table 1.
Qualification Criteria for Star labelling:
In a FPC based SWH, the collector must meet all the requirements as per ‘IS 12933
part-1:2003, Solar Flat Plate Collector- specifications’. Similarly, for ETC based SWH,
the system must meet all the requirements as per ‘IS 16544: 2015 All Glass Evacuated
Solar Water Heating system’.
In addition, the hot water storage tanks in FPC based SWH system must comply with
MNRE’s ‘Minimum Technical Requirements laid down for ensuring quality aspects of
Solar Water Heating Systems being installed in field’ released on 24.08.2012. The
specifications are mentioned in the Appendix A.
Table 1 Star labelling scheme for Solar Water Heaters
Star level System Efficiency (%��
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.
)
Minimum Maximum
1 Star 40.00 45.00
2 Star >45.00 50.00
3 Star >50.00 55.00
4 Star >55.00 65.00
5 Star >65.00
6. CHECK TESTING
BEE registered Solar Water Heater samples would be picked up at random from the
market and tested at a BEE empaneled Lab. If the first sample fails, then a second
check testing would be carried out. Under second check testing, two similar SWH
system with same rated efficiency would be picked up again from the market
randomly and both samples would have to meet the declared system efficiency. Even
if one sample fails to meet the declared system efficiency during second check
testing, the SWH will be treated as being in non-compliance with the prescribed BEE
standards.
7. FEES
With regards the S&L scheme for Solar Water Heaters, the manufacturer has to first
register his company under BEE scheme by making one- time payment of Rs.
25,000/- for MSME and Rs.1,00,000/- for rest of the manufacturers. This amount is
refundable.
7.1. The application for registration should be submitted with all applicable pre-
requisite certificate and a test report from a BIS recognized, NABL accredited
or ILAC/APLAC/APAC signatories test labs recognized by BIS.
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7.2. The application fees for each model is Rs. 2,000/-(Rupees two thousand only)
and fees for renewal/degradation for each model will be Rs.1,000/- (Rupees
One thousand only).
7.3. Labelling fee for affixation of label on each unit of SWH is INR 0.02 per LPD /-
(2 paise per Liters Per Day only)- shall be charged by BEE.
7.4. However, the labelling fees for 5 star rated models would be waived off (for
voluntary phase only) to promote higher efficiency SWH.
7.5. The label validity period would be effective from the date of launch till 31
st
December 2021.
8. LABEL DESIGN AND MANNER OF DISPLAY
8.1. Placement: All SWH must display the label on the storage tank.
8.2. Material, Dimension and Shape: The label shall be of durable material and be
printed as per the size given below.
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Figure 1 Label for SWH system
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APPENDIX -A
Components of
Storage Tank
Specification as mentioned by MNRE
Inner tank material SS 304 or 316 grade min/ MS or any other material with
anticorrosive coating for hard water with chlorine contents.
Inner tank thickness
For SS minimum thickness will be 0.5 mm when using argon
arc or metal inert gas for welding & 0.8 mm when using
other type of welding. For MS it will be 1.5 mm. No leakage
under any kind of negative or positive pressure of water will
be ensured.
Inner tank welding TIG / Seam/ pressurized weld (Open arc weld not permitted)
Storage tank capacity
Not less than system capacity. In case of ETC based system,
volume of tubes & manifold not to be included in tank
capacity.
Thermal insulation of
storage tanks
Minimum 50 mm thick CFC free PUF having density of 28-32
kg/ cu.m for domestic systems and 100mm thick Rockwool
of 48 kg per cu. m for other systems. For colder regions, it
will be 1 ½ times at least. In case of higher density
insulations, the thickness may reduce proportionately.
Thermal insulation of
hot water pipes
Minimum 50 mm thick rockwool or 25 mm thick PUF on GI
pipes. For colder regions, it will be 1 ½ times at least. In case
of composite pipes, it will depend on region to region. For
higher density insulations, the thickness may reduce
proportionately
Out cladding and
frames
Al/ FRP or GI powder coated. MS may also be used with
special anti-corrosive protective coatings. Thickness of
sheets will be strong enough to avoid any deformation of
the cladding.
Valves, cold water
tank, vent pipe, heat
exchanger, make up
tank & instruments
Of ISI mark or standard make
Support structure for
collectors, piping tanks
etc.
Of non-corrosive material or have corrosion resistant
protective coating. They will be strong enough to sustain
their pressure during the lifetime of system.
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APPENDIX-B
Table 2 General Information and specifications to be reported
Manufacturer/Laboratory name Values
Address
Date of receipt
Test report No.
Tested by
Date of testing
Reviewed by
System efficiency (%��
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.
)
��
��
(����) (for flat plate collector)
��
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�� (for flat plate collector)
��
���� (for evacuated tube collectors)
Absorptivity of selective coating (for evacuated tube
collectors)
Emissivity of Selective Coating (for evacuated tube
collectors)
Table 3 Compliance metric for storage tank (only for FPC)
Components of Storage
Tank
Specification of the
material used in
the system.
Is the material / component
meeting the MNRE
specifications? (Yes or No)
stated in Annex-A
1. Inner tank material
2. Inner tank thickness
3. Inner tank welding
4. Storage tank capacity
5. Thermal insulation of
storage tanks
6. Thermal insulation of
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Components of Storage
Tank
Specification of the
material used in
the system.
Is the material / component
meeting the MNRE
specifications? (Yes or No)
stated in Annex-A
hot water pipes
7. Out cladding and frames
8. Valves, cold water tank,
vent pipe, heat
exchanger, make up
tank & instruments
9. Support structure for
collectors, piping tanks
etc.
In addition to above mentioned information, all the specifications of the product
and results of testing must be reported as per the Annex D of ‘IS 16368:2015 test
procedure for thermosyphon type domestic solar water heating systems.’
