© PowerOptimal (Pty) Ltd 2017. The content of this document is confidential and all rights to the intellectual
property and/or information contained herein remain vested in PowerOptimal, except if otherwise agreed in
writing.
PowerOptimal Elon 100 Installation and User Manual
Version number: 1.19
Enquiries: info@poweroptimal.com
Address: PO Box 39521
Capricorn Square
7948
Cape Town
© PowerOptimal (Pty) Ltd 2017. The content of this document is confidential and all rights to the intellectual
property and/or information contained herein remain vested in PowerOptimal, except if otherwise agreed in
writing.
SAFETY WARNING
• Installation of the Elon 100 should ONLY be performed by an electrical
contractor registered with the Department of Labour (the so-called
“wireman’s licence”) and strictly according to the installation instructions
in this manual. The electrician should provide you with a Certificate of
Compliance (CoC) once installation is completed.
• We strongly recommend that you use a reputable and experienced solar
photovoltaic (PV) system installer to install your solar PV modules.
• Solar PV modules exposed to the sun are live (i.e. will produce electricity)
and can give an electric shock. Special care should be taken and only
trained solar PV installers should install the modules.
• Do not attempt to alter or service the electrical installation, or open the
Elon 100 unit or controller for any purpose.
• Use the Elon 100 only for its intended purpose.
• Always make sure that every wiring connection is properly tightened.
• Do not earth either of the solar module wires (but do earth the frames).
• All installation wiring should be at least 2.5mm².
• Avoid coiling, since DC switching can create damaging spikes.
• Keep all wires as short as possible.
© PowerOptimal (Pty) Ltd 2017. The content of this document is confidential and all rights to the intellectual
property and/or information contained herein remain vested in PowerOptimal, except if otherwise agreed in
writing.
Refer to our online instruction video for
easy to understand instructions on how to
use the PowerOptimal Elon
TM
100:
www.poweroptimal.com/elon100
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Table of Contents
Table of Contents .................................................................................................................................... 4
1. Introduction ........................................................................................................................................ 5
1.1 System overview ........................................................................................................................... 5
1.2 Main system components ............................................................................................................. 6
1.3 Deciding on size of Elon system (basic guide) ............................................................................... 6
1.4 Deciding on size of solar array (expert guide) .............................................................................. 6
1.5 PV array and geyser (water heater) element matching (expert guide) ...................................... 11
2. Installation ........................................................................................................................................ 12
2.1 Required tools ............................................................................................................................. 12
2.2 Basic wiring diagram ................................................................................................................... 13
2.3 Solar PV array installation ........................................................................................................... 14
2.4 Elon 100 installation .................................................................................................................... 16
2.5 Element installation (retrofit) ..................................................................................................... 16
3. Operation .......................................................................................................................................... 17
3.1 Elon 100 Controller ..................................................................................................................... 17
3.2 Mains / solar indicator lights ...................................................................................................... 17
3.3 Efficiency dial .............................................................................................................................. 17
3.4 Override button .......................................................................................................................... 18
3.5 How to maximise your savings .................................................................................................... 18
4. Maintenance ..................................................................................................................................... 20
4.1 Solar PV module maintenance .................................................................................................... 20
5. Basic troubleshooting ....................................................................................................................... 21
Appendix A. Solar yield ......................................................................................................................... 23
A1. Solar irradiance levels ................................................................................................................. 23
A2. Geographic features ................................................................................................................... 24
A3. Azimuth / horizontal angle ......................................................................................................... 24
A4. Inclination or tilt angle ................................................................................................................ 24
A5. Shading ....................................................................................................................................... 24
A6. Ambient temperature ................................................................................................................. 25
Appendix B. Technical Specification: Elon 100 ..................................................................................... 26
Appendix C. IEC/SANS Test Certificate: Elon 100 .................................................................................. 27
Appendix D. Warranty .......................................................................................................................... 28
Appendix E. Terminology ...................................................................................................................... 29
Notes ..................................................................................................................................................... 31
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1. Introduction
Thank you for buying the PowerOptimal ElonTM 100 solar PV water heating unit! You can look forward
to many years of savings and free energy from the sun.
1.1 System overview
The PowerOptimal Elon 100 operates on a very simple principle: it enables direct current (DC)
electricity produced by solar PV modules to be used directly for water heating using a standard geyser
with alternating current (AC) heating element and AC thermostat.
You can connect the system completely off-grid, or integrate with your existing grid AC power supply.
Connecting the system to the existing grid supply allows for grid power backup in case of cloudy /
overcast days, or where your hot water use exceeds the generation capacity of your solar PV array.
Note: the system is designed in such a way that there is no possibility of solar array-produced
electricity feeding back into the grid.
Below is a simplified layout of the main components of the water heating system.
An array of solar modules (a string of 3 to 6 solar modules connected in series, or two parallel strings
of 4, 5 or 6 solar modules each) is connected to the Elon 100. Grid electricity is also connected to the
Elon 100.
The Elon 100 is connected to the geyser element and thermostat.
When the solar modules are producing electricity, the Elon 100 feeds this into the geyser element to
heat water, until the water reaches the temperature setting on the thermostat.
Depending on the Elon 100 efficiency setting (see Section 3.3) or when the user presses the override
button, the Elon 100 will boost the water heating with grid electricity.
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1.2 Main system components
The main components of the system are as follows:
• Solar modules with struts, brackets and cabling
• PowerOptimal Elon unit with controller
• Existing or new water heater or geyser (hot water tank with AC heating element and AC
thermostat)
• Isolators for grid and solar connections
1.3 Deciding on size of Elon system (basic guide)
The table below provides a basic guide to selecting the size of your Elon system based on number of
people in the household and/or hot water use. Refer to Sections 1.4 and 1.5 for a detailed guide (for
solar PV experts).
Elon kit
Showers
per day*
No. of people
50%+ of hot
water use
No. of
people
off-grid
Solar PV
array size
kW
p
Geyser
element
kW
Geyser (water
tank) size
litres
Kit 1 – Solar Boost
3 – 4
2-3
1-2
1.5 – 1.7
2
100 – 150
Kit 2 – Solar Living
5 – 6
3-4
2-3
2.4 – 2.7
4
150 – 200
Kit 3 – Solar Pro
7 – 8
4-5
3-4
3 – 3.5
4
200 +
* 6-minute showers at 40 ºC with 8 litre/min (low-flow) showerheads
1.4 Deciding on size of solar array (expert guide)
Solar power is generated by solar cells, which are arranged in framed modules, typically of 60 or 72
cells each. The total set of solar PV modules installed on your rooftop is referred to as a solar PV array1.
1
Image source: http://ohioline.osu.edu/factsheet/AEX-652-11.
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TABLE 1. ANNUAL AVERAGE LITRES OF WATER HEATED PER DAY
The below example table indicates the average number of litres of water per day that the system will
heat from 15 to 60 °C over a year period for different solar array peak power ratings. (The amount of
water heated will vary with weather conditions, by geographic location and by season. Water heated
per day will be significantly lower in winter and significantly higher in summer. These numbers indicate
heating capacity – i.e. if no hot water is used on a given day, there will be less water heated on that
day. This is only an approximate guide.)
Solar + Elon
Annual average litres of water heated per day for X kWp installed solar capacity
Location
kWh/kWp/yr
0.8 kWp
1 kWp
1.2 kWp
1.4 kWp
1.6 kWp
1.8 kWp
2 kWp
2.5 kWp
3 kWp
3.5 kWp
Bloemfontein
1894
80
99
119
139
159
179
199
249
298
348
Cape Town
1624
68
85
102
119
136
154
171
213
256
299
Durban
1447
61
76
91
106
122
137
152
190
228
266
Jhb/Pretoria
1724
72
91
109
127
145
163
181
226
272
317
Mbombela
1627
68
85
103
120
137
154
171
214
256
299
Port Elizabeth
1565
66
82
99
115
132
148
164
205
247
288
Upington
1912
80
100
121
141
161
181
201
251
301
352
Saldanha
1623
68
85
102
119
136
153
170
213
256
298
Example:
For a solar array of 1.2 kWp, an installation in Johannesburg would yield about 1724 kWh/kWp/yr, or
1724 x 1.2 kWp = 2069 kWh/yr. This would be sufficient to heat on average 109 litres of water per
day. For a family of 2 each using 80 litres of hot water per day, this would provide about 109 ÷ (80 x 2)
or 68% of the annual hot water requirement.
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TABLE 2. ANNUAL AVERAGE NUMBER OF SHOWERS PER DAY
The below table indicates the average number of showers per day for which the system will supply
hot water over a year period for different solar array peak power ratings. (The amount of water heated
will vary with weather conditions, by geographic location and by season. Water heated per day will be
significantly lower in winter and significantly higher in summer. These numbers indicate heating
capacity – i.e. if no hot water is used on a given day, there will be less water heated on that day. This
is only an approximate guide.)
Solar + Elon
Number of showers per day (based on annual average) for X kWp installed solar capacity
Location
kWh/kWp/yr
0.8 kWp
1 kWp
1.2 kWp
1.4 kWp
1.6 kWp
1.8 kWp
2 kWp
2.5 kWp
3 kWp
3.5 kWp
Bloemfontein
1894
2.4
3.0
3.6
4.2
4.8
5.4
6.0
7.5
9.0
10.4
Cape Town
1624
2.0
2.6
3.1
3.6
4.1
4.6
5.1
6.4
7.7
9.0
Durban
1447
1.8
2.3
2.7
3.2
3.6
4.1
4.6
5.7
6.8
8.0
Jhb/Pretoria
1724
2.2
2.7
3.3
3.8
4.3
4.9
5.4
6.8
8.2
9.5
Mbombela
1627
2.1
2.6
3.1
3.6
4.1
4.6
5.1
6.4
7.7
9.0
Port Elizabeth
1565
2.0
2.5
3.0
3.5
3.9
4.4
4.9
6.2
7.4
8.6
Upington
1912
2.4
3.0
3.6
4.2
4.8
5.4
6.0
7.5
9.0
10.5
Saldanha
1623
2.0
2.6
3.1
3.6
4.1
4.6
5.1
6.4
7.7
9.0
The table is based on 6-minute showers at 40 °C and 8 litres/min low flow showerheads. Old
showerheads can use up to 15 litres/min and would substantially reduce the number of showers.
Example:
For a solar PV array of 2.5 kWp, an installation in Johannesburg would yield about 1724 kWh/kWp/yr,
or 1724 x 2.5 kWp = 4 310 kWh/yr. This would be sufficient for about 6 to 7 showers per day.
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TABLE 3. PERCENTAGE OF ANNUAL HOT WATER REQUIREMENT
The below example table indicates what % of the annual hot water requirement will on average be
supplied by the system for 2 people each using 80 litres of hot (60 °C) water per day. (The amount of
water heated will vary with weather conditions, by geographic location and by season. Water heated
per day will be significantly lower in winter and significantly higher in summer. These numbers indicate
heating capacity – i.e. if no hot water is used on a given day, there will be less water heated on that
day. This is only an approximate guide.)
Solar + Elon
Annual average % of hot water requirement supplied for 2 people each using 80 litres of hot
water per day for X kWp installed solar capacity
Location
kWh/kWp/yr
0.8 kWp
1 kWp
1.2 kWp
1.4 kWp
1.6 kWp
1.8 kWp
2 kWp
2.5 kW
p
3 kW
p
3.5 kW
p
Bloemfontein
1894
50%
62%
75%
87%
99%
112%
124%
155%
187%
218%
Cape Town
1624
43%
53%
64%
75%
85%
96%
107%
133%
160%
187%
Durban
1447
38%
47%
57%
66%
76%
85%
95%
119%
142%
166%
Jhb/Pretoria
1724
45%
57%
68%
79%
91%
102%
113%
142%
170%
198%
Nelspruit
1627
43%
53%
64%
75%
85%
96%
107%
134%
160%
187%
Port Elizabeth
1565
41%
51%
62%
72%
82%
92%
103%
128%
154%
180%
Upington
1912
50%
63%
75%
88%
100%
113%
126%
157%
188%
220%
Saldanha
1623
43%
53%
64%
75%
85%
96%
107%
133%
160%
186%
Examples:
An array of 1.2 kWp will provide approximately 64% of the annual hot water requirement for a family
of two people in Cape Town.
An array of 2 kWp will provide approximately 124% x (4 / 2) = 62% of the annual hot water requirement
for a family of four people in Bloemfontein.
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TABLE 4. PEAK POWER OUTPUT FOR VARIOUS SOLAR MODULES AND ARRAY SIZES
The peak power production (Wp) of the modules at STC (Standard Test Conditions) and at NOCT
(Nominal Operating Cell Temperature) are provided by the solar PV module manufacturer. The below
table indicates the peak power at STC for a range of solar module power ratings and array sizes.
No. of cells
per module
Module STC
power rating (Wp)
Total peak power at STC in kWp for an array of X modules
3 modules
4 modules
5 modules
6 modules
2 x 4 (8)
modules
2 x 5 (10)
modules
2 x 6 (12)
modules
60
250
0.75
1.00
1.25
1.50
2.00
2.50
3.00
60
255
0.77
1.02
1.28
1.53
2.04
2.55
3.06
60
260
0.78
1.04
1.30
1.56
2.08
2.60
3.12
60
265
0.80
1.06
1.33
1.59
2.12
2.65
3.18
60
270
0.81
1.08
1.35
1.62
2.16
2.70
3.24
60
275
0.825
1.10
1.375
1.65
2.20
2.75
3.30
60
280
0.84
1.12
1.40
1.68
2.24
2.80
3.36
60
285
0.855
1.14
1.425
1.71
2.28
2.85
3.42
60
290
0.87
1.16
1.45
1.74
2.32
2.90
3.48
72
295
0.885
1.18
1.475
1.77
2.36
2.95
3.54
72
300
0.90
1.20
1.50
1.80
2.40
3.00
3.60
72
305
0.915
1.22
1.525
1.83
2.44
3.05
3.66
72
310
0.93
1.24
1.55
1.86
2.48
3.10
3.72
72
315
0.945
1.26
1.575
1.89
2.52
3.15
3.78
72
320
0.96
1.28
1.60
1.92
2.56
3.20
3.84
72
325
0.975
1.30
1.625
1.95
2.60
3.25
3.90
72
330
0.99
1.32
1.65
1.98
2.64
3.30
3.96
72
335
1.005
1.34
1.675
2.01
2.68
3.35
4.02
72
340
1.02
1.36
1.70
2.04
2.72
3.40
4.08
Examples:
An array of 4 x 300 Wp modules in series will have a total peak power (at STC) of 1.2 kWp.
An array of 2 parallel strings of 5 modules of 280 Wp each (10 modules of 280 Wp in total) will have a
total peak power (at STC) of 2.8 kWp.
NOT ALLOWED
(exceeds maximum rated Elon
100 voltage)
NOT ALLOWED
(exceeds maximum rated Elon
100 voltage)
NOT RECOMMENDED
(poor matching efficiency
with heating element
)
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1.5 PV array and geyser (water heater) element matching (expert guide)
TABLE 5. PV ARRAY AND GEYSER (WATER HEATER) ELEMENT MATCHING
It is important to match PV array specifications and heating elements for maximum power transfer
efficiency. See the below table for the recommended heating element power rating for different solar
module power ratings and array sizes.
No. of
cells
Module STC
power
rating (Wp)
Module
NOCT
V
mpp
(V)
Module
NOCT
I
mpp
(A)
Best element size match (rated power in kW @ 230 V AC) for an array of X
modules
3 modules
4 modules
5 modules
6 modules
2 x 4 (8)
modules
2 x 5 (10)
modules
2 x 6 (12)
modules
60
250 – 290
28 – 29
6.5 – 7.3
4 kW
3 kW
2 kW
2 kW
NR
4 kW
4 kW
72
295 - 340
33 – 35
6.5 – 7.3
3 kW
2 kW
2 kW
NA
4 kW
4 kW
NA
* mpp = maximum power point
STC = Standard Test Conditions (irradiance 1000 W/m², spectrum AM 1.5, cell temperature 25 °C)
NOCT = Nominal Operating Cell Temperature (800 W/m², spectrum AM 1.5, cell temperature ~ 43 – 45 °C)
NA = Not Allowed (exceeds maximum rated Elon 100 voltage)
NR = Not Recommended (poor array-heating element matching efficiency)
Example:
For 4 x 300 Wp (1.2 kWp) solar modules, the best heating element match is a 2 kW AC element (as
rated at 230V).
TABLE 6. ALTERNATIVE MATCHING (ABOUT 5 – 10% EFFICIENCY LOSS COMPARED TO THE ABOVE
TABLE)
No. of
cells
Module STC
power
rating (Wp)
Module
NOCT
V
mpp
(V)
Module
NOCT
I
mpp
(A)
Best element size match (rated power in kW @ 230 V AC) for an array of X
modules
3 modules
4 modules
5 modules
6 modules
2 x 4 (8)
modules
2 x 5 (10)
modules
2 x 6 (12)
modules
60
250 – 290
28 – 29
6.5 – 7.3
3 kW
2* or 4 kW
3 kW
NR
NR
NR
3 kW
72
295 - 340
33 – 35
6.5 – 7.3
4 kW
3 kW
3* kW
NA
NR
3 kW
NA
* Marginal (10%+ loss)
Example:
For 4 x 300 Wp (1.2 kWp) solar modules, the best heating element match is a 2 kW AC element (as
rated at 230V), but a 3 kW element can also be used. It will have about 5 - 10% efficiency loss compared
to a 2 kW element.
Contact PowerOptimal for advice on array-element matching if module properties (V
mpp
and I
mpp
at
NOCT) are significantly different to the values provided in the table.
DO NOT DEVIATE FROM THE RECOMMENDED ARRAY-ELEMENT MATCHING CONFIGURATIONS
WITHOUT CONSULTING POWEROPTIMAL.
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2. Installation
2.1 Required tools
The following tools are required for the installation. Use insulated tools wherever applicable.
• Solar modules (mounting) - please refer to solar module / mounting installation instructions –
the below is only a guideline:
o Cordless screwdriver with bits
o Drill
o Set of drill bits (wood, steel, stone)
o Set of screwdrivers
o Set of Allen (hex) keys
o Tape measure
o Grinder (tile roof installations)
o Permanent marker
o Chalk
o Hammer
• Solar modules (electrical):
o AC/DC Clamp meter
o Side-cutting pliers
o Screwdriver set
o Crimping tool
o 4 mm² wire (double insulated) (or other size as determined by solar PV voltage and
wire length)
o Cable ties
• Elon 100 - the following additional tools:
o Drill or punch (to make holes for glands)
o 4 mm² wire (2-core Norsk or Surfix wire is recommended)
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2.2 Basic wiring diagram
Note: Both AC & DC isolators should be installed within 1.5m of the geyser (water heater), line of sight.
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2.3 Solar PV array installation
Modules should only be installed by a trained solar PV installation technician. Array position and
orientation have a major impact on power production (see Appendix A).
Review the instructions from your solar PV module supplier / manufacturer on installation.
Please note: A South African standard for low voltage embedded generation installations is
being developed (SANS 10142:3). In the absence of this standard, your solar PV installation
technician should follow SANS 10142:1 (Standard for low voltage installations), and can refer
to interim guidelines in anticipation of the SANS 10142:3 standard – see for example the
document provided by PQRS:
http://pqrs.co.za/wp-content/uploads/2016/01/PV-System-Interim-Guidelines-GoodPractice-for-Solar-PV-Installations-South-Africa-.pdf
SAPVIA (South African Photovoltaic Industry Association) has made available an excellent
guide to solar PV installations. See:
https://www.pvgreencard.co.za/Solar%20PV%20Guidelines%20-%20Digital%20
Spread%20High-res.pdf
The below installation steps are a general guide only – refer to the abovementioned standards and
guidelines.
1. A very important starting point is safety gear: ensure that all installers wear a helmet and
insulated safety gloves, as well as fall protection safety gear if work will be done on a roof or
elevated area.
2. The solar PV array should only consist of one string of 3 to 6 modules in series, or two parallel
strings of 8 (2 x 4), 10 (2 x 5) or 12 (2 x 6) modules as per Tables 4 to 6. Do not exceed the DC
voltage or current ratings of the Elon 100 (220V DC and 20A DC) under any circumstances.
3. Attach bracket / mounting structure to roof. Use mounting structure recommended by solar
module supplier for roof type and size of solar modules.
4. Fix the solar PV modules to the mounting structure whilst connecting the module cables to
each other.
5. If practical, cover the modules to ensure that there is no potential for electric shock whilst
installing the system.
6. Ground the mounting structure only.
7. Install the wiring from the solar PV array to the Elon 100 unit in the ceiling space. Ensure
isolators are in the “Open” position. Installation of a Surge Protective Device (SPD) between
the solar PV array and the Elon 100 is recommended.
8. Last step is to connect the array to the rest of the wiring, making sure that both the positive
and negative wires are fully isolated from ground and keeping isolators in the “Open” position.
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Some “DO’s & DON’T’s” when installing solar PV arrays:
Your solar PV installer should not make any of these basic mistakes, but they are listed here just in
case.
1. DO earth the PV array structure.
2. DO isolate the wires from the PV array structure.
3.
DON’T use different sizes, types or specifications of modules together in the same string or
array.
4.
DON’T install solar arrays where they will be partially shaded during any season of the year if
it can be avoided at all.
5. DO install the arrays so that there is space for inspection or maintenance when needed.
6. DO use cabling of the correct size for your solar array.
7.
DON’T install the solar array flush with your rooftop. Use struts / brackets that ensure an
unrestricted air gap of at least 40 mm between the roof and the modules.
8. DON’T walk on the modules.
9. DO ensure that connectors are kept clean and away from water.
10. DON’T leave exposed modules in short circuit.
11. DO ensure that all connectors are securely fastened.
12. DON’T exceed the voltage ratings of any components.
13. DO properly route and secure all cables.
14. DON’T coil cables.
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2.4 Elon 100 installation
1. Isolate the geyser – switch off the geyser circuit breaker at the main electrical distribution
board (DB) AND switch off the geyser isolator at the geyser.
2. Confirm with a multimeter that there is no voltage across the wires.
3. Install isolator for solar PV (DC) supply. Also install AC supply isolator if there is none. NB
Ensure that the DC isolator is rated for the DC voltage and current of the installed array.
4. The isolators must be installed within 1.5m of the geyser, and must be line of sight / visible
(i.e. do not install them at the back of the geyser).
5. The DC wires must not be earthed – i.e. they must be fully isolated from earth. Do NOT test
with a Megger.
6. Keep the DC wires as short as possible.
7. Avoid any coils in DC wires.
8. Recommended wiring size is 4 mm². 2-core Norsk or Surfix wire is recommended. Shield can
be earthed to PV array structure.
9. Install the Elon 100 unit according to wiring diagram (see Section 2.2). Mount the Elon 100
unit close to the geyser and protect from outside elements. Mount the controller (remote
control) inside or next to the main DB in the house.
10. Attach installation diagram sticker (as provided) to the front of the geyser or close by in a
clearly visible position.
11. Once installation is complete, switch on the AC & DC isolators, remove the covering from the
solar modules and switch on the geyser circuit breaker at the main DB.
12. Check that Elon 100 unit is operational (refer to LED lights on controller – see Section 3.2).
a. Confirm solar PV array supply voltage and DC power to geyser when thermostat is
closed. (If thermostat is not closed, open hot water tap in house until it closes.)
b. Test mains override.
c. Confirm that no power is supplied to geyser element when thermostat is open.
13. Set efficiency to desired level on controller (see Section 3.3).
Note: if doing any maintenance, rewiring or disconnecting the Elon 100 or geyser element for any
reason, it is good practice to first swith off both the AC & DC isolators, and then disconnect one of the
wires between the Elon 100 and thermostat before disconnecting the rest of the wires.
2.5 Element installation (retrofit)
If you need to exchange the element on an existing geyser (see Section 1.4), please follow the
instructions provided by the element supplier.
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Instruction video: www.poweroptimal.com/elon100
Refer to our easy to understand instruction video on how to use the Elon 100.
3. Operation
3.1 Elon 100 Controller
Your Elon 100 has a controller that is typically
installed next to your DB (distribution board). The
controller has three main functions:
1. Indicating heating activity through the
mains (red) & solar (green) indicator
lights
2. Setting the efficiency on the efficiency
dial.
3. Forcing the system to use grid (mains)
electricity for one heating cycle using the
override button.
3.2 Mains / solar indicator lights
The Mains & solar indicator lights indicate the following conditions:
Lights
Meaning
Mains (red) light flashing
Grid / mains electricity is being used to heat water
Solar (green) light flashing
Solar power is being used to heat water. Rate of flashing indicates
rate of solar energy supply
Red & green alternating
No power is being supplied to the geyser element. (Either the water
is on temperature already, or the unit is in solar mode and there is
not sufficient sunlight)
Red or green flashing very
fast
Isolation fault (contact electrician)
Both lights OFF
No power to unit (e.g. no sun and a power failure, or no sun and
geyser breaker at DB board is switched off)
3.3 Efficiency dial
You can use a screwdriver to turn the efficiency dial. The dial is
recessed so that people do not change the efficiency setting
unnecessarily or too frequently.
The ratio of installed solar power capacity to overall hot water use
level will determine what solar efficiency level will deliver the
maximum savings whilst ensuring hot water availability.
3.3
Efficiency
dial
3.4
Override
button
3.2 Mains
/ solar
indicator
lights
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At the “MINIMUM” efficiency setting, the Elon 100 will use grid power to boost the water temperature
at night, until approximately 3 am in the morning, and again from approximately 11 am onwards (“top-
up time”) if the sun is not shining.
As the efficiency is increased (by turning the efficiency dial anti-clockwise with a screwdriver), the
Elon 100 will only boost the water heating with grid power later in the day (i.e. it will give the solar
power supply more time to heat the water before boosting with grid power).
When the efficiency dial is set to “SOLAR ONLY”, the Elon 100 will ONLY use solar power to heat water.
Note that the override button is still functional at the “SOLAR ONLY” setting, in case you need to
boost water heating on a cloudy day or when using a lot of hot water.
If you set the Elon efficiency setting to “SOLAR ONLY” (highest efficiency), you can increase the geyser
thermostat temperature above 60 ºC to get maximum benefit from your solar array installation. For
example, you can set the thermostat temperature to 65 or 70 ºC.
Remember to reduce the thermostat temperature to 60 ºC again if you reduce the efficiency setting.
Warning: Do not set thermostat temperature above 70 ºC due to increased scalding risk.
Be careful when opening hot water taps located close to your geyser. You can install a
thermostatic mixing valve to reduce the risk of scalding – ask your plumber.
3.4 Override button
If you would like to override the functioning of the Elon 100 and force it to use grid power for water
heating (for example in case of prolonged cloudy weather, or having used a lot of hot water), press
and hold the override button for more than 10 seconds.
This will force the Elon 100 to switch to grid (mains) power for one heating cycle (in other words,
heating the water with grid electricity to the thermostat set point from whatever temperature it is at
the time of pressing the override button).
Only the red mains light on the controller should start flashing at this point. (If both red and green
lights are flashing (alternating), the water is already at the thermostat set point, and pressing the
override button will have no effect.)
3.5 How to maximise your savings
Efficiency dial
The best way to maximise your savings is to set the Elon efficiency dial to “SOLAR ONLY”. This will
ensure that the unit will never use grid (mains) power for heating water. You can still override / boost
with mains power (for example on a cloudy day) using the override button as described above.
If you do not have enough solar power for the number of people and overall level of hot water use in
the household, you might not reach the desired water temperature with the “SOLAR ONLY” setting,
and might need to reduce the efficiency setting, or reduce your hot water use.
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Please note: The water in your geyser should be heated to 60 °C at least once a week to
prevent Legionella bacterial growth2. If you have heavily overcast weather for more than a
week, use the override button to supplement the solar water heating with grid electricity to
reach the thermostat temperature setting.
When is the best time to shower?
If the efficiency dial is set to “SOLAR ONLY”, it is best for people in the household to shower either in
the morning or in the evening, but not both. (If you shower in the evening, cold water will mix with
the remaining warm water overnight, and you will have cold water the next morning. If you do not
shower again in the morning, the water will be heated during the day.)
If the efficiency dial is set to lower efficiency than “SOLAR ONLY”, it is best to shower in the morning
for maximum savings.
General hot water energy saving tips
• Shower, don’t bath
• Install water-saving / low flow shower heads (these also save energy because of reduced hot
water use!)
• Reduce shower duration
• Check that your geyser is well insulated
South Africa is a water-scarce country – reducing hot water use saves both energy and water!
2
See for example: http://www.eskom.co.za/sites/idm/Documents/Legionaires_Fact_sheet_hot_water
_bacteria_simple_facts.pdf and http://standards.nsf.org/apps/group_public/download.php/
30413/How%20to%20Avoid%20LD%20at%20Home.pdf
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4. Maintenance
The Elon 100 has been designed to last for a very long time, and has no moving parts aside from two
electrical relays. No maintenance is required on the Elon 100.
4.1 Solar PV module maintenance
It is recommended that a qualified electrician inspect your solar PV installation at least once a year.
1. At least once a week, check whether any of the indicator lights are flashing rapidly. (This
indicates an isolation fault – refer to Section 3.2.)
2. Perform regular visual checks (at least once a year). Check for soiling or any visible damage to
any of the modules.
3. If the modules have been soiled by dirt, dust, debris, bird droppings or any other materials,
use water only and a sponge or soft cloth to clean them. Do the cleaning early in the morning
or late in the afternoon, as the modules are hot during the day. Avoid using a water jet that
may leave streaks on the modules.
4. Visually inspect cables for any degradation or loose fittings.
5. Look for any shading problems, such as trees that may have grown.
6. An electrician can check solar power production on a sunny day to ensure that the system is
still producing power at expected levels. A thermal imaging camera can be used to inspect
modules for hot spots.
7. Follow any specific maintenance instructions from the solar PV module manufacturer.
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5. Basic troubleshooting
Below is a table with basic troubleshooting tips. If you cannot resolve the problem using the below
table, please contact your installer.
Issue
Possible causes
What to do
Water temperature
too low
a. High hot water usage
levels
b. Cloudy day
c. Soiled solar modules
d. Mains circuit breaker
has tripped
e. Thermostat connection
or thermostat defective
a. Press override button (3.3) OR
Reduce efficiency setting (3.2) OR
Reduce hot water use (3.5) OR
Add additional solar modules to your solar
installation (first consult with your
installer)
b. See a. above
c. Inspect solar modules. If they are soiled,
clean them with water and sponge (4.1)
d. Check mains circuit breaker
e. Call electrician for inspection
Water temperature
remains low after
mains power boost
a. Sufficient time has not
been provided for
water to be heated
after override button
has been pressed
b. It is a cloudy day and
there is a mains power
failure
c. There is an electrical
fault or the Elon 100 is
defective
d. Thermostat connection
or thermostat defective
a. Wait for 2 hours after pressing the
override button
b. You will have to wait until either the solar
or grid power returns to heat the water
c. Check if only the mains light on the Elon
100 controller starts flashing after you
press the override button for 10 seconds.
If it does not and your water remains cold,
call your electrician to inspect the
installation for any electrical fault.
d. Call electrician for inspection
Water temperature
too high
a. Thermostat
temperature setting is
high and you are using
hot water from a tap
close to the geyser
b. Thermostat connection
or thermostat defective
a. Reduce thermostat temperature set point
OR
Open the cold water tap first
OR
Install a thermostatic mixing valve
b. Call electrician for inspection.
Hot water
production is lower
than it used to be
a. Soiled solar modules
b. Trees / plants have
grown and are causing
shaded areas on solar
modules
c. Damage to solar
modules
a. Inspect solar modules. If they are soiled,
clean them with water and sponge (4.1)
b. Trim trees and plants
c. Installer or electrician should test solar
array power production in sunny
conditions and compare with
specifications. If one or more modules are
damaged and they are still under
warranty, contact manufacturer for
replacement
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Issue
Possible causes
What to do
Both indicator
lights off
a. Power failure and
overcast / night-time
b. Geyser breaker at DB
board switched off
a. Wait until power or sun returns and check
if any indicator light comes on.
b. Switch on breaker at DB board.
Red indicator light
flashing
a. Isolation fault
a. Please call your electrician.
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Appendix A. Solar yield
Note: only basic information is provided here. Your solar PV installation technician should advise on
the best configuration for your specific location, roof structure, etc.
The yield produced by solar PV modules depends on a number of factors:
• Solar irradiance levels at your location (which varies with time of day, season and weather
conditions)
• Geographic features at your location (e.g. mountains or buildings causing morning or
afternoon shade)
• Azimuth and tilt of the modules
• Shading
• Ambient temperature (also influenced by wind)
A1. Solar irradiance levels
The map below shows the general solar irradiance levels (GHI or Global Horizontal Irradiance) in South
Africa3:
3
CRSES (Centre for Renewable and Sustainable Energy Studies). Website:
http://www.crses.sun.ac.za/files/research/publications/SolarGIS_GHI_South_Africa_width15cm_300dpi.png.
Last accessed: 07/04/2017.
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You can expect the following approximate energy generation from solar modules for various
locations4:
Location
Electricity generated
kWh/kWp per year
Bloemfontein
2055
Cape Town
1762
Durban
1570
Johannesburg / Pretoria
1871
Mbombela
1766
Port Elizabeth
1698
Upington
2075
A2. Geographic features
Major geographical features (such as hills or mountains) can reduce the total solar yield.
A3. Azimuth / horizontal angle
The azimuth refers to the horizontal orientation of the modules
– in the Southern Hemisphere, by how many degrees they are
oriented away from north
Due north is best in the Southern hemisphere. Modules should
preferably not be oriented more than 15º away from due north.
A4. Inclination or tilt angle
The tilt angle refers to the vertical orientation of the modules – a rough guide is that the modules
should be tilted at the site’s latitude. For example, Musina is 22º S, Pretoria & Johannesburg are 26º
S, Bloemfontein is 29º S, Durban is 30º S and Cape Town & Port Elizabeth are 34º S. To optimise winter
performance, one can add 15º to the tilt angle. (Note: as long as you are within about 15º of the
optimal latitude, the loss in efficiency is not substantial.)
A5. Shading
Solar modules lose a lot of efficiency if even a small part of the module is shaded. For example, just
3% shading can cause a 25% loss in power! Shaded cells on a module also causes hotspots, which will
reduce module lifetime.
It is thus important to place the solar modules on a rooftop area that is free from shading for as much
as possible of the day (and throughout the year).
4
Urban Energy Support. Website: http://www.cityenergy.org.za/uploads/resource_274.pdf. Last accessed:
07/04/2017.
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A6. Ambient temperature
Solar PV modules’ performance decreases with increasing temperature. Wind will reduce the
temperature of the solar array and will thus improve performance. Thus, it is important to install
rooftop solar modules with an air gap of at least 40 mm between the modules and roof5.
5
D’Orazio M et al. 2013. Performance assessment of different roof integrated photovoltaic modules under
Mediterranean Climate.
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Appendix B. Technical Specification: Elon 100
SPECIFICATIONS
Rated input voltage
250V AC, 220V DC
Rated input current
25A AC, 20A DC
Mains (AC) voltage range
-50% to +100% (but will disconnect all loads when breach is greater
than +/- 15%)
System power supply
Solar or 230V AC mains
Shutdown
Sufficient power supply capacity to manage processor, switching and
data storage if both mains and solar supply fail
Solar voltage
20 – 220 V DC
Solar energy availability
Automatically determines availability of sufficient solar energy
before supplying load from solar modules
Efficiency control
Can be adjusted to run from “solar only” to substantial AC mains
power usage
Override switch
A request (override) switch to force the managed load to use AC
mains for one heating cycle is provided
Thermostat
Uses the standard normally open thermostat switch associated with
the geyser element as a sensor only, with less than 10mA sense
current, to control power to the element
Reverse polarity protection
Protected against reverse connection of solar array
Switching timing
Built-in random numbers generation staggers switching times where
more than one Elon 100 is deployed
Annual energy production
compared to inverterbased system
> 90% when solar array and geyser element are matched correctly
It is important to match modules and heating elements for maximum power transfer efficiency. See
the tables in Section 1.4 for the recommended heating element power rating for different solar
module specifications and array configurations.
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Appendix C. IEC/SANS Test Certificate: Elon 100
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Appendix D. Warranty
If the PowerOptimal ElonTM 100 (“the Product”) is found to be defective, you will be entitled to a repair
or replacement within 2 (two) years of the date of delivery of the Product to you. Please keep your
receipt as proof of purchase. If you are a consumer as defined in the Consumer Protection Act No. 68
of 2008 (“the CPA”), you will be entitled to such remedies as are made available under the CPA in
relation to the return of goods.
PowerOptimal will not have any liability or obligation to you where the Product has been subjected to
abuse, misuse, improper use, improper testing, negligence, accident, alteration, tampering or repair
by a third party.
To the maximum extent permitted by applicable law, in no event shall PowerOptimal be liable for any
special, incidental, indirect, or consequential damages whatsoever, including, without limitation,
damages for loss of business profits or business interruption, arising out of the use or inability to use
this product.
Please note that this unit must be installed by an electrical contractor registered with the Department
of Labour. Failure to do so may invalidate this warranty.
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Appendix E. Terminology
AC Alternating Current – an electric current that reverses its direction many times a
second at regular intervals, with voltage typically varying in the form of a sine wave.
CoC Certificate of Compliance – to be issued by the electrician installing your Elon 100
system
CPA Consumer Protection Act No. 68 of 2008
DB Distribution board – the main electrical distribution board / panel in your home,
containing circuit breakers and switches.
DC Direct Current – an electric current flowing in one direction only. Solar PV modules
produce direct current electricity.
ECBSA Electrical Conformance Board of South Africa
Geyser South African term for a water heater
IEC International Electrotechnical Commission
I
mpp
The solar module current at maximum power point (MPP). Manufacturers usually
report two I
mpp
values: one at STC and one at NOCT.
kWh A derived unit of energy equal to 3.6 MJ (megajoules). The amount of energy used by
a 1 kW electrical device over a period of 1 hour.
kWp or Wp The peak power rating in kilowatt (kW) or watt (W) of a solar module or array – i.e.
the output power achieved under full solar radiation. This is usually reported at STC
and NOCT.
MPP Maximum power point. This is the point on a solar cell, module or array’s power or I-
V (current-voltage) curve that has the highest power output.
NOCT Nominal Operating Cell Temperature. This refers to the temperature that open
circuited solar PV modules will reach under conditions that more closely match actual
field operational conditions than STC. The modules are tested at 800 W/m² simulated
solar irradiance, 20 °C ambient temperature, 1 m/s wind velocity and open back side
mounting. Depending on the quality of the cell / module design, the NOCT can reach
anything from 33 to 58 °C6. Since solar PV cell power output reduces with increase in
temperature, a lower NOCT is better.
PV Photovoltaic – referring to the production of electric current at the junction of two
materials exposed to light.
SANS South African National Standards
6
Source: http://pveducation.org/pvcdrom/modules/nominal-operating-cell-temperature.
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STC Standard Test Conditions for solar cells – 1000 W/m² simulated solar irradiance and
25 °C solar cell temperature, and an air mass 1.5 spectrum (AM1.5).
V
mpp
The solar module voltage at maximum power point (MPP). Manufacturers usually
report two V
mpp
values: one at STC and one at NOCT.
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Notes
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