1. Calculation PV Array Maximum Voltage
This is a guide on how to calculate what the max voltage will be of the array

2. PV Array Maximum Voltage
No longer Voc X 1.2
Voc array at STC corrected for lowest expected temperature
With the release of AS5033 we no-longer use the Voc X 1.2 calculation, to determine the PV array max voltage.
We need to calculate it using the voltage temp co-efficient for the panel and the lowest expected temp (get it from the BoM)
Clause 4.2 – PV Array Max Voltage

3. PV Array Maximum Voltage
Voltage Change per ⁰ C
This is a spec sheet of a Conergy Powerplus panel
We need to know what the change in Voltage is per degree of temperature change. The example here is of the 250W module. As you can see for every degree the cell is above 25 it will produce .12V less than Voc.
A lot of manufacturers don’t give you Volts per degree like it is in this spec sheet.
They give a percentage

4. PV Array Maximum Voltage
Determining V / ⁰C from %
37.9 X % =
37.9 X /100 =
37.9 X =
-0.12 V / ⁰C
If your spec sheet only has a percentage you need to muiltply this percentage by the Voc.
As you can see from this example the Voc is 37.9 and the voltage temp coeff. Is -0.33%
Therefore we multiply 37.9 X -0.33%
Because it is a percentage we need to divide it by 100.
Therefore we get Voc (37.9) X and that equals
-0.12V

5. PV Array Maximum Voltage
Minimum Temperature of Site
That was step 1.
Next we need to determine the minimum temp of the site
You can get this from the Bureau of meteorology
When the site opens you need to
Select “Climate & Past Weather”

6. PV Array Maximum Voltage
Minimum Temperature of Site
On the Climate and Past Weather screen
Select “Weather & Climate data”

7. PV Array Maximum Voltage
Minimum Temperature of Site
Change selected data to Temperature
Change observations to monthly
Select lowest temperature from the drop down
Type in the area of interest and press find so in this example it is Melbourne

8. PV Array Maximum Voltage
Minimum Temperature of Site
After pressing find
Select the matching town
Select the nearest bureau station
Click “get data”

9. PV Array Maximum Voltage
Minimum Temperature of Site
Scroll right to the bottom to Summary statistics for all years
Get the annual lowest temp (for Melbourne it is -2.8C)

10. PV Array Maximum Voltage
Calculate the difference from STC (25 ⁰C)
Melbourne = -2.8⁰C (21 July 1869)
For the ease of the calculation use -3 ⁰C
Tmin - Tstc =
-28 ⁰C
The panel Voc is at Standard Test Conditions which is 25C
We need to calculate what the temperature difference is between -3 and 25
So we take the STC temp away from min temp

11. PV Array Maximum Voltage
Determine the voltage of the panel at -3 ⁰C
Voc + (V / ⁰C X Temp diff)
Multiply by No of panels (14)
(-0.12 X -28)=
(3.36V)=
Voc_temp = 41.26V
PV Array Max Voltage = 41.26V X 14 = 577.6V
Now we start getting technical.
We know what the voltage is at 25C (STC) “37.9”
We have how many volts per degree the panel changes (-0.12V/degree)
And we have how many degrees below STC the cell is (28)
Multiply by -28 (NOTE: 2 negatives makes a positive)
Add that to the Voc. Therefore these panels at -3C will have a Voc of 41.26V
Lastly multiply by the number of panels.
Therefore this system can be installed in a domestic premises as of PV array max Voltage is less than 600Vdc.
Clause 4.2 – PV Array Max Voltage

12. PV Array Maximum Voltage
Difference in number of panels between STC and lowest temp:
Temp adjusted= 41.26V X 14 = 577.6V
STC= 37.9V X 15 = 568.5V
AS / NZS 5033 Clause 3.1
Inverter Max Voltage
Switch Disconnector Rating
Temp adjusted = V X 15 = 619V
Why is this important?
Temp adjusted 14 panels is under 600Voc
At STC (25C) we can have 15 panels and still be under 600Voc
BUT 15 panels at -3C is over 600Voc
What is this Voltage used for?
Clause 3.1 of 5033 System must have a PV array max voltage of less than 600Vdc
To ensure we do not go over the Inverter Max Voltage spec
Determining the Switch Disconnector Rating
Clause 4.2 – PV Array Max Voltage

13. In summary it is a 4 step process:
Determine what the voltage change per ⁰C is for the panel
Determine the lowest temperature of the site
Calculate what the temperature adjusted Voc of the panel will be at the lowest temperature
Multiply the temp. adjust Voc by the number of panels
In summary it is a 4 step process:
Determine what the voltage change per ⁰C is for the panel
Determine the lowest temperature of the site
Calculate what the temperature adjusted Voc of the panel will be at the lowest temperature
Multiply the temperature adjust Voc by the number of panels to give you the PV Array Maximum Voltage

14. Or call us on the melbourne number show on the slide.
Thank You
Contact CEC:
Web:
Phone: (03) Press 1 for “Install / Accreditation Enquiries”
Press 3 for “Technical Advice”
Thank you.
If you have any question you can us at
Or call us on the melbourne number show on the slide.