The recent introduction of higher power solar modules in the Australian market has created some concern among solar installers regarding compatibility with common residential inverters. More specifically, the concern is that the short circuit current of these solar modules exceeds the rated current carrying capacity of the inverter under AS/NZS 5033:2021.
There is no need to fear. This situation only applies to “some” of the new high wattage solar modules when used with residential inverters.
To increase the output of a solar module engineers can either increase the current, increase the voltage or increase both to varying degrees.Power (watts) = I (amps) x V (volts)
There are some manufacturers who have focussed on increasing the current to an extent where it is exceeding the allowable current rating for some residential inverters under AS/NZS 5033:2021. Other solar module manufacturers are focussed on increasing voltage rather than the current. The problem of exceeding the inverters current rating is not an issue for manufacturers with this approach.
These manufacturers are increasing the voltage rather than the current because there are less I2R (Power) losses and hence the overall solar system is more efficient.
V = IR and P=VI
If we substitute V we get P = I2R
For example, the new REC high power module, the Alpha Pure R has a short circuit current rating even lower than the existing model for this reason. Less power losses means greater efficiency.
Existing REC Alpha Pure 410W Isc = 10.35A
New REC Alpha Pure R 410W Isc = 8.81AHyundai’s range of solar modules, designed for residential applications, only have a maximum short circuit current of 11.12A
All of the solar modules we currently supply, designed for residential applications, do not exceed the current carrying capacity of all the residential inverters we supply.
Put simply, if you purchase solar modules and inverters from AC Solar Warehouse you can be sure you’re compliant with the latest standards in this regard.
Obviously, there is more to selecting the right solar module than just the short circuit current. So, if you require assistance with matching solar modules with inverters to achieve the optimum performance, ease of installation and compliance with the latest standards, please contact one of our engineers on ph: 07 4028 3979. We are more than happy to help you select the optimum solution.
Enphase Microinverters
Enphase microinverters comply with AS/NZS 5033:2021 clause 4.2.2, in that, there is no requirement to increase the current rating by 25%. Please refer to Technical Note 230522 from Enphase here.The most used microinverter for residential applications is the IQ7A which has a Maximum DC Short Circuit current (module Isc) of 15A and a Maximum continuous input DC current of 10.2A. The Minimum start voltage is 33V and the maximum voltage is 58V. The power point tracking range is 18V to 58V.
When matching a high-power solar module 400+ to this inverter you need to select a module that operates within these current and voltage windows.
The REC Alpha Pure 410W REC405AA solar module can be used with the IQ7A
The Hyundai 390W S390UF solar module can be used with the IQ7A
To check whether other makes and models of solar modules are suitable please use the Enphase module capability calculator here
When selecting a solar module, you need to also consider the clipping that may occur during periods of peak power output in addition to the current rating. The inverter can current limit during periods when the current is above 10.4A.
If you would like to learn more about clipping and whether you should be concerned about this with your designs, please click here. If you require help please contact one of our engineers to discuss.SolarEdge DC optimised inverters
The short circuit current is the same as the sum of the Isc current of the DCU’s. A DCU is a DC Conditioning Unit aka DC Optimiser. There is no requirement to increase the capacity by 25% under AS/NZS 5033:2021.The most common DC optimiser used for residential applications is the S440. This has a rated DC power of 440W with a Maximum input voltage (Voc) of 60V and Maximum short Circuit current (Isc) of 14.5A. So essentially, if you use a solar module that is less than 440W at STC and the voltage and current are below these limits you are fine.
The range of SolarEdge Smart Modules, which have built-in S440 optimisers, are suitable for use
The REC Alpha Pure 410W REC405AA solar module can be used with the S440 optimiser
The Hyundai 390W S390UF solar module can be used with the S440 optimiser
It is suggested to use the SolarEdge design tool to confirm the solar module compatibility for your selected inverter.Sungrow Inverters
The residential range of Sungrow inverters have a maximum input current to suit most solar modules. Please refer to the Sungrow update below (6 June 2022)