Can Enphase microinverters be used with modules larger than 350W in Australia and New Zealand? Short answer – yes.
As solar modules continue to creep up in size, we are more regularly being asked if Enphase Energy microinverters can be used with modules rated at greater than 350W. There has been some confusion around this issue since the publication of AS NZS 5033:2014 which contains a clause which over the years has been subject to a variety of opinions and interpretations.
First of all it should be understood that when it comes to Australian Standards, and in particular AS NZS 5033, there are often sections and phrases that are open to interpretation. There is no single authority that determines if something complies with the standard or not. Very occasionally the Clean Energy Council or a state energy authority will provide advice as to their interpretation of the standard, but it’s ultimately up to the users of the standard to interpret it and determine a reasonable position in situations where multiple conclusions can be drawn. If compliance with an Australian Standard was ever argued in a court of law, the court would use the opinion of recognised industry experts to determine what would be considered a reasonable interpretation.
Under section 220.127.116.11 of AS NZS 5033:2014, installations classified as “Small micro inverter installations” are not required to have separate switch-disconnectors installed between the modules and the microinverters. The solar module DC connectors are deemed to provide an acceptable means of isolation provided there is a warning attached to the connectors prohibiting disconnection under load. (The Multi-contact MC4 connectors used on Enphase microinverter installations carry this warning) This section of the standard is quite unambiguous.
It is section 4.3.12 of AS NZS 5033 that defines “Small micro inverter installations” which has lead to some confusion. This section states:
Enphase microinverter installations typically comply with all sections of this clause, but it is section (d) which has caused some debate around whether the microinverters can be used with modules rated at more than 350W.
If we look at this clause more closely there are 2 parts to section (d).
Part 1 Each input shall be limited to 350 W maximum PV power at STC…
Enphase microinverters only have one input. Enphase limit this input via hardware and software controls to a maximum of 350W. This is confirmed in Note 2 on the datasheet for the IQ7 series of micros which states: “Maximum DC input limited to 350 W at 25oC as per AU/NZS 5033:2014 4.3.12(d).”
The wording of this clause does not specify a maximum solar module size of 350W, it clearly specifies that the input shall be limited to a maximum of 350W.
Enphase microinverters comply with this part of section (d) by limiting the input to a maximum power of 350W at STC (Standard Test Conditions).
Part 2 …at a maximum input voltage no greater than ELV
Enphase microinverters have different maximum input voltages depending on the model, but all of them are less than ELV. (120V ripple free DC). Enphase microinverters therefore also comply with the second part of clause (d).
It is therefore entirely reasonable to conclude that Enphase microinverters comply fully with Section (d) of AS NZS 5033:2014 Clause 4.3.12, and that this clause does not limit the use of modules rated at greater than 350W.
This is the stated position of the manufacturer (Enphase Energy) and there has been no alternative interpretation provided by the Clean Energy Council or any of the state energy regulators.
The maximum module size for each model of Enphase microinverter should be determined by applying the Clean Energy Council Grid-connected Solar PV Systems Design Guidelines for Accredited Installers (Jan 2013). These guidelines require the nominal AC power rating of the inverter to be no less than 75% of the peak power rating of the module. The maximum module ratings for the current range of IQ7 microinverters are therefore as follows:
AS NZS 5033:2014
Clean Energy Council Grid-connected Solar PV Systems Design Guidelines for Accredited Installers (Jan 2013)