Electrical Services for the Solar Industry

Earth Fault Detection for

Charge Controllers & Batteries

– PV over 120V DC

AS/NZD 5033 [Installation of Photovoltaic (PV) Arrays]  clause 3.4.3 outlines:

“In systems where the PV array is operating at LV, an earth fault alarm system shall be installed which, on an earth fault, causes an action to be initiated to correct the earth fault.”

 Table 3.2 in the same standard advises systems ≤20kVA should have these alarms configured to activate with an insulation resistance of <30kΩ.

 Battery Systems

AS/NZD 5139 [Electrical installations – Safety of battery systems for use with power conversion equipment]  clause & outlines:

“For all pre-assembled battery systems separated from earth (i.e. floating)…   and operating at DVC-B or DVC-C, an earth fault alarm SHALL be installed.”

 If your systems includes a transformerless charge controller (galvonically isolated charge controllers do not require this monitoring) with a PV array over 60V Vmpp an earth fault alarm is required if not already part of the charge controller or another inverter on the PV bus.

If your batteries operate at over 60V DC, an earth fault alarm is also required if not built into the inverter or batteries.  Many multimode inverters use an isolated transformer (port classified as DVC-A) to seperate the low voltage (48V) batteries from the higher voltage PV, removing the need for an earth fault alarm on the battery side.



Product currently out of stock, we currently recommend AERL’s product for most installations involving transformer-less charge controllers.

We have offered an affordable product that allows you to detect an earth fault <30kΩ on isolated systems (neither + or – grounded). Many devices on the market rely on the negative being grounded. In Australia we don’t ground the negative of low voltage systems (>120V DC Vmpp).

This device activates either a Piezo buzzer or Beacon, when either the positive or negative start to fail to ground, preventing a fire.


 AERL also manufacture a device (EarthGuard) to detect ground faults on batteries and arrays that do not have an earth reference.



Most AC coupled systems already have a built in earth fault monitor to trigger an alarm or relay. This often hasn’t been the case for DC coupled charge controllers (battery charger powered directly from you solar array).

By buying these devices in bulk we have been able to reduce the cost to hopefully encourage the industry to install them.

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