Surge Protection Devices (SPDs): When AS/NZS 3000 Requires Them

By ARCK Electrical � Trade counter, North Parramatta � Reviewed May 2026

Quick Q&A - click to expand

Does every domestic install really need an SPD now? +

AS/NZS 3000:2018 with amendments recommends an SPD on every domestic board after a risk assessment - and most installers now treat it as a default specification rather than an optional upgrade. The cost is small ($80-$200 trade) and the protection scope (every appliance downstream) makes it a sensible standard. Some new estates and apartment specs now mandate it explicitly.

Type 1 vs Type 2 - which do I need? +

Type 2 is the default for almost every domestic and commercial install. Type 1 is needed only where direct lightning strikes are a real risk: rural acreage, tall isolated structures, properties near transmission infrastructure, or sites with external lightning rods that need to coordinate. If you're not sure, Type 2 covers ~95% of Australian residential installs.

How do I know when an SPD has reached end of life? +

Every SPD has a status indicator - usually a visible window on the front (green = OK, red = failed) or an LED. Surge events progressively degrade the internal varistors. When the indicator flips, replace the cartridge (or whole unit). Visual inspection during 6-monthly switchboard checks catches this; some units also have a dry contact for remote monitoring on commercial boards.

Does an SPD work with RCBOs and other protection? +

Yes - SPDs are independent of RCBOs / RCDs / MCBs and don't interfere with their operation. The SPD has its own dedicated backup MCB (per manufacturer's spec) on the supply side. RCBOs continue to protect their downstream final sub-circuits independently. Coordination is handled by the board manufacturer's compatibility chart for that brand's SPD + protection range.

What about Type 3 SPDs at the powerpoint? +

Type 3 sits at the point of use - built into a powerpoint, surge-protected power strip, or fixed equipment. It catches residual surges that pass the main-board Type 2. For a typical domestic install, Type 2 is enough. Type 3 adds value for valuable / sensitive equipment: medical electronics, server gear, high-end AV. Not usually a code requirement - a customer preference.

Surge protection devices (SPDs) used to be an optional upgrade. They're now effectively a default on new domestic switchboards under AS/NZS 3000 amendments. This guide covers what each type does, where it goes on the install, and the typical residential and commercial setup.

The three SPD types

AS/NZS 1768 (the lightning protection standard) and IEC 61643 classify SPDs into three types by where they sit in the installation:

Type	Location	Protects against	Typical site
Type 1	Main switchboard, on the supply side	Direct lightning strikes (10/350?s waveform)	Rural / elevated / lightning-prone properties; commercial sites with exposed mains
Type 2	Main switchboard or sub-board	Transient overvoltages from the network and induced surges (8/20?s waveform)	The default on every modern domestic and commercial board
Type 3	At the point of use (powerpoint, fixed equipment)	Residual surges that pass through upstream protection	Computer / AV / sensitive medical equipment

For a typical Sydney domestic install, a Type 2 SPD on the main board is the standard pick. Type 1 is added where direct lightning strikes are a real risk (rural acreage, tall isolated buildings, sites near transmission infrastructure). Type 3 is a customer upgrade for protecting sensitive equipment downstream of the board.

What's changed in AS/NZS 3000

The 2018 edition with amendments significantly raised the profile of SPDs:

• Risk assessment recommended for every install - most installers now spec an SPD on every domestic board as standard practice
• SPD installation rules (clauses around protective bonding, disconnection time, downstream coordination) are spelled out
• Replacement and indication - every SPD must have a visible status indicator (window or LED) and be replaceable without disturbing the rest of the board

Most insurers also now favour insured properties where the switchboard has a Type 2 SPD - for the cost (typically $80-$200 trade for a domestic unit), it's a small upgrade that protects everything downstream.

How an SPD sits on the board

A Type 2 SPD takes 1 or 2 modules on the DIN rail, usually right next to the main switch. It's wired between:

• Active(s) ? SPD (one per phase)
• Neutral ? SPD
• SPD ? main earth bar

When a transient overvoltage hits the active conductor, the SPD's internal varistors or gas discharge tubes conduct briefly to ground, clamping the voltage to a safe level. The energy flows to earth instead of into the downstream circuits.

The SPD needs a dedicated backup protection - typically an upstream MCB rated to the SPD manufacturer's spec (commonly 25A-63A depending on the unit). On Clipsal Resi MAX, Hager Resi9 and Connected Switchgear boards, this is a standard component matching the brand's SPD.

What it actually protects

A typical domestic SPD protects against:

• Switching surges from the distribution network - appliances cycling, neighbouring industrial loads, distribution faults
• Indirect lightning - strikes on the network or nearby that induce surges down the supply
• Inductive load switching - large motors, transformers, HVAC starting

What an SPD does NOT protect against:

• Direct lightning strikes to the building (that's Type 1)
• Sustained overvoltage (e.g., a broken neutral that lifts the phase voltage permanently) - that's an overvoltage protection device, different category

For domestic, the realistic protection scope is: an everyday network transient that would otherwise blow up consumer electronics, LED drivers, inverter circuits in appliances, and modern induction cooktops.

Sizing and selection

For a typical single-phase 80A or 100A domestic main:

• Imax (max discharge current): 20-40 kA Type 2 unit
• Up (residual voltage): ?1.5 kV for AC230V supply
• Modules: 1 or 2 module wide on the DIN rail
• Replaceable cartridges: preferred - when the SPD has absorbed enough surge events to be at end-of-life, swap the cartridge instead of the whole unit

Three-phase commercial: 4-pole Type 2 (3 phases + neutral) with matching Imax for the site fault current.

Order from ARCK

We stock SPDs from Clipsal Resi MAX, Hager Resi9, NHP and Connected Switchgear - Type 2 domestic, Type 1 for rural / commercial, three-phase 4-pole, replaceable cartridges. Same-day pick-up from North Parramatta.

Browse the circuit protection range, or call the counter on (02) 9890 9693 to spec the right SPD for a specific board and supply authority. Mon-Fri 6:30am-5pm, Sat 7:30am-1pm.