Amber Switch

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Each Amber Switch will control one appliance and is wired into the cable supplying the appliance. If several loads are available, and particularly on larger systems, more than one Amber Switch can be installed.


The Amber Switch requires no user intervention and will automatically switch the appliance on when the system frequency is higher and switch it off when the frequency is lower. The frequency setpoint can be adjusted during installation.

Amber Switch incorporates a number of features to ensure stable operation of an islanded power system:

  • When the frequency goes above the switch-on setting there is a delay before the load is connected.
  • The switch-off setting is a lower frequency than the switch-on setting, to ensure stability.
  • A range of setting frequencies is available.
  • The delays are randomised, to avoid several devices switching simultaneously in systems with multiple switches installed.

Load selection

Both types: Amber Switch can control loads up to 13A (3kW at 230V; 1.5kW at 120V). Only use Amber Switches on non-essential loads (ones which can be switched off or on automatically without a problem).

Independent Type: The most appropriate loads are heaters (water heaters, storage heaters, space heaters). Appliances with pumps are not appropriate due to the potential for frequent switching of loads.

Load Shedding Type: Heaters are very suitable, and appliances with pumps, such as fridges or freezers, are also OK with this type. This is because the long switch-on delay avoids rapid on-off cycling.



Amber Switches are load control devices for small-to-medium islanded power systems, in particular those with ac-coupled renewable generation. They are suitable for any power system which operates with a variable system frequency.

Amber Switch responds to a change in the system frequency. Each Amber Switch switches on when frequency is higher, and off when frequency is lower. No control wiring or signals are needed.

  • The Independent Type Amber Switch can switch on an additional load when surplus renewable generation is available, which cannot be used or stored. The system frequency is raised by the battery inverters, signalling a high state of battery charge. On a diesel or hydro generator with frequency droop, higher frequency indicates low load.
  • The Load Shedding Type Amber Switch can help avoid overloads on off-grid hydro or diesel generator sets, and assist with start-up of all types of off-grid system by staggering energisation of some loads.