Collection: Geyser Timers, Pool Timers and 12V Timer Switches: How to choose

A timer switch is used to schedule on/off operations of an electrical system or device:

• Geyser timers and pool timers typically run on 220-240V AC (single phase)
• A 12V timer (12V DC) is well suited to battery- and solar-operated systems (gates, fans for chicken coop, aquaponics, drip irrigation etc)
• A timer switch can be digital or mechanical, and can be programmed over 1 day or 7-day periods
• Digital timers with an internal battery keep time when they are not powered: this is a critical feature in South Africa or any place that experiences loadshedding or power blackouts (the clock of a mechanical timer stops during a blackout: not compatible with load shedding)
• Geyser timer switch: pay attention to the max power / amp rating (see below calculation)
  
• Infinite timers, also called repeat timers, switch on and off repeatedly at set intervals: they are mostly used for lighting and commercial signage and bells (school bells... ;)
• 1-second interval timers are used for applications that require a short "on" interval, such as automatic animal or fish feeders or gates 

Timer max amperage for inductive and resistive loads
To calculate the max amperage you need for your timer:

• P=UI, or I(A) = P(W) / U(V), so 2300W / 230V = 10A (Ohm's Law)
• "Inductive" loads (pumps, compressors, fridges, A/C units, fans, anything with a motor): use a power factor of 2, so 2 x 2300W / 230V = 20A
• "Resistive" loads (timer for geyser, lights): use a power factor of 1

Electricity savings with a timer
Using a timer is a great way to save electricity. In South Africa, households with an electric geyser spend 40% of their electricity bill on heating up water on average... 60% of which can be saved by using a geyser timer set on 2 (continuous) hours per day. The same applies to your pool pump: the rule of thumb is to run your pump long enough to filter the entire content of your pool once a day. If your pump can handle the volume of your pool in 6 hours, a pool timer will save you 75% of electricity.

Timer switch intervals

• Digital timers come with a 1-minute interval as a standard: you can schedule the switch to go ON or OFF between 7:00am and 7:01am for example.
• 1-second interval timer switches come with a 1-second interval: you can schedule the switch to go ON or OFF between 7:00:00 and 7:00:01 for example. This is particularly useful to control drives/motors that open and close something: gates, feeders for cattle, etc 
• Mechanical timers usually come with 12-, 15- or 20-minute intervals: you can schedule the switch to go ON or OFF between 7:00am and 7:20am.