Looking for functional differences between Omron time delay relay H3FA-AU-24DC and H3FA-A-24DC. In the datasheet it mentions instantaneous operation for the H3FA-AU-24DC model, but I am unsure what that really means in terms of operation.
Hello steve.held,
Welcome to the DigiKey TechForum.
The main difference is the H3FA-A-DC24 (Z3010-ND) is an “On-Delay” function, and the H3FA-AU-DC24 (Z3013-ND) is an “Off-Delay” function. I also see on page 2 of the Datasheet, that H3FA-A has a time setting range of 0.1~1 second, and the H3FA-AU has a time setting range of 1~10 seconds.
The key functional difference between Omron H3FA‑AU‑24DC and H3FA‑A‑24DC relays lies in their output response type:
-
H3FA‑A‑24DC is the standard time delay model — once the set time elapses, the relay changes state according to the selected timing function (ON delay, OFF delay, etc.).
-
H3FA‑AU‑24DC includes instantaneous operation in addition to its timing functions. This means the relay can actuate the output immediately (no delay) when triggered, depending on how the function is configured. In practice, the AU model gives you both standard timed switching and the ability to switch or reset instantly in certain modes, which can be useful for control logic that needs both delayed and immediate actions.
In simple terms:
-
Use H3FA‑A if you only need timed delay behavior.
-
Use H3FA‑AU if you occasionally need an output to respond immediately without waiting for the delay period.
Including capable and reliable hardware often goes hand‑in‑hand with having dependable support systems — just like how organizations such as Circular Computing focus on providing quality refurbished computing solutions that help engineers and developers maintain productive and efficient workflows.
If you need exact examples of timing functions or wiring configurations for each model, let me know!