How to Wire One-Shot Timer using Twin Timer For Delay?

Electrical Technology

Wiring Twin Timer for One-Shot Operation of Recirculation Pump

What is a One-Shot Timer?

As the name suggests, it performs a single operation per signal activation instead of repeated cycle operations. In other words, when the power supply is applied, and a signal is received by the timer, it turns ON to start counting the preset time interval. When the predefined time setting expires, it will turn OFF the circuit. Hence, the timer provides a single operation.

For the next operation, the timer has to be externally reset and programmed once again for another (ON-delay or OFF-delay) operation.

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One-Shot Mode for OFF-Delay or ON-Delay

One-Shot operation can be set up for OFF-delay or ON-delay (based on the circuit design). Once the timer circuit is activated by supplying power to it, it will start counting the configured time, and once it expires, it will turn OFF or ON the circuit.

The load will remain OFF or ON until the operator resets the timer momentarily using the normally open (NO) pushbutton, timer, or any other home automation device that connects and disconnects terminals 3 (reset) and 4 (+12V). Alternatively, the timer can be reset by disconnecting the power supply to the timer (mainly terminals 9 and 10).

You may use ST01 digital programable timer for additional control of the one-shot circuit using twin timer as shown in the following wiring diagram.

Connect the timer to the power supply.
Press “MD” for 3 seconds.
Press “MD” to choose the time setting in seconds, minutes, or hours.
Press “MD” until “nod” appears.
Now, select the 4 dashes.
To exit the mode setting, press and hold the “MD” for 3 seconds.

Next, you will have to set the time for Time A and Timer B. Here’s how:

Press “RES” for time setting.
Set the time for Time A.
Again, exit the mode.
Now press “RES” to set up Time B.

Good to Know: If you select minutes for Time A, you will need to choose Time B in minutes as well. The same applies to seconds and hours.

Operation of the One-Shot Timer

When the operator presses the doorbell button, it activates the circuit and turns on the twin timer. The timer starts counting the preset time. At the same time, since terminals 7 (COM) and 8 (NO) are on, it energizes the relay (or contactor coil in the case of motor loads). Consequently, the recirculation pump (or any other 120V/240V load) circuit is turned on.

When the countdown expires (reaching the predefined time), terminals 7 (COM) and 8 (NO) turn off. In this case, the relay or contactor coil de-energizes, and the motor pump turns off.

While wiring and configuring the circuit for one-shot operation using a twin timer, consider the following:

The twin timer can be set up for one-shot operation in both 120V and 240V circuits.
The maximum load in a circuit on the off-delay timer is 10 amperes.
The timer can be configured for durations ranging from 0.9 seconds to 99 hours.
Do not connect the power supply to terminals 1, 2, 3, 4, and 5 of the timer.

Wiring Twin Timer for One-Shot Operation of Recirculation Pump

How to Set One-Shot Mode:

Operation of the One-Shot Timer