How to Set an Omron H3CR Septic Timer: ON/OFF Settings Explained
The Omron H3CR-F8 twin timer is commonly used in septic drip irrigation and timed dosing control panels. It controls repeating ON and OFF intervals, allowing wastewater to be distributed in separate doses.
This guide explains the two pointers, time-unit selectors, and shared dial scale, then walks through a sample setting.
How the Omron H3CR-F8 Timer Works
The H3CR-F8 described here uses Flicker OFF Start operation. When power is applied, it completes the OFF interval first, switches its output ON for the selected ON interval, and repeats.
A timer programmed for 10 minutes OFF and 30 seconds ON follows this sequence:
These settings describe the timer's output. Actual pump operation also depends on the control panel's wiring, float switches, and other controls.
Understanding the Timer's Controls
Green Pointer: OFF Time
The green pointer sets the OFF interval. Read its position against the numbered dial and combine that number with the OFF-time unit shown in the upper-right window.
Orange Pointer: ON Time
The orange pointer sets the ON interval. Combine its dial reading with the ON-time unit shown in the lower-right window.
Upper-Right Selector: OFF-Time Units
This selector determines whether the OFF interval is measured in seconds, minutes, hours, or one of the corresponding ×10 units.
Lower-Right Selector: ON-Time Units
This selector determines the units used for the ON interval. The ON and OFF intervals can use different units.
Lower-Left Selector: Shared Time Range
The time range selector changes the numbered scale used by both pointers. Its full-scale choices are 1.2, 3, 12, and 30.
The selected value is the highest number on the dial. It does not determine whether the timer measures seconds, minutes, or hours.
How the Time Range Selector Works
Think of the time range selector as choosing the numbers available around the dial. With the scale set to 12, the dial displays values up to 12. You can place the green pointer at 10 and the orange pointer at 3.
The separate time-unit selectors determine what those numbers mean:
- Green pointer at 10, with OFF units set to min, means 10 minutes OFF.
- Orange pointer at 3, with ON units set to 10s, means 30 seconds ON.
What the Time-Unit Markings Mean
| Marking | Meaning | Pointer at 3 |
|---|---|---|
| sec | Seconds | 3 seconds |
| 10s | ×10 seconds | 30 seconds |
| min | Minutes | 3 minutes |
| 10m | ×10 minutes | 30 minutes |
| hrs | Hours | 3 hours |
| 10h | ×10 hours | 30 hours |
Interval = pointer value × selected time unit. Choose a scale and unit combination that accommodates each required interval.
Example: 30 Seconds ON and 10 Minutes OFF
Step 1: Select a Shared Scale of 12
With power off, use the lower-left time range selector to select 12 as the dial's full-scale value. This accommodates both required pointer settings: 10 and 3.
Step 2: Set the OFF-Time Units
Use the upper-right selector to display min in the OFF-time window.
Step 3: Set the Green Pointer to 10
Turn the OFF-time setting knob until the green pointer aligns with 10. The result is 10 × 1 minute = 10 minutes OFF.
Step 4: Set the ON-Time Units
Use the lower-right selector to display 10s in the ON-time window.
Step 5: Set the Orange Pointer to 3
Turn the ON-time setting knob until the orange pointer aligns with 3. The result is 3 × 10 seconds = 30 seconds ON.
Step 6: Verify the Settings
| Control | Setting |
|---|---|
| Shared full-scale setting | 12 |
| OFF-time unit | min |
| Green OFF pointer | 10 |
| ON-time unit | 10s |
| Orange ON pointer | 3 |
Seat each selector fully in its detent. Do not leave it between positions. After power is restored, time a complete cycle to verify the actual intervals.
What the Indicator Lights Mean
- Green OFF indicator: The timer output is OFF.
- Orange ON indicator: The timer output is ON.
An ON indicator does not, by itself, confirm that the pump is running. Other components in the control panel may still determine whether the pump operates.
Frequently Asked Questions
Why is the interval longer or shorter than expected?
Check the time-unit window as well as the pointer. A pointer at 3 means 3 seconds with sec selected, but 30 seconds with 10s selected. Also confirm the shared scale: changing it changes the numbers associated with both pointer positions.
Why doesn't the pump start immediately after power is restored?
This H3CR-F8 model begins with its OFF interval. It waits through that interval before switching its output ON.
Can the ON and OFF intervals use different units?
Yes. Each interval has its own unit selector. For example, you can measure OFF time in minutes and ON time in seconds.
Can I set both intervals to zero?
Do not set both intervals to zero. Omron warns that this can cause relay chatter.
How do I determine the correct dosing schedule?
Use the schedule specified in your system's design or operating instructions. Your septic service provider or designer can help confirm the appropriate settings.
Need a Replacement Omron Septic Timer?
Before ordering, verify the complete model number, supply voltage, socket configuration, and operating mode against your existing equipment.
Shop the Omron H3CR TimerThis guide applies to the specified OFF-start model; other H3CR versions may operate differently.
