Omron H3BF-8 | Twin Timer Relay — 8-Pin Octal / 0.5 s–5 hr / 4 Ranges / 100–240V AC / 5A / Discontinued

Twin Timer — Two Timers, One Octal Socket

The H3BF-8 is a twin timer relay — a single device that combines two timing functions within the same 8-pin octal body. Twin timer operation produces a flicker or cycle output: Timer 1 sets the ON duration and Timer 2 sets the OFF duration, with the two timing intervals cycling repeatedly. This makes the H3BF-8 appropriate for intermittent operations where a load must switch on and off at defined intervals — alarm horn cycling, intermittent lubrication pump control, signal lamp flashing, and similar repeated timing sequences.

Each timer is set independently by an analog dial on the front face, reading against the selected scale. The four selectable time ranges cover 0.5 seconds to 5 hours in scale steps, with the range selector choosing which part of the total span the dials operate within. Wide supply voltage acceptance — 100–240V AC without range selection, or 24–110V DC — means the H3BF-8 works directly on the panel supply without additional voltage conversion.

The 8-pin octal plug-in format mounts in standard octal sockets (PF085A, PL08, or equivalent). Existing panels with octal timer sockets accept the H3BF-8 directly.

Key Specifications

Replacement — H3CR-F8 Series

Omron's documented replacement for the H3BF-8 is the H3CR-F8 solid-state timer. The H3CR-F8 provides equivalent twin timer functions across the same time range. The H3CR-F8 body is approximately 12mm shorter than the H3BF-8 — when using PF085A sockets, Y92H-8 hold-down clips replace the Y92H-2 clips used with the H3BF-8; when using PL08 sockets, Y92H-7 clips replace Y92H-1. For time ranges beyond 30 hours (not applicable to the H3BF-8's 5-hour maximum), the H3CR-F8-300 covers up to 300 hours.

FAQ

Q1: What is "twin timer" operation and how does the H3BF-8 cycle?

A twin timer produces a repeating ON/OFF cycle. Timer 1 controls the output ON duration; Timer 2 controls the output OFF duration. When power is applied, Timer 1 starts — the output activates after Timer 1 elapses. Then Timer 2 starts — the output deactivates after Timer 2 elapses. The cycle then repeats from Timer 1. Both timers are set independently by their respective dials.

Q2: What octal socket is required for the H3BF-8?

The 8-pin octal format uses PF085A (flush panel mount, front connecting), PL08 (DIN rail/back connecting), or equivalent 8-pin octal relay sockets. The H3BF-8 fits any of these. Confirm hold-down clip compatibility with the socket type if replacing an existing H3BF-8 installation.

Q3: What is the output contact rating, and can it switch 240V AC loads?

The output contact is rated 5A at 250V AC resistive. At 240V AC, the contact handles 5A — suitable for standard 240V AC control loads within this current. For inductive loads (contactors, solenoids), the contact rating is typically reduced from the resistive rating; check the specific inductive load current against the derating guidance in the H3BF datasheet.

Q4: Is the H3BF-8 compatible with the H3CR-F8 replacement in the same panel socket?

The H3CR-F8 uses the same 8-pin octal footprint and fits in the same socket. The body is approximately 12mm shorter, so the hold-down clip must be changed (Y92H-8 for PF085A sockets, Y92H-7 for PL08 sockets). The field wiring and socket remain unchanged — only the clip is swapped.

Q5: The H3BF-8 output does not cycle as expected. What should be checked?

Verify both timer dials are set to non-zero values within the selected time range — a dial at zero on either timer stops the cycle. Check that the supply voltage is within the rated range. Confirm the selected scale matches the intended time range for both timers. If the output activates once and does not cycle, check the operating mode selection — ensure twin timer (cycle) mode is selected rather than a single ON-delay mode if the unit has a mode selector.