OMRON H3BA-8H Solid-State Timer

The H3BA-8H is an older model discontinued in 1997. It only supports single ON-delay operation, with 1 time-limit SPDT + 1 instantaneous SPDT contact. It is an 8-pin socket-mounted type. Do not confuse it with the newer H3BA-N8H, as they are different models entirely.

✅ Core Functions

Operating Mode: ON-delay only (Mode H). No flicker, OFF-delay, one-shot or other multi-mode functions.

Output: 1 time-limit SPDT + 1 instantaneous SPDT (1c each). The instantaneous contact operates immediately upon power-up; the time-limit contact switches only after the preset time elapses. Widely used for star-delta motor starting.

Reset Method: Power reset only (power cycle reset). No external reset terminal.

Base: 8-pin socket (PF085A / P2CF-08 or equivalent 8-pin timer bases).

✅ Time Ranges (Selected via DIP Switch)

4 time multipliers + 4 time units (sec / 10s / min / 10h)

Multipliers: 1.2, 3, 12, 30

Total timing coverage: 0.12 s ~ 300 h

✅ Electrical Specifications (Older H3BA-8H)

Power Supply: AC100~120 V / AC200~240 V / DC24 V (varies by suffix)

Contact Rating: 5 A at AC250 V (resistive load)

Repeat Accuracy: ±2% FS (Full Scale)

Panel Size: 48×48 square; surface or flush mounting

Power Consumption: Several VA; RC solid-state timing circuit

✅ Model Differentiation (Common Pitfall)

1. H3BA-8H (Discontinued Older Model)

Single ON-delay only; fixed 1 time-limit + 1 instantaneous contact; 8-pin; no multi-mode selector switch.

2. H3BA-8 (Discontinued Older Model)

Single ON-delay only; 2 time-limit contacts (2c), no instantaneous contact.

3. H3BA-N8H (Current Production New Model)

Multi-function model; toggle between two output configurations: Mode A (2 time-limit contacts) or Mode H (time-limit + instantaneous contact). It supports 8 operating modes.

✅ Officially Recommended Replacement

H3CR-A8E (AC/DC24 V, DC48~125 V); H3CR-A8EL (AC100~240 V)

Same 8-pin footprint; matches ON-delay + instantaneous output exactly.

Note: The H3CR body is shorter. If reusing the original PF085A socket, fit Y92H mounting clips. Installing a new P2CF-08 base is the simplest option.

✅ Typical Applications

Star-delta reduced-voltage motor starting; instantaneous bypass circuit energized on power-up, then switched to main circuit after delay. Used for fans, air compressors, and conveyor sequential control.

✅ Troubleshooting Guide

1. Instantaneous contact fails to actuate on power-up: Check power terminals and poor socket contact.
2. Timing inaccuracy: Verify range & unit DIP switch settings. Worn potentiometers are the top failure cause on aged H3BA-8H units.
3. Contact fails to switch after timing elapses: Internal solid-state component failure. No spare parts available for this discontinued model; replace directly with H3CR-A8E.

H3BA-8H (Discontinued Model) Accuracy Specification

Important Note: The H3BA-8H uses an RC analog solid-state timing circuit. All accuracy figures are calculated against the full scale (FS) of the selected range, not against the set time value. This is the most frequent mistake with analog timers.

Factory datasheet rating: Repeat accuracy ±2% FS (Full Scale).

Breakdown of Accuracy Specifications

1. Repeat Accuracy (Cycle-to-cycle fluctuation with identical setting): ±2% FS

Example: 30 s full-scale range → maximum fluctuation ±0.6 s.

If you set only 3 s, the fluctuation remains ±0.6 s, resulting in much higher relative error.

2. Dial Setting Error (Mechanical dial deviation): ±5% FS ±0.05 s

Intrinsic error of analog potentiometers; more significant on short time ranges.

3. Voltage Influence: ±0.5% FS
4. Temperature Influence: ±2% FS
5. Fixed offset for the minimum 1.2 s range: ±10 ms

Operating Mode Clarification

No mode selector switch. Flicker, OFF-delay, one-shot and other timing sequences are not supported.

Timing Sequence:

Power ON → Instantaneous contact closes immediately

Timing starts simultaneously. When preset time expires → Time-limit contact switches

Reset only via power cut; no external reset terminal.

Output hardware is fixed at factory: 1 time-limit SPDT + 1 instantaneous SPDT. No contact reconfiguration possible. This is the key difference from the newer H3BA-N8H.

⚠️ Easy Confusion: H3BA-N8H (Current New Model)

The H3BA-N8H lets you switch between two output combinations, but the base operation remains ON-delay only:

Mode A: 2 time-limit contacts (no instantaneous output)

Mode H: 1 time-limit + 1 instantaneous contact (star-delta use)

It still does not support OFF-delay, flicker or one-shot modes — only contact combination selection.

✅ True Multi-Model Unit: H3BA-N (11-pin)

The H3BA-N offers 8 selectable operating modes:

A ON-delay, B Flicker (OFF-start), B2 Flicker (ON-start), C Signal ON-delay, D Signal OFF-delay, E Interval, G Signal ON-delay, J One-shot.

One-Sentence Summary

The older H3BA-8H supports only ON-delay timing, with fixed 1 time-limit + 1 instantaneous contact. No timing mode switching is available.

Factors Affecting Timing Accuracy of H3BA-8H

The H3BA-8H is an RC analog solid-state timer based on resistor-capacitor charging/discharging. All errors stack on top of the ±2% FS base rating.

1. Internal Component Aging (No.1 On-Site Issue for Old H3BA-8H)

Timing electrolytic capacitors: Capacitance decay and increased leakage current are the leading cause of timing drift and unstable speed. Timing error far exceeds factory rating after long-term energization.

Adjustable potentiometer: Oxidation and contact wear cause inconsistent resistance at the same knob position, degrading repeatability.

Drift of timing resistors and comparator ICs with temperature.

This model has been out of production for decades. On second-hand or legacy equipment, aging drift almost always outweighs voltage and temperature errors.

2. Ambient Temperature

Temperature changes alter resistance and capacitance of RC components. Factory-rated temperature drift: ±2% FS.

High temperature near contactors, inverters and heat-generating loads leads to fast/slow timing drift. Low temperature also causes deviation.

Operating temperature range: -10 ~ +55 °C. Do not use below freezing point.

3. Supply Voltage Fluctuation

Voltage variation changes the capacitor charging slope. Factory voltage error: ±0.5% FS.

Voltage sags and sudden drops caused by large motor startup directly alter timing.

Always operate within the rated voltage range; error spikes sharply beyond the voltage tolerance.

4. Time Range Selection (Critical Setup Mistake)

Analog timer error is calculated on full scale (FS), not on the set value.

Example: 30 s full range → ±0.6 s maximum error. If you set only 3 s, relative error becomes very large.

✅ Best Practice: Select the smallest suitable range; set the time close to the upper limit of the range. Avoid short timing on a large full-scale range.

5. Manual Setting Error

Intrinsic dial error: ±5% FS ±0.05 s

Parallax reading error, loose knob, mis-set DIP switches (sec/min/h mix-up). Wrong time unit causes multiple-fold timing deviation.

Always double-check the time unit DIP setting.

6. Electromagnetic Interference (EMI)

Noise from inverters, contactors, solenoid valves and welding equipment disturbs the internal comparator circuit, leading to random timing jumps, premature or delayed switching.

Wiring Recommendation: Separate control wiring from power cables; do not run alongside inverter output cables in the same trunking.

7. Reset Condition (Power-Only Reset Characteristic)

The H3BA-8H has no external reset terminal; reset is only achieved by cutting power.

Insufficient power-off time leaves residual charge on the timing capacitor. Next power-up starts timing from an incorrect baseline, resulting in shorter-than-set time.

Ensure adequate power-off reset time to guarantee consistent timing cycle after cycle.

8. Vibration, Humidity and Dust

Vibration: Poor potentiometer contact and cracked solder joints lead to unstable timing.

High humidity, dust and oil contamination: Circuit board oxidation and leakage current shift the RC timing parameters.