External Relay Module for Overfill Prevention
Adding safe relay switching to the FINCH 5332
The FINCH 5332 display, joined with the External Relay Module (TTEXT-RLY), provides a reliable way to control higher-load devices — horns, pumps, valves — in petroleum hauling applications, enabling safe, spill-free tank loading.
Relay Capacity and Fail-Safe Design
The 5332 display includes three relays that are activated by safety alarms, such as FILL, HH, and SPILL alarms. Each relay can be assigned to control external equipment, such as a horn, pump, or valve, when the corresponding alarm is triggered. Because the relays in the 5332 display are not designed to carry heavy loads for extended periods, the TTEXT-RLY provides the needed current capacity.
Fail-safe by design
The HH-NC terminal controls the solenoid relay, K2. When the signal ground is present, the solenoid terminal stays energized, allowing fail-safe operation: if power fails or is off to the 5332E system, the pump will not work.
Signal Loop Operation
The system uses a loopback circuit. The relay alarm signals being switched are ground signals, not power — 12VDC power is connected to both relays, since only the ground signals are switched, except for the SOLENOID terminal, which is controlled by relay K2.
When the PTO is grounded, this energizes the first relay, which switches on the ground signal to the system loop. The ground signal exits the PTO relay and connects to the Fail-COM terminal, wired to Fail-COM on the FINCH 5332E. From FAIL-NC it connects to HH-COM. The loop signal runs through the HH relay from HH-COM to HH-NC and is wired back to HH-NC in the relay module — see the Basic Shutdown drawing below. When the HH alarm is reached, the HH relay energizes and shuts down the pump by removing voltage from the SOLENOID terminal.
The Fail-COM terminal provides the ground signal to the alarm loop, which consists of the SPILL and HH relays jumper-wired together in a series arrangement.
The Fill or Fall relay is wired through to the relay module to keep the wiring centralized in the system. This relay is for a horn or lights, not the pump.
Relay Module (TT EXTRELAY)
Basic Shutdown Drawing Using TT EXTRELY Module