The HMS1655 uses relay output 1 (RL-1) as the alarm output for the monitored fume hood. This output can trigger a remote alarm annunciator or audible alarm. The Relay Setup option on the Controller Setup menus enables configuration of the alarm relay output as required by the specific application. This option opens the Relay 1 Trigger Mode configuration screen. You can configure the alarm relay output to trigger with one of three methods:
- Setpoints Mode: uses a pair of setpoints (face velocity) to determine when to activate or deactivate the alarm relay.
- Operating Mode: uses the fume hood’s operation mode to determine when the alarm relay is active or inactive.
- Timer-Based mode: enables the alarm relay output to activate upon the expiration of a timed-occupied mode event triggered, which can activate an automatic sash closer device.
If you select Setpoints Mode as the trigger mode for the alarm relay, you are prompted for high and low setpoints. The high setpoint determines the threshold at which the alarm relay activates if in direct acting mode, or deactivates if in reverse acting mode. The low setpoint determines the threshold at which the alarm relay deactivates if in direct acting mode, or activates if in reverse acting mode. After you specified the high and low setpoints, you are promoted to set the acting mode and delay associated with the alarm relay. In direct acting mode, the alarm relay activates when the sensor input exceeds the high setpoint, and deactivates when the sensor input falls below the low setpoint. In reverse acting mode, the alarm relay deactivates when the sensor input exceeds the high setpoint, and activates when the sensor input falls below the low setpoint. The alarm relay delay may be up to 180 seconds, or three minutes, in duration.
If you select Operating Mode as the trigger mode for the alarm relay, you are prompted to select whether the alarm relay activates or deactivates for the three operating modes. Next, you are prompted to set the acting mode and delay to be associated with the alarm relay. If the HMS1655 is configured for a sash switch with a delay setting greater than zero, then the sash switch delay counts down before the alarm relay delay begins counting down. Otherwise, the alarm relay delay begins counting down immediately after the trigger condition is achieved, and the alarm relay activates or deactivate when the timer expires, depending on the acting mode selected for the alarm relay.
If you select Timer-Based Mode as the trigger mode for the alarm relay, you are prompted to set the acting mode and the activation duration associated with the alarm relay. This trigger mode activates the alarm relay only if the sash switch is enabled and the specified duration timer expires.