Vulcan-Hart ML-126857, ML-126853, VHX24E5, MHB24E, ML-126852 manual Auxiliary Low Level Cut-Off

VHX SERIES STEAMER - ELECTRICAL OPERATION

Auxiliary Low Level Cut-Off

This control serves as a safety backup to the main water level control (WLC) board to meet CSD-1 code requirements. The operation of the auxiliary control board is identical to the low level cut-off (LLCO) function of the main WLC board but performs a single function: 1) Provide auxiliary low level cut-off protection to shut off the heat source in case the water level drops below the auxiliary low level cut-off (Aux LLCO) probe. A single Aux LLCO probe, identical to the LLCO probe on the main WLC board, is connected to the auxiliary control.

The auxiliary control board has input voltage (120VAC) across terminals 11 and 12 which powers the primary side of the transformer. On one side of the transformer secondary, power is provided to the control by a series path through chassis ground (terminal 10). The other side of the transformer secondary (12VAC) is attached to the Aux LLCO probe that directs power to the other side of the auxiliary control board relay (LLCO). As water enters the boiler, it becomes part of the auxiliary water level control’s circuit. When the water level in the boiler reaches the Aux LLCO probe, the circuit is completed.

When the main power switch is turned on, power is supplied to the auxiliary control board but no switching occurs. Also, the low water level indicator light (amber) on the boiler base control panel comes on.

When the water level reaches the auxiliary low level cut-off (Aux LLCO) probe, the LLCO relay is energized (LLCO-1 close) and the LLCO LED lights up. The LLCO relay will remain energized and its LED will stay lit until the water level in the boiler drops below the Aux LLCO probe.

When the boiler stops filling, press the manual reset switch on the boiler base control panel. This turns off the low water light and energizes the heat source.

F25154 (February 2004) Page 30 of 48