Is the Water Regulating Valve (aka thermostatic activated valve) and Water Shut Off Valve to my hydraulic power unit (HPU) heat exchanger normally closed / powered open or normally open / powered closed?
Water Regulator Valve
It is normally closed and powered open. As the temperature of the oil rises the valve will open to allow more water to flow through to the heat exchanger.
Water Shutoff Valve
It is normally closed powered open. It is open only when the HPU motor is running. This prevents water from continuing to flow to the sewer after the pump is shut off. Without this valve, water would continue to flow until the oil temperature dropped enough to completely close the water regulator valve.
Examples from hydraulic schematics showing the Water Regulating Valve and Water Shut Off Valve in their normal states (Figures 1 and 2).
Figure 1 – Models 510.10 and 510.21 HPS Hydraulic Schematic showing Water Regulating Valve (highlighted) in normally closed position.
Figure 2 – Models 505.20 and 505.30 HPU Hydraulic Schmematic showing Water Regulating Valve and Water Shut Off Valve (highlighted) in normally closed position.