Harvest Pressure Regulating; (H.p.r.) System - Manitowoc S Service Manual

Section 7

HARVEST PRESSURE REGULATING

(H.P.R.) SYSTEM

Remotes Only
GENERAL
The harvest pressure regulating (H.P.R.) system
includes:
• Harvest pressure regulating solenoid valve (H.P.R.
solenoid). This is an electrically operated valve which
opens when energized, and closes when de-
energized.
INLET
Figure 7-11. H.P.R. Solenoid
• Harvest pressure regulating valve (H.P.R. valve).
This is a non-adjustable pressure regulating valve
which modulates open and closed, based on the
refrigerant pressure at the outlet of the valve. The
valve closes completely and stops refrigerant flow
when the pressure at the outlet rises above the valve
setting.
Figure 7-12. H.P.R. Valve
Part Number 80-1480-3
OUTLET
FLOW
SV1427
INLET
SV3053
OUTLET
FREEZE CYCLE
The H.P.R. system is not used during the freeze cycle.
The H.P.R. solenoid is closed (de-energized), preventing
refrigerant flow into the H.P.R. valve.
HARVEST CYCLE
During the harvest cycle, the check valve in the
discharge line prevents refrigerant in the remote
condenser and receiver from backfeeding into the
evaporator and condensing to liquid.
The H.P.R. solenoid is opened (energized) during the
harvest cycle, allowing refrigerant gas from the top of the
receiver to flow into the H.P.R. valve. The H.P.R. valve
modulates open and closed, raising the suction pressure
high enough to sustain heat for the harvest cycle,
without allowing refrigerant to condense to liquid in the
evaporator.
In general, harvest cycle suction pressure rises, then
stabilizes in the range of 75-100 psig (517-758 kPA).
Exact pressures vary from model to model. These can
be found in the "Operational Refrigerant Pressures"
charts.
Refrigeration System
7-25