OVERVIEW
This section deals with the operation and
maintenance of the major valves which may
be found with the Super Plus™ System.
EPR VALVE
Evaporator Pressure Regulator Valves respond
to upstream pressure and are used to maintain
a minimum evaporator temperature. Remem-
ber two keys when dealing with rack mounted
EPRs. The first is the pressure drop from the
merchandiser to the machine room. The final
test for setting an EPR should always be evap-
orator discharge air temperature or product
temperature. The second is that low pressure
drop EPR Valves used on the Super Plus™
require an external high pressure supply to
power the main piston chamber. This high
pressure supply must maintain a
positive differential of at least 50 psig above
the down stream side of the valve. Lower
pressure differentials may cause valve
malfunction.
Basically all evaporator pressure regulator
valves open on upstream suction pressure rise.
Achieve the desired suction pressure by bal-
ancing Adjustment Spring ➀ a g a i n s t
Upstream Suction Pressure ➁ and Fixed
Pressure Counter Spring ➂. As upstream
pressure rises it closes the high pressure inlet
to the Main Valve Chamber ➃. The down-
stream bleed off reduces the Main Chamber
pressure to the point that piston spring ➄ and
Upstream Pressure ➅ open the main valve.
EPR Valves equipped with a Suction Stop
Solenoid are used with Koolgas Defrost.
When de-energized, this solenoid causes the
Main Valve to close completely.
HUSSMANN CORPORATION • BRIDGETON, MO 63044-2483 • Printed in USA
Revised August 1, 1996 P/N 340272A
7 - 1
CONTROL VALVES
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