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September 1, 1997
OVERVIEW
This section deals with the operation and mainte-
nance of the major valves which may be found
with the Scroll Plus™ System.
EPR VALVE
Evaporator Pressure Regulator Valves respond to
upstream pressure and are used to maintain a min-
imum evaporator temperature. Remember 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 evaporator discharge air
temperature or product temperature. The second is
that low pressure drop EPR Valves used on the
Scroll Plus™ require an external high pressure
supply to power the main piston chamber. This
high pressure supply must maintain a
Figure 6-1 — Typical EPR Valve with Suction Stop Solenoid
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CONTROL VALVES
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 balancing
Adjustment Spring
Pressure
As upstream pressure rises it closes the high
pressure inlet to the Main Valve Chamber . The
downstream bleed off reduces the Main Chamber
pressure to the point that piston spring
Upstream Pressure
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.
4
5
HUSSM ANN CORPORATION • BRIDGETON, M O 63044-2483 • Printed in USA
against Upstream Suction
and Fixed Pressure Counter Spring .
open the main valve.
1
2
3
6
P/N 401789
6 - 1
and
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