Manitowoc J250 User Manual

Section 7Refrigeration System
7-28
Headmaster Control Valve
Manitowoc remote systems require headmaster
control valves with special settings. Replace defective
headmaster control valves only with “original”
Manitowoc replacement parts.
OPERATION
The R404A headmaster control valve has a non-
adjustable setting of 225 PSIG.
At ambient temperatures of approximately 70°F
(21.1°C) or above, refrigerant flows through the valve
from the condenser to the receiver inlet. At
temperatures below this (or at higher temperatures if
it is raining), the head pressure control dome’s
nitrogen charge closes the condenser port and opens
the bypass port from the compressor discharge line.
In this modulating mode, the valve maintains
minimum head pressure by building up liquid in the
condenser and bypassing discharge gas directly to the
receiver.
DIAGNOSING
1. Determine the air temperature entering the remote
condenser.
2. Determine if the head pressure is high or low in
relationship to the outside temperature. (Refer to
the proper “Operational Pressure Chart” later in
this section.) If the air temperature is below 70°F
(21.1°C), the head pressure should be modulating
about 225 PSIG.
3. Determine the temperature of the liquid line
entering the receiver by feeling it. This line is
normally warm; “body temperature.”
4. Using the information gathered, refer to the chart
below.
NOTE: A headmaster that will not bypass, will
function properly with condenser air temperatures of
approximately 70°F (21.1°C) or above. When the
temperature drops below 70°F (21.1°C), the
headmaster fails to bypass and the ice machine
malfunctions. Lower ambient conditions can be
simulated by rinsing the condenser with cool water
during the freeze cycle.
Symptom Probable Cause Corrective Measure
Valve not maintaining pressures Non-approved valve Install a Manitowoc Headmaster
control valve with proper setting
Discharge pressure extremely high;
Liquid line entering receiver feels hot
Valve stuck in bypass Replace valve
Discharge pressure low; Liquid line
entering receiver feels extremely cold
Valve not bypassing Replace valve
Discharge pressure low; Liquid line
entering receiver feels warm to hot
Ice machine low on
charge
See “Low on Charge Verification” on
next page

Manitowoc J250 Specifications

General

Brand	Manitowoc
Model	J250
Category	Ice Maker
Language	English