Service manual

30
Installation and Service Manual
COMPONENT DIAGNOSTICS
HEAD PRESSURE CONTROL VALVE
(REMOTE CONDENSERS ONLY)
A modulating control to maintain proper receiver
operating pressure for correct defrost. At outdoor tem-
peratures above 70
o
F (21.1
o
C) the refrigerant flow is from
the condenser to receiver. At temperatures below 70
o
F
(21.1
o
C) the valve will enter a "by-pass mode" and the
refrigerant flow will be from discharge line to receiver
allowing the compressor discharge vapor to increase the
receiver pressure by "by-passing" the condenser. The
head pressure control is designed to only operate in by-
pass at temperatures below 70
o
F (21.1
o
C).
Check Procedure
Install gauge at receiver and monitor pressure. With
temperature below 70
o
F (21.1
o
C) receiver pressure will
be 200 PSI (13.7Bars) to 240 PSI (16.55Bars) +/- 5 PSI
(.34Bars).
A head pressure control that stays in by-pass may
be the result of a system that is short of refrigerant. Be-
fore replacing the head pressure control, check fan cy-
cling control. If it is not cycling, add refrigerant in 2 pound
(1Kg) increments and allow product to run 10/15 min-
utes to determine operation. Do not exceed 4 pounds
(2Kg) total during this test. If the addition of refrigerant
corrects head master operation you must now locate the
leak, correct, and properly recharge the system.
CAUTION: When removing a head pressure control,
always snap off the stub line at the dome BEFORE
using a torch to heat lines to remove. When rein-
stalling be sure the dome area has ample heat-sink
BEFORE applying heat to valve.
High Pressure Cut-Out
All Servend water cooled and remote condenser
products contain a high pressure cut-out. The function
of this switch is to turn the ice maker off in the event of
excessive pressure developing in the high pressure side
of the refrigerant system. This switch will open the power
circuit to the circuit board at 450 PSI (31Bars) pressure
on current units. It is a manual reset control located be-
side the power toggle switch. To reset this control, push
in the red button.
In the event this control shuts down the machine,
please find teh reason for this shut down. Correct any
necessary problems before restarting the machine.
Water Regulating Valve
THE WATER REGULATING VALVE IS USED ON
WATER COOLED CUBERS ONLY...The valve is
mounted in the condenser water line. Its function is to
maintain the proper operating head pressure by control-
ling the amount of water flow through the condenser.
The valve is adjustable and factory set to maintain con-
denser discharge water at 105
o
/108
o
F (39
o
/42
o
C). Set-
ting the water regulating valve to maintain dishcarge
water temperature eliminates the need to enter the sealed
refrigerant system. Water temperaute should be taken
as close to the condenser discharge as possible. This
water temperature will equate to operating head pres-
sures of approximately 230/240 PSI (15.86/16.55 Bars).
Should adjustment be required, the valve has an
adjustment stem on the top. After allowing the cuber to
operate for 6 minutes into the ice making cycle to bal-
ance the system, turning the adjusting stem CW will in-
crease the discharge water temperature and CCW will
decrease the discharge water temperature.
The water regulating valve must close off condenser
water flow completely during hot gas "harvest" cycle. If
the valve fails to close during the harvest mode, the con-
denser will continue to condense the hot gas needed for
the harvest cycle and produce long harvest times.
Leaking water regulating valve are normally the re-
sult of scale build-up on the valve diaphragm and the
valve should be flushed, not replaced. To flush the valve,
open the adjusting stem full open CCW (or force the valve
spring up with a screw driver) open and close the water
supply to the condenser resulting in the flush action.
Should this not correct the problem replacing the valve
diaphragms can be done without entering the sealed re-
frigeration system.
Damage to the water regulating valve may also be
caused by water hammer. Water hammer will result from
condenser inlet and drain lines being reversed or defec-
tive valve stops in the supply line. Proper installation of
water cooled equipment should always include a anti-
water hammer standpipe or expansion tank in the sup-
ply inlet water line as close to the cuber as possible.