6
−
17
T
−
318
Prior to Cleaning:
−
Always wear goggles, gloves and work boots.
−
Avoid contact with skin and clothing, and avoid
breathing mists.
−
When mixing, add water to the sprayer first, then the
cleaner.
−
ALWAYS provide for proper ventilation when cleaning
indoor evaporator coils (rear doors must be open).
−
Be aware of surroundings
−
food, plants, etc., and the
potential for human exposure.
−
Always read directions and follow recommended
dilution ratios. More is not always better. Using
non
−
diluted cleaner is not recommended.
Cleaning Procedure:
a. Remove the upper evaporator access panel inside of
the unit.
b. Spray the surface with water before applying the
cleaning solution. This helps the cleaner work better.
c. Liberally apply the prepared cleaner solution (5 parts
water and 1 part cleaner).
d. Allow the cleaner to soak in for 5 to 7 minutes.
e. Assess area for rinsing. Follow all local regulations re-
garding disposal of waste water.
f. Thoroughly rinse the cleaner and surrounding area,
floor, etc. When rinsing where heavy foaming solution
is present, it is very important to take the time to thor-
oughly rinse the equipment and surroundings.
g. Always rinse the empty coil cleaner bottle, cap tightly
and dispose of properly.
6.19 SUCTION MODULATION VALVE
On start up of the unit, the SMV will reset to a known
open position. This is accomplished by assuming the
valve was fully open, driving it fully closed, resetting the
percentage open to zero, then opening to a known 21%
staging position.
2-1/8 inch Nut
Figure 6-23 Suction Modulation Valve (SMV)
6.19.1 Pre-check Procedure
a. Check unit for abnormal operation.
b. Check charge. If refrigerant is low repair as required
and again check operation.
c. If sufficient capacity cannot be maintained or unit is
tripping excessively on high pressure switch (HPS) in
high ambients, check coils and clean if required.
d. If capacity or control cannot be maintained, turn unit
OFF, then back ON. This will reset the SMV in the
event the controller lost communication with the
valve, and may correct the problem.
NOTE
Carefully listen to the valve. During reset, the
valve will make a ratcheting noise that may be
heard or felt as it is attempting to close. If this
can be heard or felt, it indicates that the control-
ler and drive module are attempting to close the
valve, and may serve as a quick indication that
the drive module is in working order.
e. During the first few minutes of unit operation, com-
pressor reliability enhancement logic (CREL) may be
in effect. This places the valve at a 21% staging posi-
tion and is sufficient to drive the temperature of the
supply probe down several degrees during this inter-
val.
f. After the CREL time-out has been met, the valve will
start responding to the control logic and open or close
relative to the demand. Scrutinize the unit operation
for a few minutes. While in pulldown, the unit will open
the SMV to a maximum discharge pressure of 325
psig in high ambient conditions, or as much as the
current setting and control logic will allow. The current
level should be high. A lower discharge pressure will
be seen in lower ambient temperatures. Once the unit
has reached set point, the SMV will go into control
mode. Both the discharge/suction pressures, and
current draw will go significantly lower. Once below
set point, the suction pressure should go into a vacu-
um within several minutes. Should the operation dif-
fer as mentioned, the SMV, controller, or wiring, may
be faulty.
g. Check for correct wire location at the stepper motor
plug and the environmental connector (EC). Make
sure that the wires terminate in accordance with the
wire markings (addresses).
h. Attach a manifold gauge set (refer to paragraph 6.2).
If the unit is operating in the perishable mode, pro-
ceed to step i. If the unit is operating in the frozen
i. Perishable operation: If the operation of the unit is in
question, place the set point to approximately 6
°
C
(11
°
F) less than the current box temperature, so the
unit goes into pulldown. Run the unit for approximate-
ly one minute. Record readings on gauges and cur-
rent draw. The current draw and pressures should go
up. Place set point 0.5
°
C (0.9
°
F) above current box
temperature to fully modulate valve, and run for
approximately one minute.
NOTE
The unit may shut off for a short time. Wait until
the unit self starts and sufficient time has
elapsed to cause the valve to fully modulate.
Record new gauge readings and current draw. The
suction pressure should go into a vacuum and the
current draw should have gone down. If little or no
change to the suction pressure or current draw oc-
curs, this is an indication of a malfunctioning SMV.
