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2



SEQUENTIAL DEFROST



Table of Contents

Introduction
4

COLD-WEL Auto-Sequential Holdover Blower System
5

COLD-WEL Sequential Defrost System Configurations
7

Refrigeration System Description
10

Refrigeration System Equipment Items
12

Sequential Defrost Operation
13
Sequential Defrost With Heat Operation
15
Sequential Defrost With Manual Initiate Operation
17
Sequential Defrost With Manual Initiate & Heat Operation
19
Operation of Defrost Cycle Termination
21

Control Settings
22

Troubleshooting
23
Blower Motor Fails to Run Over the Road
23
Blower Motor Will Not Operate on AC Power
23
Defrost Cycle Fails To Terminate
24
Battery Drained While operating on AC
25

Reduced Air Flow From Blower
26
Blower Motor Reverses Direction
26
Winter Heat Failure
27
Cycle Timer Will Not Advance
27
System Will Not Go Into Defrost
28
Ice Buildup on Plates
28
Ice Buildup on Compressor
29

Charging the System
30
Replacement Parts
31
Warranty

32


3

List of Illustrations


Figure 1 Cold Wel System Variations
9

Figure 2 Refrigeration System
11

Figure 3 Sequential Defrost Electrical Schematic
14

Figure 4 Sequential Defrost with Heat Electrical Schematic
16

Figure 5 Sequential Defrost with Manual Initiate Electrical Schematic
18

Figure 6 Sequential Defrost w/ Manual Initiate and Heat Electrical Schematic 20


































4

Introduction

The purpose of this manual is to describe the Dole Sequential Defrost Cold-Wel and to
present information relative to its maintenance. An attempt has been made to offer as
much practical assistance as might be required to troubleshoot and resolve problems
that may arise.

A Cold-Wel ready for installation in a truck.











5
Cold-Wel Auto Sequential Holdover Blower System

Features of Cold-Wel Sequential Defrost Holdover Blower Systems:

1. The special dual circuit zero degree F. holdover plates provide twice the
plate-surface-to-body air temperature difference as plus 18 degrees F. plates in
other holdover blower systems. This feature results in Cold-Wels having the
capacity to cool an enclosure at twice the rate of other systems.

Cold-Wel units can contain three or four plates, each plate having two
independent coils. One coil is used for cooling and freezing the eutectic solution
while the other is used for defrosting the eutectic solution by means of circulating
hot gas.

2. The top air intake and discharge openings result in a cold "trap" within the
Cold-Wel. This trap prevents cold heavy air from flowing out of the unit when the
blower fan is off. This feature eliminates product freezing and the "waste" of
holdover cooling when truck doors are open, and/or the truck thermostat is not
calling for cooling. Since the Cold-Wel frame is insulated, product can be stored
up next to the unit without fear of freezing.

3. Dual blowers on a double-shafted motor provide a high velocity blast of air
along the ceiling to the rear of the body for full product protection. The blower
motor is powered from the truck battery while on the delivery route and by
external power when the condensing unit is plugged into external power at
dockside for the purpose of refreezing eutectic in the plates.

4. The air inlets are located near the top of the unit to receive the warmest air in
the body. This is especially important after a door opening has resulted in an
inrush of air from outside with its accompanying higher temperature.

5. The closed bottom of the unit permits product to be stacked against the
exterior of the Cold-Wel, a feature that permits full use of available floor space.
This feature also prevents water, which flows off of the plates during defrosting,
from flooding the truck body floor.

The rapid reduction of body temperature after door openings, inherent in the
Cold-Wel design, results in reduced total blower motor heat load, and a reduction
in the total load on the truck battery.

6. During the plug-in period, hot gas is directed to the hot gas coil in the
preselected eutectic plate. This hot gas circulates through the coil and melts the
eutectic in the plate. The warmed solution melts the plate's surface frost. The
defrost cycle may be initiated automatically or manually, depending upon the
configuration of the Sequential Defrost system employed. The defrost cycle is
terminated when a temperature sensor in the hot gas return line indicates the
plate's eutectic solution has been sufficiently heated to eliminate surface frost
(approx. 70 degrees).

6
7. A winter heat option is available in all Cold-Wels. This option can prevent
product freezing when the unit is plugged into external power at dockside in
Northern climes where heating may be required due to extremely low outside
temperatures.













































7
Cold-Wel Sequential Defrost System Configurations

Cold-Wel sequential defrost is offered in fo ur different configurations:

-Sequential Defrost
-Sequential Defrost with Heat
-Sequential Defrost with Manual Initiate
-Sequential Defrost with Manual Initiate & Heat

Figure 1 illustrates the differences between the different configurations.

Sequential Defrost

In this configuration, plugging in external 230VAC power will automatically initiate
defrost of a selected plate. At the instant the external power is applied to the unit, the
Cycle Timer in the unit's Control Panel selects a plate for defrost. Refrigerant and hot
gas solenoid valves are opened and/or closed to permit hot gas to circulate through the
selected plate and to allow refrigerant to flow through the other plates.

The defrost cycle will be terminated when a temperature sensor indicates that the hot
gas exiting the plate undergoing defrost has reached 70 degrees F. At that time the
defrosted plate will be placed in the refrigerate mode and refrigerant will flow through its
coil.

Should external power be interrupted for any reason, i.e. power failure or intentional
disconnect as a result of moving the truck, the defrost cycle for the selected plate will be
terminated. Subsequently, when external power is restored, the Cycle Timer will select
the next plate due for defrost and will position the refrigerant and hot gas valves in such
a manner that this plate will be in the defrost mode and the remaining plates will
undergo refrigeration.

Sequential Defrost with Winter Heat

In this configuration, a manually operated selector switch is included which can place
the unit in the Refrigerate or in the Heat mode. In the Refrigerate mode, the system
operates in the same manner as the Sequential Defrost just described. When placed in
the Heat mode, a heater in the Cold-Wel energized and air flows over the heater when
the truck thermostat calls for heat. While in the Heat mode, the Condensing Unit is
electrically locked out. Heat is available only at dockside since the heaters are 240VAC
elements.









8
Sequential Defrost with Manual Initiate

When external power is connected to the truck, depressing the momentary contact
Manual Initiate Switch on the external Control Box will cause the Cycle Timer to select a
plate for defrost and place the remaining plates in the refrigerate mode. This operational
mode will be maintained until the defrost cycle is completed, at which time the defrosted
plate will be refrigerated, as was the case in systems without the Manual Initiate feature.

Should the power be interrupted for any reason, a resumption of power will permit the
system to continue operating in the same mode as before power was interrupted. This
is accomplished by a latching relay in the external Control Box. In other words, if power
was interrupted with a specific plate in the defrost mode, subsequent restoration of
power will permit the continuation of defrost of that plate. For any plates in the
refrigerate mode at power interruption, restoration of power will allow the refrigeration of
those plates to continue.

Sequential Defrost with Manual Initiate & Heat
A system in this configuration operates in the same manner as the one just described
except, as was the case with Sequential Defrost, placing the Refrigerate/Heat Switch in
the Heat position prevents the Condensing Unit from operating and places the unit's
blower under the control of the truck's thermostat. Whereas this thermostat will call for
cooling with rising temperature when the system is in the Refrigerate mode, it will call
for heating with falling temperature when in the Heat mode. Heat is available only at
dockside since the heaters require 240 VAC.

9
Figure 1 System Variations





10
System Description
A Dole COLD-WEL with Sequential Defrost contains three or four plates filled with a
zero degree F. eutectic solution. Each plate has an internal refrigeration coil (13) and
an internal defrost coil (21). Upon the application of external power, a plate is selected
for defros