Chromalox Thermostat PK471 4 User Manual

Installation  
4
WCRT  
and  
(Supersedes PK471-3)  
PK471-4  
161-562767-001  
OPERATION INSTRUCTIONS  
DECEMBER, 1998  
WCRT Weather-Corrosion  
Resistant Room  
Thermostat  
Specifications – Table A  
Maximum Rating  
Temperature Switch  
Range (°F) Action  
Model  
Description  
120 Vac 240 Vac 277 Vac  
Full Load Inductive  
16.0A  
80.0A  
25.0A  
125VA  
12.0A  
60.0A  
25.0A  
125VA  
10.0A  
55.0A  
22.0A  
125VA  
WCRT-100  
40-100  
SPDT Locked Rotor  
Non-Inductive  
Pilot Duty  
UL LISTED  
Figure 1  
GENERAL  
Type WCRT thermostats are intended for use in harsh environ-  
ments. They tolerate continuous spraying with water, high humid-  
ity, airborne contaminates and moderately corrosive conditions.  
The nickel plated sensing bulb is attached directly to the bottom of  
the case where it is shielded from damage or accumulations of  
insulating particles. The molded Noryl case is sealed at the cover  
with a neoprene gasket and the adjusting knob opening is closed  
with a lubricated O ring. Underwriters Laboratories has tested the  
WCRT and found it meets the requirement for NEMA 4X areas.  
High levels of accuracy and sensitivity, 21/2° differential, are pro-  
vided by the WCRT. Switching is done by heavy duty, precision,  
single stage, SPDT line voltage snap action switch. Setting is  
accomplished by rotating the adjusting knob. The dial face is print-  
ed with large, contrasting numbers and letters on a lustrous back-  
ground for good visibility. Color coding clearly identifies the func-  
tion of each conductor.  
NOTICE: Type WCRT thermostats are designed for temperature  
control service only. Because they do not fail safe, they should  
not be used for temperature limiting duty.  
WARNING: Users should install adequate back-up  
controls and safety devices with their electric heat-  
ing equipment. Where the consequences of failure  
may be severe, back-up controls are essential.  
Although the safety of the installation is the  
responsibility of the user, Chromalox will be  
glad to make equipment recommendations.  
Principle of Operation – Control action of these thermostats is  
provided through the principle of liquid volume change. With a  
variation in temperature, the liquid in the sensing element expands  
or contracts, causing a bellows to actuate the switching mechanism.  
WARNING: Not for use in hazardous environments as  
described in National Electrical Code. Failure to com-  
ply can result in explosion or fire.  
Applications – Automatically controls room temperature by turn-  
ing electric air heaters on and off. Can be used to control the air  
heaters directly, within thermostat rating. For higher ratings use  
thermostat with magnetic contactor. Place thermostat on inside wall,  
away from undue heating or cooling influences, about 4 feet above  
the floor.  
LO Setting is positive open (black to red) for heating loads and  
is positive closed (black to blue) for cooling loads.  
Note: It is not recommended to switch systems directly from heat-  
ing to cooling and vice versa.  
© 2010 Chromalox, Inc.  
 
WIRING  
Figure 3  
Figure 4  
WIRING DIAGRAMS  
Control  
Voltage  
Ground  
Red  
Opens On  
Temperature Rise  
Ground  
Blue  
Black  
Blue  
Common  
Red  
Closes On  
Temperature Rise  
Black  
Pilot Light  
Figure 5  
Line  
Contactor  
Ground  
Blue  
Red  
Black  
Heating Load  
Pilot Light  
Pilot Light  
Heating Load  
Pilot Light  
Cooling Load  
Cooling Load  
Single Phase When Load or Voltage Does Not  
Exceed Thermostat Rating.  
Three Phase and Single Phase When Load Exceeds  
Thermostat Rating.  
Figure 6  
Figure 7  
 
TESTING AND OPERATION  
After installation and wiring, to check the operation of heating  
To check the operation of the cooling systems:  
systems:  
1. Disconnect power.  
1. Disconnect power.  
2. Place the heat/cool selector switch, if applicable, in the cool  
position.  
2. Place the heat/cool selector switch, if applicable, in the heat  
position.  
3. Adjust the setpoint ten or more degrees above the temperature  
3. Adjust the setpoint ten or more degrees below the temperature  
of the controlled space.  
of the controlled space.  
4. Restore power.  
4. Restore power.  
5. Slowly adjust the setpoint downward. When the setpoint  
approximates the temperature of the controlled space, the cool-  
ing equipment should start.  
5. Slowly adjust the setpoint upward. When the setpoint reaches  
the approximate temperature of the controlled space, the heat-  
ing equipment should start.  
Limited Warranty:  
Please refer to the Chromalox limited warranty applicable to this product at  
1347 HEIL QUAKER BLVD., LAVERGNE, TN 37086  
Phone: (615) 793-3900  
 

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