Thermostat User Manual

ManualsBrandsChromalox ManualsThermostatPK471-4

(Supersedes PK471-3)

PK471-4

WCRT

161-562767-001

DECEMBER, 1998

OPERATION INSTRUCTIONS

Installation

and

WCRT Weather-Corrosion

Resistant Room

Thermostat

Temperature Switch

Maximum Rating

Model Range (°F) Action Description 120 Vac 240 Vac 277 Vac

Full Load Inductive 16.0A 12.0A 10.0A

WCRT-100 40-100 SPDT Locked Rotor 80.0A 60.0A 55.0A

Non-Inductive 25.0A 25.0A 22.0A

Pilot Duty 125VA 125VA 125VA

Specifications – Table A

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, 2

/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.

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.

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.

WWAARRNNIINNGG::

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.

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.

Figure 1

UL LISTED

Summary of content (4 pages)

PAGE 1
Installation 4 and WCRT PK471-4 (Supersedes PK471-3) OPERATION INSTRUCTIONS 161-562767-001 DECEMBER, 1998 WCRT Weather-Corrosion Resistant Room Thermostat Specifications – Table A Model WCRT-100 Temperature Switch Range (°F) Action 40-100 SPDT Description Maximum Rating 120 Vac 240 Vac 277 Vac Full Load Inductive 16.0A 12.0A 10.0A Locked Rotor 80.0A 60.0A 55.0A Non-Inductive 25.0A 25.0A 22.
PAGE 2
MOUNTING Note: Do not mount control where it will be subject to vibration or shock. Do not mount adjacent to a large magnetic contactor, as vibration and shock will cause thermostat to interact erratically – resulting in chattering of the contactor. 1. The proper location of a heavy duty room thermostat is important to assure good performance. A. Locate where air circulates freely. B. Never install on or near outside wall. C. Keep away from windows or doors. D.
PAGE 3
WIRING Figure 3 Figure 4 WIRING DIAGRAMS Control Voltage Ground Red Black Blue Opens On Temperature Rise Ground Common Closes On Temperature Rise Blue Red Black Figure 5 Pilot Light Line Contactor Line Load Ground Blue Red Black Heating Load Pilot Light Pilot Light Heating Load Line 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.
PAGE 4
TESTING AND OPERATION After installation and wiring, to check the operation of heating systems: 1. Disconnect power. 2. Place the heat/cool selector switch, if applicable, in the heat position. 3. Adjust the setpoint ten or more degrees below the temperature of the controlled space. 4. Restore power. 5. Slowly adjust the setpoint upward. When the setpoint reaches the approximate temperature of the controlled space, the heating equipment should start. To check the operation of the cooling systems: 1.