Chromalox PK471-4 User Manual

(Supersedes PK471-3)

PK471-4

WCRT

161-562767-001

DECEMBER, 1998

4

OPERATION INSTRUCTIONS

Installation

and

WCRT Weather-Corrosion

Resistant Room

Thermostat

© 2010 Chromalox, Inc.

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 environ­ments. They tolerate continuous spraying with water, high humid­ity, 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

1

/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 print­ed with large, contrasting numbers and letters on a lustrous back­ground for good visibility. Color coding clearly identifies the func­tion of each conductor.
Applications – Automatically controls room temperature by turn­ing 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 heat­ing 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 com­ply 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 heat­ing to cooling and vice versa.

Figure 1

UL LISTED

MOUNTING

WARNING: Hazard of Electrical Shock. Disconnect

all power before wiring or servicing this control.

1. Electric wiring must be installed in accordance with the

National Electrical Code and with local codes by a qualified
person. WARNING: Use copper conductors only.

2. Entrance for wiring is provided by one 1-inch conduit hole in

top of housing. Wiring to control housing should be in mois­ture-resistant conduit.

3. Remove cover by removing four screws (see Figures 3 and 4).

4. The Chromalox type WCRT thermostat has an enclosed SPDT

switch and may be wired to open on temperature rise (black
to red) or to close on temperature rise (black to blue). (See
Figure 5.)

5. Connect wires according to wiring diagrams (Figures 6 and 7).

Note: Electrical connections should be made with generous loops

of wire – approximately 6” per lead.

6. Replace cover and cover screws. Tighten screws to 4-5 inch

pounds torque.

7. Note: If load amperage or voltage rating exceeds switch rating

and for 3 phase loads, a contactor must be used. Contactor and
wiring to be supplied by customer (see Figure 7).

WARNING: Non-metallic enclosure requires the use
of ground type hub and a jumper wire for ground­ing the thermostat.

NOTICE: Thermostat is UL Listed for NEMA-4X areas. For it to
retain this listing the sealed conduit hub must also be so listed.
Example Myers Nos. ST-1, ST-2, STR-1, STR-2 or engineering
equivalent.

WIRING

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 impor-

tant 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. Do not locate too close to strong light or other false source

of heat, such as sunlight, steam lines, etc.

E. If electrical conduit leads into cooler or warmer room, plug

up space around wires in the conduit with rock wool.

2. Use sheet metal or wood screws through the four

1

/4” diameter

mounting holes in the housing to mount control. (See Figure 2.)

3. WARNING: Any deformations of bulb or capillary
that result in leakage of fluid from control ren­ders control inoperative.

Figure 2

Dimensions

11/2”

1” Dia.

35/16”

61/4”

23/8”

1

/4” Dia. (4 Places)

215/16”

23/4”

3

/4”

7”

57/8”

31/2”