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PK410-1
161-048634-001
JUNE, 1989
4WR
Installation Instructions
(Supersedes PK410)
Type WR Room Thermostat
© 2010 Chromalox, Inc.
Specifications – Table A
GENERAL
Positive accuracy, long and reliable service, 3° differential.
Heavy-duty, single stage, SPST line voltage snap-acting switch.
Patented hydraulic element. WR-80 has internal sensing element
and thermometer on cover; WR-90 has external, coiled sensing
element but no thermometer. Both have a low position which
drops control point to keep heater off. WR-80 and WR-90 fin-
ished in tough metallic gray with chrome trim; mounting plate
fits outlet or conduit box.
Uses – Automatically controls room temperature by turning elec-
tric air heaters on and off. Can be used to control the air heaters
directly, within thermostat rating. For higher ratings use thermo-
stat with magnetic contactor. Place thermostat on inside wall,
away from undue heating or cooling influences, about 4 feet
above the floor. WR-90 is especially useful in holding lower tem-
peratures, for example, in garages, warehouses, factories, etc.
NOTICE: Type WR thermostats are designed for temperature
control service only. Because they do not fail safe, they should
not be used for temperature limiting duty.
CAUTION: 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 responsi-
bility of the user, Chromalox will be glad to make equipment rec-
ommendations.
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.
CAUTION: Not for use in hazardous environments
as described in National Electrical Code. Failure to
comply can result in explosion or fire.
WR-80
40 to 80°F
UL Listed
Maximum Rating
Range
Model (°F) 120Vac † 115Vac 240Vac † 230Vac 277Vac 480Vac
WR-80 40-80 125va pilot 125va pilot 125va pilot
25 amps duty (use 22 amps duty (use 18 amps duty (use
WR-90 20-90 or 3000 with d-c or 5280 with d-c or 5000 with a-c
total watts contactor) total watts contactor) total watts contactor)
WR-90
20 to 90°F
UL Listed
† d-c ratings not UL listed
5
3
/8”
2
1
/2”
2
1
/4”
2
9
/16”
6”
2
3
/4”
2
1
/2”
Note —
WR-80 is
not a
Fail-Safe
Device.