Operation And Checkout - Honeywell T4031A Product Data

OPERATION AND CHECKOUT

When the temperature at the sensing bulb rises above the
controller setpoint, a circuit is made between the R-W termi-
nals. During a temperature fall, the R-W circuit breaks at the
setpoint temperature minus the switch differential. Controllers
with a B terminal break the B-R terminal circuit on a tempera-
ture rise to the setpoint. B-R makes again when R-W breaks on
a temperature drop. See Fig. 6.
For example, if a controller with a 3°F (1.7°C) differential is set
at 39°F (3.9°C), R-W makes when the bulb temperature rises to
39°F. Then during a temperature fall, R-W breaks when the
temperature drops to 35°F (1.7°C) (39°F minus the 3°F
differential [3.9°C minus the 1.7°C differential]).
On models with a B terminal, B-R makes when R-W breaks.
Then the temperature has to climb past the control differential
to the set point of 39°F (3.9°C) before the B-R circuit breaks
and the R-W circuit makes.
B R-W
CONTROL
SETPOINT
39°F (4°C)
B-R MAKES
R-W BREAKS 3.5°F (1.6°C)
DIFFERENTIAL
B-R W
SWITCH ACTION ON
TEMPERATURTE RISE
Fig. 6. Operation of switch on temperature rise and fall.
SETTING
Set the controller to the system manufacturer's recommended
settings, if available.
Temperature Setpoint Knob—Turn the knob on the front of the
case until the pointer indicates the temperature to be main-
tained in the controlled medium.
Screw—Insert a flatheaded screwdriver into the slot on the
shaft, which is located in the center of the scaleplate. Turn the
screwdriver clockwise
control point. Turn the screwdriver counterclockwise
decrease the temperature control point.
Adjustable Differential—With the cover off, turn the differential
adjustment wheel (marked 3-6-9-12°F) until the desired
differential is aligned with the notch in the frame. See Fig. 7.
Fixed differential models are 3.5°F at midscale.
T4031A,B,P; T6031A,B REFRIGERATION TEMPERATURE CONTROLLERS
B R-W
39°F (4°C)
35.5°F (2°C)
B-R MAKES
R-W BREAKS
B-R W
SWITCH ACTION ON
TEMPERATURE FALL
M4495
to increase the temperature
Calibration
All controllers are carefully tested and calibrated at the factory
under controlled conditions. If the controller is not operating at a
temperature corresponding to the scale and differential setting,
verify that the bulb senses the average temperature of the
medium. If the temperature of the controlled medium is
changing rapidly, the differential will appear wider than its
setting.
Fig. 7. Internal view showing differential adjustment wheel
For calibration, take an accurate temperature reading of the
controlled medium. Place an accurate thermometer near the
bulb of the controller, or refer to a thermometer installed as part
of the system. If the bulb of the controller is installed in an
inaccessible area, or if the controlled medium is unstable,
remove the bulb and place in a controlled bath for accurate
calibration.
These controllers are calibrated so the dial setting is the point
at which the R-W switch contacts make (B-R contacts break)
on a temperature rise. Measure the temperature at the bulb.
Rotate the dial counterclockwise
scale, simulating a temperature rise, until the R-W switch
contacts make. Note the dial reading. If it differs from the
setpoint, calibrate the dial as follows:
1. Determine the number of degrees difference between the
set point and the point at which the contacts make.
2. Remove the dial knob and slip the fingers of the calibra-
tion wrench into the slots of the dial. Rotate the dial until
the fingers of the wrench drop into the slots of the
calibration nut under the dial. Note the dial indication at
this point. Turn the dial and the calibration nut up or down
scale the number of degrees that the set point differs
from the point at which the contacts make (determined in
step 1). For example, move the dial from 45 to 65
degrees for a 20 degree change in calibration.
3. Check the calibration adjustment by moving the dial up
and down the scale while watching the contacts make
to
and break. If dial is still out of calibration, repeat calibra-
tion procedure.
4. To install tamper-resisting insert on TRADELINE®
model, remove screw from adjustment knob, remove
knob, and install insert.
5
TERMINAL SCREWS (3)
T6031 DIFFERENTIAL
ADJUSTMENT
(applicable models).
from the top of the
M4497
60-2177—3