Cashco 764T Temperature Controller - Manual (Page 6)

IOM- 764T 6
SECTION IV
START-UP
Prior to pressurizing thru the airset, disconnect the
IAS at the airset inlet, open the IAS block valve
and air-blow the supply piping/tubing to clear of
any debris, moisture, etc. Re-connect to the airset.
Disconnect IAS tubing at the 764T, open the IAS
block valve at the airset and air-blow. Repeat for
IAS to the positioner, if supplied.
Set airset to 18 psig (1.24 Barg) outlet pressure.
Blow down the airset dripwell.
Establish fl ow past the bulb, allowing the bulb to
"sense" the actual temperature.
It is recommended that the control valve that
receives the output SIG of the 764T be manually
isolated at "cold" start-up. To prevent initial tem-
per a ture overshoot/undershoot while the sys tem
reaches thermal stability, initiate fl ow in the control
valve loop by manually bypassing.
Observe actual temperature of the fl uid being
temperature controlled utilizing a separate ther-
mom e ter instrument. As the control tem per a ture
approaches the "setpoint" temperature, be gin to
manually close the control valve bypass. At tempt
to establish steady-state manual control. NOTE: It
may take a time frame of 15 minutes or greater to
establish any level of steady-state man u al con trol;
DO NOT MOVE TOO FAST!
Observe the action of the control valve in re sponse
to the action of the 764T temperature controller.
Confi rm that the proper combined "loop action" is
occurring. If not correct, review the required action
desired, and reverse action of either the control
valve or 764T. To reverse action of a 764T, the
IAS to the 764T must be removed from the "as
installed" 764T port, and re-connect in reverse; i.e.
if IAS was installed to Port "B", change to Port "A",
and vice versa. (See Tables 1 and 2).
NOTE: The 764T is factory calibrated to ap prox i-
mate ly mid-range; i.e. a 50-220°F (10-104°C) tem-
perature range will have setpoint at ap prox i mate ly
135°F (57°C). It is recommended that the unit be
shop calibrated, if required. Field calibration is, in
most cases, not practical. See Section VI.
Adjust setpoint by rotating the adjusting screw
(2.3) until the desired temperature is indicated on
the thermoneter.
NOTE: The PB and setpoint adjustments are
"interacting", meaning that to change one will likely
cause the other to have to be changed. With each
of these ad just ments, the temperature indicated
on the thermometer and the amount of rotation of
the adjusting screw (2.3) may be growing apart,
although the actual set point may not be chang-
ing. [If this setpoint deviation is objectionable,
determine the de vi a tion after all the ad just ments
have been com plet ed on the 764T.
NOTE: The 764T is shipped with the proportional
band (PB) set at a minimum value of ap prox i mate ly
3%. Match marks are factory placed on the hous-
ing (1) and needle valve (3) head cor re spond ing
to the 3% PB value.
1.
2.
3.
4.
5.
6.
7.
8.
Rotate needle valve (3) CCW approximately 1/4
of a full revolution; this corresponds to ap prox i-
mate ly 6% PB.
NOTE: The needle valve (3) may be adjusted
only 1-1/2 revolutions CCW from the initial 3%
PB min i mum value until the maximum 20% PB is
reached. Do not rotate needle valve (3) beyond
the 1-1/2" revolution limit.
IV.
Set Point
Adjustment
Porportional band
Adjustment
1/4" NPT
Outlet Conn.
1/4" NPT
"A" Conn.
1/4" NPT
"B" Conn.
Temperature Dial
Output Gauge
Figure 8: Front View
CAUTION
Do not rotate the needle valve (3) CW below the 3%
PB value, as the unit will be rendered inoperative.
3
Min Porportional band
Alignment Mark
9.