WIKA TCA - Manual (Page 3)

INSTRUCTION MANUAL
NI-491E
Rev. 5 11/02
5.1 PRELIMINARY OPERATIONS
CAUTION: do not open the cover of explosionproof temperature
switches (Series TCA) when energized, in explosive atmos-
pheres.
With reference to Fig. 3 unscrew the screw (b) until the blocking
device (a) can be turned 180°; then unscrew the cover.
Fig. 3 - Weatherproof temperature switch blocking device
a. Cover blocking
device
b. Blocking screw
c. Screw blocking the
adjustment bush ac-
cess plate
d. Flexible steel wire
e. Plumbing
f. Adjustment
bush
access plate
5.2 CALIBRATION CIRCUIT AND OPERATIONS
Prepare the control circuit as indicated in Fig. 4.
The warning lamps should be connected to the contact in the NO
or NC position according to the required contact action.
If the instrument is equipped with two microswitches, take into
account that they actuate simultaneously within rated tolerances.
The warning lamps can either be connected by means of a test
prod thimble with a maximum diameter of 2.5 mm or by means of
a test plug with a diameter of 2 mm to be inserted in the appropri-
ate holes situated frontally beside the terminal screws (see fig. 2).
Fig. 4 - Calibration circuit
TS -
Temperature switch
TT - Test thermometer
TB - Thermostatic bath
Connection of C and NO terminals
• If the circuit is open at the working temperature, the switch
closes the circuit as the temperature increases when the desired
value is reached (MAX. closing).
• If the circuit is closed at the working temperature, the switch
opens the circuit as the temperature decreases when the desired
value is reached (MIN. opening).
Connection of C and NC terminals
• If the circuit is closed at the working temperature, the switch
opens the circuit as the temperature increases when the desired
value is reached (MAX. opening).
• If the circuit is open at the working temperature, the switch
closes the circuit as the temperature decreases when the de-
sired value is reached (MIN. closing).
The test instrument should have a measurement range approxi-
mately equal to or slightly wider than the temperature switch
range and should have an accuracy consistent with the precision
required to calibrate the set point.
The temperature switch must be mounted in the normal installa-
tion position, i.e. with the stem or capillary outlet downwards.
Avoid forcing the microswitch by hand or with tools. This could
affect the instrument functioning.
With reference to figure 3, free the access to the adjustment bush
by loosening the screw (c) which holds the closure plate (f).
Increase the circuit temperature up to the desired microswitch set
point value.
Turn the adjustment bush using the adjustment rod with which the
instrument is equipped (fig.2) until the relative lamp turns on (or
turns off); then turn it in the opposite direction until the lamp turns
off (or on). Slowly turn the bush again until the lamp turns on (or
off).
Check the calibration value (varying the temperature in the circuit
accordingly) and register it, using a pen with indelible ink, on the
ratings.
5.3 FINAL OPERATIONS
5.3.1 Disconnect the instrument from the control circuit.
With reference to figure 2, insert the adjustment rod into the
appropriate seat; close the access to the adjustment bush by
rotating the closure plate (4) and tighten the relative screw (6).
Take the cover, ensure that the sealing gasket is correctly fitted
into its seat, insert the cover onto the case and turn it clockwise
until the cover is closed.
With reference to figure 3 turn the blocking device (a) 180° sliding
the tongue into the appropriate seat in the cover; tighten the
blocking screws (b).
Replace the supplied protection cap on the cable conduit.
CAUTION: the protection cap should only be definitively removed
during the connection steps (see § 7).
6 - INSTRUMENT PLUMBING
The plumbing, aimed as a guarantee against possible tampering
of the calibration, can be carried out using a flexible steel wire (d)
inserted into the holes in the screw (c) and the adjustment bush
closure plate provided for this purpose (see Fig. 3).
7 - MOUNTING AND CONNECTIONS
7.1 MOUNTING
Surface mount the instrument by means of the holes provided, or
pipe mount using the appropriate bracket (see figures 6 and 7) in
a vertical position (with the stem or capillary outlet pointing down-
wards). The chosen position must be such that vibrations, acci-
dental shocks or temperature changes are within tolerable limits.
The above also applies to direct mounting. For the instruments
equipped with capillary the difference between the bulb and the
case must not exceed two metres.
CAUTION: positions other than vertical are allowed provided
environmental conditions do not cause condensation to form or
water to enter the instrument through the ventilation path.
7.2 BULB AND CAPILLARY
With reference to figure 5 svitare il raccordo (3) dal premiguarni-
zione (2) e sfilarlo dal bulbo (5).
unscrew the fitting (3) from the seal press (2) and slide it off from
the bulb (5).
Mount the fitting (3) on the thermowell (4) and tighten it using the
appropriate key.
Insert the bulb (5) into the thermowell (4) after covering it with the
paste to improve the transmission of heat.
Verify that the bulb touches the bottom.
Insert the PTFE seal with the relative stainless steel washers into
the fitting (3).
Screw the seal press (2) onto the fitting (3) taking care not to
bend the capillary and relative sheath and tighten until the PTFE
seal is tight on the capillary tube.