Chromalox PK413-4 specifications Thermostat SUB Assembly Replacement

CALIBRATION

DANGER: Calibration will involve exposure of inter- nal control terminals to ambient conditions during some part of the recalibration procedure. Combustible materials which cause hazardous conditions must not be present during recalibra- tion process — otherwise explosion may result.

1.Heat water bath or the equipment in which the control is installed (tank, die, platen or machine) to the selected calibra- tion temperature. The entire sensing bulb and at least one foot of its capillary tube are to be exposed to calibrating tempera- ture. With thermostat energized, allow process or bath to reach setpoint. This is accomplished when thermostat begins cycling action.

2.Compare adjustment knob cut off temperature indication against actual temperature to which sensing bulb is exposed. Figure 15 shows example of a control knob showing a control indication of 250°F when true process temperature measured 230°F. In this example, the control knob must be rotated 20° counterclockwise to bring the 230°F knob marking under the index mark in order to recalibrate the control.

3.Without disturbing the shaft setting, loosen the thermostat knob set-screw and re-align dial setting accordingly. Retighten knob set-screw.

4.Recheck for thermostat operation as per steps 2 and 3 and make further calibration adjustment if indicated.

5.Recheck of thermostat operation following final adjustment completes the calibration procedure.

IMPORTANT: Under no circumstances must the temperature range, and in particular, the maximum temperature setting of con- trol be increased above maximum temperature indicated on control nameplate. Such changes voids U.L. listing of the control.

Thermometer

Load (Tank, vat, die or platen)

Figure 14

Indicated Temp. True Temp

250
A	200

Figure 15

THERMOSTAT SUB ASSEMBLY REPLACEMENT

1.Before removing enclosure cover, turn thermostat knob to the OFF position (counterclockwise). Place a piece of masking tape over the knob to keep it in the OFF position.

2.Remove the enclosure cover by removing four fastening screws (Figure 5).

3.Remove the white shaft coupler for safe-keeping.

4.Remove the thermostat mounting screws (2).

5.Loosen the capillary-seal retaining cap set screws and then remove the retaining cap.

Note: Do not remove the entire capillary seal fitting from the enclosure.

6.Remove the capillary seals and thermostat from the enclosure.

7.Remove the calibration cap (Figure 1) and insert pin from the old thermostat. Rotate the position of the calibration cap, for use in the next step.

8.With replacement thermostat in the OFF position (shaft complete- ly counterclockwise), install insert pin and calibration cap. Install calibration cap with same orientation as noted in step 7 above.

9.If excess capillary, on old thermostat, had been coiled in enclo- sure, it may be necessary to coil an equal amount on replace- ment thermostat per step 4D mounting instructions.

10.After proper capillary length is obtained on replacement ther- mostat, insert capillary in the enclosure and thru the capillary seal fitting.

11.Recheck for proper capillary length (external to enclosure) and adjust if necessary.

12.Align spacer plate and replacement thermostat to mounting holes in the bottom of enclosure using mounting screws (2 – #10-32 x 3/8 Lg.) to secure thermostat to enclosure.

13.Slide the capillary seals into the capillary fitting making sure the capillary is positioned in the center groove of the seals.

WARNING: If capillary is not located in the cen- ter groove properly, damage to the capillary will result, rendering the thermostat inoperable or unreliable.

14.Replace capillary seal retaining cap and tighten set screws to lock in position.

Note: Per the NEC, all threaded connections in a hazardous environment must be tightened sufficiently to engage five full threads.

15.Rewire replacement thermostat per appropriate wiring dia- grams (Figures 7 thru 11).

16.Replace the white nylon coupling on the calibration cap and enclosure cover per step 7 of the wiring section.

17.Replacement thermostat control should be monitored to insure proper operation. If calibration is required, see the calibration section for instructions.

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