Honeywell T675A User's Manual
Contents
1. Interstage differential adjustment on a T678A 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 setting and differential setting check to see that the sensing bulb senses the average temperature of the medium controlled If the temperature of the controlled medium is changing rapidly the differential will appear wider than its setting continued on page 4 60 0017 5 For calibration an accurate temperature reading of the controlled medium must be taken Place an accurate thermometer near the sensing bulb or refer to a ther mometer that has been installed as part of the system if the sensing bulb is installed in an inaccessible area or if the controlled medium is unstable the bulb should be removed and placed in a controlled bath for accurate calibration T675A These controllers are calibrated so that the dial setting indicated by the pointer on the adjustment knob is the point at which the R W switch contacts make on a tem perature rise Measure the temperature at the bulb Rotate the adjustment knob counterclockwise from the top of the scale simulating a temperature rise until the R W switch contacts make Note the dial reading If it differs from the bulb temperature calibrate the dial as follows 1 Determine the number of degrees difference be tween the bulb tempera2. BE NECESSARY TO ADAPT SPUD TO TAPPING rasac Fig 5 Mounting the sensing bulb using a capillary compression fitting WIRING Disconnect the power supply before making wiring connections to prevent electrical shock and equipment damage A l wiring must comply with applicable electrical codes and ordinances If using the controller with a flame safeguard control use moisture resistant No 14 wire suitable for at least 167 F 75 C for a primary control such as an RA890 or for at least 194 F 90 C for a programming control such as an R4140 For high temperature installations use moisture resistant No 14 wire selected for a temperature rating above the maxi mum operating temperature Two knockouts for 1 2 inch conduit are provided one in the top and one in the bottom of the case Fol low the wiring instructions furnished with the heating or cooling system Fig 6 shows the switching action T678A HAS 2 SPDT SWITCHES THAT OPERATE IN SEQUENCE LEFT SWITCH OPERATES AT A HIGHER TEMPERATURE THAN THE RIGHT SWITCH SWITCHES BREAK R TO B AND MAKE R TO W ON TEMPERA TURE RISE RIGHT SWITCH MAKES R TO W FIRST 14148 Fig 6 T678A switching action T675A is similar but it has only one spdt switch T675B has one spst switch that opens on temperature fall OPERATION T675A As the temperature of the controlled medium falls below the set point less differential the T675A switch makes terminals R to B and energizes a no
3. Honeyvell APPLICATION The T675 and T678 Temperature Controllers are designed to control the temperature of air or liquids in ducts pipes tanks and boilers Typical uses include control of dampers and valves in heating cooling or heating cooling systems The T675A has 1 spdt switch It makes or breaks a circuit on a change in temperature at the sensing bulb Fast response models with adjustable differential are available for duct installation They respond approxi mately 4 times faster than standard models The T675B is a low limit temperature controller with 1 spst switch It breaks a circuit on a temperature fall and must be manually reset The T678A has 2 spdt switches which operate 2 inde pendent circuits in sequence Fast response models operate 4 times faster than standard models INSTALLATION WHEN INSTALLING THIS PRODUCT 1 Read these instructions carefully Failure to follow them could damage the product or cause a hazardous condition 2 Check the ratings given in the instructions and on the product to make sure the product is suitable for your application 3 Installer must be a trained experienced service technician 4 After installation is complete check out product operation as provided in these instructions Disconnect power supply before beginning instal lation to prevent electrical shock and equipment damage The installation should be made within the limits specified below ELECTRICAL
4. L RESET BUTTON INDICATED BY DASHED LINES tasea Fig 1 Dimensions of the T675 and T678 Temperature Controllers in in mm in brackets NOTE When pressure fittings are used in areas of vibra tion such as pipe lines the bulb must be adequately supported TI 2 INCH 50 mm EE HOLE N OLCT WALL 1315208 i CAPILLARY FAST RESPONSE ELEMENT SCREWS 2 Fig 2 Mounting a fast response element in an air duct continued on page 2 ss epc REV 10 80 Energy Products Center Form Number 60 0017 5 CONTROLLED 3 4 INCH 19 1 mm AREA HOLE IN DUCT WALL SENSING BULE F eee PLATE SCREW HOLES 2 MOUNTING SCREWS 2 a N Fig 3 Mounting the sensing bulb and capillary holder in an air duct INSULATION OF BOILER OR STORAGE TANK WALL OF BOILER OR STORAGE TANK SPUD SCREWS CAPILLARY w N EXTERNAL THREADS N ON SPUD N N NI D A REDUCER FITTING MAY BE NECESSARY TO ADAPT SPUD TO TAPPING 112622AA IMMERSION WELL ASSEMBLY 1 2 14 NPT 112630AA IMMERSION WELL ASSEMBLY 3 4 14 NPT Fig 4 Mounting the sensing bulb in an immersion well SENSING ae Be ae SPUD SCREWS INTO TAPPING Pai a IN BOILER OR N E A NPT OR 3 4 14 NPT M EXTERNAL THREADS ON SPUD 1044844 4 2 IN OR B 3 4 iN CAPILLARY COMPRESSION FITTING SLOTTED BRASS WASHERS ASSEMBLE IN PAIRS Pq THUS i H 4 COMPOSITION osc an CAPILLARY PACKING NUT A REDUCER FITTING MAY
5. RATINGS T675A models with adjustable differential and T678A 120 Vac j2 Vac 277 Vac Full Loa 80A 51A 4 2 A Locked Rotor 48 0 A 30 6A 25 2 A Pilot Duty 125 VA 125 VA 125 VA T675A models with fixed differential 125 VA at 120 208 240 277 Vac T675B 125 VA pilot duty up to 277 Vac T678A maximum connected load 2000 VA MAXIMUM BULB PRESSURE 50 psi 344 7 kPa for direct immersion LOCATION AND MOUNTING The controller may be installed in any convenient position Mount it with 3 screws through the slotted holes in the back of the case Fig 1 Be sure to consider the length of the capillary before mounting the controller T675A B AND T678A TEMPERATURE CONTROLLERS Install the sensing element where it is exposed to the average temperature of the controlled medium The sensing bulb may be directly immersed or mounted in a weil T675A or T678A fast response models must use the capillary holder furnished with the device Fig 2 The remote sensing bulb of standard models should be held in place with a capillary holder immersion well or compression fitting Figs 3 5 Sharp bends or kinks in the capillary tubing affect the efficiency of the contro ler and must be avoided Excess capillary should be carefully coiled and left directly beneath the controlier Z 22 2 CIA KNOCKOUT BOTH ENDS 9 51 1 16758 DOES NOT HAVE AN ADJUSTMENT KNOB 2 T675B HAS A MANUA
6. WITCH rater TEM a ON RISE TEMPERSTORE HT biFFERENTIAL A P tL Ea OAN PREIE RAN INTERSTAGE ONAL DIFFERENTIAL A SET POINT BREAK R E MAKE R W ADJUSTABLE RIGHT SWITCH ON RISE DIFFERENTIAL A e BREAK R W MAKE R B ON FALL A DIFFERENCE BETWEEN THE TEMPERATURES AT WHICH THE 2 SWITCHES MAKE R W ADJUSTABLE FROM 3 TO 10 DEGREES F 1 7 TO 5 6 DEGREES C ON STANDARD MODELS OR FROM 3 6 TO 12 DEGREES F 2 0 TO 6 7 DEGREES C ON 55 TO 175 F 13 to 79 C MODELS AN 2 SPDT SWITCHES OPERATE IN SEQUENCE EACH SWITCH DIFFERENTIAL IS FIXED AT APPROXIMATELY 3 DEGREES F 1 7 DEGREES C ON STANDARD MODELS OR AT 3 6 DEGREES F 2 0 DEGREES C ON 55 TO 175 F 13 TO 79 C MODELS PLUS A FEW OTHERS 79208 Fig 10 Operation of the T678A The T678A Temperature Controller has an adjustable interstage differential The set point adjustment knob determines the temperature at which the right switch operates The left switch can be adjusted to operate from 3 to 10 degrees F 1 7 to 5 6 degrees C or 3 6 to 12 degrees F 2 0 to 6 7 degrees C on some models above the point of operation of the right switch An illustration depicting the operation of the T678A is shown in Fig 10 The interstage differential is adjusted by turning the star wheel with a narrow screwdriver inserted into the rectangular hole in the chassis Fig 11 LEFT SWITCH Fai SWITCH STAR WHEEL INTERSTAGE DIFFERENTIAL ADJUSTMENT Fig 11
7. ion NOTE The T675B is a manual reset device specifically designed for freeze up protection T675B Used as a low limit controller the T675B interrupts the operation of equipment if the temperature of the controlled medium falls below the set point The device is reset manually after a rise in temperature of approxi mately 10 degrees F 5 6 degrees C push in the manual reset button on the front of the case The operation of the T675B is shown graphically in Fig 9 T675B OPERATION MANUALLY RESET TO MAKE CONTACTS TEMPERATURE RISE rt RESET DIFFERENTIAL 10 DEGREES F 5 6 DEGREES C MAXIMUM N FACTORY SET CONTACTS BREAK AND LOCKED ON FALL AT 37 F 3C oe NOTE THE TEMPERATURE OF THE CONTROLLED MEDIUM MUST ORIFT UPWARDS THROUGH THE RESET DIFFERENTIAL BEFORE THE SWITCH CAN BE MANUALLY RESET 1417A FIG 9 OPERATION OF THE T675B T678A When the temperature at the sensing element rises above the set point of the controller the switch on the right makes R W Should the temperature continue to rise through the preselected interstage differential of the controller the switch on the left will make R W Conversely on a temperature fall the switch on the left makes R B providing first step switching If the temperature continues to fall the switch on the right makes R B to provide sequencing of equipment T678A OPERATION po BREAK R B LEFT S
8. mperature range of the air or liquid being controlled Make sure that the controlled equipment operates as intended Honeywell Automation and Control Solutions Honeywell International Inc Honeywell Limited Honeywell Limit e Printed in U S A on recycled 1985 Douglas Drive North 35 Dynamic Drive paper containing at least 10 Golden Valley MN 55422 Scarborough Ontario post consumer paper fibers M1V 4Z9
9. rmally closed solenoid valve to provide heat In cooling applications the T675A makes terminals R to W as the temperature rises above the set point energizing cooling equipment Fig 7 shows the operation of the T675A Fig 8 shows the location of the adjustment dial on models with an adjustable differential T675A OPERATION R W MAKES R B BREAKS A ON RISE SWITCH DIFFERENTIAL ADJUSTABLE FROM APPROXI MATELY 3 TO 10 DEGREES F 1 7 TO 5 6 DEGREES C ON STANDARD MODELS OR FROM 3 6 TO 12 DEGREES F 2 0 TO 6 7 DEGREES C ON 55 TO 175 F 13 TO 79 C MODELS SET POINT ADJUSTABLE TEMPERATURE RISE R W BREAKS R B MAKES ON FALL MODELS ALSO AVAILABLE WITH A FIXED DIFFERENTIAL OF APPROXIMATELY 1 DEGREE F 0 6 DEGREE C 1416A Fig 7 Operation of the T675A TERMINAL SCREWS 3 V NOTCH T675A DIFFERENTIAL ADJUSTMENT DIAL Fig 8 Location of the adjustment dial on T675A models with an adjustable differential FREEZE UP PROTECTION hen using the T675A auto recycling for freeze up protection the recommended set point is 38 F 3 3 C plus the switch differential Example Set point of 38 F 3 3 C plus 1 degree F 0 6 degree C fixed differential mode equals an actual set point of 39 F 3 9 C Example Set point of 38 F 3 3 C plus 3 degrees F 1 7 degrees C adjustable differential model equals an actual set point of 41 F 5 C This provides an adequate safety factor for freeze up protect
10. switch contacts break Note the dial reading If it differs from the bulb temperature follow the cali bration procedure outlined for the T675A Tighten the locking screw and replace the cover T678A These controllers are calibrated so that the dial set ting indicated by the pointer on the adjustment knob is the point at which the R W contacts of the right switch make on a temperature rise If the temperature con tinues to rise the R W contacts of the left switch make at the dial setting p us the interstage differential The interstage differential is adjustable as shown in Figs 10 and 11 Measure the temperature at the bulb Rotate the adjustment knob counterclockwise xN from the top of the scale simulating a temperature rise until the R W contacts of the right switch make Note the dial reading If it differs from the bulb temperature follow the calibration procedure outlined for the T675A After calibrating the dial check the setting of the interstage differential Set the adjustment knob at the bulb temperature Then rotate the adjustment knob counterclockwise s N simulating a temperature rise until the R W contacts of the left switch make Note the dial reading The difference between this reading and the bulb temperature is the interstage differential The interstage differential may be adjusted if necessary Fig 11 CHECKOUT Check the operation of the controller by raising and lowering the set point through the te
11. ture and the dial reading at which the R W switch contacts make 2 Remove the adjustment knob and slip the fingers of the calibration wrench accessory Part No 801534 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 bulb temperature differs from the point at which the contacts make determined in step 1 For example move the dial from 45 to 65 if the dial reading in step 1 was 45 degrees and the bulb temperature was 65 degrees 3 Check the calibration adjustment by moving the adjustment knob up and down the scale while listening for the contacts to make and break If the dial is still out of calibration repeat the calibration procedure T675B NOTE The cover must be removed to see the dial All T675B models have been factory set and locked at 37 F 3 C These controllers are calibrated so that the dial setting indicated by the fixed pointer at the top of the dial is the point at which the switch contacts break on temperature fail Measure the temperature at the bulb Remove the cover of the controller Loosen the locking screw Insert a screwdriver in the slot in the center of the dial Start with the dial at the bottom of the scale and rotate the dial counterclockwise s to simulate a temperature fall until the
Download Pdf Manuals
Related Search