Troubleshooting - Honeywell B Service Data

TP970 AND TP9600 SERIES PNEUMATIC THERMOSTATS

TROUBLESHOOTING

See Table 7 for troubleshooting procedures.
Problem
Excessive noise
Slow response
Thermostat instability
Inaccurate readings
Thermostat not switching
over at changeover pressure
Air leak
Cannot calibrate thermostat
*If these solutions fail, replace the thermostat.
75-7134—1
Table 7. TP970 Series Thermostat Troubleshooting Procedures.
Possible Cause
If there is an antihum spring, it is not
touching the throttling plate.
If there is no antihum spring or cone,
the adhesive paper dot has fallen off of
the throttling plate.
Air leak in restrictor block and filter
assembly.
Oil or moisture in lines.
Inadequate air flow caused by a
partially clogged restrictor block
assembly and/or filter cartridge.
System gain is too high.
Inaccurate calibration.
Metal cover setscrews over-tightened.
Backplate over-tightened.
Pressure at thermostat is incorrect.
Switchover pressure in thermostat is
incorrectly calibrated.
Branch line plug leaking.
Oil or moisture in lines.
Reposition spring to touch throttling plate.
Stick an adhesive paper dot on the throttling
plate across the hinge between the two rivets
so that the dot is directly below the "A" in MAX
printed on the bimetal.
Stick an adhesive paper dot on the throttling
plate as described above.
Use a bubble solution to locate the leak and
repair it.
Replace the restrictor block assembly and
filter.
Install Stiffener Plate 14004609-001 on the
backplate.
Replace the restrictor block assembly and
filter. Also ensure that the air supply to the
thermostat is dry and clean.
Replace restrictor block assembly and/or
filter.
Move throttling range adjustment toward MAX
position and then recalibrate.
Recalibrate thermostat.
Turn setscrews in.
Install Stiffener Plate 14004609-001 on the
backplate.
Readjust compressed airline to proper
switching pressure.
Turn switchover adjustment screw to
recalibrate pressure for proper switching.
Install Plug 14002172.
Replace the restrictor block assembly and
filter. Also ensure that the air supply to the
thermostat is dry and clean.
14
Solution*