Product Overview
Technical Instruction
Document No. 155-067P25
Rev. 1, July, 1999
Page 12 Siemens Building Technologies, Inc.
Landis Division
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Before troubleshooting thermostat per Table 5, make certain there is clean dry supply air
at 18 psi (124 kPa) for day control and 25 psi (172 kPa) for night. Use test probe gauge
and needle adapter to measure control pressure at thermostat test port.
The output pressure test port is accessible without removing the thermostat cover
through the 8th opening from the top left side.
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Air supply Low supply pressure As required
Nozzle or flapper
Dirt on nozzle or
flapper
Clean nozzle or replace
thermostat
Restrictor Clogged restrictor Replace restrictor
Control pressure
stays at
approximately zero
Calibration Out of calibration Recalibrate
Nozzle Clogged nozzle Clean nozzle or replace
thermostat
Control pressure
stays at
approximately
supply pressure
Calibration
Dirt on either supply
or exhaust valve seat
Alternately close and
open nozzle by gently
pushing down the
bimetal
Excessive air
leakage from
exhaust port on
left side of
thermostat
Supply and return
line connection
Connections are
interchanged or
connection to port is
incorrect
As required