Service Guide - Bryant 935CA Installation, Start-Up, Operating And Service And Maintenance Instructions

Single-stage, upflow/horizontal communicating, variable speed ecm, ultra low nox, 35-in tall condensing gas furnace

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935CA: Installation, Start-up, Operating and Service and Maintenance Instructions

SERVICE GUIDE

LED CODES STATUS

CONTINUOUS OFF

CONTINUOUS ON

RAPID FLASHING

If status code recall is needed, disconnect the "R" thermostat lead, reset power, and put setup switch "SW1-1" in the ON position. To clear the status code history put setup switch

"SW1-1" in the ON position and jumper thermostat terminals "R", "W/W1", and "Y/Y2" simultaneously until#11 is flashed.

NOTE: W2 has no function on this model, connect W from thermostat to W/W1 on control for Heating Operation.

EACH OF THE FOLLOWING STATUS CODES IS A TWO DIGIT NUMBER WITH THE FIRST DIGIT DETERMINED BY THE NUMBER OF SHORT FLASHES AND THE

SECOND DIGIT IS THE NUMBER OF LONG FLASHES.

LED ACTIVITY

NO PREVIOUS CODE - Stored status codes are erased automatically after 72 hours or as specified above.

BLOWER ON AFTER POWER UP (115VAC or 24VAC) - Blower runs for 90 seconds, if unit is powered up during a call for heat (R-W closed) or (R-W opens) during a

blower on-delay period. If BTS is also open, the inducer will operate as well.

LIMIT CIRCUIT LOCKOUT - Lockout occurs if a limit is open. Control will auto-reset after three hours. Check for:

- Loose blower wheel

- Dirty filter or restricted duct system

IGNITION LOCKOUT - Control will auto-reset after three hours. Refer to status code #34.

BLOWER MOTOR LOCKOUT - Indicates Blower failed to reach 250 RPM or the blower failed to communicate with 30 seconds after being turner ON in two successive

heating cycles. Control will auto rest after 3 hours. Refer to status code #41.

GAS HEATING LOCKOUT - Control will NOT auto-reset. Check for:

- Mis-wired gas valve

- 24VAC sensed at gas valve when should not be present

ABNORMAL FLAME - PROVING SIGNAL

- Flame is provided while gas valve is de-energized. Inducer will run until fault is cleared.

Check for:

- Leaky gas valve- Stuck-open gas valve

PRESSURE > 0.15" w.c. AT START-UP. Check for:

- Obstruction in pressure tubing or Transducer vent holes

SECONDARY VOLTAGE FUSE IS OPEN. Check for:

- Short circuit in secondary voltage (24VAC) wiring

INVALID MODEL SELECTION OR SETUP ERROR - Indicated either the model plug is missing or incorrect. If code flashes 4 times on

power-up control is defaulting to model selection stored in memory

BURNER THERMAL SWITCH (BTS) open - If switch is open during call for heat (W), then a permanent lockout will occur. Cycle power to reset lockout. Check for:

- Blocked burner inlet

PRESSURE TRANSDUCER INPUT DOES NOT SENSE TARGET PRESSURE OR PRESSURE IS OUT OF RANGE. Check for:

- Excessive wind

- Defective inducer motor

- Low inlet gas pressure (if LGPS used)

- Frozen or blocked drain

GNITION PROVING FAILURE - Control will try ignition four times before lockout #14 occurs. If flame signal lost during blower on-delay

period, blower will come on for the selected blower off-delay. Check for:

- Oxide buildup on flame sensor (clean with fine steel wool)

- Proper flame sense microamps (.5 microamps D.C. min., 4.0 - 6.0 nominal)

- Manual valve shut-off

- Gas valve defective or turned off

- Inadequate flame carryover or rough ignition

- Green/Yellow wire MUST be connected to furnace sheet metal

BLOWER MOTOR FAULT - Indicates the blower fails to reach 250 RPM or fails to communicate within 30 seconds after being turned ON, or the blower RPM falls below

250 RPM for more than 10 seconds or fails to communicate for more than 20 seconds during steady-state operation.

INDUCER MOTOR FAULT the RPM pulses are not detected from the inducer motor within 20 seconds after a heat request, the inducer is

outside of its valid range of operation, or the inducer RPM signal was lost for 5 seconds during operation, Inducer exceeds model specific RPM

limit. Check for:

- Proper vent sizing

- Improper or loose motor wiring or bad connection

CONTROL CIRCUITARY LOCKOUT Auto-reset after one hour lockout due to:

- Gas valve relay stuck open

Reset power to clear lockout. Replace control if status code repeats.

LED CODES STATUS

Indicated the blower motor tested OK. Visual check of inducer motor and hot surface igniter required.

SETUP ERROR - Reference code 25 above.

BLOWER MOTOR FAULT - Indicates blower motor failed test. Check blower, wiring, and furnace control.

INDUCER MOTOR FAULT - Indicates inducer motor failed test. Check inducer, wiring, furnace control and tubing for poor connections. See code 42 above.

The repeat component test turn setup switch "SW1-6" OFF and then back ON. After component test is completed put setup switch "SW1-6" in the OFF position and reconnect the

"R" thermostat lead.

COMPONENT TEST

To initiate the component test sequence, shut OFF the room thermostat or disconnect the "R" thermostat lead. Reset power and then put setup switch "SW1-6" in the ON position to

start the component test sequence. Once initiated the furnace control will turn the inducer ON at 25% duty cycle for 15 seconds then leave ON. The inducer motor will run for the

entire test. The hot surface igniter and blower motor will be turned ON for 15 seconds each. When the component test is completed one or more of the above codes will flash.

Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.

Check for 115VAC at L1 and N, and 24VAC at SEC-1 and SEC-2

Control has 24VAC power.

Line voltage (115VAC) polarity reversed. Check for poor or no ground (GND).

- Restricted vent

- Proper vent sizing

- Defective switch or connections

- Defective control (valve relay)

- Blocked burner mesh

- Proper vent sizing

- Inadequate combustion air supply

- Disconnected or obstructed pressure tubing