Status Code 31 - Medium-Heat Switch Or Hpsr Relay Did Not Close Or Reopen - Bryant 355CAV A Series Troubleshooting Manual

Status Code 31
MEDIUM-HEAT PRESSURE SWITCH OR HPSR RELAY DID NOT CLOSE OR REOPENED - This status code can occur under the
scenarios shown below. Keep in mind that whenever the variable speed furnace control shuts unit down, gas remains off or
shuts off immediately, inducer continues running for 15 seconds, and if the blower is running, it remains running at low heat
airflow or reduces to low heat airflow for the selected off-delay.
- LOW HEAT
1. STEADY-STATE - If the medium heat pressure switch input turns ON the variable speed furnace control begins flashing status code 31 and
transitions to medium heat. After the call for heat is satisfied and the blower off-delay is completed the control will stop displaying status
code 31.
- MEDIUM HEAT
1. PREPURGE - If the medium heat pressure switch MPS does not make within 45 seconds after the low-heat pressure switch LPS made the
variable speed furnace control begins flashing status code 31, shuts unit down, waits 2 minutes, stops flashing status code 31, and restarts
heating cycle.
If medium heat pressure switch MPS opens before ignition, the variable speed furnace control ramps inducer RPM up until the medium heat
pressure switch MPS remakes. When the medium heat pressure switch MPS remakes the variable speed furnace control continues the
heating cycle. If medium heat pressure switch MPS does not remake within 45 sec after opening, the variable speed furnace control starts
flashing status code 31, shuts unit down, waits 2 minutes, stops flashing status code 31, and restarts heating cycle.
2. LOW HEAT TO MEDIUM HEAT TRANSITION - If the medium heat pressure switch MPS fails to make within 45 seconds after medium
heat was requested the variable speed furnace control shuts unit down and begins flashing status code 31. After the blower off-delay is
completed the variable speed furnace control will stop displaying status code 31 and if there is a call for heat, begin a new heating cycle.
3. STEADY-STATE - If the medium heat pressure switch MPS opens the variable speed furnace control ramps inducer RPM up until the
medium heat pressure switch MPS remakes. When the medium heat pressure switch MPS remakes the variable speed furnace control
continues the heating cycle. If medium heat pressure switch MPS does not remake within 45 sec after opening, the variable speed furnace
control starts flashing status code 31 and shuts the unit down. After the blower off-delay is completed the variable speed furnace control will
stop displaying status code 31 and if there is a call for heat, begin a new heating cycle.
4. MEDIUM HEAT TO LOW HEAT TRANSITION – When transitioning to low heat the medium heat pressure switch MPS must open
within 5 seconds. If the medium heat pressure switch MPS does not open within 5 seconds the variable speed furnace control switches back
to medium heat and starts flashing status code 31. After the call for heat is satisfied and the blower off-delay is completed the variable speed
furnace control will stop displaying status code 31.
- HIGH HEAT
1. PREPURGE - If the medium heat pressure switch MPS does not make within 45 seconds after the low-heat pressure switch LPS made the
variable speed furnace control begins flashing status code 31, shuts unit down, waits 2 minutes, stops flashing status code 31, and restarts
heating cycle.
If medium heat pressure switch MPS opens before ignition, the variable speed furnace control ramps inducer RPM up until the medium heat
pressure switch MPS remakes. When the medium heat pressure switch MPS remakes the variable speed furnace control continues heating
cycle. If medium heat pressure switch MPS does not remake within 45 sec after opening, the variable speed furnace control starts flashing
status code 31, shuts unit down, waits 2 minutes, stops flashing status code 31, and restarts heating cycle.
2. MEDIUM HEAT TO HIGH HEAT TRANSITION - If the medium heat pressure switch MPS opens while transitioning to high heat, the
variable speed furnace control ramps inducer RPM up until the medium heat pressure switch MPS remakes. When the medium heat
pressure switch MPS remakes the variable speed furnace control continues heating cycle. If medium heat pressure switch MPS does not
remake within 45 sec after opening, the variable speed furnace control starts flashing status code 31, shuts unit down, waits 2 minutes, stops
flashing status code 31, and restarts heating cycle.
3. STEADY-STATE - If the medium heat pressure switch MPS opens the variable speed furnace control starts flashing status code 31 and
ramps inducer RPM up until the medium heat pressure switch MPS remakes. When the medium heat pressure switch MPS remakes the
variable speed furnace control stops flashing status code 31 and continues heating cycle. If medium heat pressure switch MPS does not
remake within 45 sec after opening, the variable speed furnace control shuts the unit down and continues flashing status code 31. After the
blower off-delay is completed the variable speed furnace control will stop displaying status code 31 and if there is a call for heat, begin a new
heating cycle.
4. HIGH HEAT TO MEDIUM HEAT TRANSITION - If the medium heat pressure switch MPS opens while transitioning to medium heat, the
variable speed furnace control ramps inducer RPM up until the medium heat pressure switch MPS remakes. When the medium heat
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