Thermo Pride CHX3-75N Installation And Operation Manual page 55

All installations and services must be performed by qualified service personnel.
memory, the LED will flash two green flashes. The control will flash the most recent error first and the
oldest error last (last in first out). There will be 2 seconds between codes. Solid LED error codes will not
be displayed.
DIAGNOSTIC FEATURES
The 50V51 control used on this furnace continuously monitors its operation and the operation of the
system.
If the sensed failure is in the system (external to the control), the red LED will flash in the following flash-
pause sequences to indicate failure status (each flash will last approximately 0.25 seconds, and each
pause will last approximately 2 seconds):
Red LED Flash (DS1)
1 - flame sensed when no flame should be present
2 - pressure switch stuck closed / inducer error
st
3 - 1 stage pressure switch stuck open / inducer error
4 - open limit switch
5 - open rollout / aux limit
6 - pressure switch cycle lockout
7 - external lockout (retries)
8 - external lockout (recycles)
9 - grounding or reversed polarity
10 - gas flow with no call for heat
11 - limit switch open – blower failure
12 - ignitor failure
Solid - internal GV error, micro, and frequency check
nd
3 double - 2 stage pressure switch stuck open / inducer error
The LED will also flash once at power-up.
Amber LED Flash (DS1)
1 – normal call for first stage heat
2 – normal call for second stage heat
3 – W2 present with no W1
4 – Y present with no G call
Rapid – low flame sense current
Green LED indicator (DS2) is present to obtain an estimate of the air flow rate (in CFM) produced by the
house air blower. This LED cycles regularly by providing a constant light, followed by a sequence of
flashes. Each flash can be translated to programmed CFM by using the following:
1 flash per 100(programmed) CFM
: Power must be disconnected before servicing.
49