Tx I&O Manual │Display Menu Guide
Minimum firing rate – allows the installer to increase the minimum modulation/firing rate of the
boiler; this may be necessary for troubleshooting. Range = 20-44%
Maximum firing rate CH – allows the installer to decrease the maximum modulation/firing rate of
the boiler when operating on a central heat demand; this may be necessary for troubleshooting or de-
rating the boiler for operation with glycol. Range = 60-100%
Maximum firing rate DHW – allows the installer to decrease the maximum modulation/firing rate of
the boiler when operating on a domestic hot water demand; this may be necessary for troubleshooting
or de-rating the boiler for operation with glycol. Range = 60-100%
Firing rate test – allows the installer to force maximum or minimum modulation rates for the purpose
of troubleshooting and burner setup (i.e. combustion analysis):
0 = Automatic; burner modulation is controlled by the controller.
1 = Minimum; burner operates at the minimum modulation rate.
2 = Ignition; burner operates at the ignition/light-off modulation rate.
3 = Maximum; burner operates at the maximum modulation rate.
Note: control will end test (return setting to 0) if the boiler outlet temperature exceeds 176⁰F. Return
setting to 0 when testing is complete.
Service reminder status – a service reminder, indicated by “Att 7” on the screen, occurs every 365
days. The service reminder is reset by adjusting 2-16 to “OFF”.
Boiler pump postpurge – length of time the Boiler Pump output remains powered once all demands
end. Range = 10-90seconds
CH pump postpurge – length of time the CH Pump output remains powered at the end of a central
heat demand. Range = 0-90seconds
DHW pump postpurge – length of time the DHW Pump output remains powered at the end of a
DHW demand. Range = 0-255seconds
Cascade boiler address – assign a unique boiler address for each boiler in a cascade; managing boiler
address must be set to 1. Managing boiler must have S4 switch set to ON; all others must be set to
OFF. Central heat and DHW demands and setpoints are received and set at the managing boiler only.
A boiler that is not part of a cascade must have the boiler address set to 0.
Range = 0-16
Emergency setpoint – used only for a cascade system, assigns a permanent boiler operating
temperature that is used if communication between boilers is lost, or if the system temperature sensor
becomes disconnected. Must be set on each boiler in the cascade. Range = 104-190⁰F
Rotation interval – establishes the time between the rotation of start and stop sequences of boilers in
a cascade. Range = 0-30days (0=disable)
DHW boiler address – feature not available with first generation Tx boilers.
System pump postpurge – feature not available with first generation Tx boilers.
Flame failures – accumulation of the number of flame outages that occurred during run.
Ignition attempts success – accumulation of the number of successful ignitions.
Ignition attempts failed – accumulation of the number of failed ignition attempts.
Run time CH – accumulation of the number of hours that the burner has been firing for the purpose
of central heating.
Run time DHW – accumulation of the number of hours that the burner has been firing for the purpose
of DHW.
Post purge time – length of time the combustion blower operates at the end of a burner sequence.
Recommend increasing post purge time for installations with long exhaust venting.
Range = 5-60seconds
Units selection – allows the installer to select US or metric units. Range = ⁰F or ⁰C
External Ignition – determines the power source for the igniter spark. Range = OFF or On
OFF = internal ignition transformer (serial numbers prior to 72171)
On = external ignition transformer (serial numbers greater than 72170)