Display Menu Guide │ Tx I&O Manual
CH mode – determines the operational mode for central heating:
0 – no outdoor sensor is needed; central heat demand is generated by a thermostat call to
boiler terminals 7 and 8. Boiler operates to setting 2-01; there is no outdoor reset.
1 – outdoor sensor is needed; central heat demand is generated by a thermostat call to boiler
terminals 7 and 8. Boiler operates in-between settings 2-01 and 2-05 depending on OD temp.
2 – outdoor sensor is needed; central heat demand is generated when the OD temp is below
the Warm weather shutdown setting (2-04). Boiler operates in-between settings 2-01 and 2-
05 depending on OD temp. An optional “nighttime setback” or “time of day” switch can be
applied to terminals 7 and 8; contact closure initiates “Night Setback Mode”, where the boiler
target temperature is reduced by the Night Setback Temperature setting (2-33).
3 – no outdoor sensor is needed; central heat demand is always present, boiler operates to
setting 2-01.
4 – setpoint from external analog input (0-10VDC); 2 volts for minimum CH setpoint, 10
volts for maximum CH setpoint. Use of an addition interface board through Argus Link is
required.
5 – modulation from external analog input (0-10VDC); 2 volts for minimum modulation, 10
volts for maximum modulation. Use of an addition interface board through Argus Link is
required.
Warm weather shutdown – inhibits central heat operation when the outdoor temperature reading goes
above this setting. Range = 35 to 100⁰F
CH setpoint (at OD = 70⁰F) – establishes the boiler operating temperature during central heat
demands when the outdoor temperature is 70⁰F or greater. Set to the minimum desired boiler
temperature for the application, e.g. 70-90⁰F for infloor; 100-120⁰F for cast-iron; 110-140⁰F for
baseboard. Range = 60 to 140⁰F
Temperature boost – determines the increase in boiler target temperature for every 15 minutes of
continuous central heat demand. Only applicable when an outdoor sensor is used (i.e. CH modes 1 &
2). Target temperature will not exceed CH setpoint setting 2-01. Range = 0 to 36⁰F
DHW setpoint – establishes: a) tank temperature setting for DHW mode 1 [e.g. 130-140⁰F], b) boiler
outlet setpoint for DHW mode 2 [e.g. 170-190⁰F] or c) DHW temperature for Tx-Combi [e.g. 120-
140⁰F]. Range = 104-190⁰F
DHW mode – determines the operational mode for DHW; for non-combi models Tx51-200 choose
between options 0, 1 and 2; for Tx-Combi models choose between options 0 and 5:
0 – off; boiler will not attempt to heat DHW in any way.
1 – tank sensor, NTI P/N: 84632, is installed in the indirect water heater and wired to boiler
terminals 3 and 6. Tank temperature is adjusted via setting 2-07.
2 – tank thermostat is installed in the indirect water heater and wired to boiler terminals 3 and
6. Setting 2-07 determines boiler outlet temperature during DHW demands. (Default setting
for Tx51-200)
3 & 4 – settings are not applicable.
5 – DHW mode setting for Tx-Combi model. Setting 2-07 determines DHW outlet
temperature.
DHW priority timer – a timer that accumulates during a simultaneous DHW and CH demand. Each
time the timer exceeds the “DHW priority timer” setting, the priority switches from one demand to the
other (i.e. DHW to CH). Note: DHW is assigned priority first. Range = 1-240 minutes
Preheat mode – when set to ON, the boiler preheats the DHW inside the brazed plate heat exchanger
of a Tx-Combi model, to reduce the time required for hot water to reach the fixture. Preheat helps
limit the effect of “cold water sandwich” (not applicable for non-combi models Tx51-200). When set
to OFF, the boiler does not preheat the DHW. Range = ON/OFF
Appliance selection (type) – indicates what boiler model the controller is configured to operate with:
(See Section 17.0 for instruction on changing the appliance selection (type)).
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