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Thermostats — Three thermostats are available for field
installation:
Honeywell T834C manual changeover, single-stage heat
thermostat features:
• off-cool-heat system switch
• on-auto fan mode switch
• single-stage electric heat
• outside air signal
Honeywell T8500 digital, automatic/manual changeover,
2-stage heat thermostat features:
• digital display of temperatures and all functions
• off-cool-heat-auto system mode buttons
• single speed fan operation
• on-auto fan mode button
• single or two stage electric heat signal
• outside air signal
• remote temperature sensor available
Sunne T170 single-stage heat, 2-pipe heat/cool auto
changeover thermostat features:
• digital display of ambient temperature and operating
mode
• single fan speed operation, power and operating mode
buttons
• continuous fan operation, cycling water control valve
• 4-pipe ACO/MCO (automatic changeover/manual
changeover) with “on-auto” fan mode button
• one or 2 stage electric heat signal available
• purge cycle and temperature sensor for 2-pipe cold
water/hot water systems
• programmable operating range, dead band, digital dis-
play, temperature set-back
THERMOSTAT FUNCTIONS
LEGEND
Valve packages — Valve packages are factory assembled
for field installation. Motorized valves (24 v) can be operat-
ed with power on with spring return or power off/power
on.
It is recommended that basic motor controls are ordered
when valve packages are ordered.
SYSTEM FUNCTION CHANGEOVER
THERMOSTATS
Honeywell
T834C
Honeywell
T8500
Sunne
T170
2Pipe HW-Heat Only ACO — XX
2 Pipe CW-Cool Only ACO — XX
2Pipe
CW/HW
Heat/Cool
MCO ——X
ACO ——X
2Pipe
CW/HW
Heat/Cool with
Aux. Electric Heat
MCO ——X
ACO ——X
2Pipe
CW-Cooling with
To t al Electric Heat
MCO X X X
ACO — XX
4Pipe
CW/HW
Heat/Cool
MCO X X X
ACO — XX
ACO — Automatic Changeover
Aux — Auxiliary
CW — Chilled Water
HW — Hot Water
MCO — Manual Changeover