Honeywell Prestige 2.0 THX9421 - Page 147

THX9321 PRESTIGE
®
2.0 AND THX9421 PRESTIGE
®
IAQ WITH EIM
147 68-0311—07
Fig. 337. Geothermal radiant heat with geothermal forced air and backup heat using separate transformer for the
radiant heat.
1 U1, U2 or U3 terminals must be used for geothermal radiant heat (ISU 2010). Thermostat allows 2 stages of radiant
heat—geothermal (stage 1) and boiler (stage 2).
2 “U” terminals are normally open dry contacts when set up for geothermal radiant heat. You must install a field jumper if
radiant heat is powered by system transformer. Do NOT install a field jumper if radiant heat has its own transformer.
3 L/A terminal sends continuous output when thermostat is set to EM HEAT mode except when set up for Economizer or
TOD. See “Economizer Module Wiring Diagrams” beginning on page 154.
4 Y2 used with heat pumps that have 2 compressor stages.
NOTE: For setup and operation, see “Geothermal Radiant Heat” beginning on page 100.
O/B
AUX1
AUX2
O
W1
W2
Y
Y2
G
R
C
O
Y
Y2
R
C
TRANSFORMER
24
VAC
120
VAC
L/A
TO THERMOSTAT
THERMOSTAT/EIM
HEAT PUMP
FURNACE
HEAT PUMP
M34525
RADIANT HEAT
ZONE MODULE
VALVE
PUMP
END SWITCH
C
R
3
4
1