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THX9321 PRESTIGE
®
2.0 AND THX9421 PRESTIGE
®
IAQ 2.0 WITH EIM
68-0311—01 110
Fig. 221. 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—geo-
thermal (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 116.
4 Y2 used with heat pumps that have 2 compressor stages.
NOTE: For setup and operation, see “Geothermal Radiant Heat” beginning on page 62.
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
M31481
RADIANT HEAT
ZONE MODULE
VALVE
PUMP
END
SWITCH
C
R
3
4
2
1
OPTIONAL
JUMPER