Thermostat Sub Bases

Q539 Series 
 Sub Base Specifactions SheetQ674 Series Sub Base Specifactions Sheet

Part # For Thermostat System Switch Fan Switch Terminal Designations
Q539A1014 T87F Series Cool-Off-Heat On-Auto R,W,Y,B,G,O
Q539A1121 T87F Series Cool-Off-Heat On-Auto R,W,Y,B(a),G,O
Q539J1006(b) T87F Series Cool-Off-Heat On-Auto R,W,Y,B,G,O,P
Q674B1075(b) T874A-D Electric
Heat Applications
Heat-Off-Cool Auto-On R1,Y1,Y2,W1,W2,G,O,B
Q674E1049 T874A-D Off-Heat-Auto-Cool Auto-On Rh,Rc,Y1,Y2,W1,W2,G,O,B(c)
(a)   Sub-base has "4" terminal, which is same as Honeywell "B" terminal
(b)  Auto fan on both heat and cool. For electric heat applications
(c)  O and B terminals are continuously energized in the Auto mode
Related Items
Standard Heat/Cool Thermostats   |   Digital Thermostats   |   Programmable Thermostats   |   Line Voltage Thermostat
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