Thermostat Sub Bases

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
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