FAN
RELAY
R
AIR HANDLER
C
G
Y1
1ST STAGE
COOL
L1
L2
120
VAC
24
VAC
IMPORTANT!
The thermostat B
terminal is for reversing
valve-heat. DO NOT
connect the B terminal
to common side of
transformer.
G
Y1
W1
Y2
W2
RH
RC
O
APRILAIRE MODEL
8870 THERMOSTAT
COMMUNICATION
TERMINALS
B
C
RSB
RSR
RSC
R
RSA
B+
A-
A+
B-
REF
REMOTE
SENSOR(S)
NOTE: HVAC installer may need to connect
24V AC to the R and C terminals to check the
HVAC operation. If the Automation system
is to be installed after the HVAC installation,
leave the R and C terminals connected to
ensure the HVAC system operates. If the
automation system is installed before the
HVAC wiring, then DO NOT connect HVAC
wires to R and C.
1ST
STG
COOL
AIR CONDITIONER
Y1
C
1ST
STG
HEAT
W1
C
120
VAC
24
VAC
L1
L2
R
BOILER
SEE
NOTE
24V FIELD WIRING
FACTORY WIRING
OPTIONAL 24V
FIELD WIRING (SEE NOTE)
19
DIAGRAM 4 – BOILER WITH AC (TWO TRANSFORMERS)
Summary of Contents for 8870
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