APRILAIRE MODEL
8570 THERMOSTAT
FAN
RELAY
1ST STAGE
AUX. HEAT
R
INDOOR UNIT - AIR HANDLER
C
G
Y2
Y1
W1
W2
L1
L2
120
VAC
24
VAC
2ND STAGE
EMER. HEAT
L
O
Y2
Y1
W1
C
R
1ST STAGE
COMP.
2ND STAGE
COMP.
REV.
VALVE
DEFROST
SERVICE
OUTDOOR UNIT - HEAT PUMP
SUPPLIED JUMPER
1ST STAGE COMP.
2ND STAGE COMP.
ZA
ZB
I+
I-
6504
CONNECTION
B
O
Y2
Y1
G
RC
R
RH
W1
W2
C
AHC
CONNECTION
SINGLE/MULTI – SET TO
MULTI FOR TWO STAGE
HEAT PUMP
ELECT/GAS- SET TO
ELECT FOR ELECTRIC
AUXILIARY HEAT, SET TO
GAS FOR FOSSIL FUEL
(DUAL FUEL) AUXILIARY
HEAT
O/B– SET TO “O” IF HEAT
PUMP REVERSING VALVE
MUST BE ENERGIZED
WHEN COOLING, SET TO
“B” IF IT IS TO BE
ENERGIZED IN HEATING
THERMOSTAT
CONFIGURATION
SWITCH SETTINGS
OUTDOOR (ODT)
& INDOOR (IDS)
TEMPERATURE
SENSORS
HC
SINGLE
B
GAS
HP
MULTI
O
ELECT
4
3
2
1
ON
NC
NO
COM EVENT
TRIGGERED
OUTPUT
(ETO)
IDS
ODT
GND
Diagram 8: Two-Stage Heat Pump
- 16- - 17-
(6) OPTIONAL – WIRE THE EVENT TRIGGERED OUTPUT (ETO)Terminals NO, COM and NC are the
Normally Open, Common and Normally
Closed outputs, respectively, of a relay
that can be used to control auxiliary
equipment. When the relay is on, a
circuit is complete between NO and
COM; when the relay is off a circuit is
complete between NC and COM. The
relay is programmed to be on or off,
with each of the programming events.
Examples of where this output might
be used include:
• Turn on outdoor ventilation for
programming periods of the day
when the building is occupied and
turn it off when unoccupied.
• Have an electronic air cleaner turn
on and off only when the building is
occupied to reduce maintenance
time/cost.
Y2
Y1
O/B
G
W2
W1
RH
RC
R
C
GND
ODT
IDS
I-
I+
MODEL 8570 THERMOSTAT
(shown with enclosure face removed)
ZB
ZA
NO
COM
NC