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ILLUSTRATION 1 – System Components
Model 8870 Thermostat
RS-422 Communicating Thermostat controls single
or multi-stage heat/cool or heat pump HVAC systems.
Model 8811 Protocol Adapter
Use to convert RS-485 communication signal from Aprilaire
Communication System to RS-232 communication signal
readable by host computer. Supports up to 32 thermostats.
Model 8061 and 8062 Support Modules
Up to four can be connected to a single thermostat
to sense temperature or relative humidity at a
location remote from the thermostat.
Model 8818 Distribution Panel
Switches in the Distribution Panel allow power or
communications to be turned off at each individual
thermostat to make installation and troubleshooting easy.
RX TX
DATA
RS-232
RX TX
ENABLE
RS-485
RX TX
DATA
RS-485
POWER
Model 8811 Protocol Adapter
Power
7.5VAC RS-485 RS-485 RS-232
B+ B- REFA-
RCA+ A- B+ B- R CA+ A- B+ B- R CA+ A- B+ B- R CA+ A- B+ B-
A
B
A+
OFF ON
OFF ON
OFF ON
OFF ON
OFF ON
OFF ON
OFF ON
OFF ON
ON OFF
ON OFF
ON OFF
ON OFF
ON OFF
ON OFF
ON OFF
ON OFF
PWR
PWR
PWR
PWR
PWR
PWR
PWR
PWR
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
MAIN
PWR
ON OFF
RC
24VAC
FUSE SPARE FUSE
RCA+A-B+B-RCA+A-B+B-RCA+A-B+B-RCA+A-B+B-
1
COMPONENTS YOU WILL NEED… (see ILLUSTRATION 1)
• One Aprilaire
®
Model 8870 Communicating Thermostat for each
zone or single zone HVAC system
• One Aprilaire Model 8818 Distribution Panel per eight (8)
thermostats in the system
• One Aprilaire Model 8811 Protocol Adapter per 32 thermostats
or one per Model 8823 system controller
• 4 to 8 conductor thermostat cable depending on equipment
stages (18 – 20 gauge)
• Category 5 communication wire (4-pair twisted cable)
• One 24V AC transformer, ungrounded (part number 8027) per
8818 Distribution Panel
• RS-232 or RS-485 based automation system such as the
Aprilaire Model 8823 System Controller
• OPTIONAL: Aprilaire Model 8061 Temperature Support Module
or Model 8062 Temperature/Humidity Support Module
GET ALL THE COMPONENTS YOU WILL NEED
Step 1
TOOLS YOU WILL NEED…
• Small flat head screwdriver for terminal
screws (1/8” wide tip)
• Medium size flat/phillips head screwdriver for
component mounting screws
• Volt/ohm meter
• Computer with available com port (RS-232)
and terminal emulator such as HyperTerminal
(for system checkout)
• Wire strippers
• Small level (use to mount components level,
required for appearance only)