Aprilaire 8800 Operating and maintenance manual

Model 8800 Communicating Thermostat
Model 8800 Communicating Thermostat
Programmer’s Manual
READ AND SAVE THESE INSTRUCTIONS
TABLE OF CONTENTS
Introduction............................................. 1
Protocol ................................................ 1
System Interface ........................................ 2
Timing and Synchronization .............................. 2
Host Message Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Response Expected ...................................... 3
No Response Expected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Node Message Types .................................... 3
Explicit Address Command Response ....................... 4
Global Address Command Response ........................ 4
Unsolicited Message..................................... 4
Command Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Host Command Syntax ................................... 5
Node Message Syntax ................................... 5
Commands Table of Contents ............................. 6
Command Details........................................ 8
Thermostat Configuration Commands ....................... 8
Communication Control Commands . . . . . . . . . . . . . . . . . . . . . . . . 15
Change of State Report Control Commands ................. 18
Setup Commands ...................................... 20
Alarm Commands ...................................... 25
Lockout Commands ..................................... 27
Sensor Commands...................................... 31
Temperature Control Commands .......................... 36
Humidity Control Commands ............................. 44
Program and Schedule Commands......................... 46
Status Commands ...................................... 52
Messaging Commands .................................. 55
INTRODUCTION
This document contains information needed to write interface code for the Aprilaire Model 8800 Communicating Thermostat. For wiring and
thermostat setup refer to the 8800 System Installation Manual (RPC part no. 10009416).
PROTOCOL
The proprietary ASCII protocol is for communication between a Host controller and up to 64 Model 8800 Communicating Thermostats. The
protocol is based upon the Model 8870 Communicating Thermostat protocol, but has an expanded command set to utilize the additional features
of the Model 8800 Communicating Thermostat.
1

SYSTEM INTERFACE
The System Network communication interface is a non-isolated, 4-wire, full-duplex RS-485 communication link. The ‘A’ terminals are transmit
(reference automation system) and the ‘B’ terminals are the receive pair (reference automation system). The baud rate is 9,600 bps by default.
It can be changed using the user interface (See Setup Screens) or through a command from the Host controller. When the baud rate is changed,
the protocol timing is scaled as well.
TIMING AND SYNCHRONIZATION
The protocol uses time division multiple access (TMDA) to allow each node to have exclusive control of the receive lines of the Host controller
for a specified duration.
The communication frame is divided into a maximum of 64 time slots. The number of time slots are based on the setting for number of
thermostats on the network. The default setting is 64. Each slot is divided into four sub-slots. Legacy timing is based on 16-bit timer running at
1MHz (e.g. 65536 * 1/1MHz = 65.536 ms).
Baud Rate Slot Width Sub-slot Width
9,600 262.144 ms 65.536 ms
19,200 131.072 ms 32.768 ms
The four sub-slots of a slot are:
Sub-slot Name Description
1Solicited Response Sub-slot For a node to respond to a Host command
2Unsolicited Message Sub-slot For a node to send an unsolicited message to the Host
3Expansion Sub-slot 1 Reserved
4Expansion Sub-slot 2 Reserved
The following figure depicts the communication frame and slot divisions. (NOTE: Timing shown is for 9,600 bps and is rounded for illustrative purposes.)
Communication Frame
Slot 1 Slot 2 Slot 3 Slot 4 Slot 5 ••• Slot 63 Slot 64
262 ms
Solicited Response Sub-slot Unsolicited Message Sub-slot Expansion Sub-slot 1 Expansion Sub-slot 2
65 ms 65 ms 65 ms 65 ms
Slot
2

In a TDMA system, all thermostats and the Host controller must be synchronized to ensure proper timing for control of the Host controller’s
receive lines. This is accomplished by synchronizing on the receipt of the Carriage Return <CR> character. Upon receipt of the <CR> character,
each connected node resets its communication timer, slot counter and frame counter, regardless of message syntax or content. The node may not
begin sending unsolicited messages until a carriage return is received and synchronization has occurred. In addition, the Host controller transmits
a <CR> every 12 hours to ensure accurate synchronization. Also, upon completion the last slot (maximum address), the Communication Frame
resets, setting the slot counter to 1, and the cycle repeats. The following figure depicts slot timing with and without receipt of a carriage return.
Slot 1 Slot 2 Slot 3 Slot 4 Slot 5 ••• Slot 63 Slot 64 Slot 1 Slot 2 Slot 3 Slot 4 Slot 1 Slot 2 Slot 3 Slot 4 •••
t = 0 Time
Slot counter is reset
after max address
slot is completed
Slot counter is reset
after Carriage Return
is received
NOTE: The number of slots shown is based on the max number of thermostats and thus a max address of 64. Applications with a lower max
node address restarts the slot counter after the max address slot has completed.
HOST MESSAGE TYPES
Host controller message transmissions are not governed by slot timing since the Host controller is the only device on its respective transmit line.
The Host controller does however need to meet specific timing to prevent missed commands and collisions. Command timing is determined by
the type of response as follows:
When a response to an Explicit Address Command is desired, slot width + sub-slot width time must elapse after issuing an Explicit Address
Command before issuing a second command to the same node.
When a response to a Global Address Command is desired, slot width * max node address time must elapse after issuing a Global Address
Command before issuing a second command when a response is desired.
RESPONSE EXPECTED
When no response to either an Explicit Address Command or Global Address Command is desired, slot width + sub-slot width time must
elapse after issuing either command before issuing a second command to the same node.
NO RESPONSE EXPECTED
NODE MESSAGE TYPES
There are three node message types. Each message type has a specific time for the node to transmit a message. The three message types are
as follows:
1. Explicit Address Command Response
2. Global Address Command Response
3. Unsolicited Message
As shown in the figure below, during the nth slot the nth node responds to a global or explicit address command during the first sub-slot and/or
sends an Unsolicited Message during the second sub-slot.
Slot n
Address nGlobal or Explicit
Response Sub-slot
Address nUnsolicited
Message Sub-slot Expansion Sub-slot 1 Expansion Sub-slot 2
3

Explicit Address Commands are commands sent by the Host controller to a single node at a specific address. Upon receipt of a completed Explicit
Address Command from the Host controller (including the <CR>), each node determines if it is the addressee of the command. If the node is not
the addressee of the command, the command is discarded. If the node is the addressee of the command, it interprets and executes the command
and then prepares a response for the Host controller (depending on the command response control setting C1 – C19).
The command response (if required by the command response control setting) is transmitted by the node during the Solicited Response Sub-slot of
the slot. Since the communication timing and control variables are reset upon receipt of the <CR> from the Host controller, Slot 1 and the Solicited
Response Sub-slot are the currently active slot and sub-slot. As such, if the explicit address command was for node 1, the node may begin
transmitting the response immediately after the command is received. The entire response must be transmitted within the Solicited Response
Sub-slot of the slot. (Maximum bytes per response: 62 = 65ms * 10 / 9600.)
EXPLICIT ADDRESS COMMAND RESPONSE
Global Address Commands are commands sent by the Host controller to all thermostats. Upon receipt of a completed Global Address Command
from the Host controller (including the <CR>), each node determines that the command is a global command. Each node interprets and executes
the command and then prepares a response for the Host controller (depending on the command response control setting C1 – C19).
The command response (if required by the command response control setting) is transmitted by the node during the Solicited Response Sub-slot
of Slot n, where nis the node address. Since the communication timing and control variables are reset upon receipt of the <CR> from the
Host controller, each node must wait for its respective slot before transmitting its response. The slot time from the reset caused by the <CR>
synchronization can be calculated using the following equation:
t = (n–1) x (slot width)
Where nis the node address and slot width is the duration of a slot based on the baud rate.
The node may begin transmitting the response once the communication timer matches the calculated time t, which corresponds to the start of
the Solicited Message Sub-slot of its respective slot. The entire response must be transmitted within the Solicited Response Sub-slot.
(Maximum bytes per response: 62 = 65ms * 10 / 9600.)
GLOBAL ADDRESS COMMAND RESPONSE
Unsolicited Messages are messages sent by the node to the Host controller when a Change-of-State (COS) is detected. Change of State
responses are sent by the node so that the Host controller need not poll each node to determine if any node control variable change has
occurred.
An Unsolicited Message is transmitted by the node during the Unsolicited Response Sub-slot of Slot n, where nis the node address. Slot timing
is synchronized upon a previous receipt of a <CR>. Each node must wait for its respective slot and sub-slot before transmitting its response. The
transmit time from the last synchronization or Communication Frame restart (start of Slot 1) can be calculated using the following equation:
t = (n–1) x (slot width) + (sub-slot width)
Where nis the node address and slot width and sub-slot width are the durations of a slot and sub-slot, respectively, based on the baud rate.
The node may begin transmitting the message once the communication timer matches the calculated time t, which corresponds to the start
of the Unsolicited Message Sub-slot of its respective slot. The entire response must be transmitted within the Unsolicited Response Sub-slot.
(Maximum bytes per response: 62 = 65ms * 10 / 9600.)
UNSOLICITED MESSAGE
4

COMMAND SYNTAX
The Model 8800 Communicating thermostat command set includes the Model 8870 Communicating thermostat commands with the addition of a
subset of commands for programmable thermostat functionality and general feature enhancements.
The Host controller has two types of commands: query and assignment. Each of these command types has a specific syntax. Command syntax is
not case sensitive. All commands begin with SN.
A query type command has the following syntax:
SN[#][command]?<CR>
An assignment type command has the following syntax:
SN[#][command]=[value]<CR>
The following table details each component of the command syntax:
Identifier Descriptor Description
SN Command start First two characters of all commands.
[#] Address Explicit Address Commands immediately follow SN with the address [#]. The address
range is 1 – 64 and corresponds to the thermostat address. Single-digit addresses may be
sent as a two-digit address by prepending the address with a zero.
Global Address Commands may follow SN with the address zero (0) or the address may be
omitted entirely.
[Command] Command name See Command Table for list of commands.
?Query Indicates a query type command.
=Assignment Indicates an assignment type command. (Always immediately followed by [value]).
[value] Assignment value Value for assignment type command.
<CR> Command terminator All commands are terminated with the carriage return character.
NOTE: Following the initial SN[#] syntax, the space character may be used to separate the components of the command for readability and
clarity with the exception of =[value].
HOST COMMAND SYNTAX
A node message is in the form of a command response or an unsolicited message. The node has three message syntaxes which are determined
by the command and if a name has been assigned. All messages are upper case and only use the space character to separate the address
and command and within the assignment value (i.e. after the equals sign). Commands that cannot be interpreted are ignored. There is no error
response message.
For short messages, the following syntax is used:
SN[#] [command]=[value]<CR>
In addition, if a location name is assigned, the following syntax is used:
SN[#][name] [command]=[value]<CR>
For the NAME command response, the following syntax is used:
SN[#] [value]<CR>
NODE MESSAGE SYNTAX
5

The following table details each component of the message syntaxes:
Identifier Descriptor Description
SN Message start First two characters of all messages.
[#] Address Node address.
[name] Thermostat name Thermostat location name.
[Command] Command name See Command Table for list of commands.
=Assignment Used to show assignment of the variable referenced by the command.
[value] Variable value Value of the variable referenced by the command.
<CR> Message terminator All messages are terminated with the carriage return character.
COMMANDS TABLE OF CONTENTS
Command Description Page
Thermostat Configuration
EQUIPCONFIG Thermostat heat source, staging and equipment
type
8
EQUIP Thermostat control setup and auxiliary stages 8
CT Temperature or humidity controller configuration 9
DIF1 1st Stage differential value 9
DIF2 2nd Stage differential value 9
DIF3 3rd Stage differential value 9
DIF4 4th Stage differential value 9
EXTFAN Extended fan configurations 10
INTEGRAL PI control integral factor period 10
AUTOM Auto changeover mode setting 11
EQONTIME Minimum equipment on time 11
HOFFTIME Minimum heat equipment off time 11
COFFTIME Minimum compressor off time 12
ACHGTIME Minimum auto changeover time 12
DBAND Auto mode deadband configuration 12
RECOV Progressive recovery configuration 13
HIBP High balance point configuration 13
LOBP Low balance point configuration 14
OFFSET Offset applied to control and display
temperature
14
Command Description Page
Communication Control
NETAD Network communication address 15
<NULL> Report connected nodes 15
NETST Number of connected nodes 15
BAUD Network communication baud rate 16
ID Thermostat model and software revision 16
NAME Thermostat location name string 17
CR Command response control 17
Change of State Report Control
CP COS reporting configuration 18
C1 COS C1 report setting 19
C2 COS C2 report setting 19
C3 COS C3 report setting 19
C4 COS C4 report setting 19
C5 COS C5 report setting 19
C6 COS C6 report setting 19
C7 COS C7 report setting 19
C8 COS C8 report setting 19
C9 COS C9 report setting 19
C10 COS C10 report setting 19
C11 COS C11 report setting 19
C12 COS C12 report setting 19
C13 COS C13 report setting 19
C14 COS C14 report setting 19
C15 COS C15 report setting 19
C16 COS C16 report setting 19
C17 COS C17 report setting 19
C18 COS C18 report setting 19
C19 COS C19 report setting 19
6

Command Description Page
Setup
SCALE Command temperature scale 20
TIME Thermostat time 20
DATE Thermostat calendar date 21
PROGFMT Program format configuration 21
EVTCFG Program event configuration 22
EVTSDAY Number of events per day configuration 22
DLS Daylight savings configuration 23
BLTLVL Backlight intensity level 23
CONSTBLT Constant backlight configuration 24
BLTON Backlight activation 24
Alarms
FLTALMP Air filter alarm period configuration 25
FLTALM Air filter alarm status 26
WPALMP Water panel alarm period configuration 25
WPALM Water panel alarm status 26
HUMTYP Humidifier type configuration 26
DEHALMP Dehumidifier alarm period configuration 25
DEHALM Dehumidifier alarm status 26
SYSALMP HVAC system alarm period configuration 25
SYSALM HVAC system alarm status 26
Lockout
FANLK User fan mode lockout configuration 27
MODELK User system mode lockout configuration 27
NETLK User network override lockout configuration 28
UPDNLK User setpoint lockout configuration 28
LKTIME Time-limited lockout temporary change period 29
LKLIMIT Temperature setpoint change lockout limit 29
PIN Security pin code setting 30
Sensors
TEMP, T Report thermostat room temperature control
value
31
HUM Report humidistat room humidity control value 31
RSM Identify all external sensors on the node’s local
network
32
RxSy Report local network sensor value 33
OT, R Outdoor temperature value 34
OH Report outdoor humidity value 35
BIHUM Report thermostat built-in humidity sensor value 35
RTS Report thermostat remote temperature sensor
value
35
Command Description Page
Temperature Control
MODE, M Thermostat or humidistat control mode setting 36
FAN, F Thermostat fan mode setting 37
SH Controlling heat setpoint value 38
SH++ Increments the controlling heat setpoint value 39
SH-- Decrements the controlling heat setpoint value 39
SC Controlling cool setpoint value 40
SC++ Increments the controlling cool setpoint value 41
SC-- Decrements the controlling cool setpoint value 41
SControlling setpoint value 42
SP++ Increments the controlling setpoint value 43
SP-- Decrements the controlling setpoint value 43
Humidity Control
SHUM Humidification setpoint value 44
SHUM++ Increments humidification setpoint value 44
SHUM-- Decrements humidification setpoint value 44
SDEH Dehumidification setpoint value 45
SDEH++ Increments dehumidification setpoint value 45
SDEH-- Decrements dehumidification setpoint value 45
Program and Schedule
PROGDxEy Program event (Day: x = 1-7; Event: y = 1-4) 46-47
COPYDx Copy from program day x 48
PERMHOLD Permanent hold 49
VACHOLD Vacation hold configuration 50
TEMPHOLD Temporary hold configuration 51
Status
HVAC, H Thermostat relay output status 52
RECOVSTAT Progressive recovery status 52
HOLDSTAT Thermostat hold status (TEMP and VAC are
read-only)
53
HOLD Network communication override status 53
PROGUPDT Program modification status 54
ERROR Node error status 54
Messaging
PMES1 First message in permanent message sequence 55
PMES2 Second message in permanent message
sequence
55
PMES3 Third message in permanent message sequence 55
PMES4 Fourth message in permanent message
sequence
55
TMPMES Temporary message 55
7

COMMAND DETAILS
Default values are in bold.
EQUIPCONFIG Thermostat node equipment configuration settings COS:NA
Permissions: Read only
Query
Command
Syntax: SN[#] EQUIPCONFIG?<CR>
Description: Requests the thermostat master/slave, gas/electric, number of stages and equipment type settings.
Response Syntax: SN[#] EQUIPCONFIG=[w][x][y][z]<CR>
Example: SN1 EQUIPCONFIG=0101<CR>
Node address 1 responds with slave, gas, single and heat/cool settings.
Parameters Range
w: master or slave code [0 – 1]
0: slave
1: master
x: gas or electric heating code [0 – 1]
0: electric
1: gas
y: single or multi stage code [0 – 1]
0: single
1: multi
z: heat pump or heat/cool equipment type code [0 – 1]
0: heat pump
1: heat/cool
The equipment type is selected using the HP/HC option switch. The master/slave setting is always set to slave and cannot be modified.
EQUIP Additional thermostat equipment configuration settings COS: N/A
Permissions: Read only
Query
Command
Syntax: SN[#] EQUIP?<CR>
Description: Requests the thermostat control setup, auxiliary stages and extended fan settings.
Response Syntax: SN[#] EQUIP=[x][y]<CR>
Example: SN1 EQUIP=01<CR>
Node address 1 responds with heat and cool control setup and 1 auxiliary stage settings.
Parameters Range
x: control setup code [0 – 2]
0: heat and cool
1: heat only
2: cool only
y: auxiliary heat stages [1 – 2]
1: 1 stage
2: 2 stages
NOTE: Control setup is only applicable for heat/cool equipment type and auxiliary heat stages is only applicable for heat pump equipment type.
THERMOSTAT CONFIGURATION COMMANDS
8

CT Temperature or humidity controller configuration COS: N/A
Permissions: Read only
Query
Command
Syntax: SN[#] CT?<CR>
Description: Requests the controller configuration setting.
Response Syntax: SN[#] CT=[value]<CR>
Example: SN1 CT=0<CR>
Node address 1 responds with a controller configuration of thermostat.
Parameters Range
value: controller setting code [0 – 1]
0: temperature controller (thermostat node)
1: humidity controller (humidistat node)
DIF1, DIF2, DIF3, DIF4 Stages 1 – 4 differential settings COS: N/A
Permissions: Read/Write
Query
Command
Syntax: SN[#] DIF[n]?<CR>
Description: Requests the stage [n] differential.
Example: SN[#] DIF1?<CR>
Assignment
Command
Syntax: SN[#] DIF[n]=[value]<CR>
Description: Sets the stage [n] differential to [value].
Example: SN1 DIF2=3<CR>
Response Syntax: SN[#] DIF[n]=[value]<CR>
Example: SN1 DIF1=1<CR>
Node address 1 responds with stage 1 differential setting of 1.
Parameters Range
n: equipment stage [1 – 4]
1: 1st stage
2: 2nd stage
3: 3rd stage
4: 4th stage
value: differential setting code stage 1: [0 – 9]; stages 2-4: [1 – 9]
0: reserved
1: 1F or 0.5C
2: 2F or 1.0C
3: 3F or 1.5C
4: 4F or 2.0C
5: 5F or 2.5C
6: 6F or 3.0C
7: 7F or 3.5C
8: 8F or 4.0C
9: 9F or 4.5C
NOTE: Sending a DIF1 assignment command with a value of 0 resets the thermostat.
9

EXTFAN Extended fan control configurations COS: N/A
Permissions: Read/Write
Query
Command
Syntax: SN[#] EXTFAN?<CR>
Description: Requests the heat and cool extended fan configurations.
Assignment
Command
Syntax: SN[#] EXTFAN=[x][y]<CR>
Description: Sets the heat extended fan based on [x] and cool extended fan [y].
Example: SN EXTFAN=01<CR>
Response Syntax: SN[#] EXTFAN=[x][y]<CR>
Example: SN1 EXTFAN=00<CR>
Node address 1 responds with both extended fan configurations disabled.
Parameters Range
x: extended fan in heating code [0 – 1]
y: extended fan in cooling code [0 – 1]
0: disabled
1: enabled
This command is ignored if the controller type is set to humidistat.
INTEGRAL PI control integral factor period COS: N/A
Permissions: Read/Write
Query
Command
Syntax: SN[#] INTEGRAL?<CR>
Description: Requests the integral factor period setting.
Assignment
Command
Syntax: SN[#] INTEGRAL=[value]<CR>
Description: Sets the integral factor period to [value] minutes.
Examples: SN1 INTEGRAL=2<CR>
SN2 INTEGRAL=OFF<CR>
Response Syntax: SN[#] INTEGRAL=[value]<CR>
Example: SN1 INTEGRAL=4<CR>
Node address 1 responds with an integral factor period of 4 minutes.
Parameters Range
value: integral factor period in minutes [OFF, 1 – 5]
Default: 2
This command is ignored if the controller type is set to humidistat.
10