W8635A
Equipment Interface Module
INSTALLATION INSTRUCTIONS
APPLICATION
The W8635A Equipment Interface Module (EIM) provides 24 Vac control of single or multistage conventional
HVAC equipment when used with a T8635L Microelec-
Table 1. Description.
Model Application Stages Terminals Comments
W8635A Conventional gas, oil
or electric heat
Up to 2 heat/
2 cool
INSTALLATION
tronic Communicating Programmable Thermostat. The
W8635A can be used w ith up to 2 heat/2 cool conventional applications. See Table 1.
1, 2, 3, C, R, Rh, Rc,
G, W1, W2, Y1, Y2
1.
Use with T8635L Communicating
Thermostat
Locate the W8635A in the equipment room near
the HVAC equipment. See Fig. 1.
When Installing this Product…
Read these instructions carefully. Failure to follow
1.
these instructions can damage the product or
cause a hazardous condition.
Check the ratings given in the instructions and on
2.
the product to make sure the product is suitable for
your application.
Installer must be a trained, experienced service
3.
technician.
After completing installation, use these instructions
4.
to check out the product operation.
W8635
CAUTION
Voltage Hazard.
Can cause electrical shock or equ ip m ent
damage.
Disconnect power before supply before beginning
installation.
POSSIBLE
MOUNTING
LOCATION
W8635
POSSIBLE
MOUNTING
LOCATION
Location
CAUTION
Mounting Location Hazard.
Mounting W8635A inside HVAC equipment
can damage the EIM.
Mount the W8635A only on the outside of HVAC
equipment.
® U.S. Registered Trademark
Copyright © 2000 Honeywell Inc. • • All Rights Reserved
FURNACE OR BOILER
Fig. 1. Selecting W8635A Equipm ent
Interface Module location.
Remove the cover from the W8635A by pulling on
2.
the edge of the module.
Locate the two mounting holes. See Fig. 2.
3.
WATER HEATER
M16637A
69-1339- 2
W8635A EQUIPMENT INTERFACE MODULE
FOR WRAPAROUND
CONNECTION—
STRIP 7/16 IN. (11 MM)
FOR STRAIGHT
CONNECTION—
STRIP 5/16 IN. (8 MM)
M16639
W8635
WALL
W8635
MOUNTING
HOLES (2)
Fig. 2. Mounting W8635A
Equipment Interface Modul e.
Position the W8635A on the wall or on the cold air
4.
return.
Level the W8635A for appearance only; the device
5.
functions properly even when not level.
Use a pencil to mark the position of the mounting
6.
holes on the wall or cold air return.
Remove the W8635A from the wall or cold air
7.
return and drill 3/ 1 6 in . ho l e s in th e wall (if drywall)
where marked. For firmer materials such as plaster
or wood, drill 7/32 in. holes.
When mounting on the cold air return, drill a pilot
8.
hole where marked.
Gently tap the anchors (provided) into the holes
9.
until flush with the w all.
Reposition the W8635A over the holes.
10.
Loosely insert the screws into the holes and tighten
11.
each screw.
WIRING
All wiring must comply with local electrical code s and
ordinances. See Fig. 4 through 6 wiring diagrams for
specific equipment applications. Refer to Table 2 for
terminal designations.
CAUTION
Voltage Hazard.
Can cause electrical shock or equ ip m ent
damage.
Disconnect power before beginning installation.
Loosen the terminal screws on the W8635A and
1.
connect the system wires. See Fig.3.
Securely tighten each terminal screw.
2.
1
2
3
C
R
R
H
R
C
G
W
W
Y1
Y2
1
2
MOUNTING
SCREWS (2)
M16636
Fig. 3. Wiring the W8635A terminals.
Table 2. Terminal Designations.
W8635A
Terminal
Designations Function
1 To Communicating Thermostat
Terminal 1
2 To Communicating Thermostat
Terminal 2
3 To Communicating Thermostat
Terminal 3
R 24 Vac System Transformer
Rh 24 Vac Heating Transformer
Rc 24 Vac Cooling Transformer
C 24 Vac Transformer Common
GFan Relay
W1 Stage 1 Heat Relay
W2 Stage 2 Heat Relay
Y1 Stage 1 Cool Relay
Y2 Stage 2 Cool Relay
Green LED Indicates Data Communication
T8635L
OT
OT
W8635A
1
2
3
C
R
R
H
R
C
1
FACTORY INSTALLER JUMPERS.
1
G
W1
W2
Y1
Y2
L2
L1
(HOT)
SYSTEM
TRANSFORMER
C7089B
OUTDOOR
TEMPERATURE
SENSOR
1
Fig. 4. 2H/2C single transformer.
69-1339—22
2
3
FAN
RELAY
HEAT 1
RELAY
HEAT 2
RELAY
COOL 1
RELAY
COOL 2
RELAY
M13429
W8635A EQUIPMEN T INTERFACE MODULE
T8635L
3
OT
FAN
RELAY
HEAT 1
RELAY
HEAT 2
RELAY
COOL 1
RELAY
COOL 2
RELAY
L1
(HOT)
L2
SYSTEM
TRANSFORMER
C7089B
OUTDOOR
TEMPERATURE
SENSOR
1
1
T8635L
OT
OT
W8635A
1
2
3
C
R
R
H
R
C
FACTORY INSTALLER JUMPERS.
2
1
G
W1
W2
Y1
Y2
Fig. 5. Three zone configuration.
WIRE NUT
M13378
Fig. 6. Using wire nut to pigtail a connection when
three or more wires are terminated at one terminal.
Discovery Mode
Discovery mode begins when the T8635L Thermost at
and W8635 EIM are first installed and power is
connected:
— The W8635 EIM transmits i nformation to the T8635L
Thermostat that indicates the maximum number of
stages that are enabled and the type of EIM
connected.
— The thermostat receives informati on from the W8635
and then sets the cycle rates and equipment types
automatically.
Stage Configuration
The W8635A automatically configures the T8635L for
two stages of heat and two stages of cool. If using the
W8635A and the T8635L on a one heat/one cool
application, set Installer Setup No. 5 and 8 to 1 when
configuring the T8635L Communicati ng Thermostat.
For configuration combinations, see Table 3.
T8635L
OT
2
1
3
546Z
213X
546Z
213X
546Z
213X
TROL-A-TEMP
MODEL AOBD
ZONE DAMPER
OT
W8703A
1
OT
OPEN
CLOSE
OPEN
CLOSE
OPEN
CLOSE
OPTIONAL
TROL-A-TEMP
MODEL ARD-PC
OR MODEL ZD
2
3
ZONE AZONE B
TR1
TR2
COM
ZONE C
1
2
3
Table 3. Stage Combinations.
Heat Stages Cool Stages
10
20
01
02
11
22
Cycle Rate
The thermostat automatically sets the cycle rate based
on the information it received during Discovery M ode.
See Table 4.
To change the default cycle rate settings:
— enter T8635L Thermostat Installer Setup and select
the desired cycle rate settings for each stage. (All
stages can be set bet ween 1 and 12 cph.)
Table 4. Default Cycle Rate Settings.
st
1
W8635A
Equipment
Interface
Module
Stage
Heat
2nd
Stage
Heat
6 cph 6 cph 3 cph 3 cph
1st
Stage
Cool
Electric Heat Setting
When using the W8635A on an electric heat application,
set the T8635L Thermostat Installer Setup No. 4 to 1.
This instructs the W8635A EIM to energize the fan with
any call for heat.
L1
(HOT)
L2
EXTERNAL
40 VA
TRANSFORMER
M13430A
2nd
Stage
Cool
3 69-1339—2
W8635A EQUIPMENT INTERFACE MODULE
Flash COM OK LED Description
LED blinks rapidly
mitting information on the communications bus.
LED blinks once
acknowledged a message.
LED on constantly
device.
LED off constantly
device is not functioning properly and there is no
LED activity at least once a minute. Check wiring to
communications bus terminals 1, 2 and 3.
NOTE: It is normal for LED to blink continuously dur-
ing startup and discovery.
LED blinks continuously
if device is not functioning properly and there is a
continuous series of LED blinks. Check wiring to
communications bus terminals 1, 2 and 3.
—indicates device is currently trans-
—indicates device received and
—indicates device failure. Replace
—indicates a wiring probl em if
—indicates a wiring problem
CAUTION
Equipment Damage Hazard.
Minimum compressor off-tim e is bypassed
during Installer System Test.
Do not allow compressor rapid cycling (on and
off).
Observe compressor protection period.
To start the Installer System Test:
Press and hold the T8635L Thermostat increase
1.
and decrease ▼ keys at the same time until 10
▲
appears. All display segments display before the
10 appears. See Fig. 7 and 8.
Set Program
Hold for
Em Ht
Aux Ht
Mon
TueWedThuFriSatSun
Wake
System Fan
Heat
Em
INSTALLER SYSTEM TEST
Use the Installer System Test to check the thermostat
and W8635A EIM operation for each thermostat in the
system. Table 5 lists the available system tests.
Table 5. Installer System Tests.
Test Number System Test Description
10-12 Heating stages can be turned on and
30-32 Cooling stages can be turned on and
40-42 Fan and damper test
70-74 Thermostat information including date
Heating Equipment Sys te m Test
Cooling Equipment Sy stem Test
off in sequence
off in sequence
60 Keyboard keys test
code and software versions are
displayed.
Fig. 8. Installer Test Number display.
Refer to Table 6 for Installer System Test option.
2.
Table 6. Installer System Test Options.
Key to Press Test Number Description
10 Enter Heating Equipment system test.
▲
▲
▼
▼
11 First Stage Heat turns on.
12 Second Stage Heat turns on.
11 Second Stage Heat turns off.
10 First Stage Heat turns off.
30 Enter Cooling Equipment system test.
▲
▲
▼
▼
31 First Stage Cool turns on.
32 Second Stage Cool turns on.
31 Second Stage Cool turns off.
30 First Stage Cool turns off.
Temporary Setting Enrg
Set Day/Time
Start Time
AM
PM
Heat
Cool
Filter
Recovery
LeaveReturnSleep
Off Auto
Cool
In
Wait
DST
Auto
Fig. 7. LCD segments display.
TEST NUMBER
Room
%Humid
Outdoor
Repl Batt
Auto
On
M10345A
Sav
M10257A
69-1339—24
W8635A EQUIPMEN T INTERFACE MODULE
Table 6. Installer System Test Options. (Continued)
Key to Press Test Number Description
Fan and Damper Test (Damper Test available only when using W8703A)
40 Enter Fan and Damper test.
▲
▲
▼
▼
41 Fan turns on; damper for this zone opens.
42 Damper closes for this zone (if not already closed); fan stays on.
41 Damper opens for this zone.
40 Fan turns off.
Key Operation Test
60 Enter Key Operation test.
Press any key to test if the key is functional. Each time a key is pressed, a different num ber is disp lay ed. This
indicates the key is functioning properly . Pressing enters the next test .
Thermostat Information
70 Enter Thermostat Information mode.
▲
▲
▲
▲
71 Production date code is displayed. The fir st two large digits are
the month and the third digit is the last digit of the year (exam pl e:
031 = March 2001).
72 Software identification code is displayed.
73 Software revision number is displayed.
74 EEPROM identification code is displayed.
Exit Installer Test Mode
Run
Program
Thermostat returns to normal operating mode.
TROUBLESHOOTING GUIDE
Refer to Table 7 for troubleshooting informat ion .
Table 7. Troubleshooting Guide.
Symptom Possible Cause Action
Display does not come
on at thermostat.
“1 COM”, “2 COM” or
“3 COM” is displayed.
System Switch setting
displays “off only.”
Thermostat is not being powered. Check if the therm ost at is mounted and latched on the
Thermostat is unable to
communicate with the W8635A.
During Discovery Mode, the
thermostat did not correctly set
the number of heat or cool stages.
wallplate; if not:
—mount and latch the thermostat on the wallplate.
Check if the circuit breaker is tripped; if it is:
—reset the circuit breaker.
Check if the fuse is blown; if it is:
—replace the fuse.
Check if the power switch at the equipment is in the Off
position; if it is:
—set to the On p o s ition.
Check for 24 Vac on terminals 2 and 3:
—replace any broken wires.
If 24 Vac is present on terminals 2 and 3:
replace the thermostat.
Check the connection to terminal 1 at the thermostat
and W8635A EIM:
—replace any broken wires.
cycle power.
Manually run Discovery Mode; see Installer Setup.
manually configure heat and/or cool stages
(Installer Setup 5 and 8).
5 69-1339—2
W8635A EQUIPMENT INTERFACE MODULE
Table 7. Troubleshooting Guide. (Contin ued)
Symptom Possible Cause Action
Heating does not come
on. System on indicator
( = heat) displays.
Cooling does not come
on. System on indicator
( = cool) displays.
“wait” is displaye d and
the call for Cool has not
started.
nd
2
stage heat or cool
does not energize.
Fan does not come on
with a call for electric
heat.
Communication is not being
completed.
Heat load at W8635A is not
connected correctly.
Communication is not being
completed.
Cool load at W8635A is not
connected correctly.
Compressor protection is in
effect.
Stage configuration not set
correctly to match the number of
selected stages.
Cool load at W8635A is not
connected correctly.
Electric heat setting is not
configured.
Fan load at W8635A is not
connected correctly.
End and repeat the call for heat. Check the Flas h COM
OK LED on the W8635A EIM while the call is being
made.
If the Flash COM OK LED does not blink:
check communication Bus wiring.
If the Flash COM OK LED blinks:
check that 24 Vac is present at W1 terminal.
If 24 Vac is not present:
check R to Rh connection.
If the connection is good:
replace the W8635A EIM.
End and repeat the call for cool. Check the Flash COM
OK LED on the W8635A EIM while the call is being
made.
If the Flash COM OK LED does not blink:
check communication bus wiring.
If the Flash COM OK LED blinks:
check that 24 Vac is present at Y1 terminal.
If 24 Vac is not present:
check R to Rh to Rc jumper connection.
If the R to Rh to Rc connection is good:
replace the W8635A EIM.
Compressor protection can be set from 0 to 5 minutes
to prevent compressor damage due to rapid cycling.
Wait until the compressor protection period expires.
To bypass compressor protection during the installat ion
phase, see the Installer System Test section.
Set the Stage configuration in Ins tal ler Setup for two
stages or heat and/or two stages of cool.
Check that 24 Vac is present at Y2 or W2 terminal. If
24 Vac is not present, all connections are good and the
thermostat is correctly configured, replace W8635A EIM.
Set Installer Setup No. 4 to 1 for electric heat.
Check that 24 Vac is present at G terminal. If 24 Vac is
not present, all connections are good and the thermostat
is configured, replace the W8635A EIM.
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Honeywell Inc. Honeywell Limited-Honeywell Limitée
Honeywell Plaza 155 Gordon Baker Road
P.O. Box 524 North York, Ontario
Minneapolis, MN 55408-0524 M2H 3N7
69-1339—2 G.H. Rev. 6-00 www.honeywell.com
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