W8835 ENVIRAZONE PANEL
68-0258—04 10
Heat Pump Operation
The panel can control one or two compressor stages plus
auxiliary heat. Set DIP switch 1 and 2 to Off; set DIP switch 7
to On for a single-stage compressor and to Off for a two-stage
compressor.
Table 8. Heat Pump Equipment Configuration
Wire the reversing valve to the O/B equipment terminal. DIP
switch 9 configures this terminal to operate as an O (cool) or
B (heat) changeover terminal.
Hydronic Heat Operation
The W8835 is a forced air panel. However, it can be wired to
control hydronic valves as shown in figure 13. To control
valves or circulators on a hydronic panel, see figure 14.
Thermostat Operation

Dual Fuel Equipment

The W8835 can operate Dual fuel equipment when used with
an external fossil fuel kit. Locate the thermostat on the fossil
fuel kit instructions and wire the W8835 equipment terminals
there.

Emergency Heat Control

Emergency heat is defined as using an auxiliary heat source
without using the heat pump. The W8835 energizes the E
terminal on a call for emergency heat. The thermostat system
switch is set to Em Heat to engage this function. When active,
any zone calling for heat uses Emergency Heat, not the
compressor.
The panel energizes W3 as auxiliary heat with the Y1 and Y2
for compressor control in when not in emergency heat.

Manual and Automatic Changeover Operation

Each of the thermostats can be set for manual or automatic
changeover. If one or more thermostats call for cooling while
one or more thermostats call for heating, the panel attempts to
satisfy the greatest demand first.
Then, based on the relative demand for heating and cooling,
the panel intelligently switches between heating and cooling.
The system attempts to satisfy both the heating and cooling
demands, and does not lock out one demand in favor of the
other.
Discovery
Discovery is an automatic system configuration program where
the panel configures itself to operate with controls connected to
the EnviraCom bus. The panel enters Discovery when the
Discovery button on the panel is pressed.
Rebooting Microprocessor
To reset the microprocessor, press and release the Boot
button. The system reboots and enters the Purge mode.
EnviraCom Furnace
For furnaces with EnviraCom communications built in,
configure the panel as shown below. In this case, no
conventional equipment wiring is necessary because the
W8835 uses the 3-wire EnviraCom bus to control the HVAC
equipment. In these installations, the panel is powered from
the HVAC equipment via the 1, 2, 3 wires. Because of this, the
transformer R and C terminals on the W8835 are not used.
Instead, leave the XFMR jumpers in their default disconnected
position and wire the transformer to T1 and T2.
Table 9. Furnace Type Configuration
Humidity, De-humidity and Ventilation Control
The panel can control humidity, de-humidity, and ventilation by
receiving messages from the VisionPRO® IAQ thermostat.
The thermostat designated as zone 1 will have control of these
functions. Configure this thermostat as found in the installation
instructions for the thermostat.
The humidity, de-humidity, and ventilation terminals are all dry-
contact terminals; the relay contacts close when active. So
devices that need dry contact control like a ventilator can be
wired directly to the VENT terminals, or a steam humidifier can
be wired directly to the HUM terminals. Devices that need to be
powered like a ventilation damper or some models of
evaporative humidifiers are wired using the VENT or HUM
terminals wired through the R terminal as shown in Fig. 3.
If using a Honeywell TrueSteam humidifier, configure the zone
one VisionPRO IAQ thermostat installer setup #374 to "3", and
wire the TrueSteam GF terminal to the HVAC fan terminal, and
wire the TrueSteam GT terminal to the G on the W8835.
NOTE: When controlling a steam humidifier, set all thermo-
stats to HEAT. Do not set thermostats to AUTO. This
prevents the panel from humidifying on zone 1, when
another zone is calling for cooling. Alternatively, set
zone 1 thermostat Installer Setup 374 to “2” to allow
humidification only during calls for heat.
Equipment Type DIP 1 DIP 2
Heat Pump Off (Down) Off (Down
Compressor Stages DIP 7
1 Stage On (Up)
2 Stage Off (Down
Heat Pump Changeover DIP 9
O (Cool) On (Up)
B (Heat) Off (Down
Type of Equipment DIP 3
Conventional On (Up)
EnviraCom Off (Down)