W8835A ENVIRAZONE PANEL
68-0258ES-1
10
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.
Thermostat Operation
Conventional Equipment
Conventional equipment of up to three stages of heat and two
stages of cool can be controlled by the W8835. The panel is
configured to control equipment stages using DIP switches 1,2
and 7.
Heat Pump Equipment
Heat pump equipment with up to two heat-cool compressor
stages and auxiliary heat can be controlled by the W8835. The
panel is configured to control equipment stages using DIP
switches 1,2, and 7.
Emergency Heat Control
Emergency heat is defined as using an auxiliary heat source
without using the heat pump. 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, on
a call for heat.
Manual and Automatic Changeover Operation
Each of the T8635L 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.
Zone of Greatest Demand
The panel designates the zone that has the highest
requirement for heat or cool as the Zone of Greatest Demand.
It is then the only zone that can energize the equipment; all
other zones receive only damper control.
The equipment then cycles more regularly than other zone
control systems because the zone that requires conditioning
the most energizes the equipment and the other zones close
as they become satisfied. Also, more dampers are simul-
taneously open more often on calls for equipment, resulting in
less bypass damper usage and more efficient equipment
usage. All zones are satisfied; however, because if, at any
moment, another zone has a higher demand, it becomes the
Zone of Greatest Demand.
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
W8875 uses the 3-wire EnviraCom bus to control the HVAC
equipment.
Humidity, De-humidity and Ventilation Control
The panel can control humidity, de-humidity, and ventilation by
receiving messages from humidity, de-humidity, and ventilation
EnviraCom controls when they become available in the future.
Discharge Air Temperature Sensor DATS
The C7835A1009 Discharge Air Temperature Sensor (not
included) is a supply-duct-mounted temperature sensor probe
used to control capacity and prevent over-heating or coil-icing.
The sensor is wired to the EnviraCom bus using three wires.
When a high or low limit is reached, the panel shuts off the
equipment and keeps the fan operating for a minimum of two
and one-half minutes. After this time, and any applicable
minimum-off times imposed by the thermostat, it re-energizes
the equipment when the discharge air has recovered by ten
degrees. When the high or low limit is exceeded, the Heat (red)
or Cool (green) LED on the DATS flashes.
When the DATS is in a limit condition, the Heat, Cool and
Purge LEDs on the W8835A panel continue to operate as if the
DATS were not turning the equipment off.
The high and low limit is set on the DATS. The high
temperature limit is set from 110 °F to 160°F with a small
screwdriver or using fingers and the low limit is set at 40°F or
48°F degrees with a jumper. The recommended high limit
setting for fossil fuel/ electric systems is 160°F (default factory
setting). For heat pump systems, the recommended setting is
120°F.
The recommended low limit is 40°F for most appliances. If
condensation due to high humidity is a concern, then set the
low limit to 48°F.
Compressor Stages
DIP 7
1 Stage
On
2 Stage
Off
Heat Pump Changeover
DIP 9
O (Cool)
On
B (Heat)
Off
Type of Equipment
DIP 3
Conventional
On
EnviraCom
Off
