Blower Heat Off Delayt; Comfortnet™ System; Overview; Airflow Considerations - Goodman *MVM96 Installation Instructions Manual

In general lower heating speeds will: reduce electrical consump-
tion, lower operating sound levels of the blower, and increase the
outlet air temperature delivered to the home. The speeds avail-
able allow the blower performance to be optimized for the particu-
lar needs of the installation.
B H O D
LOWER EAT FF ELAY
The integrated control module provides a selectable heat off delay
function. The heat off delay period may be set to 90, 120, 150, 180
seconds using the DIP switches or jumper provided on the control
module. The delay is factory shipped at 150 seconds but may be
changed to suit the installation requirements and/or homeowner
preference. Refer to the DIP switch chart in the back section of
this manual for switch positions and corresponding delay times.
C N ™ S
OMFORT ET YSTEM
O
VERVIEW
NOTE: DIP switch #13 MUST be set to match thermostat
type. To use the CTK01 communicating thermostat, DIP switch
#13 must be set to ON position. This is also the correct set-
ting for a non-communicating 2-stage thermostat. To use the
CTK02** or CTK03 modulating thermostat, check to make
sure DIP switch #13 is in the OFF position (factory posi-
tion). This is also the correct position when using a non-
communicating single stage thermostat.
The ComfortNet system is a system that includes a ComfortNet
compatible furnace and air conditioner or heat pump with a CTK0*
thermostat. A valid ComfortNet system could also be a compat-
ible furnace, CTK0* thermostat and non-compatible, single stage
air conditioner. Any other system configurations are considered
invalid ComfortNet systems and must be connected as a tradi-
tional (or non-communicating) system (see Electrical Connec-
tions for wiring connections).
A ComfortNet heating/air conditioning system differs from a non-
communicating/traditional system in the manner in which the
indoor unit, outdoor unit and thermostat interact with one another.
In a traditional system, the thermostat sends commands to the
indoor and outdoor units via analog 24 VAC signals. It is a one-
way communication path in that the indoor and outdoor units
typically do not return information to the thermostat.
The indoor unit, outdoor unit and thermostat comprising a
ComfortNet system "communicate" digitally with one another, cre-
ating a two-way communications path. The thermostat still sends
commands to the indoor and outdoor units. However, the thermo-
stat may also request and receive information from both the indoor
and outdoor units. This information may be displayed on the
ComfortNet thermostat. The indoor and outdoor units also inter-
act with one another. The outdoor unit may send commands to or
request information from the indoor unit. This two-way digital
communications between the thermostat and subsystems (indoor/
outdoor unit) is the key to unlocking the benefits and features of
the ComfortNet system.
Two-way digital communications is accomplished using only two
wires. The thermostat and subsystem controls are powered with
24 VAC. Thus, a maximum of 4 wires between the equipment and
thermostat is all that is required to operate the system.
T

IMINGS

A C
IRFLOW ONSIDERATIONS
Airflow demands are managed differently in a communicat-
ing system than they are in a non-communicating wired sys-
tem. The system operating mode (as determined by the
thermostat) determines which unit calculates the system air-
flow demand. If the furnace is responsible for determining
the airflow demand, it calculates the demand and sends it to
the ECM motor. If the outdoor unit or thermostat is respon-
sible for determining the demand, it calculates the demand
and transmits the demand along with a fan request to the
indoor unit. The furnace then sends the demand to the ECM
motor. The following table lists the various ComfortNet sys-
tems, the operating mode, and airflow demand source.
System Operating
System
Air Conditioner +
Furnace
Continuous Fan
Heat Pump Heating
Heat Pump +
Furnace
Auxiliary Heating
Continuous Fan
Furnace + Non-
Comm 1stg Air
Conditioner
Continuous Fan
For example, assume the system is an air conditioner
matched with a furnace. With a call for low stage cooling,
the air conditioner will calculate the system's low stage cool-
ing airflow demand. The air conditioner will then send a fan
request along with the low stage cooling airflow demand to
the furnace. Once received, the furnace will send the low
stage cooling airflow demand to the ECM motor. The ECM
motor then delivers the low stage cooling airflow. See the
applicable ComfortNet air conditioner or heat pump installa-
tion manual for the airflow delivered during cooling or heat
pump heating.
In continuous fan mode, the CTK0* thermostat provides the
airflow demand. The thermostat may be configured for one of
three continuous fan speed settings allow for 25%, 50% or
75% airflow, based on the furnaces' maximum airflow capa-
bility. During continuous fan operation, the thermostat sends
a fan request along with the continuous fan demand to the
furnace. The furnace, in turn, sends the demand to the
ECM motor. The ECM motor delivers the requested continu-
ous fan airflow.
43
Airflow Demand Source
Mode
Cooling Air Conditioner
Heating Furnace
Thermostat
Cooling Heat Pump
Heat Pump
Only
Furnace
Thermostat
Cooling Furnace
Heating Furnace
Thermostat