Indoor Fan Motor Function; Ductwork - Bosch 19 SEER Series Operation Manual

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6 Indoor Fan Motor Function

System Operation and Function
Two Stage Fan Control
The IDP supports two stage fan control which requires a two stage
thermostat (Y1&Y2). When there is a call for Y2, the blower motor will
turn to high speed setting. When there is a call for Y1, the blower motor
will turn to low speed setting. Unit will run at low speed setting when there
is only G call. It will run in high speed setting when there is W/W1/W2
signal (when the electric heat kit is on).
The X13 ECM motor supports 5 speeds. Customer can select the suitable
speed by adjusting the SW6-1 and SW6-2 dip switches. Refer to Airfl ow
Performance Table (Table 6) for reference airfl ow. Refer to Fig. 48 for dip
switches settings.
If 2 stage thermostat is not available, single stage thermostat may be
used, please refer to Wiring Diagram section for wiring instructions. If Y1
and Y2 are jumped, the unit will only run in high stage fan speed.
Anti-Cold Air Fan Delay
The Anti-Cold Air Fan Delay function utilizies a sensor (T2) located on the
indoor coil, which prevents the blower from turning on until the coil has
reached a certain temperature. This feature prevents cold air blow during
heating operation.
1. When SW6-3 dip switch is set to the "ON" position and the unit is
in heating mode, the Anti-Cold Air Fan Delay function will activate
based on the following entry conditions (all 3 conditions must be
met):
a. Indoor Coil Temperature (T2) < 82.4℉
b. Electric heat kit is turned off
c. There is a call for Y1 from thermostat to indoor unit
2. This function will deactivate if ONE OF the following exit conditions
are met OR the system has been operating in heating mode for 15
minutes.
a. T2 ≥ 89.6℉
b. Heater kit is turned on
c. The system is NOT running Heat mode
3. During the heating mode, if one of the exit conditions of Anti-Cold
Air is satisfi ed, the blower motor will turn on in fi rst stage fan
speed.
4. During the heating mode, if all of the entry conditions of Anti-Cold
Air are met and maintained for 120s, the blower motor will change
to fi rst stage speed.
Heating Fan Delay
If SW6-3 dip switch is set to the "OFF" position and the unit is in heating
mode, the blower will operate with a 90 second delay with the fan speed
dictated by Y1 or Y2 signal.
Passive Dehumidifi cation (Optional)
IDP has a Passive Dehumidifi cation function which lowers the fan
speed (fi rst stage) with a DH call from the thermostat. This function
requires proper DH wiring from the indoor unit to the thermostat (with a
humidistat).
If DH wire is not connected, the unit will still function normally.
Data subject to change

7 Ductwork

Field ductwork must comply with the National Fire Protection Association
NFPA 90A, NFPA 90B and any applicable local ordinance(s).
WARNING: FIRE HAZARD AND CARBON MONOXIDE

Do not, under any circumstances, connect return
ductwork to any other heat producing device such
as fireplace insert, stove, etc. Unauthorized use of
such devices may result in fire, carbon monoxide
poisoning, explosion, personal injury or property.
Sheet metal ductwork run in unconditioned spaces must be insulated and
covered with a vapor barrier. Fibrous ductwork may be used if constructed
and installed in accordance with SMACNA Construction Standard on
Fibrous Glass Ducts. Ductwork must comply with National Fire Protection
Association as tested by U/L Standard 181 for Class I Air Ducts. Check
local codes for requirements on ductwork and insulation.
 Duct system must be designed within the range of external static
pressure the unit is designed to operate against. It is important that the
system airflow be adequate. Make sure supply and return ductwork,
grills, special filters, accessories, etc. are accounted for in total
resistance. See airflow performance tables in Section 5 of this manual.
 Design the duct system in accordance with "ACCA" Manual "D" Design
for Residential Winter and Summer Air Conditioning and Equipment
Selection. Latest editions are available from: "ACCA" Air Conditioning
Contractors of America, 1513 16th Street, N.W., Washington, D.C.
20036. If duct system incorporates flexible air duct, be sure pressure
drop information (straight length plus all turns) shown in "ACCA"
Manual "D" is accounted for in system.
If an elbow is included in the plenum close to the unit, it must
not be smaller than the dimensions of the supply duct fl ange on
the unit.
NOTICE:

The front flange on the return duct (if connected
to the blower casing) must not be screwed into the
area where the power wiring is located. Drills or
sharp screw points can damage insulation on wires
located inside unit.

Secure all ducts to roof curb and building structure on downflow
discharge units. Do not connect ductwork to unit. For horizontal
applications, unit is provided with flanges on the horizontal
openings. All ductwork should be secured to the flanges using
proper fasteners for the type of duct used and tape the duct-to
unit joint as required to prevent air leaks.
Installation & Operation Manual
03.2019 | BTC 761701105 A