External Operation Icm2; Precautions Icm1 And Icm2; Coil Choke L13; Ecm Switching Frequency - Lennox G21Q3-40 Unit Information

2 − External Operation ICM2
(Speed Tap Priority)
Figure 40 shows the two quick connect jacks (J48 and
J49) which connect the motor to the G21V/GSR21V. Jack
J48 is the power plug and jack J49 connects the unit con
trols to the motor.
Line voltage must be applied to J48 pin 5 in order for the
motor to operate. When using 120VAC pins 1 and 2 must
be jumpered. When control voltage is applied to J49 pin 3
and 15 (single stage heating and cooling), the motor is en
ergized on the low speed heat/cool tap.
When voltage is applied to J49 pin 2 in addition to pin 3 and
15 (second stage heating), the blower is energized on the
high speed heating tap. When voltage is applied to J49 pin
10 in addition to pin 3 and 15 (second stage cooling), the
blower is energized on the high speed heating tap. The mo
tor assigns priority to J49 pin 2 so that if a call for cooling
and a call for heating are concurrent, heating call overrides
and the blower operates on high speed heating tap.
BLOWER B3 HARNESS CONNECTORS
POWER
CONNECTOR J48 CONNECTOR J49
1
J48
PIN 1 Jumper PIN 1 to PIN2 for 120VAC line input only.
PIN 2 Jumper PIN 1 to PIN2 for 120VAC line input only.
PIN 3 Ground
PIN 4 AC Line
PIN 5 AC Line
FIGURE 40
DANGER
Do not attempt to repair electronically controlled
blower motor or VSP2 1. There are no field service
able parts. If either component appears to be faulty
after following checkout procedure, replace entire
component then recheck for proper operation.
CONTROL
J49
PIN 1 C1
PIN 2 W / W1
PIN 3 C2
1
PIN 4 Delay
PIN 5 Cool
PIN 6 Y1
PIN 7 Adjust
PIN 8 0ut
PIN 9 0
PIN 10 BK / PWM
PIN 11 Heat
PIN 12 R
PIN 13 EM / W2
PIN 14 Y / Y2
PIN 15 G
PIN 16 Out +
3 − Precautions ICM1 and ICM2
If the G21V/GSR21V or its electronically controlled blower mo
tor is improperly or inadequately grounded, it may cause tele
vision interference (commonly known as RFI or radio frequen
cy interference).
This interference is caused by internal switching frequencies of
the motor controller (see figure 41). TV interference may show
up as small specks or lines which randomly appear on the TV
screen accompanied by pops or clicks in the sound. Before at
tempting any service, make sure the indoor unit is causing the
interference. To check, disconnect power to indoor unit then
check TV for continued signs of interference.
TV interference may be stopped by making sure the motor is
solidly grounded to the cabinet (metal to metal) and by making
sure the cabinet is solidly grounded. If TV interference persists,
make sure the television (and all affected RF appliances) are
moved away from the G21V/GSR21V. Also make sure af
fected appliances are connected to a separate electrical cir
cuit.
A coil choke is used on G21V3 / GSR21V3 (early model V3
motors will not use a choke) and G21V5 / GSR21V5 units. The
choke is located on the blower housing and is used to block
radio frequency interference.

ECM SWITCHING FREQUENCY

The electrical pulses to the windings cycle on and off at a rate of
20,000 cycles per second (20Khz, this is called the switching frequen
cy). The effective d.c. voltage can be varied by changing the pulse
width. The switching frequency is necessary in order to vary the speed
of the motor. If the motor is not securely grounded to the cabinet and
if the cabinet is not securely grounded, the switching frequency may
cause television interference.
OUTPUT FROM CONTROLLER TO MOTOR WINDINGS
One Pulse
325VDC
Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç
O volts
Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç
325VDC
O volts
Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç
325VDC
Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç
O volts
PULSE ON
PULSE OFF
Ç Ç Ç Ç
WINDING OFF
Ç Ç
Page 35

Coil Choke L13

One cycle
WINDING #1
WINDING #2
WINDING #3
ONE
ELECTRICAL
PULSE
325VDC
O volts
Switching Frequency
20Khz
FIGURE 41