Vsp2 Blower Control Board (A24); Vsp2−1 Blower Control Board (A24) - Lennox G21Q3-40 Unit Information

B − VSP2 Blower Control Board (A24)
V" Models Only G21V−5 to −8 & GSR21V
−10 to −15 (Figure 13)
IMPORTANT
If fan off time is too low, residual heat in heat ex
changer may cause primary limit S10 to trip result
ing in frequent cycling of blower. If this occurs, ad
just blower to longer time setting.
G21V / GSR21V units are equipped with a variable speed mo
tor that is capable of maintaining a specified CFM throughout
the external static range. The unit uses the VSP2−1 variable
speed control board, located in the blower compartment,
which controls the blower speed and provides diagnostic
LEDs. The control has both a non−adjustable, factory preset
ON" fan timing delay and an adjustable OFF" fan timing
delay (see figure 15).
The VSP2−1 also senses limit trip condition and turns on the
blower. The G21V / GSR21V limit switch is located in the vesti
bule wall. When excess heat is sensed in the heat exchanger,
the limit switch will open and interrupt the current to the gas
valve, while at the same time the VSP2−1 energizes the blower
on heating speed. The limit automatically resets when the unit
temperature returns to normal and the blower is de − ener
gized.
Diagnostic LEDs located on the VSP2−1 control board are pro
vided to aid in identifying the unit's mode of operation. Certain
scenarios will arise depending on the jumper positions.
VSP2−1 BLOWER CONTROL BOARD (A24)
JP2 13 PIN PLUG (BOARD TO MOTOR)
1
JP2
HIGH LOW
1 1
2 2
3 3
4 4
SELECTOR PINS
HEATING STAGE
HEAT
SELECTOR PIN
HTG.
BLOWER
DS2
1 2
JP1 15 PIN (BOARD TO FURNACE)
JP1
1
FIGURE 13
ADJUST HEAT
TEST 1
− 2
+ 3
NORM 4
DS3 HI/LOW DS4
ON/OFF DS1 CFM
DIAGNOSTIC DS LEDS
FAN OFF
TIMING PINS
210
150

VSP2 BLOWER CONTROL BOARD (A24)

J46
HIGH
BLOWER
1
J73
1
J73
PIN 1 C 24 VAC common.
PIN 2 G Input signal from thermostat's fan signal.
PIN 3 W2 Input signal for second stage heat from the thermostat.
PIN 4 DS Input signal for the blower speed regulation.
PIN 5 Limit Input signal from the external limit.
PIN 6 R 24 VAC power to the thermostat.
PIN 7 C 24 VAC common.
Pin 8 C 24 VAC common.
PIN 9 CI Input signal from the fan limit control.
PIN 10 CO Output signal to the ignition control.
PIN 11 HT Input signal from the fan limit control.
PIN 12 ACC 24 VAC accessory output.
PIN 13 24V Input 24 VAC power for the VSP2 1.
PIN 14 24V Input 24 VAC power for the VSP2 1.
PIN 15 V Input signal from the gas line.
J46
PIN 1 Heat Heat speed input signal to the ICM2 motor.
PIN 2 C 24 VAC common.
PIN 3 C 24 VAC common.
PIN 4 High Tap High Speed programming input.
PIN 5 Low Tap Low speed programming input.
PIN 6 On / Off On / off output signal to the ICM2 motor.
PIN 7 Adjust Tap ICM2 mode selection.
PIN 8 Hi / Low Speed regulate input signal to the ICM2 motor.
PIN 9 Hi / Low Speed regulate input signal to the ICM2 motor.
PIN 10 Ref. V ICM2 reference voltage.
PIN 11 Heat Tap Heating blower speed programming.
PIN 12 C 24 VAC common.
PIN 13 cfm Motor speed diagnostic signal.
VOLTAGES INTO VSP2
Voltage across J73 pins 13 to 1 and 6 to 1 is 24VAC as shown here.
Refer to unit wiring diagram.
34 volts
0 volts
−34 volts
Voltage across J73 pins 4 to 1 is approximately 15 20VDC (straight voltage) if CCB
is used. If Harmony is used a voltage of 0−25VDC should be present.
If CCB or Harmony is not used, pin 4 to 1 voltage is 21VAC.
VOLTAGES FROM VSP2 TO ELECTRONICALLY
CONTROLLED BLOWER MOTOR
Voltage across J46 pins 6 to 3 and 1 to 3 is half rectified AC as shown here.
Refer to unit wiring diagram.
Approx.
34 volts
0 volts
Voltage across J46 pins 8 and 9 to 3, is approximately 15 20VDC if CCB is used. If CCB or
Harmony is not used, pins 8 and 9 to 3 voltage is approximately 21VAC. If Harmony is used
a voltage of 0−25VDC should be present.
Page 17
1
LOW ADJUST HEAT
1 1 TEST
2 2 −
3 3 +
4 4 NORM
HTG.
HEAT DS3 HI/LOW
DS2 ON/OFF DS1
2
24VAC @ 60Hz.
24VAC Half Rectified (DC Pulse)
FIGURE 14
1
2
3
4
DS4
CFM
210
150
@ 60Hz.