K9 Isolation (Heat) Relay; Vsp1 Blower Control - Lennox G21Q3-40 Unit Information

8 − K9 Isolation (Heat) Relay
Q" Models Only
Fan timing control (A28) with part number 79J65 con
tains a single pole, single throw isolation relay (K9).
When there is a heat demand through W1, K9 is ener
gized closing the normally open contacts K9 1 in the
ignition circuit. The addition of an isolation relay in the
W1 circuit will eliminate electrical noise feeding from the
electronic thermostat back to the electronic ignition
control.
9 − K109 Accessory Relay V" Models Only
G21V−5 to −8 & GSR21V−10 to −15
A single pole, single throw accessory relay is located inside
the control box to provide power to additional accessories
which may be used with the G21V / GSR21V.
10 − VSP1 Blower Control Board (A24)
V" Models Only G21V−1 to −3 &
GSR21V−1 to −9 (Figure 9)
VSP1 BLOWER CONTROL BOARD (A24)
J46
4
OUTPUT
PLUG
DS3 DS2 DS1
DIAGNOSTIC
LEDS
120V
ACCESSORY
TERMINAL
ACC
L1
L1 LINE
VOLTAGE
FIGURE 9
The VSP1 (A24), a printed circuit board located in the con
trol box, serves four primary functions:
1− Controls blower timings during heating to accommo
date the required initial heat−up and cool−down times of
the heat exchanger.
FRONT VIEW
12 9 6
3
1
1
J73
VSP1 CONTROL
PLUG
150
210
FAN OFF
TIMING PINS
2− Senses limit trip condition and turns on the blower.
3− Controls the accessory relay.
4− Interfaces the 24VAC thermostat with the blower.
When operating in heating mode, VSP1 controls the blower
and monitors limit and gas valve operation. The VSP1 con
trols the fan on" and fan off" timings. Fan on timings are
pre set and non adjustable. Fan off timings are adjustable.
Fan on timing is the amount of time the unit operates before
the blower is started. This period allows for heat exchanger
warm up. The fan on timing is pre set at 45 seconds and is
not adjustable.
Fan Off timings (time that blower operates after heating
demand has been satisfied) are determined by the ar
rangement of a jumper on the VSP1 board. To adjust fan off
timings, gently disconnect jumper and reposition it across
pins corresponding with new timing (see figure 10). The
fan off timing is factory set at 270 seconds.
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.
FAN OFF TIME ADJUSTMENT
TIMING
JUMPER
270
150
The VSP1 includes a 120 VAC accessory terminal. The ter
minal is wired directly to terminal block TB2 and powers the
accessory connection on the terminal block. The terminal
is energized when the blower is running. It can be used for
any desired accessory equipment such as an electronic air
cleaner or humidifier.
Page 15
IMPORTANT
DANGER
Shock Hazard. VSP1 fan control is
connected to line voltage. Discon
nect power to unit before changing
pin timings. Can cause personal
injury or control damage.
To adjust fan−off timings:
Remove jumper from VSP1 and se
lect one of the other pin combina
tions to achieve the desired time.
Leave jumper off to achieve
210
330 second fan−off timing.
TIMING PINS (seconds)
Fan off timing is factory
set at 270 seconds
90
FIGURE 10