Lennox Harmony III Installation Instructions Manual page 6

Blower Control Adjustment
Variable-speed furnaces and blower coil units are
equipped with a variable-speed control board. The blower
motor speed must be adjusted to produce the zoning CFM
requirements managed by the zone control system.
The variable-speed motor (VSM) in the furnace is con-
®
trolled by the SureLight
in the variable-speed blower coil unit is controlled by the
BDC3 drive control. Adjustment of these drive controls is
by jumper setting selection and is described in the follow-
ing paragraphs.
Variable-Speed Furnace − Jumper Settings
®
Locate the SureLight board in the furnace control box
area. Switch settings on this board control blower CFM.
Before connecting the zone control board to the Sur-
®
eLight board, complete the applicable electrical adjust-
ments.
®
SureLight Control Board Selections
IMPORTANT! − Be sure to read the Electrical Adjustments
immediately following before cutting jumpers.
IMPORTANT:
CUT JUMPER
w914
Figure 5
505023M 04/06
furnace control board. The motor
®
be sure
jumper on
t'stat pins is
set on two"
JUMPER
W951
JUMPER
W915
IMPORTANT
Be sure to cut jumper W914; if not cut, the zone con-
trol board DS fuse will blow.
Electrical Shock Hazard! Disconnect
power from unit and wait at least five
minutes to allow capacitors to dis-
charge before attempting to adjust
motor speed tap settings.
1. Electrical Adjustments − SureLight
In all cases, cut jumper W914 (between R & DS,
D
see figure 5); if not cut, the zone control board DS
fuse will blow.
D IF dual fuel − cut jumper W951 (between R & O).
IF 2-stage outdoor unit, cut jumper W915 (be-
D
tween Y1 & Y2).
D In all cases − be sure T'STAT jumper is on TWO".
In all cases − cut and tape wires 2 & 13 on the VSM
D
harness connecting SureLight
(figure 6).
SureLight
8
16
cut and tape
wire #13
(furnace
application only)
2. Set Upper CFM Limit
D Determine the maximum system CFM require-
ments (sum of all the individual zones).
From the Blower Motor Performance table (see
D
unit installation instructions) determine the HIGH
Speed cool dip switch setting that corresponds to
this CFM.
Set the HIGH Speed cool dip switch setting on the
D
board to this value.
NOTE − The lower limit of blower CFM is factory set. It is
not field adjustable.
Page 6
WARNING
®
®
board to motor
®
Board Cable Modifications
(LOOK FOR RAISED
NUMBERS ON BACK
OF PLUG)
7
6
15
5
14
4
13
3
12 2
11 1
10
9
CUT & TAPE WIRE #2
Figure 6
Board