12
INSTALLER’S GUIDE
Figure 16. Single Enthalpy Changeover Set Point
Single enthalpy:
The enthalpy change-
over set point is set to return the outdoor
air damper to minimum position when the
enthalpy rises above its set point. The
enthalpy set point scale markings, located
on W7459, are A,B,C,D; see table for the
corresponding control point. The factory-
installed R4 WHITE 620-ohm jumper must
be in place across ter and SR.
NOTE:
A (G) signal is required for the economizer to oper-
ate. As shipped, the economizer will not operate when there
is a signal for Heating Modes utilizing gas heat.
Fan Only (G):
When the thermostat sends a signal for fan
only (G), the economizer will open to the minimum posi-
tion setting regardless of the outdoor air conditions and the
indoor blower will operate at approximately 50% airflow.
Heating (W1), (W2), (Y1, Y2 on Heat Pump or Dual Fuel
Models):
When the thermostat sends a signal for auxiliary
heat (G) +(W1) or first stage heat (G) + (Y1,Y2), the econo
-
mizer will open to the minimum position setting. When the
ambient temperature may be below 70
o
F, the economizer
will not fully open to the economizing position, when there is
a signal for heat. In order to receive fresh air and open the
dampers to the minimum position setting, you must provide
a G signal to the unit from the thermostat or comfort control
being used.
FREE COOLING NOT AVAILABLE:
When the outdoor air
conditions are not sufficient for “Free Cooling” the Econo
-
mizer will open to the minimum position setting only and the
unit will function.
FREE COOLING AVAILABLE:
1st Stage Cooling (Y1) + (O for Heat Pumps and Dual
Fuel models):
When outdoor air conditions are sufficient
for “Free Cooling” and the thermostat sends a signal for 1st
stage cooling (G) + (Y1) + (O for Heat Pumps and Dual Fuel
models), the economizer will modulate accordingly and the
indoor blower will run at approximately 70% airflow.
2nd Stage Cooling (Y1) + (Y2) + (O for Heat Pumps and
Dual Fuel models):
When outdoor air conditions are suf-
ficient for “Free Cooling” and the thermostat sends a signal
for 2nd stage cooling (G) + (Y1) + (Y2) + (O for Heat Pumps
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
4
4
4
6
90
10
0
80
70
60
50
40
30
20
10
ENTHALP
Y—BTU
PER PO
UND DRY
AI
R
85
(29)
90
(32)
95
(35)
100
(38)
105
(41)
110
(43)
35
(2)
35
(2)
40
(4)
40
(4)
105
(41)
110
(43)
45
(7)
45
(7)
50
(10)
50
(10)
55
(13)
55
(13)
60
(16)
60
(16)
65
(18)
65
(18)
70
(21)
70
(21)
75
(24)
75
(24)
80
(27)
80
(27)
85
(29)
90
(32)
95
(35)
100
(38)
APPROXIMATE DRY BULB TEMPERATURE— F ( C)
A
A
B
B
C
C
D
D
M11681
RELATIVE
HUMI
D
ITY (%
)
1
1
HIGH LIMIT CURVE FOR W7459D.
CONTROL
CURVE
CONTROL POINT
APPROX. F (C)
AT 50% RH
A
73 (23)
B
70 (21)
C
67 (19)
D
63 (17)
Sequence Of Operation
and Dual Fuel models), the economizer will modulate ac-
cordingly, the compressor will operate on low speed, and the
indoor blower will operate at 100% airflow.
Unit “OFF” Mode
When the economizer is not receiving a 24V signal to the TR
terminal, or if power is disconnected to the unit, the damp-
ers will be fully closed to the outside air and fully open to the
return air.
NOTE:
Free Cooling refers to the process of circulating
unconditioned outside air, without operating the compressor,
to cool the structure.
5A. CHECKOUT - For Units using a Honeywell
W7459 Control, Only.
Operate the motor through its complete open-close stroke.
Check for proper operation, making sure that the linkage
does not bind and that the motor travels smoothly through-
out its fully open and closed position. Table 1 describes how
to drive the motor to the full open and full closed positions
(power connected). Make necessary minor adjustments until
desired operation is obtained, and tighten all nuts and set
screws. This motor checkout ensures that:
1. The motor operates the load.
2. The motor responds properly to the controller.
3. There is no binding of the linkage or motor
stalling at any point of travel.
If motor does not operate properly, check for proper voltage
or mechanical binding in linkage or damper.
If questions arise regarding this product, contact your dis-
tributor or representative.
