Bryant 547K 04-07 Series Service And Maintenance Instructions page 55

Economizing
Available
Not Available
Temperature
ENTHALPY TEMP. DRY
CURVE BULB (°F)
ES1 80
ES2 75
ES3 70
ES4 65
ES5 60
HL 86
The W7220 calculates the enthalpy and dew point using the
OA temperature and humidity input from the OA enthalpy sen-
sor. When the OA temperature, OA humidity and OA dew
point are all below the selected boundary, the economizer sets
the economizing mode to YES, economizing is available.
When all of the OA conditions are above the selected bound-
ary, the conditions are not good to economize and the mode is
set to NO.
Figure 73 shows the 5 current boundaries. There is also a high
limit boundary for differential enthalpy. The high limit bound-
ary is ES1 when there are no stages of mechanical cooling en-
ergized and HL (high limit) when a compressor stage is
energized.
TWO-SPEED FAN OPERATION
NOTE: Two-Speed Fan operation applies to size 07 models only.
The W7220 controller has the capability to work with a system
using a 2-speed supply fan. The W7220 does not control the
supply directly but uses the following input status to determine
the speed of the supply fan and controls the OA damper to the
required position, see Table 28.
Table 28 — Fan Speed
STATE
OCC
Y1
Y2
W
The W (heating mode) is not controlled by the W7220 but it re-
quires the status to know where to position the OA damper for
minimum position for the fan speed.
The 2-speed fan delay is available when the system is pro-
grammed for 2-speed fan (in the System Setup menu item).
Fig. 73 — Single Enthalpy Curve Boundaries
Table 27 — Single Enthalpy and Dual Enthalpy High Limit Curves
TEMP. ENTHALPY
DEWPOINT (°F) (btu/lb/da)
60 28.0
57 26.0
54 24.0
51 22.0
48 20.0
66 32.4
FAN SPEED
Low
Low
High
High
POINT P1
HUMIDITY
TEMP. (°F)
(%RH)
80 36.8
75 39.6
70 42.3
65 44.8
60 46.9
86 38.9
The 2-speed fan delay is defaulted to 5 minutes and can be
changed in the Advanced Setup menu item. When the unit has
a call for Y1 In and in the free cooling mode and there is a call
for Y2 In, the 2-speed fan delay starts and the OA damper will
modulate 100% open, the supply fan should be set to high
speed by the unit controller.
After the delay one of 2 actions will happen:
• The Y2 In call will be satisfied with the damper 100%
open and fan on high speed and the call will turn off
OR
• If the call for additional cooling in the space has not been
satisfied then the first stage of mechanical cooling will be
enabled through Y1 Out.
CHECKOUT
Inspect all wiring connections at the economizer module's ter-
minals, and verify compliance with the installation wiring dia-
grams. For checkout, review the Status of each configured pa-
rameter and perform the Checkout tests.
NOTE: For information about menu navigation and use of the
keypad, see Interface Overview on page 45.
Power Up
After the W7220 module is mounted and wired, apply power.
Initial Menu Display
On initial start up, Honeywell displays on the first line and
economizer W7220 on the second line. After a brief pause, the
revision of the software appears on the first line and the second
line will be blank.
Power Loss (Outage or Brownout)
All set points and advanced settings are restored after any pow-
er loss or interruption.
NOTE: All settings are stored in non-volatile flash memory.
55
Dual Enthalpy
High Limit
Single Enthalpy
P2 (T,RH)
P1
(T,RH)
ES4 ES2 ES1
ES5 ES3
POINT P2
HUMIDITY
TEMP. (°F)
66.3
63.3
59.7
55.7
51.3
72.4
HL
(%RH)
80.1
80.0
81.4
84.2
88.5
80.3