67
Table 17 — Single Enthalpy and Dual Enthalpy High Limit Curves
ENTHALPY SETTINGS
When the OA temperature, enthalpy and dew point are below
the respective set points, the Outdoor Air can be used for econ-
omizing. Fig. 96 shows the new single enthalpy boundaries in
the W7220. There are 5 boundaries (set points ES1 through
ES5), which are defined by dry bulb temperature, enthalpy and
dew point.
Refer to Table 17 for ENTH CURVE set point values.
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 96 shows the 5 current boundaries. There is also a high
limit boundary for differential enthalpy. The high limit boundary
is ES1 when there are no stages of mechanical cooling energized
and HL (high limit) when a compressor stage is energized.
Table 17 provides the values for each boundary limit.
TWO-SPEED FAN OPERATION
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 18.
Table 18 — Fan Speed
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). 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 two 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 or Y2 Out.
CHECKOUT
Inspect all wiring connections at the economizer module’s termi-
nals, and verify compliance with the installation wiring diagrams.
For checkout, review the Status of each configured parameter
and perform the Checkout tests.
NOTE: For information about menu navigation and use of the
keypad, see Interface Overview on page 57.
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.
Status
Use the Status menu (see Table 7) to check the parameter val-
ues for the various devices and sensors configured.
NOTE: For information about menu navigation and use of the
keypad, see Interface Overview on page 57.
Checkout Tests
Use the Checkout menu (on page 62) to test the damper opera-
tion and any configured outputs. Only items that are config-
ured are shown in the Checkout menu.
NOTE: For information about menu navigation and use of the
keypad, see Interface Overview on page 57.
To perform a Checkout test:
1. Scroll to the desired test in the Checkout menu using the
▲ and ▼ buttons.
2. Press the button to select the item.
3. RUN? appears.
4. Press the button to start the test.
ENTHALPY
CURVE
TEMP. DRY
BULB (F)
TEMP.
DEWPOINT (F)
ENTHALPY
(btu/lb/da)
POINT P1 POINT P2
TEMP. (F)
HUMIDITY
(%RH)
TEMP. (F)
HUMIDITY
(%RH)
ES1 80 60 28.0 80 36.8 66.3 80.1
ES2 75 57 26.0 75 39.6 63.3 80.0
ES3 70 54 24.0 70 42.3 59.7 81.4
ES4 65 51 22.0 65 44.8 55.7 84.2
ES5 60 48 20.0 60 46.9 51.3 88.5
HL 86 66 32.4 86 38.9 72.4 80.3
STATE FAN SPEED
OCC Low
Y1 Low
Y2 High
W High
WARNING
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal inju-
ry, property damage, or death.
Before performing service or maintenance operations on
unit, always turn off main power switch to unit and install
lock(s) and lockout tag(s). Unit may have more than one
power switch. Ensure electrical service to rooftop unit
agrees with voltage and amperage listed on the unit rating
plate.
If any wiring changes are required, first be sure to remove
power from the economizer module before starting work.
Pay particular attention to verifying the power connection
(24 vac).
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