Carrier Weathermaster 48P030-100 Controls, Start-Up, Operation, Service, And Troubleshooting page 76

5. Use current SAT and actuator position as samples for next
comparison after next actuator move.
The control will test for a mechanically disconnected damper if all
the following conditions are true:
1. An economizer is installed.
2. The supply fan is running.
3. Conditions are good for economizing.
4. The difference between RAT and OAT > E.SOD. It is neces-
sary for there to be a large enough difference between RAT
and OAT in order to measure a change in SAT as the damper
modulates.
5. The actuator has moved at least EC.ST %. A very small
change in damper position may result in a very small (or
non-measurable) change in SAT.
6. At least part of the economizer movement is within the
range ET.MN% to ET.MX%. Because the mixing of out-
side air and return air is not linear over the entire range of
damper position, near the ends of the range even a large
change in damper position may result in a very small (or
non-measurable) change in SAT.
Furthermore, the control will test for a mechanically disconnected
actuator after E.CHD minutes have expired when any of the fol-
lowing occur (this is to allow the heat/cool cycle to dissipate and
not influence SAT):
1. The supply fans switches from OFF to ON.
2. Mechanical cooling switches from ON to OFF.
3. Reheat switches from ON to OFF.
4. The SAT sensor has been relocated downstream of the
heating section and heat switches from ON to OFF.
The economizer will be considered moving if the reported posi-
tion has changed at least ± EC.MD %. A very small change in
position is not considered movement.
The determination of whether the economizer is mechanically dis-
connected will occur SAT.T/2 seconds after the economizer has
stopped moving. The control will log a "damper not modulating"
alert if:
1. SAT has not decreased by S.CHG degrees F SAT_SET/2 sec-
onds after opening the economizer at least EC.ST%, taking
into account whether the entire movement has occurred
within the range 0-ET.MN%.
2. SAT has not increased by S.CHG degrees F SAT_SET/2 sec-
onds after closing the economizer at least EC.ST%, taking
into account whether the entire movement has occurred
within the range ET.MX-100%.
3. Economizer reported position <=5% and SAT is not
approximately equal to RAT. SAT not approximately equal
to RAT will be determined as follows:
a. SAT<RAT-(2*2(thermistor accuracy) + 2 (SAT increase
due
or
b. SAT>RAT+(2*2(thermistor accuracy) + 2 (SAT increase
due to fan))
4. Economizer reported position >=95% and SAT is not
approximately equal to OAT. SAT not approximately
equal to OAT will be determined as follows:
a. SAT<OAT-(2*2(thermistor accuracy) + 2 (SAT increase
due
or
b. SAT>OAT+(2*2(thermistor accuracy) + 2 (SAT increase
due to fan))
Except when run as part of a self-test, the control will not automat-
ically clear "damper not modulating" alerts on units with more
than one actuator (when ECON_TWO=YES); the alert will have
to be manually cleared.
to fan))
to fan))
Test for stuck/jammed actuator
The control will test for a jammed actuator as follows:
• If the actuator has stopped moving and the reported position
(ECONxPOS, where x is 1,2) is not within ± EC_FLGAP%
of the command position (ECONOCMD) after EC_FLTMR
seconds, a "damper stuck or jammed" alert will be logged;
i.e., abs (ECONxPOS - ECONODMD) > E.GAP for a con-
tinuous time period EC_FLTMR seconds.
• If the actuator jammed while opening (i.e., reported posi-
tion < commanded position), a "not economizing when it
should" alert will be logged.
• If the actuator jammed while closing (i.e., reported position >
command position), the "economizing when it should not"
and "too much outside air" alerts will be logged.
The control will automatically clear the jammed actuator alerts as
follows:
• If the actuator moves at least 1%, the alerts will be cleared.
Alternate Excess Outdoor Air Test
For units configured with outdoor air measuring stations (OCFM-
SENS=YES):

Configuration ECON
Under the following conditions:
1. Unit is not performing free cooling
2. OACFM sensor is detected as good
3. IAQ is not overriding CFM
4. Purge is not overriding CFM
If OACFM > (ECMINCFM + EX_ARCFM) for EX_ARTMR
seconds, the "excess outside air" alert will be logged.
DIFFERENTIAL DRY BULB CUTOFF CONTROL
Differential Dry Bulb Changeover
As both return air and outside air temperature sensors are in-
stalled as standard on these units, the user may select this option,
E.SEL = 1, to perform a qualification of return and outside air in
the enabling/disabling of free cooling. If this option is selected,
the outside air temperature will be compared to the return-air
temperature to disallow free cooling as shown in Table 65.
Table 65 — Differential Dry Bulb Cutoff Control
E.SEL (ECON_SEL)
(EC_DDBCO)
NONE, OUTDR.ENTH,
N/A
DIF.ENTHALPY
0°F
–2°F
DIFF.DRY BULB
–4°F
–6°F
The status of differential dry bulb cutoff will be visible under Run
 
Status ECON DISA
There will be hysteresis where OAT must fall 1°F lower
than the comparison temperature when transitioning from
DDBCSTAT=YES to DDBSTAT=NO.
ECONOMIZER SELF-TEST
The unit has some configurations with two actuators (when
ECON_TWO=YES). Because it is possible for one actuator to be-
come mechanically disconnected while the other(s) continue to
work properly, the following self-test utilizes fan characteristics
and motor power measurements to determine whether the
dampers are properly modulating. A fan that is moving more air
uses more power than a fan that is moving a lesser quantity of air.
76
 
CFM.C OCF.S=YES
DDB.C OAT/RAT
Comparison
N/A NO
OAT>RAT YES
OATRAT NO
OAT>RAT–2 YES
OATRAT–2 NO
OAT>RAT–4 YES
OATRAT–4 NO
OAT>RAT–6 YES
OATRAT–6 NO

DDBC.
DDBC
(DDBCSTAT)