Carrier 48LC 04 Controls, Start-Up, Operation And Troubleshooting page 20

Furthermore, the control shall test for a mechanically disconnected
actuator after T24CHDLY minutes have expired when any of the
following 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 shall be considered moving if the reported
position has changed at least +/- - T24ECMDB %. A very small
changed in position shall not be considered movement.
The determination of whether the economizer is mechanically
disconnected shall occur SAT_SEC/2 seconds after the economizer
has stopped moving.
The control shall log a "damper not modulating" alert if:
1. SAT has not decreased by T24SATMD degrees F
SAT_SET/2 seconds after opening the economizer at least
T24ECSTS%, taking into account whether the entire
movement has occurred within the range 0- -T24TSTMN%.
2. SAT has not increased by T24SATMD degrees F
SAT_SET/2 seconds after closing the economizer at least
T24ECSTS%, taking into account whether the entire
movement has occurred
T24TSTMX- -100%.
3. Economizer reported position <=5% and SAT is not
approximately equal to RAT. SAT not approximately equal
to RAT shall be determined as follows:
a. SAT<RAT- -(2*2(thermistor accuracy) + 2 (SAT increase
due to fan)) 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 shall be determined as follows:
a. SAT<OAT- -(2*2(thermistor accuracy) + 2 (SAT increase
due to fan)) or
b. SAT>OAT+(2*2(thermistor accuracy) + 2 (SAT increase
due to fan))
2. Actuator Stuck or Jammed
The control shall test for a jammed actuator as follows:
S If the actuator has stopped moving and the reported position
(ECONOPOS) is not within +/- - 3% of the commanded position
(ECONOCMD) after 20 seconds, a "damper stuck or jammed"
alert shall be logged.
S If the actuator jammed while opening (i.e., reported position <
commanded position), a "not economizing when it should" alert
shall be logged.
S If the actuator jammed while closing (i.e., reported position >
command position), the "economizing when it should not" and
"too much outside air" alerts shall be logged.
The control shall automatically clear the jammed actuator alerts as
follows:
S If the actuator jammed while opening, when ECONOPOS >
jammed position the alerts shall be cleared.
S If the actuator jammed while closing, when ECONOPOS <
jammed position the alerts shall be cleared.
Title 24 FDD Configuration Points
LOG.F (T24LOGFL) – "Log Title 24 Faults" – defines when Title
24 mechanically disconnected actuator faults should be logged:
EC.MD (T24ECMDB) – "T24 Econ Move Detect" – amount of
change required
economizer is detected as moving
EC.ST (T24ECSTS) – "T24 Econ Move SAT Test" – minimum
amount economizer must move in order to trigger the test for a
change in SAT, i.e., the economizer must move at least T24ECSTS
% before the control will attempt to determine whether the actuator
is mechanically disconnected.
S.CHG (T24SATMD) – "T24 Econ Move SAT Change" –
minimum amount (in degrees F) SAT is expected to change based
on economizer position change of T24ECSTS.
within the range
E.SOD (T24SRATDF) – "T24 Econ RAT- -OAT Diff" – minimum
difference (in degrees F) between RAT (if available) or SAT (with
economizer closed and fan on) and OAT to perform mechanically
disconnected actuator testing.
E.CHD (T24CHDLY) – "T24 Heat/Cool End Delay" – amount of
time (in minutes) to wait after mechanical cooling or heating has
ended before testing for mechanically disconnected actuator. This is to
allow SAT to stabilize at conclusion of mechanical cooling or heating.
SAT.T (SAT_SET) – "SAT Settling Time" – SAT_SET/2 is the
amount of time (in seconds) economizer reported position must
remain unchanged (+/- -T24ECMDB) before the control will
attempt to detect a mechanically disconnected actuator. This is to
allow SAT to stabilize at the current economizer position. This
configuration sets the settling time of the supply air temperature
(SAT). This typically tells the control how long to wait after a stage
change before trusting the SAT reading, and has been reused for
Title 24 purposes.
ET.MN (T24TSTMN) – "T24 Test Minimum Pos." – minimum
position below which tests for a mechanically disconnected
actuator will not be performed. For example, if the actuator moves
entirely within the range 0- -T24TSTMN a determination of
whether the actuator is mechanically disconnected will not be
made. This is due to the fact that at the extreme ends of the actuator
movement, a change in position may not result in a detectable
change in temperature. When the actuator stops in the range 0- -2%
(the actuator is considered to be closed), a test shall be performed
where SAT is expected to be approximately equal to RAT. If SAT
is not determined to be approximately equal to RAT, a "damper not
modulating" alert shall be logged.
20
Range=YES, NO,
YES – attempt to detect and log mechanically disconnect
actuator
NO – do not attempt to detect and log mechanically
disconnect actuator
Default=NO
in economizer reported
Range=1- -10
Default=1
Range=10- -20
Default=10
Range=0- -5
Default=.2
Range=5- -20
Default=15
Range=0- -60
Default=25
Range=10- -900
Default=240
Range=0- -50
Default=15
position before