17
STATUS CODE 36, HEATER OUTPUT NOT SENSED WHEN
ENERGIZED
Fan coil control is provided with circuitry to detect presence of a
24--vac signal on electric heater stage 1 and stage 2 outputs.
If fan coil control energizes either heater stage and does not detect
the 24--vac signal on output, Status Code 36 will be displayed on
the STATUS LED, control will continue to energize heater
output(s) and adjust blower operation to a safe airflow level for
energized electric heat stage(s).
To find the fault:
1. Check for 24--vac on heater stage outputs. Fan coil control
or sensing circuit may be bad.
NOTE
:
It may be useful as an electric heater troubleshooting
procedure to disconnect the system communications to force Status
Code 16 enabling of emergency heat mode. It is difficult to know
which heater output is energized or not energized in normal
operation. When unit is operated in emergency heat mode using
electric heaters, both outputs are energized and de--energized
together. Terminal strip inputs to fan coil control can then be
connected R to W to turn on both electric heat outputs. Heater
output sensing circuits can then be checked to resolve Status Code
36 or 37 problems.
STATUS CODE 41, BLOWER MOTOR FAULT
If MOTOR LED is lit and flashing and motor does not run:
1. Check STATUS LED. If STATUS LED is indicating Status
Code 41, motor control has detected that the motor will not
come up to speed within 30 seconds of being commanded
to run or that the motor has been slowed to below 250 rpm
for more than 10 seconds after coming up to speed. Motor
wiring harness and fan coil control are operating properly,
do not replace.
2. Check to be sure that the blower wheel is not rubbing the
housing.
3. Check motor to be sure that the motor shaft is not seized
(motor control module must be removed and electronics
disconnected from windings to perform this check
properly).
4. Check motor windings section following instructions in
Section C, Indoor Fan Motor Troubleshooting.
If all these checks are normal, the motor control module may need
replacement.
STATUS CODE 16, SYSTEM COMMUNICATION FAULT
If, at any time, system communications are not successful for a
period exceeding 2 minutes, the fan coil control will only allow
emergency heating or cooling operation using a common
thermostat, and the terminal strip connections and will display
Status
code
16
on
the
amber
STATUS
LED
(see
Non--Communicating Emergency Cooling/Heating Mode). No
further unit troubleshooting information will be available at the UI
until communications are re--established.
Check system wiring to be sure the UI is powered and connections
are made A to A, B to B, etc., and wiring is not shorted.
Mis--wiring or shorting of the ABCD communications wiring will
not allow successful communications. Correcting wiring faults will
clear the code and re--establish communications.
Shorting or mis--wiring the low voltage system wiring will not
cause damage to unit control or to UI but may cause the low
voltage fuse to open.
STATUS CODE 46, BROWNOUT CONDITION
If the secondary voltage of the transformer falls below 15--vac for a
period exceeding 4 seconds, Status Code 46 will be displayed on
STATUS LED and the UI will command the control board to turn
off compressor.
When secondary voltage rises above 17--vac for more than 4
seconds, the brownout condition is cleared and normal system
operation will resume subject to any minimum compressor
off--delay function which may be in effect. Brownout does not
affect blower or electric heater operation.
STATUS CODE 53, OUTDOOR AIR TEMPERATURE
SENSOR FAULT
If an OAT sensor is found at power--up, input is constantly checked
to be within a valid temperature range. If sensor is found to be
open or shorted at any time after initial validation, Status Code 53
will be displayed at amber STATUS LED.
Check for faults in wiring connecting sensor to OAT terminals.
Using an Ohm meter, check resistance of thermistor for a short or
open condition.
If thermistor is shorted or open, replace it to return the system to
normal operation. If fault is in the wiring connections, correcting
the fault will clear the code and return the system to normal
operation.
NOTE: If fault condition is an open thermistor or a wiring problem
that appears to be an open thermistor and the power to the unit is
cycled off, the fault code will be cleared on the next power--up but
the fault will remain and system operation will not be as expected.
This is because on power--up, the unit control cannot discern
the difference between an open sensor or if a sensor is not
installed.
F. HP/AC Control Troubleshooting
See Table 2 for HP/AC control board status codes and
troubleshooting information.
Step 2 — Sequence of Operation
The 50XT--A packaged heat pump is designed for installation with
a communicating UI. This unit will not respond to commands
provided by a common thermostat except under certain emergency
situations described in Step 1—Start--Up.
The UI uses temperature, humidity and other data supplied from
indoor and outdoor system components to control heating or
cooling system for optimum comfort. The unit will be commanded
by UI to supply airflow. The unit will operate the indoor fan at
requested airflow for most modes.
The nominal requested airflow will be 350 cfm per ton of nominal
cooling capacity as defined by unit size. Actual airflow request will
be adjusted from nominal using indoor and outdoor temperature
and indoor humidity data to optimize the system operation for
occupant comfort and system efficiency. Refer to UI literature for
further system control details.
Airflow during electric heater operation must be greater than a
minimum level for safe operation. If UI instructs unit to turn on
electric heat and the requested airflow is less than the minimum
level the fan coil control will override requested value.
NOTE
: Once the compressor has started and then has stopped, it
should not be started again until 4 minutes have elapsed. The
cooling cycle remains “on” until the room temperature drops to
point that is slightly below the cooling control setting of the UI.
50X
T
--
A
