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Installer's Guide
6. The use of color coded low voltage wire is recommended to
simplify connections between the outdoor unit, the
thermostat and the indoor unit.
Table 1 — NEC Class II Control Wiring
24 VOLTS
WIRE SIZE
18 AWG
16 AWG
14 AWG
7. Table 1 defines maximum total length of low voltage
wiring from outdoor unit, to indoor unit, and to thermostat.
8. Mount the indoor thermostat in accordance with instruc-
tion included with the thermostat. Wire per appropriate
hook-up diagram (included in these instructions).
E. DEFROST CONTROL
The demand defrost control measures heat pump outdoor
ambient temperature with a sensor located outside the
outdoor coil. A second sensor located on the outdoor coil is
used to measure the coil temperature. The difference between
the ambient and the colder coil temperature is the difference
or delta-T measurement. This delta-T measurement is
representative of the operating state and relative capacity of
the heat pump system. By measuring the change in delta-T,
we can determine the need for defrost. The coil sensor also
serves to sense outdoor coil temperature for termination of
the defrost cycle.
FAULT IDENTIFICATION
A fault condition is indicated by the flashing light on the
defrost control inside the heat pump control box.
In normal operation, the defrost control light will flash once
each second. If the light is flashing more than once per second
or not at all, refer to the service manual for that unit.
PIN IDENTIFICATION (See Figure 6.)
1. TEST_COMMON (Shorting any of the other pins to this
pin causes the function of the other pin to be executed.
Leaving this pin open results in the normal mode of
operation.)
2. TST = Test (Shorting TEST_COMMON to this pin
speeds up all defrost board timings.)
6
PIN IDENTIFICATION
4
MAX. WIRE LENGTH
150 FT
225 FT.
300 FT.
(HEAT PUMPS ONLY)
3. FRC_DFT = Forced Defrost (Short TEST_COMMON to
this pin for two (2) seconds to initiate a forced defrost.
Remove the short after defrost initiates.)
DEFROST CONTROL CHECKOUT
Normal operation requires:
a. LED on board flashing 1 time/second.
b. 24V AC between R & B
c. 24V AC between Y & B with unit operating
d. Defrost initiation when FRC_DFT pin is shorted to
TEST_COMMON pin.
If a defrost control problem is suspected, refer to the service
information in control box.
F. COMPRESSOR START UP
After all electrical wiring is complete, SET THE THERMO-
STAT SYSTEM SWITCH IN THE OFF POSITION SO
COMPRESSOR WILL NOT RUN, and apply power by closing
the system main disconnect switch. This will activate the
compressor sump heat (where used). Do not change the
Thermostat System Switch until power has been applied for
one (1) hour. Following this procedure will prevent potential
compressor overload trip at the initial start-up.
WARNING
!
Do NOT connect 24 VAC to T1 (ODS-A) terminal. ODS-A
thermistor WILL BE BLOWN.
G. OPERATIONAL AND CHECKOUT
PROCEDURES
Final phases of this installation are the unit Operational and
Checkout Procedures which are found in this instruction. To
obtain proper performance, all units must be operated and
charge adjustments made in accordance with procedures
found in the Service Facts.
H. ELECTRIC HEATERS
Electric heaters, if used, are to be installed in the air han-
dling device according to the instructions accompanying the
air handler and the heaters.
I. START CONTROL
Some models have quick start components which are factory
installed. For models that do not have factory installed start
components, provisions are made for a field installed start kit
accessory. When adding an accessory, follow the instructions
provided with the kit.
J. OUTDOOR THERMOSTAT
An outdoor thermostat TAYSTAT250B may be field installed.
For data, see wiring diagram attached to unit and instruction
sheet packaged with outdoor thermostat.
K. SEACOAST SALT SHIELD
If installed within one mile of salt water, including sea-
coasts and inland waterways, models without factory sup-
plied Seacoast Salt Shields require the addition of
BAYSEAC001 (Seacoast Kit) at installation time.
IMPORTANT:
See Limited Warranty information in Use and Care Manual.
18-BC56D1-5
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