FloAire 25HBC - Manual (Page 6)

6
Sequence of Operation
Turn on power to indoor and outdoor units. Transformer is
energized.
Cooling
On a call for cooling, thermostat makes circuits R--O and R--Y, and
R--G. Circuit R--O energizes reversing valve, switching it to
cooling position. Circuit R--Y energizes contactor, starting outdoor
fan motor and compressor circuit. R--G energizes indoor unit
blower relay, starting indoor blower motor on high speed.
When thermostat is satisfied, its contacts open, de--energizing
contactor and blower relay. Compressor and motors should stop.
NOTE: If indoor unit is equipped with a time--delay relay circuit,
the indoor blower will run an additional 90 seconds to increase
system efficiency.
Heating
On a call for heating, thermostat makes circuits R--Y and R--G.
Circuit R--Y energizes contactor, starting outdoor fan motor and
compressor. Circuit R--G energizes indoor blower relay, starting
blower motor on high speed.
Should temperature continue to fall, R--W2 is made through
second--stage room thermostat. Circuit R--W2 energizes a relay,
bringing on first bank of supplemental electric heat and providing
electrical potential to second heater relay (if used). If outdoor
temperature falls below setting of outdoor thermostat (field
installed option), contacts close to complete circuit and bring on
second bank of supplemental electric heat.
When thermostat is satisfied, its contacts open, de--energizing
contactor and relay. All heaters and motors should stop.
Defrost
The defrost control is a time/temperature control which includes a
field selectable (quick--connects located at board edge) time period
between defrost cycles (30, 60, or 90 minutes), factory set to 90
minutes.
The electronic defrost timer sequence is enabled when the T1 input
on the board is energized. The timer starts only when the defrost
thermostat is closed and the contactor is energized.
Defrost mode is identical to cooling mode except that outdoor fan
motor stops and second--stage heat is turned on to continue
warming conditioned spaces.
To initiate defrost, the defrost thermostat must be closed. This can
be accomplished as follows:
1. Turn off power to outdoor unit.
2. Disconnect outdoor fan motor lead from OF2 on control
board (see Fig. 11). Tape lead to prevent grounding.
3. Restart unit in heating mode, allowing frost to accumulate
on outdoor coil.
4. After a few minutes in heating mode, liquid line temperat-
ure should drop below closing point of defrost thermostat
(approximately 30°F/--1.11°C).
5. Short between speedup terminals with a flat--blade screw-
driver. This reduces the timing sequence to 1/25th of origin-
al time. (See Table 4.)
6. When you hear reversing valve change position, remove
screwdriver immediately; otherwise, control will terminate
normal 10--minute defrost cycle in approximately 2
seconds.
NOTE: Length of defrost cycle is dependent upon length of time
it takes to remove screwdriver from test pins after reversing valve
has shifted.
7. Unit will remain in defrost for remainder of defrost cycle
time or until defrost thermostat reopens at approximately
65°F (18.33°C) coil temperature of liquid line.
8. Turn off power to outdoor unit and reconnect fan motor
lead to OF2 on control board.
OUTDOOR FAN
RELAY
Y OUTPUT TO PRESSURE
SWITCHES AND CONTACTOR
THERMOSTAT INPUTS
T1 - ENABLES DEFROST
TIMER.MUST BE
ENERGIZED FOR
DEFROST TIMER
TO START
C - COMMON
O - REVERSING VALVE
SPEEDUP
HK32EA001
DEFROST THERMOSTAT
MUST BE CLOSED BEFORE
DEFROST TIMER BEGINS
A05332
Fig. 11 -- Defrost Control
Table 4 – Defrost Control Speedup--Timing Sequence
PARAMETER
MINIMUM
(MINUTES)
MAXIMUM
(MINUTES)
SPEEDUP
(NOMINAL)
30---minute cycle 27 33 7 sec
50---minute cycle 45 55 12 sec
90---minute cycle 81 99 21 sec
10---minute cycle 9 11 2 sec
5 minutes 4.5 5.5 1 sec
25H
B
B
/25H
B
C