506162-02
Issue 0847
Page 7 of 14
10. Rem ove charge if superheat is low and add charge
if superheat is high.
NOTE:
If a TXV is installed on indoor unit, a hard start kit
is required on all m odels with reciprocating com pressors.
Refer to the specification sheet for details. Hard start kits
are also recom m ended for areas with utility power lower
than 208 Vac.
Units w ith Indoor TXV
Units installed with TXV on indoor side, require charging
with the subcooling m ethod.
1.
Operate unit a m inim um of 10 m inutes before
checking charge.
2.
M easure liquid service valve pressure by attaching
an accurate gage to service port. Determ ine
saturation tem p. from T/P chart.
3.
Measure liquid line tem perature by attaching an
accurate therm istor type or electronic therm om eter
to liquid line near outdoor coil.
4.
Calculate subcooling (saturation tem p.— m easured
tem p.).
5.
Find the point where required subcooling
tem perature intersects m easured liquid service valve
pressure.
6.
Add refrigerant if subcooling is lower than table
below. Recover refrigerant if subcooling is high.
Heating Check Chart Procedure
To check system operation during heating cycle, refer to
the Heating Check Chart located on back of control box
cover. This chart indicates whether a correct relationship
exists between system operating pressure and air
tem perature entering indoor and outdoor units. If pressure
and tem perature do not m atch on chart, system refrigerant
charge m ay not be correct.
Do not use chart to adjust
refrigerant charge.
Charge m ust be rechecked again during the cooling
season.
Cold W eather Application
A cold weather accessory kit m ay be required for heat
pum ps operating at am bient conditions below 25
/
F.
Supplem ental heat should be provided for these conditions
due to the expected perform ance degeneration.
SYSTEM OPERATION
The outdoor unit and indoor blower cycle on dem and
from the room therm ostat. W hen the therm ostat blower
switch is in the ON position, the indoor blower operates
continuously.
Filter Drier
The outdoor unit is equipped with a bi-flow filter drier. If
replacem ent is necessary, order new dryer according to the
service parts m anual.
Em ergency Heat Function (Room Therm ostat)
An em ergency heat function is designed into som e room
therm ostats. This feature is applicable when isolation of
outdoor unit is required or when auxiliary electric heat is
staged by outdoor therm ostats. W hen the room therm ostat
is placed in the em ergency heat position, the outdoor unit
control circuit is isolated from power and field-provided
relays bypass the outdoor therm ostats. An am ber
indicating light sim ultaneously com es on to rem ind the
hom eowner that he is operating in the em ergency heat
m ode.
Em ergency heat is usually used during an outdoor unit
shutdown, but it should also be used following a power
outage. If power has been off for over an hour and the
outdoor tem perature is below 50
/
F (10
/
C). System should
be left in the em ergency heat m ode at least six hours to
allow the crankcase heater sufficient tim e to prevent
com pressor slugging. This applies only to system s with
crank case heaters.
Defrost System
The defrost system includes two (2) com ponents: a
defrost therm ostat and a defrost control.
Defrost Therm ostat
The defrost therm ostat is located on the outdoor coil of
m ost m odels and on the liquid line between the
check/expansion valve and the distributor on R-4110A TXV
equipped m odels. W hen defrost therm ostat senses 29
/
F
(42
/
on R-410A TXV’s) or cooler, the therm ostat contacts
close and send a signal to the defrost control board to start
the defrost tim ing. It also term inates defrost when the
liquid line warm s up to 60
/
F.
Defrost Control
The defrost control board includes the com bined
functions of a tim e/tem perature defrost control, defrost
relay, diagnostic LEDs and term inal strip for field wiring
connections.
The control provides autom atic switching from norm al
heating operation to defrost m ode and back. During
com pressor cycle, the control accum ulates com pressor
run tim es at 30-, 60-, or 90-m inute field-adjustable
M odel
R equired Subcooling
(± I
/
F)
2H P 13
2H P 14
4H P 13
18
14
10
12
24
9
3
14
30
13
8
17
36
9
14
10
42
11
3
16
48
8
9
7
60
12
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13