Lennox HP29 Series User Manual

LATCH RELAY K6
14
568
9
10
12
13 14
FIGURE 5
SET
RESET
Page 6
I−UNIT COMPONENTS
The HP29−090 and HP29−120 components are shown in
figures 1 and 2.
A−CONTROL BOX COMPONENTS
The HP29−090 control box components are shown in fig
ure 3. The HP29−120P control box components are shown
in figure 4.
1 − Disconnect Switch S48
(Option −2 Units)
HP29 heat pumps units may be equipped with an optional
disconnect switch S48. S48 is a factory−installed toggle
switch used to disconnect power to the unit.
2 − Outdoor Fan Capacitors C1 (all units)
and C2 (120P)
All HP29 units use single−phase condenser fan motors.
Motors are equipped with a fan run capacitor to maximize
motor efficiency. Outdoor fan capacitors C1 and C2 assist
in the start up of condenser fan motors B4 and B5. Capaci
tor ratings are on outdoor fan motor nameplates.
3 − Compressor Contactor K1 (all units)
All compressor contactors are three−pole−double break
contactors with a 24V coil. K1 energizes compressor B1 in
both HP29−090 and HP29−120 units. The contactor is en
ergized from indoor thermostat terminal Y when thermo
stat demand is present.
4 − Low Ambient Thermostat S41
(HP29−120 only)
S41 is a N.C. limit which opens on temperature fall at 55+
5_F. The switch resets when temperature rises to 65+ 6_F.
S41 opens and de−energizes K68 which de−energizes out
door fan B5. When S41 closes, fans will be re−energi
zed.This intermittent fan operation increases indoor evap
orator coil temperature to prevent icing.
5 − Latch Relay K6 (all units)
HP29 units are plumbed so that the unit is in cooling mode
when the reversing valve is energized. Latch relay K6 con
trols operation of the reversing valve and is controlled (indi
rectly) by the indoor thermostat. The combined operation
of latch relay K6 and transfer relay K8 allows the HP29
heat pumps to use a conventional heat/cool thermo
stat instead of a heat pump thermostat.
A latch relay (figure 5 ) has two coils: a SET" coil and a
RESET" coil. When 24VAC is applied to the SET" coil, the
normally open contacts close and the normally closed con
tacts open. When power is removed from the SET" coil,
nothing happens; the NO. contacts remain closed and the
N.C. contacts remain open. The contacts do not return to
their normal position until the RESET" coil is energized.
Once the contacts are reset, they remain in their normal
position when power is removed.
HP29 units use a DPDT
latch relay. Each set of nor
mally open contacts con
trols a reversing valve.
When the SET" coil is en
ergized, the normally open
contacts close to energize
the reversing valve (there
by placing the unit in the
cooling mode). When pow
er is removed from the
SET" coil (such as when
thermostat demand is satis
fied), the normally open
contacts remain closed, the
reversing valve remains en
ergized and the unit re
mains in the cooling mode.
When a heating demand is initiated, the RESET" coil is
energized. The normally open contacts open and the re
versing valve is deenergized (thereby placing the unit in
the heating mode). When heat demand is satisfied and
power to the RESET" coil is removed, the normally open
contacts remain open, the normally closed contacts re
main closed and the unit remains in the heating mode.

Lennox HP29 Series Specifications

General

Brand	Lennox
Model	HP29 Series
Category	Heat Pump
Language	English