LATCH RELAY K6
1
4
5
6
8
9
10
12
13
14
FIGURE 4
SET
RESET
Page 19
5-Start Capacitor C7
Compressor start capacitor C7 is used in CHA/
CHP16-024/030 units only, and located in the compressor
compartment. C7 is connected in parallel with capacitor
(C12). The capacitor is energized during compressor startĆ
up and is switched off by potential relay K31 when the comĆ
pressor nears full speed. See side of capacitor for ratings.
The start capacitor uses a 15K ohm 2 watt bleed" resistor
connected in parallel with the capacitor terminals. The resisĆ
tor is used to slowly discharge the capacitor when not in use.
6-Dual Capacitor C12
Single phase CHA/CHP16/20 model units use a single
dual" capacitor, connected to both the fan motor and the
compressor. A dual capacitor is two independent capacitors
inside one can. Each side of the capacitor has different ratĆ
ings and will be printed on the side.The capacitor is located
inside the compressor compartment.
7-Condenser Fan Relay K10
Condenser fan relay K10, used in all CHP16/20 units, is a
DPDT relay with a 24V coil. In all units K10 de-energizes conĆ
denser fan B4 in response to defrost demand.
8-Latch Relay K6
CHP16/20 commercial units are designed to use convenĆ
tional heat/cool thermostats and are equipped with latch
relay K6. Latch relay K6 is used in commercial heat pumps
to control operation of the reversing valves when a heat/cool
thermostat is used.
CHP16/20 series units are plumbed so that the unit is in coolĆ
ing mode when the reversing valve is energized. Latch relay
K6 controls operation of the reversing valves and is controlled
by the indoor thermostat.
A latch relay (figure 4) is a special type of relay with two coils;
a SET" coil and a RESET" coil. When 24VAC is applied to
the SET" coil, the normally open contacts close and the norĆ
mally closed contacts open. When power is removed from
the SET" coil, nothing happens; the N.O. 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.
CHP16/20 series units use a
DPDT latch relay. One set of
normally open contacts is conĆ
nected in series with thermostat
Y1 and compressor contactor
K1 while the matching normally
closed contacts are connected
in series with thermostat W1
and compressor contactor K1.
The other set of normally open
contacts is connected in series
with the reversing valve. When
the SET" coil is energized (Y1),
the normally open contacts
close to energize the reversing
valve (thereby placing the unit in
cooling mode) and to energize
the compressor contactor.
When power is removed from the SET" coil (such as when
cooling demand is satisfied), the normally open contacts remain
closed, the reversing valve remains energized and the unit reĆ
mains in cooling mode.
9-Transfer Relay K8
The combined operation of latch relay K6 and transfer relay
K8 allow the CHP16 to use a conventional heat/cool thermoĆ
stat as opposed to a heat pump thermostat. Transfer relay
K8 switches thermostat blower demand from cooling mode
to heating mode. Relay K8 routes blower demand from the
appropriate thermostat output to the blower relay depending
on whether the unit is in cooling or heating mode.
During cooling mode, the blower relay receives power from
thermostat terminal G (relay K8 deĆenergized). During
heating demand transfer relay K8 is energized. When K8 is
energized, power routing is switched so that the blower
relay receives power from heating thermostat demand
(W1).
10-Potential Relay K31
Relay K31 is used in the CHA/CHP16-024/030 models ONLY
and is located in the control box. It is a potential relay which
controls the operation of the compressor starting circuit. The
relay is normally closed when the compressor (contactor K1)
is de-energized. Capacitor (C7) is connected to a set of norĆ
mally closed K31 contacts and assists the compressor in
starting. When K1 energizes, the compressor immediately beĆ
gins startĆup. K31 remains de-energized during compressor
start-up and the start capacitor (C7) remains in the circuit. As
the compressor gains speed K31 is energized by electromoĆ
tive forces generated by the compressor. When K31 enerĆ
gizes, its contacts open to take the start capacitor out of the
circuit.
