Unit Operation - Haier GE NS18HM Service Manual

Heating Operation Mode Jumper
The Heating Operation Mode Jumper is only used on
applications installed with a conventional 24VAC heat
pump thermostat. In applications with a conventional
24VAC heat pump thermostat, the compressor capacity is
controlled to maintain the target liquid pressure setpoint.
The Heating Operation Mode Jumper has two selectable
heating modes. The two modes are Efficiency (Jumper
installed on Pins 1 & 2) and Comfort Mode (Jumper
Removed). The factory default position is the Efficiency
Mode. The Efficiency mode has a variable liquid pressure
setpoint that will vary with the outdoor temperature; as
the outdoor temperature decreases, the liquid pressure
setpoint will increase. When the Operation Mode jumper is
installed in the "Comfort Mode" the liquid pressure setpoint
is 425 psig.
Operation Mode Jumper
Jumper Position
Efficiency (default) Pin 4 to Pin 5
Comfort Jumper Off
Table 10. Heating Operation Mode Jumper
(Conventional 24VAC Heat Pump Thermostats Only)
Figure 15. Operation Mode Jumper
Target Liquid Pressure
Setting
Variable based on OAT
425 PSIG
Page 26

Unit Operation

NS18HM Unit Operation with a Conventional
24VAC 2-Stage Thermostat
When the NS18HM unit is installed with a conventional
24VAC 2-stage thermostat, a Y1 first stage heating or
cooling demand will initiate heating or cooling operation
and first stage indoor blower operation. The compressor will
be controlled in the variable capacity mode by varying the
compressor capacity to obtain the target suction pressure
set point. The Y2 second stage heating or cooling demand
will initiate second stage blower operation. Increased
air volume will increase the load on the indoor coil and
increase the suction pressure. The NS18HM compressor
capacity will continue to be controlled based upon the
suction pressure. The unit capacity will be controlled in the
variable capacity mode throughout the range of capacity
from minimum capacity to maximum capacity. If the Y2
demand remains after 20 minutes, the NS18HM control will
begin to ramp up the compressor capacity until maximum
capacity is achieved. The NS18HM unit will cycle off once
the thermostat demand is satisfied.
NS18HM Unit Operation with a Conventional
24VAC Single-Stage Thermostat
When the NS18HM unit is installed with a conventional
24VAC single-stage heat pump thermostat, a Y1 first stage
heating or cooling demand will initiate heating or cooling
operation and heating or cooling indoor blower operation.
In single stage thermostat applications, a jumper must
be installed between Y1 and Y2 on the NS18HM outdoor
control. The compressor will be controlled in the variable
capacity mode by varying the compressor capacity to
obtain the target suction pressure set point. If the heating
or cooling demand remains after 20 minutes, the NS18HM
control will begin to ramp up the compressor capacity until
maximum capacity is achieved. The NS18HM unit will
cycle off once the thermostat demand is satisfied.
Defrost Function
The outdoor unit control uses a time-dependent frost
accumulation duration demand defrost control algorithm
to provide a demand defrost when the system falls below
optimum levels. The demand defrost control algorithm
is reactive based upon the previous heat pump run time
between defrost cycles (frost accumulation time) and the
time spend in defrost (defrost time). The outdoor unit control
31-5000751 Rev. 0