Understanding The Heating And Cooling; Cycles - Dometic CapTouch Installation And Operating Manual

Operation
7 .1 Understanding the Heating and
Cooling Cycles
The heating and cooling cycles operate differently
depending on the system installed. This section
describes the possible cycles.
7 .1 .1 Normal Heating or Cooling Cycle
In AUTOMATIC mode, heating and cooling are supplied
as required to meet the cabin temperature set point.
• The system starts a cooling cycle once the cabin
temperature exceeds the temperature set point by
2 °F (1 °C) and starts a heating cycle once the cabin
temperature falls below the temperature set point by
2 °F (1 °C). The system continues the cycle until the
cabin temperature equals the set point.
• During a cycle, the cabin temperature must drop
below the set point by at least 4 °F (2 °C) before the
system switches from cooling to heating or exceed
the set point by at least 4 °F (2 °C) before the system
switches from heating to cooling. This behavior
prevents small temperature overshoots from causing
the system to switch between heating and cooling
when it is not necessary.
COOL mode supplies cooling only and HEAT mode
supplies heating only.
• The cabin temperature for either mode is maintained
within 2 °F (1 °C) of the set point by default.
• When the heating or cooling set point is satisfied,
the compressor cycles OFF and the fan returns to low
speed.
In Manual Fan Mode, the fan speed remains constant.
7 .1 .2 Chilled-Water System Operation
(CW Systems Only)
In CW systems, the water valve does not open unless the
water temperature is adequate to heat or cool the cabin.
The adequate heating or cooling water temperature is
defined by the water temperature differential setting in
the control parameters. Refer to "Selecting a Parameter"
on page 15.
10
To view the current water temperature, tap and hold
Fan and Up simultaneously for three seconds. Refer
to "Using the Control Display Panel" on page 13.
The fan remains on low speed until the adequate water
temperature is available.
I To provide heat when the required water
temperature is not available, install the optional
auxiliary electric heater, and program parameter
P-28. Refer to "Programming the Control" on page
14.
7 .1 .3 Reversing-Valve Operation
(DX Systems Only)
COOL mode or HEAT mode is determined by the
position of the reversing valve. The reversing valve is
programmed to automatically toggle in these situations:
• When the system is running and an opposite cycle is
needed to maintain the temperature, the reversing
valve will toggle to the opposite position to initiate
the opposite cycle and reduce the starting surge of
the compressor.
• When a cooling or heating cycle is initiated after the
system has been OFF for less than five minutes.
• When a cycle is interrupted by changing the display
mode to OFF or changing the set point from the
display panel.
To reduce reversing-valve noise, unnecessary valve
toggling is limited by default. Program the minimum
compressor staging delay (parameter P-3) to five
minutes or greater, to eliminate valve toggling. Refer to
"Programming the Control" on page 14.
When the system is powered up, a power-on-reset
I
always initiates a valve toggle.
7 .1 .4 De-icing Cycle (DX Systems Only)
DX systems have a de-icing cycle option to prevent ice
buildup on the evaporator coil during extended periods
of cooling operation. Installation variables, such as
grille sizes, length of ducting, insulation, and ambient
temperatures, determine the runtime required to achieve
the set point.
CapTouch Cabin Control
EN