27
6.0 NORMAL SEQUENCE OF OPERATION
The following sections provide details on how the (-)
A18AZ/(-)P18AZ outdoor heat pump systems are
designed to operate under normal conditions. Under
abnormal conditions, Active Compressor and Inverter
Protection features built into the controls may alter
how the system operates to protect the compressor
and inverter from damage. The sequence of operation
is based on the system being set up for EcoNet
TM
communications using an EcoNet
TM
enabled air-handler
or gas furnace and an EcoNet
TM
Control Center. A
section is provided at the end that describes how the
system will operate if a conventional 24VAC 2-stage
thermostat is used in emergency situations when
communication issues are encountered to allow the
system to operate until the communication issues are
resolved.
NOTE: The use of a conventional 24VAC thermostat
eliminates many of the advanced operating and
diagnostic features the customer has paid for and is
strongly discouraged except in temporary emergency
situations until communication issues are resolved.
6.1 Cooling Mode
The EcoNet
TM
Control Center will determine when
cooling is necessary and the percentage of capacity
required and will then communicate this information
to the EcoNet
TM
Universal Outdoor Control (UODC)
which will direct the Power Inverter to ramp the
compressor up to the appropriate speed to meet
the required capacity percentage being requested.
The percentage of capacity required is based on
the difference between the temperature set-point
and the room temperature measured at the Control
Center. One second after the compressor starts, the
UODC will direct the variable speed ECM outdoor
motor to operate at the appropriate speed to deliver
the necessary outdoor air-flow for that capacity
percentage. Upon a call for cooling, the EcoNet
TM
Control Center accesses the indoor air-flow parameters
found in the model data residing in the UODC memory
card and directs the EcoNet
TM
enabled air-handler or
gas furnace control board to deliver an appropriate
indoor air-flow level based on the capacity percentage
required at that point in time. The EcoNet
TM
air-handler
or gas furnace control board will then direct the
variable speed ECM indoor blower motor to start and
operate at the requested cooling air-flow level. As the
building load changes throughout the call for cooling
operation, the compressor speed, outdoor fan speed,
and indoor air-flow level will respond by ramping up
or down as required to meet the building load exactly
rather than simply cycling on and off as conventional
systems do. Should the building load exceed the
capacity of the system, the inverter will direct the
compressor to speed up and operate at greater than
100% capacity (Overdrive Mode) in an attempt to meet
the building load until the maximum compressor speed
is reached. Since the noise level of the compressor
increases as speed increases, the maximum allowable
compressor speed in the Overdrive Mode can be
lowered using the EcoNet
TM
Control Center Installer
Menu (RPM Blocking) should the homeowner find the
compressor noise objectionable in the Overdrive Mode.
When the call for cooling has ended, the EcoNet
TM
Control Center will direct the outdoor and indoor units
to shut down. The compressor and outdoor fan motor
will ramp down to zero RPM and the indoor blower
motor will ramp down to the minimum air-flow level for
30-45 seconds to extract the residual cooling from the
cold indoor coil before it stops.
6.2 On-Demand Cooling
Dehumidication
The EcoNet
TM
Control Center can be configured for
On-Demand Dehumidification. This feature allows
the system to automatically increase the level of
dehumidification in the cooling mode by decreasing
the indoor air-flow by 15% when the indoor relative
humidity measured at the Control Center rises above
the set-point. Once the relative humidity drops to or
below the set-point, the indoor air-flow level returns to
normal.
6.3 Low Ambient Cooling Mode
Some applications require for space cooling when the
outdoor ambient temperature is below normal (<55°F
[13ºC]) such as a computer room or an interior space
with a heat source that must be cooled. (-)A18AZ/
(-)P18AZ heat pumps are equipped with a special
low ambient cooling mode that allows the system to
provide cooling when the outdoor temperature is below
55°F [13ºC] by cycling the outdoor fan to maintain an
adequate condensing temperature and subcooling level
based on an input from the coil temperature thermistor.
6.4 Heating Mode
The EcoNet
TM
Control Center will determine when
heating is necessary and the percentage of capacity
required and will then communicate this information
to the EcoNet
TM
Universal Outdoor Control (UODC)
which will direct the Power Inverter to ramp the
compressor up to the appropriate speed to meet
the required capacity percentage being requested.
The percentage of capacity required is based on
the difference between the temperature set-point
and the room temperature measured at the Control
Center. One second after the compressor starts, the
UODC will direct the variable speed ECM outdoor
motor to operate at the appropriate speed to deliver
the necessary outdoor air-flow for that capacity
percentage. Upon a call for heating, the EcoNet
TM
Control Center accesses the indoor air-flow parameters
found in the model data residing in the UODC memory
Operation
To Next Page
Loading...
Need help?
General
