Maritime Geothermal ATF-45, Installation And Service Manual

Page: 32 / 110

Page 32 002000MAN-01 1-Jun-2018
BACnet Control
If controlling the system via the BACnet interface, skip the
entire Operation section. In this case, see the BACnet Interface
section later in this manual for network specification and BACnet
object names.
Air Thermostat Operation
Demand for room heating or cooling through the ducted air
system will come from a 24V 3H/2C room thermostat, described
in the Wiring section. Refer to the thermostat’s manual to set it
up for 2-stage heat pump with electric backup, and for details on
thermostat operation.
In heating dominant climates, better cooling mode dehu-
midification can be achieved by disabling compressor stage 2 in
cooling. Then cooling mode will always operate at 67% com-
pressor capacity, and longer run times will result. This setting
must be made through the PC App’s Control Panel; see PC
Application (PC App) section.
Hydronic Temperature Control
One of the features of the ATF’s GEN2 Control Board is
built in aquastat functionality known as “Setpoint Control”. This
is an internal routine to sample the water OUT temperature to
determine if hydronic heat is required; both water IN and OUT
temperatures are measured using sensors on water lines inside
the unit. The indoor circulator pump is turned on at regular in-
tervals to refresh the water temperature. If sampling is not de-
sired, there is the option to use an external accessory tempera-
ture sensor.
There is also provision to connect an external aquastat or
controller instead of using this routine, for example if two water
loops with different setpoints are being heated.
1. Hydronic Heating: Setpoint Control
It is recommended that this method be used to control the
system’s hydronic heat demand since it eliminates the need for
an external temperature sensor or aquastat.
There are two options for Setpoint Control, Indoor Loop
(ICR) method and HTS/CTS method.
Setpoint Control Method 1 - Indoor Loop (ICR)
This is the default method and uses the Indoor OUT tem-
perature probe inside the unit for temperature control. Its value
is displayed in the Hot Tank box on the PC App’s View --> Set-
point Control screen. If this temperature shows NC , then
either the probe is not connected to the board or there is a prob-
lem with it.
The heat pump will cycle the indoor circulator on and off
when the unit is idle or in air heating/cooling mode, in order to
sample the water temperature. When hydronic heating mode
ends, the indoor circulator will continue to run for 30 seconds. It
will then cycle with an OFF time and ON time as set by the Set
ICR Sampling popup which appears when
SET
is clicked on
the View --> Setpoint Control screen. The timer counts
down the time remaining before the next switch between ON/
OFF. The indoor circulator indicator will indicate when the circu-
Operation
lator is ON, OFF or SAMPLING. The default sampling times are
2 minutes ON and 6 minutes OFF. The LCD display will also
indicate when the ICR is sampling (ON). The
Timer Override
button will reduce the countdown timer to 10 seconds.
See below, and also the PC Application (PC App) section
for full screenshots of the various windows.
Setpoint Control Method 2 - External HTS/CTS
When this method is used, no indoor circulator control for
temperature sampling will occur. It requires an external temper-
ature sensor placed in a dry well in the top of the buffer tank. Its
value is displayed in the Hot Tank box on the PC App’s View -->
Setpoint Control screen. If this temperature shows NC ,
then either the probe is not connected to the board or there is a
problem with it.
A 10K Type 7 (or Type 3) NTC thermistor along with a 10K
1% or better resistor must be connected to the control board in
order to use the External HTS/CTS method. Connect the sen-
sor to the AI_5 input as shown above and on the wiring diagram
(SCH) in the Model Specific Information section. Remove the
AI_5 jumper on the control board.
For both setpoint control methods, pool water setpoint is
controlled through the LCD display or PC App (View-->Pool
Water Setpoints) .