Tranquility THW - 50 & 60Hz R410A - ClimateMaster Geothermal Heat Pumps - Rev.: 30 June, 2008B
16
ELECTRICAL - CONTROLS
Controls
User interface: Figure 10 shows the factory installed
and wired panel-mounted user interface for customizing
the MPC programming. A large dot-matrix style 2” x 2”
[5 x 5 cm] back-lit display is controlled by four arrow keys
and a select key. The main screen, as shown in figure
11, displays current outdoor and water temperatures, and
allows the user to change settings by selecting one of the
menus from the bottom of the screen (see figure 13 THW
User Interface Menu). A special installer set up mode
allows the technician to change some of the default MPC
parameters. The installer menu may only be accessed
when the unit is placed in the off mode. Holding the
up and down buttons at the same time will cause the
interface to enter the installer setup mode. See figure 14
(interface installer menu) The user interface includes a
time schedule for DHW generation, Fahrenheit/Celsius
selection, vacation mode for DHW, and other user
preference options.
Figure 10: THW User Interface
Figure 11: THW User Interface Main Screen
THW Series Control Features
The advantage of a programmable controller, as outlined
above, is the ability to integrate complex decision-
making tasks with the standard heat pump (CXM)
controls and communicate with a user interface. Below
is a list of standard features that are included in the THW
series controls.
Outdoor temperature reset: The heat pump capacity
and water temperature delivery to the heating system
must be designed for local weather conditions, usually
at the 99.6% outdoor temperature. Therefore, 99.6%
of the heating season, the heating load is less than it
is at design conditions. As the outdoor temperature
decreases, the heat loss of the structure increases,
which requires more capacity from the heating system.
If the water temperature is reduced as the outdoor air
temperature increases (and vise-versa), the heat pump
operates at higher COP most of the year. The MPC
has a built in algorithm that adjusts the buffer tank
temperature based upon outdoor air temperature to
maximize efficiency and comfort. Temperature settings
may be adjusted at the user interface if factory defaults
are not sufficient.
The base setpoint for energizing the compressor in the
heating mode is determined by subtracting one-half the
heating differential value (HTD) from the buffer tank
heating temperature setpoint. The HTD is the differential
used for controlling setpoint. For example, if the buffer
tank setpoint is 100°F [38°C], and the HTD is 6°F [3°C],
the compressor will be energized at 97°F [36°C] and will
be turned off at 103°F [39°C]. The HTD is the difference
between the compressor “call” (97°F [36°C]) and the
“satisfied” (103°F [39°C]) temperature. The buffer
tank temperature may then be reduced by the outdoor
temperature reset function, depending on the current
outdoor air temperature (OAT) value. The valid range
for the buffer tank heating setpoint is 70-140°F [21-60°C],
with a default value of 100°F [38°C]. The valid range for
the heating differential value (HTD) is 4-20°F [2-11°C],
adjustable in 2°F [1°C] increments, with a default value of
6°F [3°C].
Arrow Keys
Select Key
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CAUTION!
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CAUTION:
Maximum leaving water temperature of the
THW series equipment is 145°F [63°C]. For domestic hot
water tank temperatures or heating buffer tank temperatures
above 130°F [54°C], pump and pipe sizing is critical to
insure that the flow rate through the heat pump is sufficient
to maintain leaving water temperatures below the maximum
temperature, and to provide water flow rates within the
ranges shown in the performance section of this manual.
