T H E S M A R T S O L U T I O N F O R E N E R G Y E F F I C I E N C Y
19
c l i m a t e m a s t e r. c o m
Tr a n q u i l i t y
®
W a t e r- t o - W a t e r T H W S e r i e s
R e v i s e d : 0 2 J a n u a r y, 2 0 1 3
Electrical - Controls
Warm weather shutdown (WWSD): Radiant fl oor systems
are the most comfortable type of heating available today.
However, they do have one disadvantage – quickly
switching from heating to cooling is not possible due
to the mass heat storage in the slab. For example, in
the spring or fall, there could be times where heating
is required at night, but cooling is required during the
day. With a warm fl oor, the cooling system has to work
much harder to cool the space. WWSD shuts down the
water-to-water heat pump at a pre-determined outdoor
air temperature (adjustable at the user interface). When
a water-to-air heat pump is used for space cooling, this
unit can be enabled when WWSD is activate, allowing
the water-to-air heat pump to heat via forced air during
the shoulder seasons, avoiding the warm slab/cooling
dilemma (see cooling enable, below). A normally closed
contact is provided in the THW unit to de-energize the
heating system controls (e.g. radiant fl oor control panel)
during WWSD. WWSD does not affect DHW heating. In
other words, the water-to-water unit can still operate for
generating DHW, even if the heating distribution (e.g.
radiant fl oor) system is disabled.
The WWSD activation (i.e. when the WWSD feature is
enabled) outdoor air temperature range is 4-38°C with
a default value of 21°C. The WWSD deactivation (i.e.
when the radiant heating returns to operating mode)
temperature range is 2-35°C with a default value of
18°C and a minimum difference between activation
and deactivation temperatures of 3°C. If the outdoor
air temperature (OAT) rises above the activation
temperature, the cooling enable signal (see below) is
enabled, and the control no longer controls the buffer
tank temperature. If the OAT falls below the deactivation
temperature, the control resumes monitoring the buffer
tank temperature.
Cooling enable: Cooling enable is tied to the WWSD
feature. If desired, the water-to-air unit controls can
be wired to the THW unit controls, which will allow
the water-to-air unit to operate during WWSD, but will
disable the water-to-air unit when the THW unit is not
in WWSD mode. When a heat pump thermostat is
connected to the water-to-air unit, forced air heating
may be used for the shoulder seasons, allowing quick
heating to cooling changeover. If this feature is used,
the consumer will easily be able to tell when WWSD is
enabled because the water-to-air unit thermostat will
only be active during WWSD. Otherwise, the water-
to-air unit thermostat will be disabled, indicating that
the consumer should utilize the hydronic heating (e.g.
radiant fl oor) thermostat.
Second stage heating (backup boiler): Optimal heat
pump sizing may not include a water-to-water heat
pump that can handle 100% of the heating load.
When a backup boiler is used to supplement the
heating capacity, a 24VAC output from the THW unit
can energize the boiler. The boiler control box simply
needs a relay that can be used to interface with the
THW unit.
DHW priority: By default, DHW heating always takes
priority over space heating. Normally, the hot water
load will be satisfi ed quickly, and the unit can then
switch back to space heating.
Time schedule: DHW temperatures may be adjusted
during occupied/unoccupied times via the user
interface to save energy costs.
Vacation mode: DHW generation may be disabled
when the user interface is placed in vacation mode.
A return date and time may be set to restore normal
DHW temperatures.
Emergency DHW generation: If the THW unit is locked
out, a 24VAC signal can be sent to a contactor at the
water heater to allow the operation of the electric
elements and associated thermostat.
Enhanced heat pump lockouts: Like any ClimateMaster
unit, the CXM board locks out the compressor any
time a lockout condition occurs. The MPC reads the
lockouts from the CXM, and reports the condition to
the user interface. The user interface changes from a
blue backlight to a red backlight, indicating a lockout.
The actual lockout is reported (e.g. High Pressure)
at the interface. In addition to the standard CXM
faults, the MPC checks for bad thermistors and high
compressor discharge temperature, which are also
reported at the user interface.
Pump control: If the optional load and source pump(s)
are selected, the control energizes the pumps any time
the compressor is operating.
Variable speed fl oor pump (VSFP) output: Some radiant
fl oor systems utilize a variable speed pump on the fl oor
system, which changes fl ow based upon the number
of zones open or closed. Since the pump has built-in
controls, only a power supply is needed. An optional
power terminal is available for VSFP applications.
