Unit installation

14 Daikin IM 980-1
Operation and Maintenance
• On-Off fan and On-Off valve cycle operation: The
thermostat cycles the fan from the manually selected fan
speed to off and it cycles the valves on and off.
When the sys
tem switch is in the OFF position, the fan coil
system including the fan is shut off.
TA155: A HEAT-OFF-COOL system switch manually selects
heating or cooling mode. In the HEAT position, only the heat
output cycles with demand. In the COOL position, only the
cool output cycles with demand. In the OFF position, heating
and cooling outputs are off. Units with a two position system
switch or without a system switch must use a load transfer
switch when both heating and cooling outputs are used. This
prevents control failure and equipment damage caused by
direct cycling between loads.
TB155: An ON-OFF system switch enables auto-changeover
of heating and cooling modes. In the ON position the
thermostat activates heating or cooling outputs dependant
upon the relationship between set point and ambient
temperature. Heat on to cool on dead band is 4°F. In the OFF
position, heating and cooling outputs are off. Units without a
system switch cycle between heating and cooling with a 4°F
dead band.
FA N : Some units have a switch for manual selection of fan
speed. On these units fan operation is either internally wired
for fan continuous operation or is dependant upon connection
to the fan supply input . When internally wired for fan
continuous operation, the fan will be off when the system
switch is off. When dependant upon external connections the
fan may not be off with the system switch in the off position.
The fan supply input is switched to fan speed outputs (HI-
MED-LO).
MT158 and MT168 Thermostat-Controllers with
Digital Display
For more details refer to page 51, 55 or 59. Series MT158 and
MT168 microprocessor-based thermostat-controllers combine
a proportional integral control algorithm with adaptive logic.
They may be unit-mounted or remote-wall mounted.
Figure 16: MT158 and MT168 Thermostats
Heating and cooling outputs for the MT158 are individually
configurable for three-wire floating control valves or On/Off
valves in the Normally Open or Normally Closed modes.
Heating and cooling outputs for the MT168 provide 0-10 Vdc
or 4-20 mA for proportional modulating valve control. The
integrated, three-speed fan control switch is line voltage to
allow direct connection to the fan motors. Manual or automatic
changeover is provided with remote setback capability from a
time clock or facility management system. Features include a
Fahrenheit or Celsius digital display and a built-in purge cycle
which assists the controller to determine if the system is
supplying hot water or cooling.
Two standard control options are available:
• Continuous fan and modulating (or On-Off) va
lve
o
peration: The fan runs continuously at the manually
selected fan speed (high, medium or low). The controller
modulates the valves or, on the MT158, dip-switches can be
set to cycle the valves on and off.
• On-Off fan cycle operation and modulating
(or On-Off)
valve operation: The
controller cycles the fan from the
manually selected fan speed to off. The controller modulates
the valves or, on the MT158, dip-switches can be set to cycle
the valves on and off.
T170 Thermostat with Digital Display
Two thermostats are offered for remote installation only:
TA170 for three-speed fan control and TB170 for staged fan
operation. Both thermostats are used for On-Off control of
low- or line-voltage valves with auto changeover. Detailed
installation instructions and modes of operation can be found
in page 63.
Figure 17: T170 Thermostat with Digital Display