McQuay FCVC, Руководство по установке и обслуживанию

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McQuay IM 980-1 13
Operation and Maintenance
Operation and Maintenance Controls
A wide variety of control options are available for ThinLine
3G Vertical Fan Coils, both unit-mounted and remote-
mounted. This section provides a brief overview of these
options and their operation. For more complete information,
contact your McQuay representative.
Manual 4-Position Fan Switch
This four-position fan switch (Off, High,
Med, Low) option, shown at the right, is
available remote-mounted. It operates on
low-voltage or line-voltage power and can
be provided with a factory-mounted low-
voltage interface board, which contains
three-24 volt relays with line voltage
contactors and terminal connections. The
transformer is factory-installed and wired.
Sequence of operation
• Off: Fan is turned off. The motorized fresh-air damper, when
supplied, is closed (see Fresh Air Damper‚ page 16 ).
• High, Medium, Low: Fan runs continuously at the selected
speed. The two-position, motorized fresh-air damper, when
supplied, is opened.
Unit-Mounted, Mechanical Thermostat With
4-Position Fan Switch
The unit-mounted
option, shown at the
right, combines the
four-position fan switch
with a mechanical
thermostat. For two-
pipe systems with a
factory installed valve
package, it can be
provided with a manual
switch (shown in
picture to the right) to
change from heating to
cooling. Alternatively, the changeover can be automatic.
Sequence of operation
• Fan Switch
• Off: Fan is turned off. The two-position, motorized
fresh-air damper, when supplied, is closed (see Fresh Air
Damper‚ page 16 ).
• High, Medium, Low: Fan runs continuously at the
selected speed. The two-position, motorized fresh-air
damper, when supplied, is opened.
• Thermostat
• Cycles the valve(s) open or closed on demand based on
occupant-desired level.
• Changeover Switch: With a manual switch, the user selects
whether heating or cooling is desired. With automatic
changeover, a pipe sensor works with the thermostat to
operate the heating or cooling valve.
• Heating: Opens the valve when the temperature is below
the setpoint.
• Cool: Opens the valve when the temperature is above the
setpoint.
Digital Thermostats
McQuay offers a broad
range of unit-mounted and
remote, wall-mounted
digital thermostats with
the capabililty to control
On-Off, 3-wire and
proportional modulating
valves, and Normally
Closed or Normally Open
actuator valves. For more
information, refer to the
McQuay publication ED 18513-1 and ED 18527.
MT155 Thermostat
For more details refer to page 47 . The MT155 series thermostat
provides on-off control for low-voltage or line-voltage valves
and fan motors. This thermostat is designed as a remote-mount
with connection to the LV interface board mounted on the fan
coil unit. Options include manual or automatic changeover and
three-speed fan control for continuous or cycling fan operation.
The thermostat may be mounted on units already at the job site.
Each unit should be equipped with an LV Interface Board, if
not, a Controls Mounting Kit PN910112080 needs to be
ordered. For field installation instructions of the MT155 on a
unit, refer to
page 4 5.
Figure 15: MT155 Thermostats
Three standard control options are available:
• On-Off fan cycle operation only: The thermostat cycles the
fan from the manually selected fan speed (high, medium or
low) to off.
• Continuous fan and On-Off valve cycle operation: The
thermostat cycles the valves on and off. The fan runs
continuously at the manually selected fan speed.