Phase Fail/Under Voltage Protection; Duct Static Pressure Sensor - McQuay SWP Series Installation And Maintenance Manual

Phase Fail/Under Voltage Protection

The phase voltage monitor protects against high voltage, phase
imbalance, and phase loss (single phasing) when any one of
three line voltages drops to 74% or less of setting. This device
also protects against phase reversal when improper phase
sequence is applied to equipment and protects against low
voltage (brownout) when all three line voltages drop to 90% or
less of setting. An indicator run light is ON when all phase
voltages are within specified limits. The phase voltage monitor
is located on the load side of the power block with a set of
contacts wired to the 115-volt control circuit to shut down the
unit whenever phase voltages are outside the specified limits.

Duct Static Pressure Sensor

All units provided with variable air volume control include a
factory-mounted static pressure sensor (SPS1). The unit also
can have an optional second static pressure sensor, SPS2. The
sensor is factory wired and requires field installation of 1/8"
I.D. sensor tubing to the selected duct location.
Be sure that tubing complies with local code
Note:
requirements. Flame retardant plastic or metal tubing
may be required. Carefully select the ductwork sensing
point for the pressure sensor. Improper location of the
sensing point results in unsatisfactory operation of the
entire variable air volume system.
Adhere to the following guidelines:
Position sensors near the end of long duct runs so all
1
terminal box take-offs along the run have adequate static
pressure to operate.
Position the end of the sensing tube perpendicular to the
2
airflow to sense only static pressure.
Locate the sensing tube in a nonturbulent flow area of the
3
duct. Keep several duct widths away from take-off points,
bends, or neck downs.
McQuay IM 937
Mounting Instructions (See Figure 33.)
Drill a hole in the duct at the remote sensing point and
1
install a rubber grommet.
Insert the sensing tube 1/8" into the duct and securely
2
clamp tubing to the duct, being sure not to stress or kink the
tubing.
The end of the sensing tube must be smooth and cut
Note:
straight across. An angle cut affects operation.
Clamp a second tube to the outside of the duct at the
3
location of the sensing point.
Run both tubes along the ductwork and back to the unit.
4
Route the tubing to the pressure sensor (SPS1) by drilling
5
two holes through the unit upright post.
Use a grommet at each hole to protect the tubing and seal
6
the cabinet.
To avoid confusion between "high" and "low"
Note:
tubing, use two different tubing colors and record
this information along with the sensing point
location on the master building blueprints.
Connect tubing to the high and low ports on the sensor.
7
Figure 33: Mounting
To sensor
"LO" input
Tube clamps
Pressure
sensing
tubing
Tubing extends
thru approx. 1/8"
Unit Options
To sensor
"HI" input
Rubber
grommet
33