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18
AIR FLOW SWITCH, PRESSURE DIFFERENTIAL TYPE
HIGH LIMIT HUMIDISTAT
EXTERNAL DDC CONTROL SIGNALS
The humidifiers can also accept a 0-10 volt DC signal to
modulate the output of the humidifier. Polarity must be
observed. Input impedance is 20K ohms. If a 4-20 mA input
signal is provided to the humidifier a 470 ohm, 1/4 watt resistor
must be installed as shown.
Air flow in the duct may be sensed by using this differential
pressure switch. The differential in pressure between the interi-
or of the duct closes a switch when air is moving. Air pressure
differential as low as .07 w.g. may be sensed with this switch.
Environment:
Ambient Temperature Limits,
Shipping
-40 to 140°F (-40 to 60°C).
Operating
35 to 140°F (0 to 60°C).
Humidity,
5 to 95% RH, non-condensing.
Locations,
NEMA Type 1 indoor only.
Mounting:
In vertical position on any surface free of vibration
Switch to “N.O.” on increase of pressure
(N.C.)
(N.O.)
To Terminal 5 or 6
To Terminal 5 or 6
COMMON
•
•
•
When there is an increase of air pressure to above setpoint, the
switch is switched from normally closed (N.C.), common ground
contact to normally open (N.O.) contact. On a decrease of air
pressure to below setpoint, normally closed, common ground
contact of the switch is switched to normally closed contact. Avoid
locations where excessive moisture, corrosive fumes, or vibrations
are present.
Setpoint:
Factory Set,
0.07” (1.8mm) w.g.
Field Adjustable,
0.07 to1” (1.8 to 25.4mm) w.g.
Sensing Element:
Neoprene diaphragm.
Adjustment
Note:
Units are shipped at minimum setpoint.
To increase setpoint, turn adjustment screw clockwise. Adjustable
0.05 +0.02” to 1.0” (1.25mm +0.5mm to 25mm) w.g. To decrease
setpoint, turn adjustment screw counterclockwise.
The Model HXHAD is available to reduce the potential of
condensation occurring in the supply duct. The control must
be mounted a minimum of 10 feet downstream of the steam
distributor pipe. Setpoint range is 15-95% RH. Differential is 5%
non-adjustable.
The HXHAD may be mounted in any position on the outside
surface of the supply air duct where it is exposed to freely
circulating air (horizontal mounting is preferred).
ORANGE (COMMON)
To Terminal 8 or 10
BROWN (N.O.)
To Terminal 8 or 10
RED (N.C.)
Model HXAAE
Model HXHAD
0-10 VDC
PROPORTIONAL SIGNAL
(BY OTHERS)
0-10 VDC
PROPORTIONAL
HIGH LIMIT HUMIDISTAT
(BY OTHERS)
+ -
+ -
4-20ma
PROPORTIONAL
HIGH LIMIT HUMIDISTAT
(BY OTHERS)
470 OHM
RESISTOR
(BY OTHERS)
470 OHM
RESISTOR
(BY OTHERS)
4-20ma
PROPORTIONAL SIGNAL
(BY OTHERS)
+
- +
-
“N.C.” (Red) is switched to
common (Orange) during
RH Rise.
“N.O.” (Brown) is switched
to common (Orange)
during RH Drop.