MERLIN NX IP AND MST/TP VAV CONTROLLER - INSTALLATION INSTRUCTIONS
11 EN1Z-1076GE51 R0722
When twin tubing is used from the pickup, split the pickup 
tubing a short length to accommodate the connections.
Fig. 11. Airflow pickup connections
Differential Pressure Installation
NOTE: The controller must be powered up for a minimum 
of 1 hour before performing the zero calibration for 
the air flow sensor.
If controllers are mounted in unusually dusty or 
dirty environments, an in-line, 5-micron disposable 
air filter (use 5-micron filters compatible with pneu-
matic controls) is recommended for the high-pres-
sure line connected to the air flow pickup.
The tubing from the air flow pickup to the controller 
should not exceed three feet (1 m). Any length 
greater than this will degrade the flow sensing 
accuracy.
Use caution when removing tubing from a connec-
tor. Always pull straight away from the connector or 
use diagonal cutters to cut the edge of the tubing 
attached to the connector. Never remove by pulling 
at an angle.
NOTICE
Dust particle contamination may be present in some 
applications. Ensure appropriate measures are taken to 
minimize the effect of particulate contamination. 
The sense element is in parallel to the air stream and tends 
to direct the dust particles in the airflow stream past the 
sense element away from the sense bridge. The sense 
element is a micro-structure-based device and the bridge 
portion of the sense element structure is made up of two 
platinum sense elements and a heater. The heater tends to 
repel dust particles via a thermophoretic effect past the 
heater and tends to keep most dust off the bridge structure. 
The heat affect, along with a simple filter, can help to keep 
the dust from causing output shifts in the output of the 
device. Although the sensor naturally repels dust, some 
dust and contamination can still collect on the micro-
structure. Dust adherence to chip edges and channel 
surfaces can be prevented by using a simple filter. A 
disposable five micron filter used in series on the upstream 
side of the airflow divide will provide adequate filtering in 
most applications. See Table 4, “Recommended Filter 
Suppliers,” on page 11 below for recommended filter 
suppliers.
122°F
(50°C)
32°F
(0°C)
 ± 2.0 HO
(±500 Pa)
Air, N2, O2 
non-condensing
Secure with
cable tie
 0.20” (5.2 mm)
0.13” (3.5 mm)
0.31 in (8 mm)
Table 4.  Recommended Filter Suppliers
Pall Corporation www.pall.com
Acro 50 
The filter may be used at a common mode pressure 
of 0.17 MPa (24.6 psi) at a temperature of 80 °C [176 
°F] May be used with swag lock compression fittings 
Approximate pressure drop is 5 kPA at 1 SLPM of 
flow.
Acro cap 
May be used at an operating temperature of 55 °C 
[131 °F] and common mode pressure of 30 psi 
Sensors connections are1/4 barb fittings General 
Gas filter Pressure drop is 1 psi with a flow of 15 
SLPM Fittings are 1/8 barbed tubing.
Parker Balston 
www.balstonfilters.com
Model 
9933-05 
US and EMEA only sales offices. May be used at 
common mode pressures up to 125 psi and operating 
temperature to 135 °C [275] °F Sensor connections 
are 1/4 tube.
MAHLE: 
https://catalog.mahleaftermarket.com/eu/product.xhtml?ei
d=184
MAHLE 
KL13 
Automotive filter