4
Installation and maintenance instruction
FläktGroup DC_10396GB 20191216_R0 Specifications are subject to alteration without notice
CAPACITIES IN EXCESS OF 22 KW
If the capacity exceeds 22 kW, a symmetrically shielded cable with
concentric or in some other way symmetrically designed protective
earth conductor should be used. For recommendations governing
these installations we refer to the installation instructions for the
frequency inverter.
TO CONNECT THE SHIELDED CABLE
If the application requires you to wire the cable shield to an
earthscrew inside the motor or the frequency inverter, this must be
done in such a way that the impedance will be as
low as possible. In these cases the length of this conductor must
be restricted to 5 times the width of the conductor.
For instance, the length of a 1 cm wide conductor should
not exceed 5 cm.
OTHER DETAILS
In addition to the above, observe the following:
• type of mains power supply
• local electrical safety rules and regulations
• manufacturer’s installation instructions for the frequency
inverter.
Insulating tape
q = 1 · Δp m3/s
k
Important!
For LQLZ-42 U-tube manometers, use only
the blue manometer fluid supplied with the
instrument. Never use any other type of fluid.
Precision-adjust the zero point with the zero
adjustment screw.
If the air handling unit is supplied with a control system, the flow
can be read directly in the control panel display.
NB!
In the case of air handling units supplied with a
control system, the pressure tappings in the end
connection panels of the unit are not connected to
the airflow sensor of the fan.
If you still want to read the manometer pres-
sure with an external manometer, you can connect
the tubes from the airflow sensor of
the fan across T-nipples to the pressure tap-pings
in the end connection panel of the air handling unit.
If this external means of measuring flow will not
be permanent, the tubes must be restored to their
original condition.
If two fans are installed in the fan section, the k-value is applicable to
the total airflow generated by both fans.
q = q20 , m3/s
(273 + t)
293
TEMPERATURE CORRECTION
The flow scale on the indicating instrument and the flow formula
above apply to air with a temperature of +20 °C. For other tempera-
tures, the flow must be corrected using the following formula:
where q = the actual flow through the fan, q20 = the flow reading and t
= the current temperature in °C.
Size LQLA-aa-b k-factor Fan size
60-1, 62-1 5,37 80
60-2, 62-2 4,24 90
60-3, 64-1, 66-1, 71-1, 73-1, 80-1 3,43 100
62-3, 64-2, 66-2, 71-2, 73-2, 75-1, 80-2, 82-1 3,40 2x071
64-3, 66-3, 73-2, 75-2, 82-2, 84-1 2,69 2x080
64-4, 66-4, 73-4, 75-3, 82-3, 84-2 2,12 2x090
75-4, 84-3 1,71 2x100
A flow indicator with built-in pressure transducer (available as
an accessory) should be connected by means of tubes to the
external pressure tappings. This instrument converts the mano-
meter pressure reading to a flow (m3/s) which is shown on a
display screen and transmits a 0–10 V output signal, linear with
the flow.
The LQLA has equipment for measuring the airflow.
The airflow, q, can be measured by applying a manometer
reading of Δp (Pa), and a constant, k, using the following formula:
The manometer reading, Δp, which is the difference between the
pressure in the suction chamber by the fan inlet and the pressure
inside the inlet cone, can be read with a manometer (pressure
range of up to 6000 Pa) which should be connected
with a 4 mm dia. tube to 2 externally located pressure tappings.
The value of the constant k is specified in the table below.
AIRFLOW MEASUREMENT