Mitsubishi Electric FDT125VNVF Technical Manual page 211

OUTDOOR AIR (OA) INTAKE FOR FDT
If it is required to intake OA through FDT unit, make sure to check following points carefully in order to conform to the
requirement of customer.
If the OA intake volume through FDT unit is not satisfied with the required ventilation air volume, consider to install an
indepemdent ventilation system.
1) Be sure to calculate cooling/heating load considering the ventilation heat load and to decide the air-conditioning system.
2) Be sure the OA intake volume to FDT unit should not exceed 20% of the Supply Air (SA) volume of FDT unit and it
should be less than 2m
3) Be sure to decide the OA intake volume considering the mixed air temperature will be within the usage temperature range
of FDT unit.
Especially in following case, please consider to intake OA after processing OA or reducing the OA intake volume.
4) Be sure to equip a suitable filter for OA intaken in order to protect the dust.
(Because OA does not pass through the filter equipped on FDT unit)
5) Be sure to insulate OA duct.
(If not, it may have dew condensation.)
6) Be sure to interlock the booster fan for OA with the fan of FDT unit by using CNT connector.
(If not, the dust trapped on the filter of FDT unit may be blown out to the room by the OA being intaken during the fan of
FDT unit stopping)
7) Be sure to select a suitable booster fan for OA considering the pressure loss in the OA duct and the pressure loss at the in-
let port of FDT with following diagram.
(Please take into consideration the noise level as well)
<Selection of booster fan>
Booster fan should have a static pressure calculated with following formula
Static pressure of booster fan
= the pressure loss at the inlet port of FDT (from above diagram)
+ Pressure loss in the OA duct (In case of φ 100 duct, 5Pa/m is required)
Select the booster fan from the fan characteristic diagram
3 /min.
3
2
1
0
0 0.5
OA intake volume (m
200
150
100
50
0
0 0.5
OA intake volume (m
-
1.0 1.5
/min)
3
1.0 1.5
/min)
3
210
-
'12 • PAC-T-174
2.0
2.0