most frequent installation errors

---

• unfavourable design
• grille forgotten
• disturbed flow-in
• disturbed flow-off
• flexible connections too long/bad aligned
• too steep diffusor in front of a fan
• asymmetric confusor in front of a fan
• elbow before and behind the fan
• swirl at the fan inlet
• elbow at the fan inlet
• elbow at the fan outlet
• avoidable pressure loss at axial fans
• avoidable pressure loss at centrifugal fans
• unfavourable duct design
• parallel installation

---

unfavourable design

Unfavorable	Optimal

---

grille forgotten

false	correctly

---

disturbed flow-in

bad	better (min. space 1xd)

---

disturbed flow-off

bad	better (min. space 1,5xd)

---

flexible connections too long / bad aligned

bad / stall!	good

---

too steep diffusor in front of a fan (aperture angle max. 7°)

bad / stall!	better

---

asymmetric confusor in front of a fan

bad / stall!	better

---

elbow before and behind the fan

bad	better

---

swirl at the fan inlet

bad	better

---

elbow at the fan inlet

bad	good

---

elbow at the fan outlet

bad	better  |  good

---

avoidable pressure loss at axial fans

bad	better  |  good

---

avoidable presure loss at centrifugal fans

bad	better  |  good

---

unfavourable duct design

bad	better  |  good

---

parallel installation

bad	better  |  good