5Z vs 4Z — which Multi-Wing blade profile do I need?
If you are ordering a Multi-Wing replacement and not sure whether you need a 4Z or a 5Z, this is the quickest way to decide. Both fit the Z-series hub. The difference is chord width, airflow per RPM, and installation diameter.
4Z — mid-range workhorse
Chord width: 302mm (11.89 inches).
Diameter range: 315-1,019mm.
Applications: HVAC, condensers, warehouse extraction, process cooling, most commercial industrial ventilation.
This is the most widely installed Multi-Wing profile globally. If the installation sits between 400-900mm diameter and is general HVAC / condenser duty, 4Z is almost always correct.
5Z — large-profile wide-chord
Chord width: 424mm (16.71 inches) — significantly wider than 4Z.
Diameter range: 315-1,261mm.
Applications: cooling towers, mine main fans, large extract systems, and any high-airflow duty across the full 315-1,261mm operational range. Most commonly specified in the 900-1,260mm band where the wider chord shines.
The wider chord moves more air per degree of pitch than the 4Z. It also draws more power — verify the motor kW supports it.
Head-to-head
At overlapping diameters (e.g. 900mm), which do you specify?
- Choose 4Z if the duty is general HVAC / condenser, motor kW is modest, and airflow requirement is standard.
- Choose 5Z if the application is a cooling tower or large extract where maximum airflow matters and the motor can handle the wider-chord load.
- When in doubt, check what is already installed — matching the existing blade profile is almost always the right call.
FAQs
Can I swap a 4Z for a 5Z in the same hub?
Physically yes — both fit the Z-series hub. But the 5Z will draw more power for the same RPM, so only swap if your motor has enough headroom. A motor undersized for the 5Z can overheat or trip.
Is the 5Z more expensive than the 4Z?
Yes — the wider chord uses more material. See the 5Z and 4Z product pages for current per-blade pricing across each material (PAG, PPG, PAGAS, Aluminium).
Which profile is more common in SA cooling towers?
5Z is more commonly specified for South African cooling towers, especially in the 1,000-1,260mm diameter range typical of mid-size industrial installations.