The first hour decides the next decade: a fan commissioning checklist

A centrifugal fan that starts well tends to run well for years. A fan that starts badly announces it in the first hour — but only if someone is measuring. Engineers have commissioned fans against dimensioned drawings for more than a century; the discipline has not changed, only the instruments have. This is the fan commissioning checklist we work to on site: what to check before power, what to watch on the first run, and what to write down so the record is worth something a decade later.

Before power: the mechanical checks

None of these needs electricity, and every one of them is cheaper to fix now than after the first run. Walk the fan installation in this order:

• Foundation and hold-down. Anchor bolts torqued, baseplate fully grouted, and no soft foot — a base that rocks on one corner puts a cyclic strain into the bearings that no amount of balancing will cancel.
• Drive alignment. On a belt drive, misalignment wears belts on their sides and loads them unevenly; on a direct drive it feeds straight into the coupling and bearings. Check it with a straightedge or laser, not by eye.
• Belt tension. Set to the maker’s sag figure. Too loose and the belts slip and burn; too tight and you overload the bearings you just aligned.
• Impeller rotated by hand. It should turn freely, with the inlet-cone clearance verified all the way round — no rub, no tight spot.
• Guard and coupling. Coupling fasteners secure, guards fitted and clear of the rotating assembly before anyone reaches for the starter.
• Direction of rotation. A backward-curved fan running the wrong way does not scream — it quietly delivers only 40 to 50% of design flow, and draws higher-than-normal current doing it. Bump it and confirm the arrow on the casing and the direction air actually leaves the outlet before a full start.

First run: current, then vibration

Watch motor current against the nameplate FLA. On a star–delta starter, current in star is roughly one-third of direct-on-line — but so is torque. Close the damper for the first start and confirm the motor is near full speed before the changeover fires; a changeover at low speed slams full starting current straight back in.

Then take the vibration baseline. Read velocity RMS in mm/s at both bearing housings, in horizontal, vertical and axial directions — on the bearing housing itself, never the base frame. Assess it against ISO 14694, the fan-specific vibration standard, measured per ISO 14695. A newly commissioned fan should be at or below the start-up level for its application category — 4.5 mm/s RMS for a BV-3 fan rigidly mounted, 6.3 mm/s RMS on anti-vibration mounts. A reading above that is not a “keep an eye on it” item — it is an installation problem (foundation, alignment, clearance, balance or duct strain). Do not accept handover on that basis; find the cause first. If the number is high and you need to tell resonance from imbalance, that is a field diagnostics job, not a rebalance.

Six readings, velocity RMS (mm/s), taken on the bearing housing. These are the numbers every future maintenance visit is compared against.

Verify where the fan is running

A fan can be mechanically perfect and still parked in the wrong place on its curve. Operation to the left of the pressure peak is the unstable region — flow hunts and surges, and with two identical fans in parallel the unstable band is wider still. Confirm the measured duty sits to the right of peak, in the stable region, near the quoted duty point. If it does not, the system — dampers, duct, design assumptions — is asking a different question than the fan was selected to answer. That is a system-curve conversation, and worth having at handover rather than six months in.

Damper and VFD setup

How you control the fan belongs in the commissioning record too. On a variable-speed drive, set ramp times to suit impeller inertia — bigger wheel, slower ramp, and deceleration no faster than acceleration. Then sweep the speed range once while watching vibration: any speed where vibration jumps is a resonance. Programme it out as a skip band and record the skip frequencies. Two minutes here saves a rewind later.

The handover record

A commissioning that was not written down did not happen. The report carries the six baseline vibration readings (DE and NDE × H/V/A), the motor current, the measured duty check, and any VFD skip bands — signed by the commissioning engineer. That single sheet is the reference every future diagnosis is made against. Without it, the first vibration alarm three years from now has nothing to compare to.

Our fans ship with a commissioning procedure in the manual, and supervised commissioning is a service we catalogue — our site engineers work to exactly this checklist, trained on it as a standard module. The full checklist is available on request.

Talk to us about fan commissioning →

Jitamitra Electro Engineering · Fan-engineering notes, written for the engineer.