This table shows the maximum and recommended spacings between JetVent Fans for different levels of fan thrust. These spacing distances are guidelines for fans placed in series. When using these spacings, air velocities in most of the ventilated areas should be greater than 1m/s. AFCD analysis will determine whether this is achieved in a particular car park design. In some ideal cases, designs using the maximum distances have been effective.

Fan thrust depends on the operating speed of a particular fan unit and its thrust rating.

 

Select Isolator and Smoke Detection Kit

*Recommended Spacing & Coverage figures are to be used as a design guide only and are subject to variance with respect to car park usage type, supply/exhaust rates and car park geometry. Final spacing will be confirmed via CFD analysis.

After a preliminary fan layout is completed using the spacing distances above, the layout may be checked for total installed thrust. Successful designs typically have approximately 5N of thrust per 100m2 of car park floor area. This thrust ratio also works well for estimating purposes.

Note that using higher rated JetVent fans generally makes the system more cost effective than using more lower rated fans. This is due to the requirement of less JetVent fans and hence saving on capital costs, installation costs and running costs. However, to effectively ventilate car parks with low ceiling heights, unusual or irregularly geometries, selecting more fans with smaller thrust ratings may be necessary.

For the purpose of estimating costs, the steps below may be bypassed. Allow 5N of thrust per 100m² of car park floor area to approximate the number of fans required.

Fans should be placed in the laneways with the air blowing along them. This is to avoid obstructions such as parked cars and also ensure that the throw pattern of the selected fan is long enough to reach the next JetVent fan.

An example of how fans are sized and placed based on floor area. [Download PDF]

ComLink Design Parameters

Aviator controls should be placed in the Mechanical Services Switchboard enclosure. The RS485 ComLink line must start at the controller and then daisy chain to all the JetVent Fans and Drives. The last connection must have an End-of-Line resistor. If the line is greater than 1,000m or includes more than 32 connected devices, then a communications repeater must be added to extend the line. A repeater can also be used where the ComLink line branches off, such as at the beginning of each level in a multi-story car park.

Fantech can provide support for electrical cabling mark-up designs, to help ensure the most efficient ComLink strategy is used.

Section 4 of AS1668.2:2012 details requirements for ventilating car parks. In particular, sub-sections 4.4.3 and 4.4.4 of the standard outlines calculations of exhaust rates. In any of the two cases below, the exhaust air flow rate for a car park is taken as the greatest of the following calculations:

Car parks with more than 40 spaces	Car parks with less than or equal to 40 spaces
a) 2000 x F x T (minimum air quantity for one operating car)	a) 2000
b) 0.85 x P x (100 x n1+ n1 x d1 + n2 x d2 ) x E x T	b) 2.5 x A
c) 2.5 x A (minimum air quality based on area of car park)	c) 400 n1 x P

Supply air flows should range from 75% to 90% of the exhaust air quantity. This is based on the pressurisation of the car park, which should be 12Pa maximum.

Reference information for the calculation of exhaust air flow rates in the table above:
A = the area of the zone or level, in square metres
d₁ = the average driving distance, in metres, within the zone or level under consideration for the exit of a car parked there (see Clause 4.4.4.1)
d₂ = the average driving distance, in metres, within the zone or level under consideration for the exit of a car whose exit route passes through the zone or level under consideration, but excluding any part of the exit route designated as queuing areas and ventilated in accordance with Clause 4.6 (see Clause 4.4.4.1)
E = the staff exposure factor (E)
F = the staff usage factor (F)
n₁ = the number of parking spaces in the zone of level under consideration (see Clause 4.3.2)
n₂ = the number of parking spaces situated in other parts of the car park, having exit routes passing through the zone or level under consideration
P = the parking usage factor (P)
T = the vehicle type factor (T)

If the car park has significant queuing areas for vehicles, refer to section 4.6 in AS1668.2:2012