Presented by GJ Walker Air Handling Systems

AHU Design Combination of design principles;

Structural - Cabinet sizing - Base frame design

Insulation requirement Air movement Filtration Heat exchange performance Heat recovery design and method Acoustic considerations Spatial limits, building design or accessibility. Commercial considerations and limits!

15 Year Changes Cabinet construction Folded galvanized sheet,

pin insulated to Cool room panel ‘butt joint’ panels to pentapost modular construction.

DWDI forward curved fans, to DWDI backward curved fans, to backward curved AC plug fans, to EC plug fans.

Speed control; multispeed motors – VSD – EC. 5/8” coil tube to ½” coil tube. Commercial

reasons. Reduction in use of electric heat. Demise of hot/cold Deck Multizone units to

individually zoned MZ units.

Lower coil face velocities (

Forward Curved Centrifugal –Direct Drive - CSR

• Cheap but very inefficient, 315W motor input power more than double rated motor output!

• 3 speed hard wired but limited range b/w speeds.

• Maximum ~ 1,000 l/s @ 450Pa• Banned in Europe ERP2015 • DC brushless and EC type fans taking their

place.

ERP2015

DWDI Forward Curved Centrifugal

• Up to 250 to1000 diameter • Lower revving fan, often quieter. • Overloading type characteristics• Smaller area of overall fan curve for

application• ‘written out’ of specification due to

maximum outlet velocity and need to operate of the right of the curve.

• Impellor not as robust as backward curved• Certified laboratory values not per normal

install. • Correctly tensioned belt system leads to

approx 4% overall efficiency loss.

DWDI Backward Curved centrifugal

• 250 to 1400 diameter• High revving can be unattractive at smaller

air volumes (>2500rpm at

Backward Curved Plug Fan – AC

• Ease of installation • Direct couple fewer maintainable parts and

greater efficiency.• Standard parts re TEFC motor. • Must be VSD driven. • Motor speed v fan speed – lack of flexibility.• Flexibility in duct take off.

Backward Curved plug fan – EC

• 110 to 900 diameter, max motor 7.4kW• All in one; Fan & VSD • Many fan profiles, constantly developing.• Compact • 1 x supplier in control of whole assembly.

balancing is therefore to a much higher tolerance.

• Outside of critical applications can be hard mounted.

• EC motor – locked into one replacement supplier.

Three Phase AC Motor Limits

Motor Power v Motor Speed

Psychometrics basics

Coil Options

Coil Performance & Design

Structural Cabinet style

Galvanized sheet steel and insulated Pre-insulated panel type Pent-a-post type aluminium frame

Insulation types Single skin - Fibreglass/tontine/polyolefin. Double skin - Polyurethane/polystyrene/PIR/phenolic

structures (X-Flam) Internal panel

Foil skin/ double skin Stainless steel Perforated metal/sound steel

External Panel –All skins are not equal! Colourbond standard, colourbond permaguard, Aluminium.

Base Frame Design

Lifting point design Certified Lifting Lugs

Vibration Isolation

Open spring mount 25/50/100 deflection Seismic rated Laterally restrained RIS rubber in shear

Run Around Coil System • Low efficient heat recovery.• AHU easily accommodate additional coil in

cabinet with minimal additional plant room space.

• Return and outside air can be remote• no cross contamination of exhaust and

return• Dampers required to avoid constant

elevated pressure drop.• Can be used for ‘free’ reheat.

Heat Recovery - Rotary wheels • Highly efficient form of heat

recovery up to 75%• More moving parts than plate or

run around – maintenance high.• ‘slim’ across airway = less plant

room space• Return and outside air must run

adjacent to each other.• cross contamination of exhaust

and return – purge sector.• Dampers required to avoid

constant elevated pressure drop.• Limited pressure differential b/w

exhaust and supply.

Evaporative Cooling (direct and indirect)

• Improved development of technology, microprocessor systems controlling evaporative cooling.

• Lower pressure drop to conventional pad type system• Untreated water can be used.• Direct and indirect systems.

Plate Heat Exchanger • Highly efficient form of heat recovery up

to 75%• less moving parts than plate or run around

– maintenance low.• ‘wide’ across airway = more plant room

space• Return and outside air must run adjacent

to each other.• no cross contamination of exhaust and

return• Dampers required to avoid constant

elevated pressure drop.• Can be used for ‘free’ reheat.

Heat Pipe • Free precool and reheat• Increases latent capacity without

additional energy consumption, enables cooling coil to meet the dewpoint faster and with greater efficiency

• No moving parts to break down or wear out.

• Often allows downsizing of entire HVAC systems (per all heat recovery).

• Helps prevent IAQ problems associated with high humidity.

• Strangely our most prevalent market for this product is WA

AHU Rental Equipment

500 kW AHU

Manufacturing Rare for products to be ‘off the shelf’ outside of

smaller FCU’s. Commercial decisions more protracted , AHU’s often

critical path items in overall build programs. Lead times 4 – 6 weeks local build with stock items. Ex-stock

Motors Panel Fans (generally) Heat exchange coils – sometimes.

Low cost economy supply 10 weeks Heat exchange coils

Local 4 weeks – expensive Import – 8 weeks (50% of local price)