Fans and Air Handling Units Will Rea and Paul Pilutti February 16 th, 2011
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Contents Fans Fan Curves Fan Laws Fan Types Examples AHUs Haakon vs. McQuay Indoor vs. Outdoor Unique Designs Fans in AHUs
FANS
Motivation We use fans to move air All occupied building require some fresh air Use air to control temperature and humidity Remove smells Exhaust harmful particles
Fan Curves Do Not Select Line System Resistance Curve BHP Line RPM Curve Drawn for a one pressure, changes with altitude, temperature
Fan Types Right fan for each application! Centrifugal Forward Curved Backwards Incline (Airfoil) Radial Tubular Axial Prop Tubeaxial Vaneaxial Plenum
Static Pressure Fan Types Tubular Centrif Airfoil Plenum Forward Curve Prop Fan CFM
Fan Types Centrifugal Forward Curve Pressure: 0.5 5 Airflow: 1000 CFM 300,000 CFM + Same Slope issue Overloading
Fan Types Centrifugal AirFoil Pressure: 0.5 14 + Airflow: 1000 CFM 300,000 CFM + Variety of Blades, BI(flat), STAF, DTAF Non-overloading
Fan Types Centrifugal Tubular Pressure: 0.5 10 Airflow: 1000 CFM 100,000 CFM + Tube SW, mixed flow,
Fan Types Inline Propeller Pressure: 0 1 Airflow: 100 CFM 100,000 CFM + Exhaust from space to space, No duct work
Fan Types Inline Plenum Pressure: 1 12 + Airflow: 1000 CFM 250,000 CFM + Pressurization fan
Fan Types Inline Axial Fan Pressure: 0 6 + Airflow: 200 CFM 90,000 CFM + Pressurization fan
Fan Wall - Application 20+ direct drive plenum fans in an array How are they isolated? How do you service them? What is the efficiency Inlet damper on each fan? They do improve the second octave band sound
Fan Testing AMCA method Test from Blocked off SP -Wide open CFM
Direct vs. Belt Drive Direct Drive No drive losses Recommend 1000 CFM and lower Single fan speed More difficult to service Exception: High CFM, Medium Static, Belts can affect space Belt Drive 1000 CFM and over Can be sheaved (gear change) for any fan speed Motor service/replacement easier
Fan Laws All Constant Geometry Systems Changing RPM Law RPM change Constant CFM/RPM Law Changing Air Density Constant SP Law Changing Air Density Constant Mass Flow Changing Air Density
Example 1 - Changing RPM Law Problem AHU already installed on site Client says they want more cooling Do not want to pay more money How much more possible Current FC Fan 10000 CFM 1.56 TSP 6.4 BHP 641 RPM 10 HP Motor Installed
Example 1 - Changing RPM Law
Example 1 - Changing RPM Law Original 10000 CFM 1.56 TSP 641 RPM 6.4 BHP with 10 HP Motor Predicted Maximum 11601 CFM 2.10 TSP 744 RPM 10 BHP with 10 HP Motor (example only don t do this) Fan works, do coils, filters, dampers?
Example 1 - Changing RPM Law
Example 2 - Constant CFM/RPM Problem Fan rated for sea level Building in Calgary 3438 Tubular Centrifigual Fan Determine new conditions at 1322 RPM Current 10000 CFM 0 ft altitude 29.92 Hg 1.56 TSP 4.1 BHP
Example 2 - Constant CFM/RPM
Example 2 - Constant CFM/RPM Sea Level 29.92 Hg 10000 CFM 1.56 TSP 4.1 BHP Calgary 26.18 Hg 10000 CFM 1.37 TSP 3.6 BHP Any density/temperature change requires new fan curve
Example 2 - Constant CFM/RPM
Example 3 - Constant Mass Flow Problem Temperature done at Sea Level Building in Denver 5280 Plenum Fan Maintain constant mass flow for cooling Current 0 ft altitude 29.92 Hg 10000 CFM 3.00 TSP 6.96 BHP 1511 RPM
Example 3 - Constant Mass Flow
Example 3 - Constant Mass Flow Sea Level 29.92 Hg 10000 CFM 3.00 TSP 6.96 BHP 1511 RPM Denver 24.71 Hg 12106 CFM 3.63 TSP 10.20 BHP 1829 RPM
Example 3 - Constant Mass Flow
Example 4 - Air Balancing Report Problem Air balancer reports different than design DWDI AF Fan Set for 1961 RPM design Require design CFM Design Balancing Report 10000 CFM 9350CFM 2.5 TSP 2.3 TSP 7.7 BHP 7.8 BHP 1961 RPM 1961 RPM
Example 4 - Air Balancing Report
Example 4 - Air Balancing Report Balancing Report 1962 RPM 9350 CFM 3.00 TSP 7.8 BHP New RPM Setpoint 2098 RPM 10000 CFM 3.43 TSP 9.54 BHP
Example 4 - Air Balancing Report
Air Handling Units
Motivation Factory built unit Combine fan, heat, cool, humidity, heat recovery into one unit Were built in the field, now factory built High quality, limitless options
AHUs Treat ventilation air Commonly come with SPP Economizer section Heat recovery Coils Humidifiers Burners Integral condensing units, steam generators
Haakon vs. McQuay Haakon single product, fully custom Haakon Higher pressure rating McQuay three products, Semi-custom and packaged McQuay can be shorter McQuay is cheaper below 20000 CFM Difference in base rail
Haakon Structure Structural steel base, not formed 2 /4 fibreglass insulation Almost unrestricted configuration Almost infinite material/component options Pool, Low Temp Dehumidification, chiller, condensers... Indoor vs. Outdoor Add extra fold in roof Hoods if required Snow might come in, OA section drain pans
Haakon Unique Designs Heat Recovery, Low Temp Dehumidification, SPP
Haakon Unique Designs Heat Recovery, Gas Furnace, Integral Refrigeration, SPP
Haakon Unique Designs Angled discharge, structural cut out
Haakon Unique Designs Heat Recovery, Integral Humidification, SPP, Pipe chase inside
Haakon Unique Designs Inline Fans, Dampers, UV, Lights, Can work on while unit is operating
McQuay Rooftop Product Semi-custom, wide variety of options Heatwheels, Packaged DX, Gas heat Fixed aspect ratio, 5 box sizes Most compact in mid-large size units Vision/Skyline Near Custom Lots of components, variable aspect ratio, open sizes Can ship in sections 2 Injected Foam insulation Skyline has additional seams/paint for outdoor use
Fans in AHUs Why do you use FC, AF, Plenum, Centrif, Normal AHU (3-5, >10000CFM) DWDI AF most efficient Below use FC Any blow through, use an evase Plenum if outlet conditions are poor Worse on curve, better in reality Better acoustics for plenum Or AF with evase and silencers
ASHRAE 90.1/189.1 Efficiency Laws for Fans Mandate a maximum BHP/CFM, or maximum nameplate HP Exceptions for 1HP or less EF, and pressurized spaces Similar to chiller, higher design BHP allowed for VAV Gives credit for components (filters, RF, Heat Recovery) 189.1 (High Performance Buildings) - 10% stricter
Air Flow Monitoring Station Factory built into AHU or ductwork Provides digital readout and/or BAS signal Important in VAV/demand ventilation Some styles penetrate into airstream affect performance Haakon uses small openings on inlet bell Does not intrude into the airstream Openings on inlet
VAV Systems Fan may be selected differently Using a VFD the RPM of the fan is slowed CFM and TSP reduced along system curve System typical changes to introduce additional static
Next Time March 16 th Humidification Isothermal vs. Adiabatic Dispersion Types Steam Generators Economizer vs. Design Day