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Centralized Multi-Family Ventilation. The Central System Challenge- Ventilation Typical Design. ASHRAE 62 Exhaust Ventilation Requirement Residences Bathrooms = 20/50 cfm Kitchen areas = 5 ACH or 25 cfm/100 cfm. The Central System Challenge- Ventilation Design Standard.
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The Central System Challenge- Ventilation Typical Design • ASHRAE 62 Exhaust Ventilation Requirement • Residences • Bathrooms = 20/50 cfm • Kitchen areas = 5 ACH or 25 cfm/100 cfm
The Central System Challenge-Ventilation Design Standard • Central continuous exhaust • Roof mount fans • Fire rated duct shaft • Fire dampers or 22” sub-ducts (snorkels) • Sidewall registers
The Central System Challenge-IAQ vs. Energy Efficiency • Too little ventilation = Risk of poor IAQ • Too much ventilation = Waste of Energy IAQ and Energy Efficiency – A Balancing Act? It doesn’t have to be if you “Build it tight and ventilate it right”.
The Central System Challenge-IAQ vs. Energy Efficiency • Energy efficiency and ventilation are not opposing forces. • CONTROLLED Ventilation is the key to providing BOTH Energy Efficiency and IAQ. • Build it tight…and ventilate it right!
The Central System Challenge-IAQ Emphasis • Toilet and Kitchen Exhaust – Not just for odor removal any more. • Controlling Indoor Air Quality • Moisture removal • Providing effective Air Changes (ASHRAE 129) • Critical System for health and building sustainability.
The Central System Challenge-Controlling Proper Flow Rates • The larger the system, the more difficult they are to control. • Balancing and commissioning • Noise and pressure • Environmental factors (stack effect and wind) • Fan equipment and controls • Occupant Interaction/Adjustment • Maintenance
Setup, Balancing, & Commissioning • Central Systems are difficult and costly to balance. • Low pressure makes manual adjustment challenging • Dozens to 100’s of sidewall exhaust registers on one fan. • Traveling multiple floors is very time consuming
not to mention… Clogged Covered OFF (IAQ) Loose or Broken Belts
Ventilating High-Rise BuildingsThe Central System Challenge • Occupant interaction, or tampering with register dampers always affects system balance. • Tampering is often a result of system noise, and perception of energy waste.
Stack Effect • Definition – ASHRAE Fundamentals Chapter 26 • “Stack pressure differences exist when the building is pressurized relative to outdoors, which causes flow out of the building.” • “in the absence of other driving forces (wind), when indoor air is warmer than outdoors, the base of the building is depressurized and the top is pressurized relative to outdoors;”
Environmental Factors –Stack Effect • Assuming a perfectly balanced system… • Stack Effect can dramatically effect system performance in tall buildings
Stack Effect (Cont’d) • Stack effect is unavoidable • Partitioning the building prevents stack effect, but… • You can’t partition vertical shafts
Stack Effect (Cont’d) SUMMER • Each opening into the shaft is exposed to varying pressures.
Stack Effect (Cont’d) WINTER • Each opening into the shaft is exposed to varying pressures.
Stack Effect (Cont’d) • Huge increase in total airflow! • Large increase in thermal load and heating requirement. • Fan assisted makeup air systems must also compensate.
Stack Effect (Cont’d) • If the fan can’t compensate for stack effect, buoyancy begins to move down the shaft. • The fan will free-wheel • Air exhausted on lower floors, is supplied to upper floors. • IAQ problems may result.
Stack Effect • High duct pressure = Higher duct leakage, shafts in particular. • Higher Fan HP & Energy Consumption • Higher Noise Levels!
Dynamic System Control - A Better Solution! • A Dynamically vs. Statically Controlled System can eliminate; environmental factors, occupant tampering, and recalibration concerns. • The Solution…
Dynamic System Control • Dynamic Pressure Independent Control • Automatically adjusts to changes in pressure • Compensates for the effect of stack pressure • Allows fan operation at lower pressure
Dynamic Ventilation Control • Simplifies building pressurization control • Eliminates cross-contamination (IAQ) • Improves life safety system operation • Reduces drafts • Saves energy!!!
Dynamic Ventilation Control • How much energy can you save??? • Many factors determine actual savings, but… • Energy savings have ranged from $15 to $25+ per cfm saved
Dynamic Ventilation Control Pressure Independent Solutions – Constant Volume • Constant Airflow Regulators
The CAR-II The Constant Airflow Regulator “CAR-II” is the simple solution to balanced airflow. • Automatically Balances Airflow • Pressure Independent • Factory Calibrated • Easy Field Adjustable • Simple - Plug and Play Install • Maintenance Free • Controls Airflow for Exhaust, Supply & Return Ducts • Save Energy & Increase Comfort • Improve IAQ “One of the greatest HVAC innovations ever!”
Airflow Control The Constant Airflow Regulator is able to hold a very consistent airflow across a broad range of air pressures. As the air pressure increase the CAR is engineered to restrict airflow to maintain a consistent CFM.
The CAR-II • Available as a complete register for round or square duct, may have fire damper.
The CAR-II Over 1.5 Million units installed in North America. Actual Typical Results Below. Before CAR-II Installation After CAR-II Installation
The American ALDES Solution Solutions to complete any installation. ENERGY STAR Fans Zone Control Devices Wall/Roof Caps Timers and Controls Inline Fans/Dryer Boosters ERV’s and HRV’s Constant Airflow Regulators Make-up Air Solutions Sleeves, Boxes & Grills Backdraft dampers
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