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Wildfire Smoke and Building HVAC Systems

Wildfire smoke can infiltrate a building's HVAC (Heating, Ventilation, and Air Conditioning) system through various pathways, including outdoor air intakes, cracks, gaps, and openings in the building envelope, and leaks in the ductwork. Once inside the HVAC system, the smoke particles can be distributed throughout the building, affecting indoor air quality and potentially causing health concerns for occupants. How Wildfire Smoke Gets In The following are some mechanisms by which wildfire smoke can enter and circulate within a building's HVAC system:
  1. Outdoor Air Intakes: HVAC systems often draw in outside air to maintain indoor air quality. If the building's outdoor air intakes are not adequately filtered or located in proximity to the wildfire smoke source, smoke particles can enter the system.
  2. Building Envelope: Smoke can infiltrate a building through cracks, gaps, and openings in the building envelope, such as windows, doors, and poorly sealed joints. Once inside, the smoke can be pulled into the HVAC system through pressure differentials.
  3. Ductwork Leakage: If there are leaks or gaps in the HVAC ductwork, smoke particles can infiltrate the ...
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Different Types of Air Handler Units in Commercial HVAC Systems

As a facility management professional it is essential to have a comprehensive understanding of different types of air handler units (AHU) used in commercial HVAC systems. This document aims to provide a comparative analysis of three commonly used air handler units: Chilled Water Air Handler Unit, Package Air Handler Unit, and DX (Direct Expansion) Air Handler Unit. By exploring their unique characteristics, working principles, and applications, we can gain valuable insights into their suitability for various HVAC system configurations. Chilled Water Air Handler Units A chilled water air handler unit is a type of HVAC system that uses chilled water as a medium to cool and dehumidify the air. It consists of a cooling coil, a supply fan, filters, dampers, and a heating coil (optional). The chilled water coil removes heat from the air, and the supply fan circulates the conditioned air throughout the building. Chilled Water AHU Maintenance:
  • Regularly clean or replace air filters to ensure optimal air quality and airflow.
  • Inspect and clean the cooling coil to remove any dirt, debris, or microbial growth ...
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/ IAQ Learning Institute

How often should commercial ductwork be inspected and cleaned?

The frequency of inspection and cleaning of commercial ductwork can vary depending on several factors, including the type of facility, the level of contamination, and local regulations. However, a general recommendation is to have commercial ductwork inspected every two to five years and cleaned as necessary. Commercial Ductwork Components The components of HVAC ductwork or air conveyance systems typically include:
  1. Supply Ducts: These are responsible for delivering conditioned air from the HVAC system to various areas of the building.
  2. Return Ducts: They collect air from the occupied spaces and return it to the HVAC system for reconditioning.
  3. Air Handling Units: These units condition and circulate the air, filtering it, and adjusting its temperature and humidity.
  4. Registers and Grilles: These are the visible openings where air enters or exits the duct system and are usually located on walls, ceilings, or floors.
  5. Plenums: These are large boxes or chambers connected to the HVAC system where the air is distributed or collected.
  6. Diffusers: These are devices that distribute conditioned air into the occupied spaces, ensuring proper airflow and temperature ...
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Air Handler Anatomy and the Importance of Routine Cleaning

It is crucially important to understand the basic air handler unit anatomy of a chilled water HVAC system. This knowledge successfully steers the cleaning and maintenance for each section of the AHU. It also provides visibility to its respective impact on system performance, indoor air quality, and energy efficiency. ASHRAE Standard 62.1 Section 8 gives detailed information on the regular inspection and cleaning of these components. However, guidelines may vary depending on the manufacturer and design of the AHU in question. Air Handler Unit Anatomy Below you will find a brief description of the main sections of the air handler unit anatomy based on the typical direction of airflow through the system. Also noted are common concerns and recommendations for maintenance.
  1. Intake Section:
The intake section of the AHU is responsible for drawing in outdoor air or recirculating indoor air. It typically consists of grilles, dampers, and filters. Regular cleaning and maintenance of filters are crucial to maintain good indoor air quality by removing particulate matter, dust, and allergens. Clogged or dirty filters can lead ...
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What is delta-T and how it affects energy efficiency?

Simply put, delta-T refers to the temperature difference between the chilled water entering the air handler unit (AHU) evaporator or chilled water coil and the leaving refrigerant or water. It is a crucial factor in determining the performance and energy efficiency of not only the AHU, but the HVAC system as a whole. Here's how Delta-T Works
  1. Cooling Capacity: The delta-T directly impacts the cooling capacity of the HVAC system. A larger temperature difference means that more heat is being removed from the building, resulting in a higher cooling capacity. Conversely, a smaller delta-T indicates that less heat is being removed, leading to lower cooling capacity.
  2. Energy Efficiency: The delta-T affects the energy efficiency of the HVAC system. A larger temperature difference means the HVAC system can achieve the desired cooling effect more efficiently. This is because a larger delta-T allows the evaporator coil to operate at a higher heat exchange rate, extracting more heat from the building's air. As a result, the compressor, which consumes a significant amount of energy, doesn't have to work as ...
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