Arkansas HVACR NewsMagazine March 2024

HVACR NewsMagazine March 2024

Tech News

depressurization analysis calculator by RED Calc. You can use this calculator to determine how much CFM of fresh air you will need to bring in to offset the building leakage if you know the exhaust flow and depressurization. (You can also solve for any one variable if you know the other two variables; you can figure out depressurization if you know the building leakage at 50 Pascals and exhaust flow.) In general, the building volume matters, and you'll want to start making these calculations when the building nears 1.5 air changes per hour (ACH). It's also not recommended to add fresh air to the structure without doing calculations or testing of any sort, including a blower door test. Even then, the next step after a blower test would ideally be to monitor the indoor air quality and determine if adding fresh air is indeed the best thing to do. The goal is to provide a solution tailored to each individual house's needs. ERV sizing will depend on fresh air standards and how much exhaust air you need to offset. You can figure out how many CFM of fresh air you need to bring in by comparing ASHRAE Standard 62.2 to your exhaust needs and determining which one is greater. Then, account for an extra 30 – 50% capacity so that there is some room to vary the performance depending on the conditions. Some ERVs also have cloud-sensing capabilities. They monitor outdoor conditions and shut off if the outdoor air quality isn't adequate, such as if the humidity is too high. If the ERV dumps air into the return, then the air handler may need to run continuously at a low fan speed. The ERV will bring in some humidity only if the outside air has a moisture content than the inside air. This is because ERV Considerations

ERVs are not 100% efficient. The outside air will mix with the air in the return. If the system is running in cooling mode, the humidity from the ERV can be removed by passing over a cold evaporator coil. Otherwise, when the call for cooling is satisfied, the ERV may be designed to bypass the central duct system entirely and dump air into the space through a return grille. However, that brings a high risk of condensation in humid climates. While the installation of a dedicated duct system for an ERV has a pretty big impact on system efficacy, the theory behind it is pretty important. There are cases when the air in a home can't circulate as intended, such as when people sleep in the bedroom with their door closed or work from home and close the door for a meeting. The best way to ensure that you have the best comfort and ventilation control is to have an independent distribution system for the ERV that supplies ventilation air to each room. When you tie an ERV supply directly into the HVAC supply instead, you may have to make a choice to balance the airflow based on comfort or IAQ. You have a lot less control Dedicated Duct Systems for ERVs