Arkansas HVACR NewsMagazine March 2024

HVACR NewsMagazine March 2024

Tech News

• Not heavy in outdoor pollutants (like pollen or particulate matter from wildfires and power plants) • Adequate temperature for comfort • Safe and comfortable humidity level Fine particles also pose a problem, and the only way to remove them from the incoming air is via filtration. Recent wildfire events have forced the industry to rethink filtration for dilution air, with newer models requiring MERV 16 filters that remove ~95% of fine particles from the outdoor air (nearing HEPA levels). Humidity management can be very tricky. Dehumidifiers work a lot like air conditioning units; humid air passes over a coil, which pulls moisture out of the air. That said, in some climates, it's very difficult for ventilating dehumidifiers or ERVs to remove enough humidity from the incoming air, and the tighter building standards for new homes make dehumidification even more critical. One of the downsides of ERVs is that they don't stop regardless of the weather conditions. They'll bring in "fresh" air even on cool, rainy days, which may especially spell trouble for occupants in the Southeastern United States. The outdoor air usually has a higher humidity level than the inside about 75% of the time, even despite taking showers and cooking indoors. Not to mention, the outdoor cooling design temperature and mean coincident dry bulb (MCDB) for the dehumidification design conditions may vary by as much as 20°F in some parts of the country. In some airtight homes, one-way bathroom exhaust isn't a safe option. We will need to bring in some outdoor air to offset the pressure, and some people use ERVs to accomplish that. ERVs bring in outdoor Tying ERVs into Bath Fans

air as the indoor air is being exhausted, so it keeps things balanced. The top five ERV manufacturers have also given the bath exhaust tie-in design their seal of approval. One of the most basic ventilation kits you can install consists of a ventilation damper and controller that ties into the return. The controller communicates with the air handler and opens the damper based on runtimes, or it'll send a fan call to the air handler and open the damper if the system is not running. Basic Ventilation

This basic kit relies on the negative return side duct pressure to move the air, not a powered fan. The downside of this configuration is that you must have sufficient return duct pressure to get airflow through the damper, and higher return static pressure is usually much more desirable. This might be difficult to accomplish if your "fan on" blower speed moves less CFM than the heating or cooling fan speeds. It's the same principle that explains why we can't use passive makeup air in homes with fireplaces; equalized pressures won't allow airflow, and you can backdraft a fireplace.

How to Know What to Bring In

There are tools that you can use to determine how much air needs to come in or be exhausted. One of those is the free