HVAC Outside Airflow Measurements and COVID-19

Since the coronavirus first made headlines back in 2019, COVID-19 has been top of mind for citizens of the world around the globe. As counties and communities around the world have adjusted to this global pandemic, it has changed the way we live forever. The HVAC industry, like many other industries, has been greatly impacted by this moment in time. The impact of this moment in time will last far beyond the global pandemic, as it has shaped indoor and outdoor air requirements in a way that the industry will not return from.  

Of course, since the beginning of the COVID-19 Global Pandemic, our team has fielded many calls from customers and clients, especially those in the education industry. The world has changed, and many schools and universities are still trying to keep up and comply with new indoor air requirements mandated in order to bring students back, and to keep them safe while in school. 

First, we must cover some of the basic requirements, which can be found here on the official website for the United States Environmental Protection Agency, under the title, Healthy Indoor Environments in Schools During the COVID-19 Pandemic and Beyond. This page is not absolute in the requirements shared, but it gives a basis for understanding the changes schools and education facilities have faced since the start of the pandemic.  

The example brought to our attention by one of our customers was that as a result of the global pandemic, their team and organization had been running around with portable meters in an attempt to find an appropriate spot to read the measurements on the outside air.  

The difficulty is that spot measurements do not take into consideration varying conditions in all buildings, such as economizers, linkages, building pressure, occupancy changes, and heating vs. cooling, just to name a few.  

Instead, there are assets and tools that can be added to your existing HVAC system design to ensure that measurements are done consistently and accurately.  

This Ebtron Airflow Measurement Station stays in the ductwork for accurate and permanent monitoring, which makes it simple to get updates on your air quality. The Ebtron Transmitter has both analog outputs and optional data-logging, so you can verify continuously on the display or from your PC that you are meeting OSA requirements for your site. 

If your building needs a quicker fix, we suggest adding the Ebtron Airflow Measurement Station to the gyms, libraries, common spaces, and classrooms to provide stand-alone with data-logging to verify clean-air dilution. With this product, anyone can have the station quickly and it only requires 24vac power, making it a simple solution for all.  

For a longer-term update, connect the stand-alone Ebtron Airflow Measurements Stations to the BMS for continuous monitoring and alarming.    

Here at AirReps, we’re pros at redesigning and updating the HVAC systems in larger buildings, and we have plenty of experience with educational organizations. If you’re looking for more help, or if your building is ready for a new HVAC system design, reach out to our team today!  

Ebtron Analog Output Scaling and Testing

Recently, a long-time customer and partner was inquiring about the analog output scaling for Ebtron transmitters. It’s a great question, as there is a plethora of information to understand when diving into Ebtron transmitters.

Below, we have listed some of the most important points for when users are just getting started with their Ebtron transmitters for analog output scaling and testing.

Probe based airflow stations come default as 0-5000 feet per minute (FPM) on the analog output 1 from the transmitter.  Note that this is a VELOCITY and not a VOLUME.

Fan inlet airflow stations come default as 0-10,000 FPM since they are generally a faster speed into the inlet cone.

For most systems, we recommend that you bring all of the transmitters velocity analog output (either 0-10v or 4-20ma based on the dipswitch) into your control system Analog Input (AI) as the same analog scaling— that is, regardless of duct size all of your Ebtron probe transmitters will have the same 0-5000FPM scaling into your AI.  We like bringing all of the transmitters in with the same scaling to avoid field confusion— at least initially.

Take each AI and multiply it by the duct area to get an AV showing the VOLUME in CFM.

VELOCITY x DUCT AREA = VOLUME FLOW

Having the volume flow be an AV allows you to do other operations on it later that you can’t do with an AI*.  We can look up the area from the packing slip if you don’t have it— call us if you need this value.
*Useful AV operations:  You can write a “0” to the AV on a windy rooftop when the unit is off, so there aren’t any weird airflows on the screen to distract the operators.

Here is an example using math to showcase how to best adjust the Ebtron transmitter’s analog output for scaling and testing.

If you brought the 0-10v signal in as 0-5000FPM on a 4’x4’ duct:

5000FPM x 16Ft^2 = 80,000CFM at max flow.  This means that 5V at the transmitter should show 40,000CFM on your EMCS display.

Based on how the manual describes it, we did the “manual conversion” to give more in-depth information.

USING THE TESTOUT BUILT INTO THE TRANSMITTER:

Ebtron gave us a great tool to help commission this by going into the setup/tools menu you can force the output to a certain %, and verify that we did all of the steps correctly.  If I command the output to 50%, I can measure 5v on the output and should see the EMCS display change to 40,000CFM in the above example.

As always, if you have any further questions, please feel free to reach out to our team! We’re happy to give you the hands-on assistance you need to ensure your system is running efficiently!