Outside Airflow Measurements and Covid- Two projects (One for "right now" and one for "later")

We have had a few calls from customers lately, especially school customers who are trying to comply with outdoor air requirements to bring students back.

Here is a sample of some of the basic requirements: https://www.epa.gov/iaq-schools/epa-supports-healthy-indoor-environments-schools-during-covid-19-pandemic

One of the customers is running around with portable meters and trying get spot-measurements on outside air.

The problem with a spot measurement is that it doesn't take into consideration the varying conditions after the measurement- economizers, linkages, building pressure, occupancy changes, heating vs cooling etc.

This Ebtron airflow measurement station stays IN the ductwork for accurate and permanent monitoring: https://ebtron.com/wp-content/uploads/GTx116e-PC_Overview.pdf

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.

For a quick-project: put an Ebtron airflow station on the gyms/libraries/commons/classrooms, stand-alone with data-logging to verify clean-air dilution.  You can have the station quickly and they only need 24vac power.

In the longer term: connect the stand-alone Ebtron airflow stations to the BMS for continuous monitoring and alarming.

Ebtron Probe Installation Video

Hi- Ebtron recently released a nice video on how to install insertion type probes- the most common type to install in ductwork.

Here is the link: Ebtron Probe Install

The most common question we get is about probe spacing for multiple probes, that is covered at the 1:48 minute mark.

As always, don’t forget that we measure and mark the ducwork for free, so that they probes are in the best possible location for accuracy and servicability. NO CHARGE to come to the jobsite!

TimH

Ebtron Analog Output Scaling and Testing

Hi- A customer was asking about analog output scaling for Ebtron transmitters— Here is a good place to start:

1. 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.

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

3. 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.

4. 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 cant do with an AI*. We can lookup 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 a math example-

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.

Here is how the manual describes it, we did the “manual conversion”:

GTC-116 manual description

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, please call us if you have any questions.

Ebtron Probe Adjustments

InControl will be happy to measure and mark the mounting locations for all of our airflow stations-- we do it for free and strongly encourage it.  That way you know that you have the correct size and the best mounting location to make sure we get the full accuracy of the device.

There is some mounting flexibility in the brackets, depending on the installation type:

For internal brackets, approximately +/- .75" by adjusting the set screw on the mounting feet.  DON'T OVERTIGHTEN the screws on the feet, especially on the cable end.

For insertion mount, the probes are cut full size but there is a 1.5" stud on the non-cable end that allows for some adjustment.  About 1", especially to make the probe fit a LARGER duct than measured.

For standoff mounts, the brackets need to go straight back to the damper frame, there isn't much flexibility on these.  It would be best to get these right on or slightly larger than the damper opening.

Insertion Mount Installation

Internal Mount Installation

Standoff Mount Installation

Ebtron internal mount feet

Ebtron insertion mount stud-end