The Retrotec FlowBox

Exhaust Fan Flow Meter & Pressure Pan

The FlowBox is a passive exhaust fan flow meter that utilizes the DM32 manometer to measure exhaust only flows.

This tool is perfect for measuring flow for bath fans, kitchen exhaust, room returns and whole-house ventilation. It uses the same type of range plugs that are found on our DucTesters and Model 5000 and 6000 blower doors.

In addition, you can use the FlowBox as a pressure pan by simply using all blank range plugs.

The FlowBox has several unique design features that put it in a class of its own, including:

• A large 16.5 ” x 16.5” x 8" coverage area that can measure larger bath fan models with light assemblies
• No moving parts that will break later on
• A sturdier plastic that will last. We noticed that many testers use their exhaust fan flow meters to carry things, causing inferior products to break over time. So we made ours stronger. After all, it is a box. You’ll naturally want to put things in it.
• The ability to use it as a Pressure Pan without adding tape

With all of the holes completely plugged, the FlowBox can also be used as a pressure pan to locating leaks with a blower door. This is the only exhaust fan flow meter that can be used as a pressure pan without the need for tape.

1 x FlowBox

4 x Blank Range Plugs

1 x Range 74 Range Plug

1 x Velcro yellow handle with hole for telescoping pole (pole not included)

To use the FlowBox, make sure you update the firmware on your DM32. If you haven’t yet, you can download the DM32 configurator here.

A sticker attached on the side of the FlowBox (also shown directly below) indicates the effective open area you'll need to enter into the DM32 or DM2 gauge for the selected ranges and flow capacities. 

 Important: Adjust the hole configuration until Channel A on DM32 reads between -1 & -10 Pa
Place firmly to ensure a tight seal

FlowBox Flow Ranges

 * Table Denote Flow Rates in Cubic Feet Per Minute (CFM)
** +/- 10% Accuracy. Effective area values were determined by using NIST traceable equipment on a flow chamber.

For further details on how to how to setup this feature, or for setup with a DM2, refer to each gauge's instruction manuals:

• DM32 – Section 2.6.3 and Appendix G
• DM2 – Section 2.1.5

Those using the FlowBox with a non-Retrotec Gauge can use the "Retrotec FlowBox Lookup Table" under the Guides/Manuals tab on this page.