Short #64 - Diagnostic Duct Design

BACK

Short #64 – Diagnostic Duct Design

July 23, 2019

For a technician who comes across a customer balancing complaint, How do you think about and help to solve the problem?

Check out our most recent video

How to Evacuate an AC system, Full Vacuum Procedure

Our latest Podcast

HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

In this short podcast episode, Bryan covers some common mistakes when measuring static pressure. Static pressure is balloon pressure, not CFM or velocity pressure, but it can be an airflow indicator. The best way to start learning about static pressure is to start measuring total external static pressure.

Gas furnaces and heat pumps are different; static pressure is rated at the furnace in the former (not the cased coil, which is additional), and the static pressure includes the coil in a heat pump. The highest static pressure will always be at the blower, but restrictions on either side of the blower will raise static pressure on both sides of the blower.

Dirty components can drop the total external static pressure, which is a common point of confusion that can lead to misdiagnosis. You’ll want to determine static pressure at the blower and across components. If you want to determine if a cased evaporator coil is clogged, you can measure the static pressure drop across the coil (by measuring below and above the coil) and compare it to the manufacturer’s specifications. Dirty blower wheels can also cause problems, as they don’t move much air in the first place.

Lower static pressure at the blower is the best for amp draw and airflow, and our system designs and accessories can support low static pressure. Dialing in airflow, putting your probes in the right positions when you measure static pressure, proper register and grille selection, and minimally restrictive filters all go a long way.

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

Purchase your tickets or learn more about the 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

Subscribe to our podcast on your iPhone or Android.

Subscribe to our YouTube channel.

Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android