Static Pressure and Manometer Basics

Static Pressure and Manometer Basics

In this class, Bryan gives the Kalos techs a refresher and goes over the basics of static pressure. He also differentiates between utility manometers and precision manometers, covering their appropriate uses.
By Bryan Orr

Utility manometers are your typical standard service manometers; they are designed to measure pressure in inches of water column (“WC, “H2O, or inWC). Inches of water column are smaller units of measure than PSI, and they’re ideal for static pressure and gas pressure. Some utility manometers have one port, and others are dual-port manometers. Single-port manometers require you to zero them with the hoses on before taking the measurement. (Accurate zeroing is very important, especially as pressure continuously changes with the weather.) Dual-port manometers are often used for measuring a pressure differential, and zeroing is typically less critical because there is already another baseline for comparing the pressure.

There is no such thing as “zero pressure.” The closest we can get to “zero” pressure is 14.7 PSI, atmospheric pressure, so zeroing out single-port manometers is critical.

Precision manometers use Pascals instead of “WC, which is a much smaller scale. We use precision manometers to measure duct leakage or envelope leakage (such as through a blower door test). We can also use the tiny Pascal scale to measure pressure imbalances between rooms and mitigate pressurization/depressurization problems.

Static pressure probes look an awful lot like pitot tubes, which have tubes within tubes. A pitot tube takes a measurement that’s a combination of static pressure and directional force. Pitot tubes then subtract the static pressure to yield only the velocity pressure; these tools require precision manometers to do their jobs properly. Pitot tube usage is more common on the building science side of the industry than HVAC service.

Static pressure probes each have a closed end at the tip and some side ports, and they only measure static pressure. The probes face the opposite direction of the airflow and measure the force exerted in all directions (against the walls of the duct). Static pressure can be either positive or negative in reference to the atmosphere, and we typically measure it by putting one tube in the return before the blower and the other above the blower in the supply plenum in a fan coil or handler on a heat pump or straight-cool A/C (or below the coil on a gas furnace). In gas furnaces, the coil provides a pressure drop and is separate from the actual unit.

The rated static pressure can be found on the data tag; a static pressure that differs from the rating will affect the system’s performance (though there is typically an operating envelope). If the static pressure is higher than the test static on the data plate, a variable-speed blower will have to ramp up to maintain the airflow, increasing operating costs and the amp draw while negatively impacting the motor’s longevity. Filter changes can cause the static pressure to change over time. You can also measure pressure drops over the filter and evaporator coil to isolate problems with filters or coils.

Static pressure is NOT airflow; it’s a pressure measurement, but it can be an indicator of airflow. Before we can measure the static pressure accurately, we need to make sure the system is producing the proper airflow (high-stage, no dehumidification mode). Although checking static pressure isn’t something we need to do on EVERY call, it’s worth checking when there are airflow complaints. Total external static pressure, supply, and return static are all worth checking to see if there are restrictions across filters or coils or other possible airflow problems.

Filters can cause many problems, and static pressure readings can help you pick up restrictions caused by filters. Larger filters (4″) with greater surface areas tend to create far less of a pressure drop and last longer than shallower filters (1”), which can clog and restrict airflow quickly.

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Most popular videos

See all +
thumbnail

Tips for Cleaning an Air Conditioning Common Drain

thumbnail

Gas Furnace Overview w/ AC Service Tech

thumbnail

Motor Overload and Safeties – Kalos Meeting

thumbnail

A Common Electrical Mistake

thumbnail

5 Traits of Bad HVAC Leaders

thumbnail

Don’t Overfill Refrigerant Recovery Cylinders The Easy Way

thumbnail

How to Replace an AC Condensing Fan Motor

thumbnail

How to Braze Air Conditioning Copper

thumbnail

How to Leak Test an AC With Nitrogen Pressure

thumbnail

How to Properly Pipe a Drain on a Fan Coil

thumbnail

4 Silly Mistakes of The Green HVAC Tech

thumbnail

How to Install an AC Disconnect

thumbnail

Why a Hard Shut Off TXV Closes

thumbnail

The Importance of SST (Evaporator Temperature) and Using a Scale (Kalos Meeting)

thumbnail

Adjusting Gas Pressure on a Standard and Gemini Furnace Valve

thumbnail

How a Heat Pump Reversing Valve Works

thumbnail

Don’t Confuse TD & Delta T

thumbnail

How to Install a Thermostat

thumbnail

How and When to Use a Schrader Core Removal Tool

thumbnail

Why Does The Evaporator Coil Freeze (And How to Diagnose It)

thumbnail

How to Measure Total External Static Pressure (TESP)

thumbnail

Does a TXV Shut under Vacuum?

thumbnail

Prevent this Common Manometer Mistake

thumbnail

Facts About Fusite (Compressor Electrical Pass Through Connections)

thumbnail

See Inside a Biflow/Heat Pump Filter Drier

thumbnail

Flammable Refrigerant Safety Basics – Kalos Meeting

thumbnail

Stuck Contactor Issue

thumbnail

How is 208 volts different than 230/240 volts?

thumbnail

Tips for Hiring & Getting Hired

thumbnail

Open vs. Closed Refrigeration

thumbnail

How is a 3-Phase Motor Different than Single Phase

thumbnail

HVAC Class 11/24/2020 – Electrical Review

thumbnail

How to Measure Gas Pressure – Kalos Meeting

thumbnail

What is Common, Start and Run?

thumbnail

Perfect Flares Every Time w/ NAVAC NEF6LM

thumbnail

Ask Bryan Anything Live Call-in from 11/21/2020

thumbnail

How to Build a Sheet Metal Coil Case From Scratch

thumbnail

What Air Filter is The Best?

thumbnail

Basic Electrical Circuit Terms

thumbnail

The #1 Key to Service Success?

thumbnail

How To Keep Motors Running Cool And Efficient

thumbnail

Talk Through The Refrigerant Circuit Using The “Glass Tube” trainer

thumbnail

Top 10 HVAC Tech Tips for 100K

thumbnail

Installing a Rectangle to Round Transition into an Existing Metal Duct

thumbnail

How Humidity Impacts The Weight of Air

thumbnail

Testing Home Pressure Imbalance w/ Genry Garcia (Spanish)

thumbnail

Some of Bryan’s Favorite New Tools Giveaway Meeting

thumbnail

Bert Teaches The Basic Refrigerant Circuit + Safety

thumbnail

Heat Rise Airflow Calculation

thumbnail

LIVE Apprentice Q&A

thumbnail

Setting a Refrigerant Charge by Subcool

thumbnail

The Toxic SUPER TECH Mindset

thumbnail

Soft Skills Can Be Hard (Disciplines of Growth)

thumbnail

Double Crimp Connection

thumbnail

How to Fabricate a Metal Supply Plenum From Scratch

thumbnail

Delivered Capacity Basics – Kalos Meeting

thumbnail

Sequencer Facts – They Aren’t All The Same

thumbnail

Wire Routing & Float Switch Positioning

thumbnail

Dual Voltage and Part Start 3-Phase Motors

thumbnail

Apprentice Program Day 1 – Using Your Resources w/ Jason Obrzut

thumbnail

Bert Cleans Out His DIRTY Work Van (And You Should Too!) #BERTLIFE

thumbnail

Liquid Line VS. Discharge Line

thumbnail

Tips for Proper AC System Cleaning – Kalos Meeting

thumbnail

EPA 608 Prep – Type 3

thumbnail

Motor Replacement Tips & Tricks – Kalos Meeting

thumbnail

EPA 608 Prep – Type 2

thumbnail

Better Duct Installation Practices – Kalos Meeting

thumbnail

THIS Is How My FIRST WEEK As An HVAC Apprentice Went (I’m Being Trained By WHO?!)

thumbnail

EPA 608 Prep – Type 1

thumbnail

How to Find Refrigerant Leaks – Kalos Meeting

thumbnail

Advanced Ventilation w/ CERV2

thumbnail

Critical System Diagnosis for Residential HVAC

thumbnail

Diagnosing Open & Short Circuits

thumbnail

Installing a Mitsubishi One-Way Ceiling Cassette In An Unfinished Room (You Can See EVERYTHING!)

thumbnail

How to Use a Blower Door (Como usar el Blower Door)

thumbnail

How to Stop Drain Snot (Bacterial Zoogloea)

thumbnail

EPA 608 Core Prep – Part 2

thumbnail

EPA 608 Core Prep – Part 1

thumbnail

A Strange Contactor Issue

thumbnail

GreenSpeed Extreme Install

thumbnail

Symptoms of Low Evaporator Airflow

thumbnail

Preventing Flooding On a Walk-In Call

thumbnail

Symptoms of Overcharge

thumbnail

Diagnosing and Replacing a Run Capacitor

thumbnail

Symptoms of Low Refrigerant Charge

thumbnail

Preventing, Finding & Repairing Refrigerant Leaks

thumbnail

Proper Use of Manometers for HVAC Technicians

thumbnail

UV light and Petri Dish Demo

thumbnail

Tool Talk Live – Probes, Bags, Hand Tools, Power Tools & More

thumbnail

Cleaning BARD units with Venom Packs

thumbnail

Electrical Basic Concepts – RSES NATE Prep

thumbnail

Selling, Upselling, IAQ , Hardstart Kits and More

thumbnail

Cutting & Installing a Rectangle Duct Connection

thumbnail

How to Make a Leak Free Canvas Duct Connector

thumbnail

Cooling Commissioning Measurements Walk Through w/ MeasureQuick

thumbnail

How to Checkout Blower Settings Using a Manometer

thumbnail

Recovery Best Practices & Giveaway

thumbnail

Introduction to the Fieldpiece Joblink Manometer Set

thumbnail

HVAC SCHOOL MONEY TALK – Don’t Make This Common Mistake

thumbnail

Testing out a High Performance HVAC Installation

thumbnail

Commercial Refrigerant Retrofit Options in a Crisis Economy #LIVE

thumbnail

HVAC Myth Busting #2 – Volts Go Down, Amps Go Up

thumbnail

Rectorseal RSH 50 Installation

thumbnail

Setting Up Residential Demand Ventilation with Laser Egg

thumbnail

Residential Zoning Talk #LIVE

thumbnail

DUCTLESS Control and Humidity Hack with Cielo Breez

thumbnail

HVAC Myths and Controversy #1

thumbnail

Rectorseal Surge Protector Installation

thumbnail

HVAC Contractors Guide to COVID-19

thumbnail

Commercial Install Review

thumbnail

DIY Cloth Mask with HEPA Pocket

thumbnail

How to Make an Indoor Air Cleaner the Cheap and Easy Way

thumbnail

Electrical Diagnostic Thinking

thumbnail

Human Comfort Basics – RSES NATE Prep

thumbnail

Introducing Venom Packs

thumbnail

5 Install Mistakes that Kill Systems

thumbnail

UV Part 2 – Honest UV Facts from a Manufacturer

thumbnail

UVC Air Purification – Live Podcast Part #1

thumbnail

How to Make a Metal Duct Transition in the Field

thumbnail

Reversing Valves (RSES NATE Prep)

thumbnail

Sunday Coil Cleaning #BERTLIFE

thumbnail

Liquid Line Solenoid on Long Refrigerant Lines

thumbnail

Condensing Unit Install Practices (RSES NATE Prep)

thumbnail

HVAC Motor Types (RSES NATE Prep)

thumbnail

Relative Humidity in the Supply Air Stream

thumbnail

Advanced Combustion Analysis (HVAC) w/ Jim Bergmann

thumbnail

Advanced MeasureQuick Diagnosis w/ Jim Bergmann

thumbnail

How to Flow Nitrogen While Brazing

thumbnail

Compressor Tear Down (Don Gillis / Trevor Matthews)

thumbnail

Compressor Facts and Troubleshooting (Don Gillis / Trevor Matthews)

thumbnail

CO2 101 (with Don Gillis)

thumbnail

Nikki Kreuger – The Dripping Point

thumbnail

Inside a Scroll Compressor

thumbnail

Troubleshoot a Grounded (Shorted to Ground) Compressor

thumbnail

Using Power Factor to Check Capacitors Under Load

thumbnail

Straight Cool Air Conditioning Schematic (Carrier)

thumbnail

Charging During Low Outdoor ambient w/ Charging Jacket

thumbnail

Recovery Machine Speed Race 🏁NAVAC NRDD Digital vs. Appion G5 Twin

thumbnail

Is There Mold in my Ducks! 🦆(Ducts)

thumbnail

Inside a Sequencer

thumbnail

A thermostat miswire and distracted diagnosis #BERTLIFE

thumbnail

Cleaning large coils with CoilPro

thumbnail

Smelly Ductless #SOLVED

thumbnail

Inductive Reactance in Real Life

thumbnail

50K Subscriber Special & Behind the Scenes Tour

thumbnail

Compressor Won’t Run Diagnosis

thumbnail

A Blower and Heat Strip Dangerous Mistake

thumbnail

How to adjust a TXV, TEV or TX Valve

thumbnail

5 HVAC/R Terms That Sound Worse Than They Are

thumbnail

Fieldpiece Joblink Firmware Update Demo

loading

To continue you need to agree to our terms.

The HVAC School site, podcast and daily tech tips
Made possible by Generous support from