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.
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.
Read all the tech tips, take the quizzes, and find our handy calculators at www.hvacrschool.com/.

[@HVACUncensored]

This is an awesome Video Bryan. Very informative. I’m gonna pass this along to our techs. One the best detailed videos I’ve seen to properly explain Static Pressure. Hope all is well buddy.

[@tymitunie4892]

I love everything that he is talking about.. it was great that he tested his home unit.. too bad he did not hit on duct work installers.. not questioning duct sizing..

[@shannonhill3356]

Damnit man I live in Florida and want to come work for you guys at Kalos so bad. Tired of begging for training, classes, and certifications as if they just have handfuls of employees trying to actually better themselves around here or something. You’re a wizard, man. Please don’t stop. We out here learning thanks to you and Craig.

[@francismarotta2301]

I wish manufacturers would put in test locations for manometers

[@HVACS]

Amen

[@jonathanmark7751]

Some York RTUs actually do. I like that so there's consistency.

[@jasonssmith1991]

@@jonathanmark7751 yes I’ve noticed this on a few York RTUs

[@francismarotta2301]

York RTUS do so you can do a static drop across coil to determine air flow. I wishbthey would do the same for furnaces

[@jonathanmark7751]

@@francismarotta2301 some of the York's have a knockout with a plastic cover on the inlet and outlet of the evaporator. If it's a down discharge RTU, the supply air cover has a knockout too. It's best to read the manual because Lennox RTUs actually ask for the supply static to be measured after the first 90.

[@rvamom5914]

My 6 year old has been making us binge watch your channel lately 😅 he loves it!

[@HVACS]

Haha... does he want a job 🤣

[@mackenziegray2090]

@@HVACS I do! I would love to work for company like yours. You invest allot of time teaching your employees.

[@marshallnmoonshine]

Great video. I do HVAC at a hospital and we do a LOT of air balance and static pressures. We always take a static pressure differential across final filters on the maintenances. Recently I took a bunch of Pitot readings to evaluate plugged chillwater coils to see if they need replacement. It was definitely a learning curve.

[@skylerlewis16]

Love your videos man! I’ve been doing residential HVAC in Utah for 8 years. We’re 4,500 feet above sea level here. Almost every system I test has high static pressure. It’s almost standard that we are adding 300 to 500cfm of return duct work on every install that we do. Also having issues with pressure switches not staying closed even though the inducer is pulling 30% over the water column rating of the switch. Keep up the awesome work, I’ve learned a ton from your videos and I appreciate the content 🤘🏼

[@I_name_All_my_guns]

Watched twice. Learned something each time. Saved to watch again and again and again

[@user-pe8lm2qk8u]

I am Korean. I always think your lectures are the best.

[@nelsonv3917]

Another great video Bryan, you explain static pressure very clear. Thanks

[@gowkarranpooran4771]

Hi Bryan, These videos are awesome. IT brought me back on track and I have to give you the Cedit, for guys in the field who cannot afford hvac school this is such a blessing. Your teaching really took me to a high level with great HVAC etiquette. Honest and perfect diagnostics no guess work hence time saving and quick solutions. I thank you very much and may God bless you and keep you and yours for being so selfless. Gowkarran from Toronto Canada

[@robertwasswa8794]

I can not stop to appreciate what I learn here and apply to Temporary HVACR as a gas/oil Tech in Canada. Thanks a lot again, am asking that you guys come over North for a HVACR symposium. We would like to hear and get this information. Truly helpful and problem solving information. Thanks again.

[@michaelmaclachlan2152]

Great tip for using masking tape to seal filters that don't quite fit. I also like to use silicone and/or foil tape in cases where the filter box is not properly sealed with the rest of the duct work.

[@eddieyoung9297]

This is defiantly one of if not the best explanation of static pressure, Thanks once again Bryan and team

[@ramytk1]

Great Video. Amazing presentation!

[@737MAXPILOTO]

Thanks Brian for an awesome video ,I learn every day .

[@jorgeaguila6774]

Outstanding as always, Thanks for sharing!

[@jasonjohnsonHVAC]

Another tip to add to your discussion....if you use the different airflow ramping profiles on a variable speed blower.....especially for the humid ramping profile, where the blower will ramp up to 50% for 30 seconds then 70-75% of full speed for 7-7.5 minutes, then it finally hits 100% full speed. Wait till you get to full speed....or change the profile to a non humid profile, where it'll ramp to 50% for 30 seconds and go to full speed.....just remember to put dip switches back to what its supposed to be for the location you are at.

[@tymitunie4892]

I love this guy.. don't listen to him because he is right and every word he says is true. but my company is based on correcting mistakes related to " your field duct workers" attempt to save on material and installing undersized ducts and I will never install 1" filter rack if you pay me!.. media filters!.. I listened to every word of his lesson and I wanted to applaud that we are lucky that there are still people who understand and know what they teach.. this was great to listen to.. stay true my friend! You my friend have 👍🏻👍🏻👍🏻 and a sub.

[@jamesmooney5348]

Enjoyed vid. After watching, clear as mud. I'll watch a few more times.... Thanks for posting this info.

[@lynncomstock1255]

It is worth it. He covers a LOT.

[@charmedlife6933]

Thank you for your vital content.

[@scott5654]

Excellent video ‼️ Thanks ‼️

[@brianmcdermott2430]

Great info. Thanks Bryan.

[@texasstarniles5]

Thank you very much Bryan!!!

[@justwork_hvac]

Thank for the great video. Very informative

[@jonathanmark7751]

Thanks for another great and informative video! I've recently had to go through a crash course on using static pressure to identify ducting problems. I work in commercial HVAC and if I were to use the TEC Tru Flow with all the adapter kits, it would get very expensive with all the extra adapter kits. Majority of the RTUs I work on have 4 filters or more per RTU. Can I get away with using one adapter plate and placing in the middle of the filter rack or return ducting? I own Testo 510 and Fieldpiece SDMN 6 stand alone manometers. I find the SDMN 6 drifts quite a bit, which I believe is due to not being temperature compensated like Testo. Does the Fieldpiece wireless manometers drift as well?

[@lynncomstock1255]

Charging any AC or HP system correctly ASSUMES correct rated airflow which is usually 400 cfm per ton. This is a big point that should be emphasized.

[@aliyusuf7713]

Thanks for your hard work

[@vara6180]

Very informative.... Liked it ❤

[@coldfinger459sub0]

Excellent lead into using DEEP PLEATS HIGH MERV efficient filters on Correct size. Of course measuring pressure drop or following the chart printed on the side of the filter and always recommend upsizing.

[@derekcampbell9663]

Get like 2 inch thick filters or 5 inch thick to improve air flo

[@NA-xm7wj]

Great video cleared up a lot of things. However I have a question While performing a static pressure test should all the vents in the house need to be opened because I know not all people don’t have all vents open all the time. Or does that even matter

[@willpartin622]

Thank you for all your great vids. I was wondering if you can ever have too much return ducting. After watching your videos, I checked my external static and found 3.5 and 3.5 for a total of 7 in WC . Filter drop is .18 INWC ( 5 inch air bear) and a\c coil drop is .21INWC. ( 2.5 ton N coil.) The temp rise is 70 degrees in heat mode. Rheem says 40-70 rise is okay , so I'm at the high end of acceptable . Shooting for 55 degree rise. I'm thinking I might need more returns and supplies but don't want to over duct it. Any help or advice? Also, when is was installed they added one 10' and one 8 inch flexible return duct. this is a 70,000 BTU Rheem 95% that replaced a 115,000 Ruud 95% furnace. Thank you Reply

[@americanpie8059]

When you mention the 4 inch filters are you referring to a gas furnace or furnace where you can set it on a base with an access door to change the filter?

[@Barracuda48082]

Bryan . Q. How often is it required to have precision measuring instruments recalibrated or re certified to manufacturers specifications, as in todays procast ? Q. b Who is responsible for the process and cover the costs? I do not recall covering this subject..

[@humbertoruiz4916]

Good video I love this content

[@Anavllama]

My heat pumps Fujitsu 2 ton (ARU24RGLX) , came with a default setting of Standard static pressure: 0.18 in.WG (45 Pa). I asked the installer to show me the equations they used to match up with the proper setting for static pressure. Of course I didn't receive any such information but did get the line: The system was designed for that heat pump so its all good. In the design/tech manual the function code for static pressure is 26 and the default setting is 31 which equates to .18 in. The settings start at 03 = .12 in (30 Pa), in increments of one up to a setting of 20 = 0.8 in (200 Pa). Then one has 31 = .18in and 32 = automatic air flow adjustment. I find it hard to believe that any work was done to optimize static pressure setting but want to know if leaving it at the default is best practice for installations? Would it be feasible to set it to 32 Auto adjusting??

[@Buildingscienceacademy]

18:30 You just explained a solid portion of fan curve analytics (mechanical engineering concepts) in a very simple way. Very well done.

[@hliz8818]

great video

[@rcinfla9017]

A lot of times the grill and filter size are fine but the box behind grill/filter and getting to input of air handler is just an afterthought based on what space is available. This can affect the uniformity of air flow across the area of grill/filter, effectively making the grill and filter perform poorer (smaller) than its physical area. Common issue when grill/filter has to be offset from air handler due to an interior wall.

[@RBuell-hv2wf]

AWESOME 👏 👍

[@frijolebeans7275]

Good work

[@jpenn727]

Are you saying that to test properly, I need to set my blower speed to the MAX setting to complete the test? And then before I left the customer I would lower it to the proper CFM for the customer? It seems to me that I would test it at the normal running speed.

[@WillieMakeit]

Usually test in cooling mode where blower is higher and electric is metered for amps

[@user-kg9rb5dc7w]

What is a proper method to measure whether my dwelling is positively or negatively pressured?

[@keithcorbin4474]

How tests stat pressure or atmosphere

[@organicvids]

Inch wc is the amount of pressure needed to displace an inch of water?

[@realestateservicessaleshea99]

Thanks again for the videos! 🥃🥃🍺🍺🍺⛳️🎳 Stay safe. Retired (werk'n)keyboard super tech. Wear your safety glasses!

[@Stuart68505]

It sounds like installing 4 in thick filters will improve the system performance where it is possible to do it without too much trouble.

[@Nine_883]

I can tell you this. I have been working in engineering research for a major manufacturer for 30 years. We use tools like the old school manometer with fluid to calibrate and certify our instruments. A utube manometer is better than any electronic instrument you can buy. It cannot be wrong. I am not talking about the Amazon special, but those would work too. They are probably just not durable. We use calibrated mercury thermometers to calibrate our thermocouple reading instruments. We use scales with weights and balances. We actually still use triple beam scales and we have certified weights we can use to calibrate the triple beam so we can use it to calibrate electronic scales. 😅. We always use a wet sock psychrometers to read wet bulb temp and calculate relative humidity. Humidity sensors are the worst. A sling psychrometer is a much better tool than any electronic humidity sensor. Just use distilled water. 😅. Don’t get me wrong. We use electronic, but we use “old school” instruments to calibrate or just verify the electronic instruments. Of course we use mass flow meters and thermocouple instruments to determine the exact BTU’s and verify compressor capacity at a wide range of operating conditions. Of course we use mechanical flow meters and calculations to calinrate the mass flow Coriolis meters. What’s my point? The old school methods are how they came up with units of measurement in the first place so do not count out the old fluid filled utube manometers. They cannot be wrong. 😮

[@drg424]

I still use old school, dwer ,it works well.

[@bobpaulino4714]

Air handler usually refers to a fan coil unit integral with coil as used in a heat pump. Can't believe the percentage of homes that I've looked at since I've retired from industrial/ institutional work that have never worked correctly because some hack didn't know how to size duct. The number of contractors that tell homeowners they need a larger unit when the duct system can't support what is there is astounding. Filter manufacturers push 'allergenic' and 'high efficiency' filters that are too restrictive when brand new for the base unit's design.

[@godz1llaki11azzzz3]

Is there such thing as negative reading on supply silly question i know but just curious lol

[@raytinsman2672]

What happens if the filter is in a grill?

[@grantnortman]

Have you done an AprilAire filter review?

[@grantnortman]

rp.widen.net/content/4uiwz4kh5l/pdf/aprilaire-all-products-specification-reference-guide-2210.pdf?u=5rn8it

[@Paul-Maven]

The more I dive into HVAC, the more I want to reinvent everything, especially tools. 🙂

[@ChrisHVACguy]

What's the difference between TESP, ESP and TSP?

[@SuperFabiannnn]

Great video but I wish you would’ve showed you this in front of the furnace.

[@williamhaines7723]

Not a word about a Magnehelic gauge?

[@HVACS]

Old technology.... works good though

[@rodgraff1782]

@@HVACS I always used magnahelics, or incline manometers. May be older technology, but it’s fool proof. The newer forms are great, but need to be calibrated, and certified. I wonder how many shops get their instruments calibrated on a regular basis.

[@river1012]

Kool

[@stephwaylonwells3218]

👍

[@carlyleworkman1928]

👍🏿

[@tommeyers974]

The HVAC videos do not discuss the increase in Electric Consumption from High Static conditions. Over the life of a Furnace, or Air Handler, the waste in power is Staggering, all paid for by the unsuspecting home owner. Ex: (At 1 amp per 0.1 inch (my furnace/AC is .2 over)=0.16KWH/hr., 1,250hrs/year, 25 Years, $.185/KWH gives $950 wasted, over the life of the unit.)

[@cristobalsanchez2030]

How is +.25" - 25" wc = .5" . Wouldn't it be 0?

[@francismarotta2301]

With external pressure you ignore the negative

[@jasonjohnsonHVAC]

Its a cumulative measurement

[@michaelmaclachlan2152]

The blower essentially is doing two things at once, pulling return air in through the return, AND sending air out through the supply. Both have an effect on how hard the motor has to work, so even though they are different types of pressure, you add them together for a complete picture on what's going on. Also , make sure to have the doors on when taking static pressure, because that can effect you readings as well.

[@jericosha2842]

+. 25 - (-.25) = .50 You subtract the negative pressure return air wc from the positive pressure supply air wc.

[@Barracuda48082]

Old school number line. Zero in center of line, negative to the left of zero, pos to the right, draw 25 divisions to left of zero, and then 25 divisions to the right of the zero. TSP is from one extreme to the other..

[@juanbarajas2226]

I disagree with checking external static pressure on a high speed. And the reason being is if we design a duct system with a blower at a .5 inches of water column for a specific friction rate, why would I change that if as a result I’ll have more air flow and higher static?. It’s the same weird concept where people are changing the fan speed to high in order to check CFM on a gas furnace. Why would you add extra work just to verify air flow? Blower performance charts are usually available. I could go on all day about it. Thanks for your videos.

[@1967friend]

I am confused about how you can add together -0.25 and 0.25 and get 0.50. That’s some magic math lol. To me that is 0.0. Are we completely disregarding the negative? How would it work when using a magnehelic?

[@UnusedRap]

It’s the difference between the supply static pressure and the return static pressure. So .25 - -.25 which is essentially .25 + .25 because when you subtract a negative it is like adding the positive.

[@inailedyourmom1]

​@UnusedRap your wrong, it is in fact, math magic 😂

[@redneckways1617]

I have several ideas for new HVAC tools…I filled out the diveratech application but never heard from them…guess cause I wouldn’t completely describe the ideas without chatting to someone first for confidentiality purposes….who else does the tool invention for HVAC tools?..I have 5 different ideas

[@tylerbarbaree7007]

PSIA PSIG

[@wilfredogonzalez883]

Why .5 +0.25- 0.25 =0

[@michaelking7253]

To zero out gauges does not calibrate them. I love to watch these videos, there is good info but it seems like the instructor doesn't have much in the field experience.

[@ryanrulz4992]

That’s was not anything!? wtf

[@jnuncio]

great video