How a Variable Air Volume VAV System Works

[@garygrey650]

Thank you sir for explaining the system architecture and functioning in a simplified and systematic way. Hell of a video

[@MEPAcademy]

You're Welcome. Thanks for watching.

[@bigpermsgarage6290]

I wish I came across your video when I was an apprentice many years ago. The video is very informative.

[@MEPAcademy]

Thanks

[@ForeeverTruth]

Explanation with diagram . Thank you sir it is very easy and simple for beginner .

[@MEPAcademy]

Glad you found it easy to follow!

[@bakriegassing2548]

The minute 12:05, you mentioned the air temp from AHU will bring 55 F whether the building is on heating and cooling load. is AHU cooling only? what about heatpump AHU in this case?

[@MEPAcademy]

In this example without supply air temperature reset, the temperature coming off the coil is 55 F even when the volume of air has been reduced to the minimum to maintain ASHRAE 62.1 ventilation requirements. Heat Pumps are a completely different system, while this system is using a chilled water coil in our AHU.

[@getsnipedhockey32]

Thanks, very informative. Just graduated as a welder and all of a sudden im installing these lol

[@MEPAcademy]

Congrats on being a welder. Yeah, VAV Systems are common in commercial buildings. Thanks for watching.

[@gustavebauder1023]

Nice video very well explained. Note, in most cases the pitot tube is down stream of the damper not upstream.

[@MEPAcademy]

Thanks for the info! Thanks for watching.

[@hameddadgour]

Your videos are fantastic by the way! Very informative!

[@MEPAcademy]

Glad you like them!

[@syriaco257]

Thank you sir for explaining the system

[@MEPAcademy]

You are welcome

[@bigtoe0341]

Thank You for the info.

[@MEPAcademy]

You're welcome.

[@rogerg8089]

Hello! I am a licensed architect in California, watching your video to better understand mechanical systems. I have a question. Regarding zoning, particularly at high exposure corners on the south elevation, if the architectural team chose to increase insulation or other measures to reduce the solar exposure on that elevation, how could that be quantified to potentially reduce the peak cooling on those high exposure zones

[@MEPAcademy]

Of course an increase in the "R" factor of any insulation or other measures would increase the "U" factor used in the cooling and heating load calculation. The larger the "R" value, the lower the "U" value will be, which lowers the cooling load. This will reduce the size of the Air Handler or Air conditioner serving that zone. An energy analysis can quantify this, and show the before and after results of any increase in the "R" value under consideration. Taking this one step further, an analysis of the payback period can be determined based on the increased cost to achieve a greater reduction in the cooling load. A reduction in the cooling load effects all parts of the mechanical system, including equipment, air ducts, refrigerant piping and air distribution grilles. This is depends on the type of system used of course. Title-24 in California allows tradeoffs using the performance method to achieve an overall energy reduction goal.

[@juanfranciscobelmontetoled2058]

Amazing video. Explanations so clear and precise. Not easy to do that way. 😊

[@MEPAcademy]

Glad it was helpful! Thanks for watching.

[@vladimirfedorov6951]

Thank You very much for the video. It is so clear and informative. Great educational tool.

[@MEPAcademy]

Glad it was helpful! Thanks for watching.

[@kausalyabaissonale4804]

This is a very good video with very good explanation!!! Thank you.

[@MEPAcademy]

You are welcome!

[@nimbo9492]

Where would the AHU duct static pressure is normally located? is it right at the outlet of the AHU fan or further down?

[@MEPAcademy]

Usually 2/3rds of the way down the main supply duct.

[@leonardozeledon6604]

Awesome video, love the understanding.

[@MEPAcademy]

Thank you

[@amjadhelo3598]

Thank you for great explanation I wish to make video about trim and respond method and return fan control methods ( return duct static pressure and air flow measuring station ) ❤❤

[@MEPAcademy]

You're Welcome

[@rggiri2237]

Can AHU CFM can be selected with 20% Diversity as we are diverting air

[@MEPAcademy]

Diversity can be determined by doing an analysis (cooling & heating load) of the zones that are being supplied, it's not a random percentage.

[@rrmojo1]

excellent video!

[@MEPAcademy]

Thank you very much! Thanks for watching.

[@salimyousuf8848]

Thanks for sharing Can u tell which sensor( airflow or temperature)has high priority control over damper positions?

[@MEPAcademy]

The box damper will modulate to maintain a Supply Air CFM set point between a preset minimum air flow and maximum air flow. If the space temperature rises above the cooling set point, the box damper will modulate open from a minimum cooling CFM air flow set point, to a maximum cooling CFM air flow set point, as cooling demand increases. An air velocity pressure sensor will maintain the supply air CFM set point for pressure independent operation.

[@Forx4Ever]

According to your knowledge/experience , which is better? Zoning with VAV boxes or with zoning kits come with concealed ducts systems (splits)…I think with VAV boxes we have more customization options, do you agree with that.... Second question: In the video there is a heating coil inside the VAV box. Is this an alternative to the heating coil in the air handling unit? Can we have a coil for heating and another for cooling inside the air handling unit, and at the same time we also have a coil for heating and another for cooling inside the VAV box? Thank you....

[@MEPAcademy]

Each building needs to be reviewed for the best HVAC system type, taking into consideration many factors, such as geographical location, building size, energy cost, new or retrofit, etc. Consideration for how ventilation will be provided to each space is easier with a central Air Handler feeding VAV terminals, then having dozens of split systems everywhere, which would require a DOAS or some form of outside air to meet ASHRAE 62.1. Having a heating coil at the VAV terminal is good for external zones that will have heat loss through the building shell, while interior zones most often don't need heating coils because internal heat loads negate the need for heating.

[@火雞姐-j2n]

Why must the air duct pressure sensor be installed 2/3 downstream of the air handling unit? How about installing it remotely?

[@MEPAcademy]

In Variable Air Volume (VAV) systems, the pressure sensor placement impacts how the system modulates fan speed to maintain the desired duct pressure. Positioning the sensor at two-thirds of the duct length ensures adequate pressure is maintained for downstream zones without over-pressurizing upstream zones.

[@alemamalmahi2351]

Thanks for good explaining,, Can you help me to studying this playlist in arrange way step by step,, because there is no numbering for episodes, for example E1, E2, E3, E4,.. ect

[@MEPAcademy]

There is no sequence for viewing currently. The videos cover a wide range of topics on HVAC systems. You can search the channel for any topic that you're interested in, or suggest a topic if it's not available. Thanks for watching.

[@hameddadgour]

What is the right order in which I should watch your videos in the HVAC Engineering Basics playlist? It seems that they are out of order. Am I mistaken? Thank you!

[@MEPAcademy]

Sorry @hameddadgour, you're right. We haven't spent much time arranging the videos in any logical order, but have let them roll into the playlist as they're published. We'll put it on our list of things to do. Thanks for the idea.

[@joeschneider67]

What if that air handler is a split system or a package unit? Who will turn the condenser unit off ( if split system )or compressors off if package unit?

[@MEPAcademy]

If it's a packaged unit or split system the controller will dictate when the system runs. With a split system there will be a communication wire between the air handler and the outdoor unit. Controls are the key to controlling any system or system configuration.

[@joeschneider67]

@@MEPAcademy thanks

[@samhaazratechnicalsupport]

Very niece sir ji ❤❤❤🇮🇳

[@MEPAcademy]

Thank you.

[@ogbagiorgisabrha6355]

What is the cause of condensation in AHU

[@MEPAcademy]

Are you talking about condensation at the cooling coil. Condensation on a cooling coil typically occurs when the surface temperature of the coil is lower than the dew point temperature of the air passing over it. The dew point is the temperature at which air becomes saturated with moisture and begins to release water in the form of condensation. We have a video that will help you understand the concept of sensible and latent heat. kzbin.info/www/bejne/n36oXmR_bqxnh9k

[@angelocedeno1906]

Love this video thankyou

[@MEPAcademy]

Glad you enjoyed it!

[@WonderfulThings777]

New sub here ❤, awesome channel to get in touch with DDC

[@MEPAcademy]

Thanks for subscribing, and watching our videos.

[@diaousmane6084]

Thanks

[@MEPAcademy]

You're Welcome. Thanks for watching.

[@stephinjosephkd341]

Lets say we have one AHU, in that total 5 VAV is there for 5zones.. vav will operate based upon the temprature demand, VFD will operate based on the static pressure in the main supply header. Then what about the PIBCV valve in chw pipe. Ahu main return air duct temprature would be the average of these 5 zones.. Then how the pibcv get operates if we take feed back from return air duct.

[@MEPAcademy]

Please watch our video on Energy Valves to see if that answers your question. kzbin.info/www/bejne/jqu0YaianrGam8U

[@yaozhao7813]

If 30% open is the minimum to achieve ventilation, would 100% open be too much fresh air/outdoor air for the zone? And more energy waste on preheating and precooling?

[@MEPAcademy]

When the temperature outside is within a certain range, the use of the compressor can be reduced or eliminated. This will save on energy. Check out our two other videos that will give you a better understanding on how using outside air can be beneficial. DOAS units: kzbin.info/www/bejne/joqyh4aMi9SBaJY and Air Side Economizers: kzbin.info/www/bejne/aIamnoGpbdZ6eM0

[@hatemhik3003]

thank you

[@MEPAcademy]

You're Welcome

[@joeschneider67]

That air handler is connected to a chiller?

[@MEPAcademy]

Yes, it's very common in commercial projects that the cooling is provided by a chiller serving a chilled water coil in the air handler.

[@yassinsafieh4481]

Thank You very much

[@MEPAcademy]

You're welcome!

[@khaledel-sayed521]

Das ist sehr gut und einfach

[@MEPAcademy]

Thanks

[@pain4743]

I have a question, what is the software used to draw this schematic diagram ?

[@MEPAcademy]

Depending on what you're planning on using the diagram for, you can use anything from PowerPoint for a simple diagram all the way to a more sophisticated CAD program. What will you use the diagram for?

[@caffeinatedinsanity2324]

Funny enough, i see often times vav damper boxes being put on a system fed by a rooftop unit. We had to add a switchover for that haha.

[@MEPAcademy]

Yeah they use a VVT system on package units to try and replicate a VAV system, but they're not energy efficient. See our other video on VVT Bypass Dampers if you haven't already. kzbin.info/www/bejne/jn-1kHmljbV2b9U

[@yousefaboshadyzero]

What is the mean of DDC ?

[@MEPAcademy]

Direct Digital Control

[@manojkumarkarunkottath9838]

❤❤❤

[@MEPAcademy]

Thanks for watching.

[@myyoutubestorykitchenchoic1422]

👌👌

[@MEPAcademy]

OK, Thanks

[@what-qs6xp]

Can you explain CO2 control to me?

[@MEPAcademy]

Per ASHRAE 62.1 certain high density spaces like meeting rooms require CO2 monitoring to ensure that there is enough ventilation air when the space fills up with people, and not too much OSA when there are only a few people. See our video on "Demand Controlled Ventilation" for a visual representation of how this works with CO2 sensors.

[@efraingonzalez5523]

👍

[@MEPAcademy]

Thank you

[@johanjoy3883]

👍👍

[@MEPAcademy]

Thanks

[@alexanderruiz6479]

random but this guy sounds just like George Clooney

[@MEPAcademy]

:)

[@KirkMcLaney]

Having a single VAV box provide air into numerous zones is not a good design. If the heat load goes up in the room that the space sensor is located it will make the other zones too cold.

[@MEPAcademy]

It's much too expensive for every room to have its own VAV box. Engineering best practice is to group rooms with similar thermal profiles, such as multiple exterior office spaces that have a southern exposure. You should of course avoid mixing interior and exterior spaces on the same zone. Rooms that are periodically occupied, such as conference rooms and such should be have their own zone. There is definitely no practical reason not to group rooms together that have the same load profile as this is the most feasible and energy efficient.

[@KirkMcLaney]

@@MEPAcademy I can't tell you how many times it's caused problems. Several rooms, same size, one temp sensor in one office. Have a meeting in that office greater heat load and freeze the other offices. Bad design.