Variable Air Volume - VAV system HVAC

[@EngineeringMindset]

⚠️ *Found this video super useful?* Buy Paul a coffee to say thanks: ☕ PayPal: www.paypal.me/TheEngineerinMindset

[@ISLAHIQALB]

The Engineering Mindset awesome quite good lvvvvllyyyy

[@docbrown7916]

We had to install some VAV boxes w their own EAC (Electronic Air Cleaner) in each due to the designated rooms having commercial computer systems, each box had it's own filter just before the EAC, the puter rooms had their own HVAC systems that were specified for more than the usual room specs since puters like cold air, twice to 3 times the usual for the room size but that's just bigger units, 'been there & done that' on other jobs. Although I'm familiar w this stuff it's fun to watch and I can share the vid sites to help non HVAC ppl understand the basic physics of it all and that's really what it comes down to but so many ppl don't grasp physics or weren't taught it. Gotta question the education system. Anyway great vid and great ch, keep up the good work.

[@nathandaubis819]

solid video, worth every bit of $5/month.

[@IceyJunior]

Wow excellent Paul

[@mahaalhashemy8816]

Good job dude

[@alexanderrose46]

this was very helpful

[@mdshoukath1647]

you are doing very good work.... thanks

[@archiepalabrica6028]

Thank you for the video its so very nice

[@geesolar1282]

good idea

[@benedictlualhati3458]

so great !!

[@olalekansalami5773]

nice video, thanks... perhaps, I missed the part that explains replenishment of fresh air in the system, ... or is not accounted for in the explanation? ...

[@EngineeringMindset]

Hello 0:54 explains the supply and return duct. Fresh air is in the supply duct, used air in the return duct. Then in the AHU the dampers can divert some of the used air back into the supply, if it is clean enough.

[@perrysoe368]

Flow rate is used to control which variable, more than room temperature is controlled by modulating the damper.

[@nageshtiwari4488]

Can you please make a video on calculating the fan efficiency. .

[@nishapatil8190]

does VAV system give control over air exchange rate of every room? like can his allow one single ahu to supply at different air exchange rates for different rooms?

[@sp1arcondicionado164]

hello friend, this video is very interesting, I ask for your permission to translate it into Portuguese and be able to show my colleagues at HVAC here in Brazil, a hug

[@EngineeringMindset]

Glad you enjoyed but we do not grant permission. We have started translating our videos into Portuguese on a separate channel kzbin.info/www/bejne/bXunnql6r8dogpo

[@sp1arcondicionado164]

@@EngineeringMindset thank you for the information, I will then follow the videos in Portuguese and share with friends here in Brazil

[@yesiruz8193]

What is a common voltage used on a fan assisted vav?

[@cjmt6369]

what the diffrent beetween fancoil and ahu? because is ahu we cool or heat the aire and again in fan coil we do that again. whay?

[@benjaminjoseph4403]

What happens if you don't have a VFD on the fan motor? The pressure in the duct builds until what happens? Does the fan just stop pushing air? Or what will go wrong?

[@EngineeringMindset]

It's not a VAV system if the speed of the fan can't vary. If it stuck at full power and the dampers closed then it will likely burst the ductwork or the pressure would be too high for the damper to resist, that would force them open. There should be a high static pressure alarm on the BMS which would cut the power to the fan before this happens though.

[@EngineeringMindset]

VFD Video is now live! here: kzbin.info/www/bejne/r3azlmqIedmendE

[@arwaabougharib8698]

Does a VAV system substitute FCUs for VAV boxes? so must it be one or the other?

[@EngineeringMindset]

You need to have a controllable damper to regulate the flow rate of air for it to be a vav system.

[@abhimat]

Are the supply duct and the return duct connected? If not, where does the supply duct end?

[@EngineeringMindset]

See the graphic here: kzbin.info/www/bejne/fnPQgKybjNmjfskm30s

[@charlessadaka]

Hello why do you say that the main AHU cooling coil will use less cooling thanks to the pressure sensor ?

[@EngineeringMindset]

the pressure sensor tells the fan to slow down. less air flow = less cooling load

[@charlessadaka]

The Engineering Mindset thanks for the answer But how does the chilled water flow knows that there is less air to cool? How does the flow rate of water is reduced ?

[@EngineeringMindset]

Temperature sensor and control valve. When the air flow rate reduces the same amount of chilled water is entering the coil, the air temperature drops too low, the controller senses this and begins to close the valve to slow the flow chilled water until the air temperature is corrected and back at the desired setpoint

[@nischalmohan2656]

Why would we need a re-heater is we are sending cold air into the rooms?

[@EngineeringMindset]

Because the room is too cold so it is re-heated to reach the desired temperature

[@rediaz08]

Please make a video about choosing the right HVAC system by building type. Thanks

[@EngineeringMindset]

Learn *HOW CAV SYSTEMS* work here: kzbin.info/www/bejne/jpi0ZKlsoduikLM

[@osamamashal2602]

Thank you very much Well explained Can you make a video of the control method of VAV? Also there is another type called bypass, you didn't mention in video.

[@hendrashwan6272]

Bypass VAV means when you have a main VAV installed on the main branch from the AHU and you are connecting another VAV to that same VAV branch . It's not always recommended unless proper calculation of the CFM made

[@mikemc8495]

wow i am so thankful you made this video now i have a better understanding on how it all works together . i am about to graduate my HVAC/R this year . I,m really into this stuff

[@sagarpatankar6347]

Respected sir, Your channel is very useful, Kindly add video on duct design,static pressure, cfm calculation

[@mohamedabduljaleel6238]

Just i want to thank u very much for ur efforts...i am really enjoying ur explanation to the systems.. thank u very much Again...please keep going

[@Jay-uh1dx]

Quite explaining yet simple 👌👍🏻, best video on VAV .

[@adityadhakate6987]

hey man, Please give me the link of basic MATLAB Simulink.. I want to learn and see the output of the simulation.

[@sharukhnizamikhan7559]

Thanks ,very good, Could u please detail the pressure independent VAV box , and how VFD will get feedback signal in this method

[@toyinorodare4072]

kudos for your clear explanation. Also, can you do a video or training on HVAC and ducts design I will so much appreciate if I can get this

[@tomaswagner3666]

13°C seems like extremelly cold for office (where ambient temperature should be at least 19°C) 🤔

[@rabidlenny7221]

Why does a VAV box need to calculate the air flowing through it? Why could it not just be a motorized damper, with a PID controller, that is responding to the room thermostat temperature. If its to cold, it closes more towards its minimum position, if at minimum position, the heater turns on. If its too hot, it opens more and more, until room is at set point. Again, with a PID controller, as to not overshoot, but also not take too long to get to design.

[@Earth098]

As the supply volume flow rate varies, how does it make sure each zone recives minimum required fresh air volume flow rate? Thanks for the video!!

[@mollydong3405]

It should be adjusted by co2 level

[@zahernasserkarahasan1003]

why it is named "re-heater" instead of "heater" ? like 13 C is a cooled temperature , right ?

[@esttaifananeer4209]

So do you have to put a damper in the return duct in each space??? Otherwise the ahu would suck back more air while the space is satisfied

[@farhanquadri1235]

Thanks for all the information u r providing here, it's very helpful for me, I would like to have some more videos on different types of central ac like package ac, split ac, and also cassette ac, thanks and I hope u will consider my request

[@shahbaz2425]

Some time bms system give command to decrease temperature but vav dampers not work how can we solve this problem.

[@adrianfarhan2659]

As always amazing explanation ..

[@mohdzeeshan7489]

Tomorrow will be my hvac foremen interview for kuwait please suggest me what can i do

[@EngineeringMindset]

Just take your time to answer, think logically.

[@mostafa9750]

Is this damber work manually with thermostat or automatic with sensor

[@Concepttalks98]

Can i place return and supply linear slot diffusers in single line...i mean on a single wall ..

[@chrism7275]

On some of the bigger buildings I find they use vav for cooling the interior space and FPT for the exterior with either electric reheat or hot water actuators

[@haririalaa6487]

Best educational video I've seen , clear and to the point. Thank you..!

[@saifizmigna5029]

Thank you for the video it is really helpful. may i ask when would we require a VAV installed on the return as well as many designers are asking for it, it is really required? if yes in which applications it should be use?

[@EngineeringMindset]

It's useful to regulate the pressure in the building

[@SurojitMahato1992]

VRF Units video not available, link is there but not opening, pls check

[@EngineeringMindset]

New VRF unit video here:➡️ kzbin.info/www/bejne/apqUiZqZhZano9k

[@zuberhussain7582]

Thank you for sharing this!! One video on BTU meter please?

[@natemarszalek8615]

Great Explanation. Thank You!!

[@garyarthurs]

Another superb video. Can you explain the basic relationship between FCUs and VAVs, i.e. is the HVAC system typically either one or the other, or are there installations where they can both be used in the same HVAC system?

[@cinnamonpd1116]

usually, the FCU temperature can be controlled individually, so there is no need for a VAV, remember you only need a VAV when you are trying to control airflow. There definitely are installations where both are installed together. For some instances, simply put, one VAV could responsible for 5 to 7 diffusers. So, in this instance, it is important to have the VAV installed along the FCU.

[@benkisha]

sounds like typical engineer theory. vav systems are as varied as the buildings they are installed in. they can be simple cool only boxes using static pressure to open or close or more complex reheat boxes using hot water coils and freq drive blowers in the roof top unit. I'm not trying to knock anyone but theory is so hard to apply in the real world.

[@EngineeringMindset]

You're right, we must simplify to build our understanding and then grow from there

[@makhanirofhiwa3921]

Thank you so much!..Very helpful

[@pupsiklove2024]

Amazing way of explanation, thank you

[@ramyasreeg1245]

amazing website.. but some electrical details also ..like how to create panel and how to edit panel schedule..

[@astasna]

Excellent 3D model again. Not too complicated, with a lot of detail.

[@roninbjj498]

Thank you for the videos . Really appreciate it

[@eddiy841]

Wow this is extremely helpful, very well appreciated!

[@manojnaik4645]

please make video on Integration of AHU , Thermostat , VFD and VAV and Chiller inlet and out pipe line to AHU

[@EngineeringMindset]

VFD Video is now live! here: kzbin.info/www/bejne/r3azlmqIedmendE

[@alseekski9056]

Excellent video. In 20-25 years do you have to replace the whole box or is it most common to replace parts? Is 20-25 years the average life span of a VAV box?

[@EngineeringMindset]

Most of the parts inside will have been replaced by 25 years. The building will probably have been refitted with new equipment anyway. It doesn't have to be replaced, this is just the anticipated life expectancy.

[@asifiqbal8279]

please add video of calculating the cooling load capacity ..

[@zingozach969]

i always appreciate your videos thanks a lot for taking your time to do this

[@babaksp4235]

Fantastic, well done Very clear, useful video. Thanks alot

[@tahkorvipul612]

Ples modular chiller explanation sir

[@veroniquepelletier3177]

This is really clear !! Thank you. I would like to know how does it work if you install an electric coil with a 24v relay that also controls the electric baseboards heaters that will be installed in each room if heating should be interlocked with the air conditioning.

[@ammarkh4441]

It's been very useful sir, thank you. Where do we put the thermostat? are there any recommendations?

[@EngineeringMindset]

Check with the manufacturer. They will tell you the idea place. But basically not above a radiator, behind furniture etc.

[@بوفارسبونورا-ص7ه]

well done .👏 about powered fan VAV terninal box , what is the diffrence between parrallel and serial ?

[@EngineeringMindset]

Parallel fan-powered terminals have fans that only switch on during the heating mode to pull warm return air from the ceiling plenum. Series fan-powered terminals have fans that must run throughout the occupied mode in order to deliver ventilation air to the zone

[@mohammedowais4793]

thank you sir.....one video is missing sir chiller expansion device.....pls upload

[@ISLAHIQALB]

Awesome quite fabulous it’s great quite

[@Ag89q43G0HyA]

that looks very inneficient.

[@DirektorMira]

Thank you for the video! Do we have to install VAV dampers on exhaust air duct?

[@rodneyhickman825]

No

[@rediaz08]

Great, thorough explanation

[@tomekc1113]

those mouse clicks are so loud, gamer?

[@imranhaider9300]

I hope you are fine and doing well sir please clear me one thing if the VAVS is on auto mode heater and damper is on auto m ode set point is 28 and heater is ON desired and actual Air flow is same and damper position is accurate according to desired flow but Air supply temperature is not increasing upto 30 And space temperature is 23 .I try to increase upto 25 but supply and space temperature is not increasing.why? Please clear me in detail.

[@EngineeringMindset]

something isn't right here. likely either the air flow rate is too high or the heater is broken or blocked. Maybe the room is unable to hold the heat and air

[@koushikkillada]

how can we decide the size of VAV box

[@fluterampal]

If all vav are closed, will there be an over pressure in the system? Will the main air handling unit slow down automatically?

[@桐谷和人-n1k]

Thank you! very useful!!!

[@lancedenney2408]

Great Video, recently saw a 3rd floor building with return vents open to the area above the Drop ceiling. No return air ducting was visible. I assumed that the air was being sucked back thru the drop ceiling, it was about 4K sf. Is that legit, seems to be a really BAD idea since we're in the SF Bay Delta with tons of molding/rotting materials and dead grass and tree leaves on the ground everywhere, meaning pollen and mold/mildew spores whenever the wind blows. Between foot traffic of 3-600 people, and deliveries of boxes of equipment and paper... people are coughing and sneezing on that floor, even tho all the ceiling tiles have been replaced... I found about 8-8 return air Vent Tiles, but ZERO dedicated ducting. Thanks again!

[@umeshkale858]

Very good explanation..

[@ZohaibKhan-mo2ht]

Great Video, Sir. ❣

[@PBS-nm1uu]

just found this video great demo, thanks

[@farhanquadri1235]

And also some videos on DX systems, district cooling as well

[@mitaalamgir2588]

This is excellent, very helpful!

[@claytoncarson111]

Great video! Most of the information here is 100% correct, but if I may correct you on a few points: 1. You mentioned ‘dirty air from the rooms can be chucked outside’ but this is not really the purpose of the relief path. The set of dampers after the return fan leading to the outside are typically modulated to maintain building static pressure in relation the outside. Typically the set point is somewhere around “+0.05 in. wc.” This is necessary to keep your building positive so that unwanted air doesn’t infiltrate around doors/windows from the outside. This way the outside air necessary for maintaining indoor air quality can be introduced through the AHU and can be conditioned as desired. Dirty air is simply cleaned by the filters in the AHU and by always introducing some designed amount of fresh air through the outside air path. 2: There are typically two types of fan powered VAVs, either series or parallel. Your schematic shows the fan to not be in series with the airstream so that would be a parallel configuration in which typically the fan is only running when the zone calls for heat. In a series configuration (not pictured) the fan is always running and the primary air from the AHU must pass through the fan. that is closer to how you described it which may be a little misleading. 3: Typically the duct static pressure sensor used to modulate the supply fan is mounted approximately “2/3” of the way down the primary air duct not at the end. Anyways thanks for the video, nice work!

[@rockanrollrudy1803]

Thanks for these uploads

[@pentunit08]

Firstly, great video as it outline the basics really well which allows a young professional to grow by asking question as they relate the animation to what they experience in the field. My question is that I presently have a system with six VAVs installed on each of the main ducts leaving the AHU. Each duct(with its individual VAV) has further branches for individual rooms however it is controlled by a single thermostat sensor. So we receive frequent user complaints as the set point for the single thermostat sensor doesn't reflect the condition for all the room from that main duct. Can you suggest a possible solution for the existing setup?

[@Praveen271]

There is no proper solution for this scenario. Because the unit will deliver cold air until the set temperature is achieved at the thermostat location. Once the set temperature is achieved at the thermostat location, irrespective of the situation on any room, the unit will cut off. The only possible solution I feel right is to balance the airflow in such a way that an ideal temperature is everywhere along with the thermostat location. Do trial and error method.

[@iamjames4]

Hello, have you found a solution to your problem?

[@karenhejazi1245]

Hi Paul, is there any problem controlling humidity in single duct VAV systems?

[@ramamanikantadondapati1043]

Sir please make an video about different cooling systems that are used in deserts or dry air areas

[@EngineeringMindset]

Pretty much just air cooled chillers. Have a look at our other videos

[@kevinpoulet149]

Is the electrical reheater présent most commonly in countries where it gets cold in the winter?

[@EngineeringMindset]

Yes its common where the outside air gets to around 5*c or less

[@kevinpoulet149]

The Engineering Mindset ahh alright thank you

[@lynnattwood9988]

What are the maintenance issues with VAV boxes, what kind of maintenance access is needed to them?

[@klun018]

A clear explanation video!!

[@reanult457]

thx you for the video, but sometime the pressure sensor signal is not fast enough to send back to the VFD to slow down the AHU and it causes vibration issue. How can I speed up the pressure sensor signal to avoid it ?

[@EngineeringMindset]

VFD Video is now live! here: kzbin.info/www/bejne/r3azlmqIedmendE

[@marvinhamdan2407]

Great educational video. it very simply & easy to understand. Thank you for sharing

[@sagittariusmax5419]

is the VFD same as RTD? please explain. thank you

[@EmeraldRubyTea]

Thank you!

[@almontejuan]

Great content

[@rubenescribano4033]

Is it posible to configure a VAV System with a RTU.?

[@toyinorodare4072]

Thanks for the video. can I conclude that VAV is only applicable to spaces with same thermal zone( space with more than one ventilation room) ?

[@l.crossjr]

Great demo and animation

[@thomastrang4815]

Are the AHU and VAVs working together in conjunction based on the BAS sequencing?

[@EngineeringMindset]

The AHU will be run on a schedule, the terminals will operate from a localised thermostat. Fan assistance terminals can also circulate the room air if the AHU is off.

[@NiceMuslimLady]

Is there an advantage to having a return air duct as compared to a supply duct only?