Dedicated Outside Air System DOAS

In this video we’ll learn how a Dedicated Outside Air Systems works, better known as a DOAS unit. We’ll learn the different methods of delivering outside air into spaces, and the various HVAC systems that work with a DOAS unit, like a VRF System, Water-Source Heat Pumps, Fan Coils and Chilled Beams.
Dedicated outside air systems are used to condition all ventilation air brought into the building for the health of the occupants and as mandated by code. The outside air is either served directly to the space or in collaboration with a local HVAC system.
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[@jme_OW]

We never learned about the DOAS in school, so your video was a big help indeed!

[@MEPAcademy]

Glad it was helpful. Thanks for watching.

[@KhalilAhmad74036]

Well explained with great presentation. Thanks!

[@MEPAcademy]

You're Welcome

[@viniciusbraga5846]

Great video ! A lot of nyc projects I have worked on used the last method presented on the video

[@MEPAcademy]

Thanks

[@rider2731]

Very well presented. Thank you for sharing. I have given you a thumbs up and subscribed.

[@MEPAcademy]

Thank You

[@monirupaananya3563]

Wonderful explanation

[@MEPAcademy]

Glad you liked it. Thanks for watching.

[@Puppyforyu]

THANK YOU FOR THIS VIDEO IT HELPS ME UNDERSTAND DOAS WITH VRF UNIT COMBO VERY WELL

[@MEPAcademy]

You're Welcome

[@BasketballAve]

Awesome video

[@MEPAcademy]

Thanks

[@Md.AbuHanifa-yi2he]

WOW, Its very informative

[@MEPAcademy]

Glad you liked it. Thanks for watching.

[@yunjoonjung7594]

Such a great video. Thank you for posting this.

[@MEPAcademy]

Your Welcome

[@gloriosingui1566]

Thank you for the explanation. Few questions I have are in regard to the direct cooling using the DOAS for latent cooling and an indoor AHU for air circulation and sensible load. Since the DOAS will be providing 100% OA and the AHU circulating air: 1. Would this create and over pressurize space? 2. How is the CFM balancing done? 3. Should there be an additional relief fan?

[@MEPAcademy]

Of course whatever air that is brought in using the DOAS will have to have a corresponding exhaust or relief. This all depends on the design criteria for each of the spaces receiving Ventilation air. This is similar to a unit using an economizer. There are several examples in the videos related to economizers and the DOAS unit. Depending on the space requirements you can use the DOAS to pressurize a space or create a negative pressure by exhausting more than is supplied.

[@minjker]

In the VRF system- if the cassette is off/not calling, will the DOAS continue to supply outside air or will it only give air to the room when the thermostat calls?

[@MEPAcademy]

You would need a control damper to shutoff ventilation air to a space if that spaces AC unit was off, and have a VFD on the DOAS unit to slow down the fan when pressure built-up in the ventilation supply duct.

[@shamsheralam8862]

Very useful thanks please make more vedioes.

[@MEPAcademy]

Thank you, we will.

[@stevecoffey4884]

My designer is not using a chiller for a 10000 SF single story bldg? Doas is piped into conditioned space. AC is from a DX.

[@MEPAcademy]

Depending on occupancy schedules and space zoning, there are various system options. Only the engineer who is familiar with the particulars of the project can decide what the best system is for the building and how its planned to be operated.