100% fresh air system various exhaust methods 4

[Manu68]

Hi Experts,

In a 100% fresh air airconditioning requirement for a building. The AHU is supplying treated FA thru ducts to various rooms.
Is it mandatory to have ducts for exhausting the air from these rooms. If the leakage is the only method of exhaust it will keep on increasing the room static head as fresh air supply is continuously. the rooms are not in the periphery of the building.
Which methods would be suitable to maintain room static heads as needed, but accept only supply of the treated fresh air.

Thanks in advance.

Regards,
Manu

 

[MintJulep]

If the leakage is the only method of exhaust it will keep on increasing the room static head as fresh air supply is continuously.

No, that's not how the physics work.

 

[Manu68]

To MintJulep,

If there is no exhaust duct provided, then for a small leakage that manifests through door gaps and windows gap, the room will stablize at high static head.

 

[MintJulep]

Yes.

 

[SAK9]

You can install these pressure stabilizing dampers(

http://apreco.com/pressure-stabilisers/)on

the wall to maintain the required room pressure if the exhaust is harmless.Still you need to make provisions for the air to leave the building depending on how high the air quantity is.

 

[willard3]

This is referred to in thermo as the conservation of mass.

 

[Waramanga]

Yes you will need to provide a path for the air to get out of the room and outside. If the resitance path is too great then you will end up with doors that don't open, front doors howling etc. Maybe you should look at heat recovery and a return air fan? usually pays for itself up front.....

 

[Waramanga]

Missed that you were after fixed pressures. What is the application?

 

[Manu68]

Thanks, Warmanga. The building is a office cum DC building in Middle east. I was also about to have a Heat recovery wheel at the terrace of this single floor building. The energy recovery can exchange cooling with exhaust and do a make up. However the system as per DBR is to be 100% fresh air into the office space and a outlet of fresh air into the mechanical room where CRAH units are located adjacent to the white space DC. The AHU is positioned in the ground floor of the building, just only a heat recovery alone on the terrace that exchange cooling and arrive into the AHU in ground floor.

 

[EnergyProfessional]

if your application requires "exhaust", then you can't pressurize the room because then that air also will diffuse into adjacent rooms and doesn't "exhaust" out of the building. Per code, exhaust is defined as not to be recirculated.

The room you exhaust out of, will be negative to the adjacent rooms. For example, you have fans suck air out of a bathroom. that bathroom draws air from the adjacent rooms. You can imagine if you don't exhaust from the bathroom, that air will "spill"into the adjacent rooms and that will stink, literally.

 

[Manu68]

Thanks, the specific case was about the complete building that have AHU delivering treated fresh air into all buildings. The building is to be maintained at 8Pa static head generally. The leaks on the building periphery could carry some leaks. however to establish the static head of 8Pa wanted to have a exhaust duct that pick up hot return out of the building.