Results 1 to 12 of 12
  1. #1
    Join Date
    Mar 2017
    Posts
    22
    Post Likes

    KITCHEN EXHAUST AND COOLING ISSUE

    Hey,

    I have a common problem in all the residential building. When I am designing the kitchen exhaust system, as per the ASHRAE standard 100 cfm is extracting from there. For maintaining negative pressure inside the kitchen supply air is providing the 80% of the exhaust ( likely 80 cfm ). Now the exhaust system is working properly. But the problem arising for the cooling. Tenants complaining that in the kitchen there is no enough cooling. As per the HAP calculation the air flow required is 300 cfm.

    In these kind of situation how the air will be balanced properly without affecting the cooling.

  2. #2
    Join Date
    Jan 2010
    Location
    Sea to Sky
    Posts
    3,388
    Post Likes
    Are you also conditioning the MUA????

    Sent from my SM-G965W using Tapatalk

  3. #3
    Join Date
    Mar 2017
    Posts
    22
    Post Likes
    Thread Starter
    Make up air is considering..but it is giving to appartment area commonly...not supplying individually to kitchen.


    Sent from my iPhone using Tapatalk

  4. #4
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    24,708
    Post Likes
    You need to condition the make up air.

    If it 0° outside and you dump 80 CFM's of 0° air in there its going to be cold!

    Same with 85° humid air.

  5. #5
    Join Date
    Jan 2010
    Posts
    17,472
    Post Likes
    Quote Originally Posted by pecmsg View Post
    You need to condition the make up air.

    If it 0° outside and you dump 80 CFM's of 0° air in there its going to be cold!

    Same with 85° humid air.
    What he said

  6. #6
    Join Date
    Feb 2016
    Location
    Louisburg Kansas
    Posts
    3,509
    Post Likes
    Do you have return air grilles in the kitchen?
    No man can be both ignorant and free.
    Thomas Jefferson

  7. #7
    Join Date
    Mar 2017
    Posts
    22
    Post Likes
    Thread Starter
    Quote Originally Posted by WAYNE3298 View Post
    Do you have return air grilles in the kitchen?
    Return air grill is not there.. FCU fixed inside the kitchen.if i give return grill the smell will mix in supply air.


    Sent from my iPhone using Tapatalk

  8. #8
    Join Date
    Mar 2017
    Posts
    22
    Post Likes
    Thread Starter
    Quote Originally Posted by pecmsg View Post
    You need to condition the make up air.

    If it 0° outside and you dump 80 CFM's of 0° air in there its going to be cold!

    Same with 85° humid air.
    Make up air is already conditioned. Actualy the required supply air cfm inside the kitchen is 300 cfm.. if I am not reducing the cfm below the exhaust cfm, there will be +ve pressure.. if I am reducing the cfm there will be no cooling.


    Sent from my iPhone using Tapatalk

  9. #9
    Join Date
    Feb 2016
    Location
    Louisburg Kansas
    Posts
    3,509
    Post Likes
    The reason I ask about return air in the kitchen is supply air that is recirculated doesn't contribute to space pressure. A properly located return air grille will allow you to increase supply airflow to the kitchen without the migration of odors. If the kitchen is open to the adjoining space (no door) you can increase supply airflow without making the kitchen positive. The key is to keep the kitchen negative with respect to the rest of the space. The make-up air for the exhaust hood according to your description has to come from the adjoining space but the amount of air drawn in by the exhaust is not sufficient to cool the kitchen. Ideally the make-up air to each apartment should be sufficient to satisfy code but the space should remain negative with respect to the corridor. The apartment should be positive with respect to the out doors with the hall more positive.
    No man can be both ignorant and free.
    Thomas Jefferson

  10. #10
    Join Date
    Mar 2017
    Posts
    22
    Post Likes
    Thread Starter
    Quote Originally Posted by WAYNE3298 View Post
    The reason I ask about return air in the kitchen is supply air that is recirculated doesn't contribute to space pressure. A properly located return air grille will allow you to increase supply airflow to the kitchen without the migration of odors. If the kitchen is open to the adjoining space (no door) you can increase supply airflow without making the kitchen positive. The key is to keep the kitchen negative with respect to the rest of the space. The make-up air for the exhaust hood according to your description has to come from the adjoining space but the amount of air drawn in by the exhaust is not sufficient to cool the kitchen. Ideally the make-up air to each apartment should be sufficient to satisfy code but the space should remain negative with respect to the corridor. The apartment should be positive with respect to the out doors with the hall more positive.
    Hey ,

    Thanks for your comment. From your post I understood that the recirculating air will not affect the space pressure .So I can increase the supply cfm as per the heat load ?? If the kitchen is closed also the return air grill fixed inside the kitchen will not spread the odor or smoke in to the space ( properly located also )


    Sent from my iPhone using Tapatalk

  11. #11
    Join Date
    Feb 2016
    Location
    Louisburg Kansas
    Posts
    3,509
    Post Likes
    You are correct. Remember pressurizing a space is like blowing up a balloon. If more air goes in than is allowed to go out you have positive pressure. Recirculated air does not contribute to pressurization but does determine air changes in that space. If you put a fan in a room that is not connected to a duct it doesn't matter how much air it is moving the room pressure doesn't change. That is the principal you are dealing with.
    No man can be both ignorant and free.
    Thomas Jefferson

  12. Likes shinozahmed liked this post
  13. #12
    Join Date
    Jul 2018
    Location
    NW Louisiana aka Hell Pit of Louisiana
    Posts
    170
    Post Likes
    I have to ask, is this a commercial or a standard kitchen exhaust vent or OTR(Over The Range) microwave setup?

    If it is an OTR or standard kitchen exhaust vent, there is a damper that needs to be put in each one, depending on the setup and they usually come with the equipment, in the box when purchased

    If this is on an apartment with multiple floors and a continuous running exhaust fan or fans on the building, I would imagine, this would pull the already conditioned air from the space with the vent continuously. I have seen and worked on several older buildings with this setup and the kitchens stay hot, as well as the bathrooms due to this and the fact that, the damper systems have failed, it should have a damper on it that can be opened and closed when needed and setup according to local code, otherwise, it will remove the conditioned air in that space and it will remain hot or cold.

  14. Likes shinozahmed liked this post

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •