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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.

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.

Originally Posted by WAYNE3298

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 )


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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.

Originally Posted by pecmsg

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.


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Originally Posted by WAYNE3298

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.


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Do you have return air grilles in the kitchen?

Originally Posted by pecmsg

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

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 considering..but it is giving to appartment area commonly...not supplying individually to kitchen.


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Are you also conditioning the MUA????

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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.