help with restaurant ac system design

[friocold2008]

Dear fellows:

Most of the time I do refrigeration work, but a friend of mine is about to open a small restaurant and asked me for advice in regards to the ac system. I hope someone can help me out with this since I´m pretty much lost in this field.

There is going to be a double swing door in the wall that separates the kitchen from the dining area. There is an exhaust hood in the kitchen just above the grill and stove. There are also a few self-contained refrigeration units as well as a large ice machine, therefore I believe that additional ventilation is needed to handle these heat output.
From a previous restaurant experience, my friend believes that the only way to stop kitchen odors from entering the dining area is by allowing the kitchen exhaust to suction out some air from the dining space through the swing door. Nevertheless, I believe that if this suction action is not controlled, we might have problems with the air conditioning system performance since we are stealing away cooled air from it.
How can these two opposing actions can be put to work together?

[glenn1340]

Hi friocold,
I`m doing some restaurant work myself at the moment (and ongoing project that`s being done gradually over a few months). Ideally any air removed from the kitchen should be replaced by 80% of filtered air, this will prevent odours from seeping into the dining area but still allow gas appliances to operate correctly. As I said, that`s an ideal but it gives you something to go by,
Regards,
Glenn

[Peter_1]

Dear fellows:
...
From a previous restaurant experience, my friend believes that the only way to stop kitchen odors from entering the dining area is by allowing the kitchen exhaust to suction out some air from the dining space through the swing door. Nevertheless, I believe that if this suction action is not controlled, we might have problems with the air conditioning system performance since we are stealing away cooled air from it.
How can these two opposing actions can be put to work together?

You're both right: your friend is completely right because you must have supply to prevent odors and you're also right that you will 'steal away' the cold.

You can steal that much that the restaurant will never cool down.

There's only one good solution for this: supply fresh air from outside in the same amount as you extract. Or make a hole somewhere in the kitchen wall with a grill to the outside.

When I open the door of a restaurant, I immediately feel when opening the front door if there's supply in the kitchen.

I should take in account all the self contained machines as a heat load but not extract them to the outside.You ten again steal cold from the restaurant. Best solution of course is putting the condensers outside

[multisync]

Don't forget to factor in the kitchen extract in the equation.(if the 20% rule is right -it seems a bit high to me?)

ie
kitchen extract 100m3 hr
kitchen supply 80 m3 hr (100% fresh air)

This will give the correct air flow from the restaurant to the kitchen and up/out the extract.

The restaurant side ac will need to be big enough to supply it's load + the 20 m3hr fresh air to compensate the loss.

All fast food restaurants operate this way

[dougheret0]

Dear fellows:

Most of the time I do refrigeration work, but a friend of mine is about to open a small restaurant and asked me for advice in regards to the ac system. I hope someone can help me out with this since I´m pretty much lost in this field.

There is going to be a double swing door in the wall that separates the kitchen from the dining area. There is an exhaust hood in the kitchen just above the grill and stove. There are also a few self-contained refrigeration units as well as a large ice machine, therefore I believe that additional ventilation is needed to handle these heat output.
From a previous restaurant experience, my friend believes that the only way to stop kitchen odors from entering the dining area is by allowing the kitchen exhaust to suction out some air from the dining space through the swing door. Nevertheless, I believe that if this suction action is not controlled, we might have problems with the air conditioning system performance since we are stealing away cooled air from it.
How can these two opposing actions can be put to work together?

This topic is covered in chapter 4 of my book HVAC Design Manual – A Mechanical Designer’s Guide to Design of Small Commercial and Institutional HVAC Systems available for free download on my web site www.nettally.com/doughert. You can download the book, and print out chapter 4. You may want to print the entire book, which is written with competent contractors in mind.

Briefly, it is necessary to bring outdoor air into the dining area in exces of all of the building exhaust, including the kitchen hood. If the kitchen is air conditioned, the system must be separate from the dining area, with no outdoor air introduced. Thus, the dining area will be at higher pressure than outside, protecting against infiltration, and also higher than the kitchen, allowing excess air to freely move from the dining area to the kitchen and be exhausted by the hood, scullery, and other fans.

[Gary]

This topic is covered in chapter 4 of my book HVAC Design Manual – A Mechanical Designer’s Guide to Design of Small Commercial and Institutional HVAC Systems available for free download on my web site www.nettally.com/doughert. You can download the book, and print out chapter 4. You may want to print the entire book, which is written with competent contractors in mind.

Briefly, it is necessary to bring outdoor air into the dining area in exces of all of the building exhaust, including the kitchen hood. If the kitchen is air conditioned, the system must be separate from the dining area, with no outdoor air introduced. Thus, the dining area will be at higher pressure than outside, protecting against infiltration, and also higher than the kitchen, allowing excess air to freely move from the dining area to the kitchen and be exhausted by the hood, scullery, and other fans.

Ahhhh... A fellow author and fellow Floridian as well. Welcome to the R-E Forums.

[lowcool]

for air replacement in the kitchen i would recommend evaporative coolling and full height doors

[friocold2008]

Thank you very much for all of your kind and very clear comments!!
I´ve been reading and re-reading them and I think I am getting the whole idea.
By the way, the book download recommended by dougheretO is great and easy to follow, even for a person like me with limited knowledge on central air conditioning design.
One more question: down here in the tropics, fresh air is heavily loaded with both heat and humidity (now I understand why ac techs try to keep it at the minimum allowed). It´s my understanding that standard commercial ac units have a limited capacity for handling humidity loads. Would it be necessary to cool/deshumidify the fresh air before it gets into the ac system in order not to impose a additional load on the equipment, posibly leading to overall poor performance?
Best regards

[dougheret0]

Thank you very much for all of your kind and very clear comments!!
I´ve been reading and re-reading them and I think I am getting the whole idea.
By the way, the book download recommended by dougheretO is great and easy to follow, even for a person like me with limited knowledge on central air conditioning design.
One more question: down here in the tropics, fresh air is heavily loaded with both heat and humidity (now I understand why ac techs try to keep it at the minimum allowed). It´s my understanding that standard commercial ac units have a limited capacity for handling humidity loads. Would it be necessary to cool/deshumidify the fresh air before it gets into the ac system in order not to impose a additional load on the equipment, posibly leading to overall poor performance?
Best regards

Thanks for the kind words about my book. This topic is also discussed, but I understand that it gets more technical. In general, even in Panama, if your outdoor air is less than 20% of the supply air, you should not have to worry about pre-treatment. However, for restauraunts, outdoor air induced through the air conditioner is often much more than this. It must be at least 20% larger than the total exhaust from the building. The options are: dedicated outdoor air unit by Dectron, Addison, or Desert Aire (among others); Hot gas reheat available in most packaged units; wrap-around heat pipe - only effective near design, when the unit is operating.

I strongly recommend you contact your York, Carrier, or Trane representative for help - they have access to factory engineers and can analyze your particular problem. All have special units now designed to handle high outdoor air or low sensible heat ratio, and will work within your friend's budget and requirements. Nothing is worse than a restaurant that doesn't work!