Restaurant/Kitchen Exhaust
Restaurant/Kitchen Exhaust
(OP)
I'm reviewing a set of drawings for a restaurant. I have little experience in this area. The plan calls for an exhaust hood in the kitchen with makeup air unit. The problem is that only 60% of the exhaust air is being made up. I spoke to the hood manufacturer and was told that due to turbulance, etc. no more air can be made up through the hood. This job is in Chicago, and the local code I believe calls for 400 cfm per linear foot of hood. So my exhaust is 8,400 CFM and only 5040 in being made up.
I assume my only option at this point is to bring in the air through my main AHU and transfer it into the kitchen so that it can be exhausted. The drawings don't show this and in fact show another exhaust fan as part of the AHU return.
Flow arrows actually show air being transfered out of the kitchen into the main return/exhaust fan of the AHU. I'm raising the red flag on this, but i just wanted to see if I'm missing something here. All of the kitchen hood exhaust needs to be made up, correct? Is is OK to transfer air from the dining area to the kitchen? If so, what's the best way - transfer grilles in the wall?
I assume my only option at this point is to bring in the air through my main AHU and transfer it into the kitchen so that it can be exhausted. The drawings don't show this and in fact show another exhaust fan as part of the AHU return.
Flow arrows actually show air being transfered out of the kitchen into the main return/exhaust fan of the AHU. I'm raising the red flag on this, but i just wanted to see if I'm missing something here. All of the kitchen hood exhaust needs to be made up, correct? Is is OK to transfer air from the dining area to the kitchen? If so, what's the best way - transfer grilles in the wall?





RE: Restaurant/Kitchen Exhaust
You do want the kitchen to be a slight negative so perhaps you can bring in a fair amount of the outstanding make up air through the kitchen hvac.
You can also bring in even more air from the dining room hvac. Now be careful when you look at how air transfers from the kitchen and dining room. You do not want a jet of air, coming into the kitchen through a pass through opening, that lines up with that hood. You do not want the momentum of that air going under the hood its going to push the fumes out from under the hood.
Maybe a ceiling transfer system with a jumper duct. You do not want the transfer duct terminating near the hood with air directed at the hood.
Same thing with kitchen AC, you do not want diffusers throwing air at the hood. The cold air falls down the hood and can entrain fumes to spill
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Restaurant/Kitchen Exhaust
RE: Restaurant/Kitchen Exhaust
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Restaurant/Kitchen Exhaust
These methods may also be combined, such as a face and down discharge arrangement."
This is from a ventilation guide we use here in Southern California, A little dated, (2000), but very informative.
http://www
RE: Restaurant/Kitchen Exhaust
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Restaurant/Kitchen Exhaust
We used a transfer fan and ducted it to take air from the dining area to the kitchen. In the kitchen we distributed it not to disturb the airflow near the hood.
Also with the same company I have seen a large transfer grille between dining area and kitchen, so this is other possibility. Here I would be aware of noise from kitchen into restaurant.
As already said you need to keep the kitchen area under negative pressure.
The main flows of air are a short circuit air flow in the hood itself, meaning it comes from the directly into the hood. ( see page 3 and 4 of my attachment) and a flow from the dining area or in your case the restaurant. On the right side of page 4 there is a phone number where you can get a full copy of the HVCA DW/171 . And if you can put the copy here as well.
RE: Restaurant/Kitchen Exhaust
KX Exhaust Fan:100%
Make-up Air: 80% of hood requirement (between 250-400 CFM/feet, refer to ASHRAE 2007-Applications for kitchen equipment)
Air flow from Dining:10%
A/C supply air:10%
If you have ventilation requirements for commercial kitchen
(2-3 CFM/sqft in some states) you may add them as a part of the make up air or not (it depends of what type of hood you're using. Greenheck has very good guidelines for this.
RE: Restaurant/Kitchen Exhaust