If your restaurant is negatively pressurized (hard to open the front door), too hot or cold, or you are experienced extremely high utility bills, there is a large possibility that the air flows are not balanced. Our team of certified balancers are extremely well versed in identifying and solving these balance related problems in restaurants. Please call us today if you are interested in speaking with a member of our team regarding this type of service: 1-800-524-7352.
Kitchen Air Inc offers Certified Airflow Test and Balancing both locally and nationally for restaurant chains. We work closely with restaurant owners to ensure that the airflows for not only the hood system, but also the entire restaurants HVAC system are within design and functioning properly. We can offer timely certified reports for new construction if required by the inspector, or can also conduct retro-type balancing on existing restaurants for troubleshooting purposes.
For those that don’t know exactly what Testing and Balancing means, it is officially referred in the industry as “Testing, Adjusting and Balancing”, or “TAB” for short. It means performing air and hydronic measurements on the HVAC systems and adjusting flows as needed to achieve optimum performance of the building environmental equipment. It is a form of checks and balances system performed by a certified 3rd party company. There are currently 4 main national certifying agency’s out there that all provide quality training and specific protocol for performing TAB work. These include NEBB, NBC, AABC and TABB. In addition to performing the required protocol specified by the certifying agencies, many TAB firms go above and beyond especially when hired directly for the owner. Checking that the exhaust fan has been mechanically installed correctly with a hinge kit and grease box, that smoke capture is adequate at the hood, and the make-up air unit is heating properly are a few examples that go a long way in preventing problems down the road. Before the restaurant opens is the time to fix it! Get everything right from the beginning. Not when the restaurant is open, making it difficult to perform the repairs, and when the mechanical contractor has already been paid and is long gone.
Testing and balancing has long since had a bad connotation associated with it. You often hear murmurs of reports being “pencil whipped”, with numbers that are “too good”, exactly at design, or simply made up. It is a shame that this has come to be, because like it or not, having a properly performed Test and Balance is extremely important in ensuring that HVAC systems function as designed. If you’re going to spend all that money on complex engineering, fancy equipment, and installation of that equipment, not performing a test and balance to ensure all your airflows are within design is foolish. It would be like ice skating on frozen lake and assuming that the ice is thick enough to not fall through.
If you’re truly serious about the success and longevity of your restaurant, it’s not worth taking the risk of not ensuring your system is performing efficiently. A great deal of the effects of an inefficient, poorly balanced system can go visually unnoticed, but they are always felt. Whether it is your wallet from high utility costs, uncomfortable conditions for the customers or cooking staff, or simply customers not being able to open your front door due to negative building pressure, the summation of these negative effects can make the difference between a successful restaurant and one that fails.
A certified Test and Balance report is the first thing that a design engineer will request to see at the completion of job, or when there are comfort and performance issues reported on location after opening. Verifying that all airflow is within the specified percentage of design is also the first step in troubleshooting.
In our eyes, we don’t care what agency TAB firm is certified by, we have seen both good and bad across all agencies. To us, a good TAB firm is knowledgeable, performs their job with integrity and repeatability, and most importantly works with the trades onsite to resolve issues when found onsite. There are always things that are wrong and incomplete. The important thing is that it gets fixed.
Being certified is a good start, but being “certified” TAB firm means nothing without having properly trained technicians in the field that have integrity and commitment to performing their task well. Your test and balancing technician should be certified yes, however, what you want is a contractor who is educated on how to measure airflows correctly for hood systems. We have seen a multitude of certified firms over the years make fundamental mistakes when it comes to the measuring of airflow for kitchen ventilation systems. Whether it is applying the wrong K-factor in calculating the airflow, removing filters from the hood while measuring airflow, or obtaining inaccurate filter velocities due to using the wrong size standoff on the velgrid/matrix. More alarming is when you review a report with recorded airflows out of diffusers that are fed from an HVAC unit that does not have any power to it. TAB work is expensive, and for good reason. If you are going to pay the money to have it done, make sure the firm you select is reputable.
Test and Balance Example: Restaurant
One difference between us and our competition is that we look at the big picture. The example given below represents a typical Air Balance Summary for a standard restaurant. Keep in mind that there will be variations in quantity and size of the types of units involved in the design, however, the following 3 basic principles will remain constant in every properly designed restaurant:
- The kitchen exhaust airflow rate is always dictated by the type of cooking and appliances it is being utilized for. This should be kept to the minimal required amount without sacrificing on hood system performance regarding smoke and heat capture.
- The kitchen is always negatively pressurized relative to the dining room or adjacent spaces to confine cooking odors to the kitchen area only.
- The total building pressure is most always neutral to slightly positive relative to the outside atmosphere. We want the customers to be able to open the front door and we want to ensure all air entering the space is being treated to sustain comfort levels. (Note: There can be slight variations in design where the building pressure is negative but it is rare. Sometimes strip shopping centers require this, etc).
Air Balance Schedule:
Every restaurant, whether it is a takeover, new construction, professionally designed by an engineer or self-designed by a builder/owner should have a specific air balance schedule associated with it. All airflows need to make sense on paper before they can be set properly in the field to achieve a fully functional system. Not only is it important to review that the airflows are correct from a balance standpoint, it is critical to verify that all HVAC equipment (Newly designed or existing) can treat the amount of outside air dedicated to each unit.
How to read an Air Balance Schedule:
In the table above, each piece of HVAC (Heating, Ventilation, and AC) equipment that is serving the restaurant is listed in the far left column. Any airflow value listed in black does not affect building space pressure. Any Airflow value in red is air that is entering the space through its given unit, and any airflow value listed in blue is leaving the space and being discharged into the atmosphere. The difference between the total positive airflow being introduced into the space (red), and the total negative airflow being discharged out of the space (blue) is the Total Design Building Pressure (represented in CFM, +200 in this case).
All of the airflow values and pieces of equipment displayed in this Air Balance table have been included in the illustration below to help serve as a visual aid:
How it is Supposed to work:
- On the exhaust side, air (3000 CFM) is leaving the space by means of the Kitchen Exhaust F (EF-1), and the Restroom exhaust Fan (EF-2), (200 CFM). All smoke and heat generated by the cooking process and unwanted restroom odors are exiting the space properly.
- 80% (2400 CFM) of the kitchen exhaust airflow is brought into the space through the dedicated Make-up Air Unit (MAU-1) and distributed at the perforated supply plenum mounted across the front fact of the hood. The majority of this airflow is pulled into the canopy of the hood and has little interference with the air being treated in the kitchen by RTU-1.
- The remaining 20% (600 CFM) of the exhaust airflow not accounted for by the dedicated Make-up Air Unit is provided for from the fresh air intakes (aka economizers) on both RTU-1 and RTU-2. This remaining 20% of the total Make-up air for the hood is referred to as “transfer air” and is designed to come from across the room at a low velocity. It is important to not bring in 100% of the total makeup air for the kitchen exhaust in the form of dedicated make-up air directly at the hood. “Localized negativity” in and around the immediate area of the hood is required for proper smoke and heat capture and containment.
- The remaining outside air being pulled in at the RTU 1 and 2 not being used for the kitchen ventilation system is used to make up for the restroom exhaust and act as a buffer to ensure that the space is positively pressurized (+200 CFM).
- When the individual airflows are added up for the kitchen and the dining room areas, the kitchen relative to the dining room is -300 CFM negative. (Note: This is not air that is leaving the building, it is relative to two rooms in the building. The actual kitchen is positive to the outside atmosphere.)
Final Airflow Summary including Measured Airflows (Well Balanced System):
When all equipment is installed correctly and everything is balanced out, below is a summary of the final result including actual measured airflows. You will notice that all airflows are within the minimum tolerance of +/- 10% of design. The resulting building pressure is +77 CFM, which is acceptable. The result is a properly functioning, balanced restaurant that is comfortable to both work at as an employee and eat at as a customer. A healthy operating restaurant that is balanced will have the following characteristics:
- Kitchen ventilation system works well with no smoke or heat escaping into the kitchen/dining areas.
- The front door is easy to open for customers entering or leaving the restaurant
- There are no drafts at the front door causing comfort issues in dining room area
- The utility bill for the restaurant is at a manageable level because all of the HVAC isn’t being sucked out of the dining room by the hood.
- Humidity levels are being kept under control in the space because all of the air being brought into the building is being treated properly.
- Less turnover among employees working in the kitchen due to a comfortable working environment.
- High customer retention rate based on providing a comfortable environment to dine in.
Examples of System Deficiencies:
If a Test and Balance is never completed, maintenance is not performed, or there is a mechanical breakdown of equipment, the entire building’s balance can be compromised resulting in a multitude of comfort issues, unseen increases in utility costs, and efficiency loss.
The following are the three primary scenarios of what can occur when the airflows in a restaurant are not within design:
- Negative Building Pressure: Degradation of supply or increase of exhaust.
We have all been to a restaurant that is suffering from the effects of being under pressurized. It is usually immediately noticeable when you can barely open the door to enter the establishment. There are many reasons that can cause a restaurant to be negatively pressurized, but the most common reason is dirty filters on the make-up air unit and fresh air intakes of the RTU’s of the HVAC system. Below is a representation of how the numbers would come out in our example under these conditions:
With less supply air being provided to the space from the dedicated Make-up air unit and the RTU’s, the balance of the exhaust air will infiltrate the space from the path of least resistance (-1028 cfm). This is a large amount of air that is completely untreated and will result in the following:
- Drafts in the dining room area causing discomfort for customers
- Increased costs in utility bills for overloaded HVAC system
- Humidity infiltration into restaurant
- Disruption with performance of gravity vent flue with water heater
- Decreased performance of hood system
- Stagnant conditions in kitchen and dining room
This example shows the importance of sustaining positive building pressure with good design practices and proper filter and belt maintenance.
- Over Positive Building Pressure: Degradation of exhaust or increase of supply.
This is the opposite of what was shown in example A. Instead of the doors being hard to open, you will find that they will have a hard time closing on their own. Over pressurization of a restaurant can be the result of many factors, but it is most commonly the result of belt slippage on the kitchen exhaust fan or improper balancing at the time of startup. Below represents what the numbers would look like in our example under a scenario of over pressurization:
In this example, the fresh air intake may not have ever been set properly on the RTU’s, the Make-up air may have been sized wrong and never reduced at startup, and the belt may be starting to slip on the kitchen exhaust fan. All of these have combined to make the pressure in the restaurant positive by +1273 CFM and can result in the following:
- Increased utility bills
- Decreased smoke and heat capture at kitchen exhaust hood
- Stagnant/uncomfortable conditions in kitchen and dining room
- Outside doors that will not closed on their own
- Interference with any open flame cooking operations due to higher make-up air being distributed at the hood
This example illustrates the importance of having a Test and Balance completed at the time of startup and performing proper belt maintenance on system.
- Neutral Building Pressure: Slow degradation on both the exhaust and supply side.
This is often the scenario that gets most overlooked in the industry. In this example, no maintenance has been performed on any of the equipment, thus airflow on both the exhaust and supply side has degraded. This usually happens over a long period of time making it less noticeable. To make it even more difficult to detect, the overall building pressure can actually be within the acceptable range and “balanced” (easy to open the front door), even when airflows on both the exhaust and supply side are under design.
This example proves that it cannot be assumed that everything is in good working order based on monitoring building pressure alone. Even with the building pressure being right at design (+217 CFM), the following can result under this scenario:
- Poor Kitchen Ventilation System performance regarding smoke and heat capture
- Stagnant/unhealthy working environment in kitchen
- Uncomfortable conditions for customers in dining room area
- Unpleasant odors in restrooms/dining room
- Increased costs in utilities
- Damage to key components in mechanical equipment
This in addition to the other 2 examples, shows the importance of achieving proper design airflow at the time of startup and sustaining that proper airflow throughout the lifetime of the restaurant.
It is much cheaper to invest in having a proper Test and Balance completed and routinely maintain your equipment compared to operating a restaurant that has an inefficient system with high kitchen staff turnover, less repeat customers, and increased utility bills. Kitchen Air Inc offers both full certified Test and Balancing services for new locations, in addition to retro and troubleshooting balancing on existing restaurants.