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Commercial Kitchen Exhaust Introduction
It is important to design commercial kitchens for foodservice operations that are attractive, functional, labor efficient, and cost effective. It is important to lean on industry experts who have extensive experience working with end users, contractors, engineers, and architects when considering all aspects of kitchen design.
Schebler Chimney Systems can aid in one niche area of the wider scope of kitchen design, and that area is commercial kitchen exhaust systems. This introduction to kitchen exhaust will discuss your options when considering kitchen exhaust, along with the benefits of prefabricated systems.
Grease Exhaust Duct & Kitchen Hoods
There are two types of kitchen hoods (Type I & II) and Schebler assists as a valued partner in both. Type I hoods relate to the duct construction, installation, and maintenance to remove grease laden vapors created by the cooking process. Type II hoods are to exhaust non-grease effluent such as steam, moisture, or warm air. Exhaust duct construction and installation requirements are much less stringent.
Main Considerations when Designing Commercial Kitchens
The main concern when designing and installing kitchen components and products is SAFETY. Commercial kitchens can be one of the main locations in a commercial space for the development of a fire, and it is important to put measures in place to eliminate that risk. The second main concern is to provide operational systems in a cost-effective manner, that will meet the safety requirements of the building. It is important to refer to the proper sources when designing systems, not only to guarantee that they are code compliant, but to also guarantee worst case scenarios can be handled. Below are the codes, standards, and references to consider for commercial kitchen exhaust:
- Codes/Standards Referenced
- International Mechanical Code (IMC)
- National Fire Protection Association (NFPA) 96
- Uniform Mechanical Code (UMC)
- ASHRAE Handbooks
- UL 1978 / UL 2221 (ULC-S662, ULC-S144)
- ASTM E-2336
- ASTM E-814 (UL 1479)
Selection of Type I Grease Exhaust Systems
There are primarily two different ways grease exhaust systems are constructed: field fabricated or factory built. Over the history of building design, you will primarily see field fabricated systems provided that require on-site welding. These systems are rectangular in shape and wrapped with insulation in the field.
Recently, there has been a dynamic change toward prefabricated, UL listed and labeled products. Factory fabricated systems have many benefits relating to both safety and operation and are viewed as superior systems compared to field-welded systems.
Benefits of Prefabricated Systems
Safety
Our prefabricated systems are tested and designed based on industry requirements. Schebler takes UL testing seriously and leans on that testing to guarantee our systems will operate properly.
UL – 1978 Standard for Grease Ducts covers factory-built grease duct assemblies, and requires manufacturers have grease duct tested to receive UL listing. The tests are performed to guarantee the safety and reliability of the duct under hazardous conditions: continuous operation at 500°F and intermittent operation at 2,000°F, simulating a grease fire. Examples of the tests that factory-built grease ducts are submitted to are:
- Joint Leakage and Torsion
- Vertical support
- Side impact
- Longitudinal force
- Load test for grease duct elbows
UL - 2221 Classification tests are intended to determine the fire resistance of grease duct enclosure assemblies. These requirements limit the combustibility, the surface flammability, and the smoke generation potential of the coverings used to enclose the grease duct. In addition, these requirements evaluate the effectiveness of the combination of the grease duct and the enclosure as a fire rated enclosure system and through penetration firestop system, as well as the enclosure's effect on the grease duct. This testing process consists of two tests: an internal temperature test and an external temperature test. To test the internal temperature, a total of 32 thermocouples are attached to the duct on the exterior of the duct. If any of the thermocouples exceed 130 degrees, the product fails to meet the standard. To test the external temperature, the entire chimney assembly is hung in a concrete slab and lowered into a large furnace. It is then heated to 2000 °F and held at that temperature for two hours. The assembly is then pulled by a system of pulleys from the furnace. After a 15-minute wait period, it undergoes a hose stream test to simulate a fire department blasting it with water. It needs to be able to structurally handle the dramatic differences in temperature.
Field-fabricated kitchen exhaust ducts are required to meet ASTM E 2336-04 – Standard Test Methods for Fire Resistive Grease Duct Systems which is a materials specification. The individual materials in a field fabricated system are tested, but the assembly is not. Manufacturers bearing the UL 1978 listing have had the assemblies tested assuring a more consistent level of quality.
Installation and Maintenance
Factory-built grease ducts can alleviate time and costs for the installing contractor. Our prefabricated systems are provided to you in modular sections, eliminating the cost of on-site welding. The install team is provided with a clear roadmap (drawing) with each component labeled to eliminate concerns of parts being installed in an inco
rrect location. This pre-engineering guarantees the system includes all the necessary supports to ensure the structural integrity of the system.
One ongoing concern for design teams with prefabricated systems is space. The perception is prefabricated systems do not fit in the spaces of field fabricated. Schebler can meet space requirements with our wide range of products. For tight overhead spaces, our flat oval product, SlimVent®, can meet the same footprint used by rectangular ducts. In addition to that, our UL listed systems require less slope than field-welded systems.
Maintenance and cleaning of prefabricated systems can be both cost-effective and efficient. The round shape aids in less build-up of grease throughout the layout of the system, which also help eliminate the risk of a lasting fire in the duct. The stainless-steel design is also superior to the design of carbon steel most often used for field fabricated duct systems.
Inspection
Prefabricated systems can eliminate multiple inspections because the duct is only inspected one time. With field-welded systems, the duct is first inspected for the construction and a follow-up inspection is required once the system has been wrapped.
Engineering and Design
Schebler takes pride in our ability to partner with our distribution network, and their customers. Our design team has years of design experience specifically related to UL listed exhaust systems. We can provide product selection advice to guarantee the correct system is utilized and walk with you through every step of the design journey. It is our goal to be a consultative manufacturing partner who excels in fully engineered, customizable systems.
Schebler Chimney Systems is ready and able to assist you with the design and purchase of your factory-built commercial kitchen exhaust system. Reach out to us at chimneysales@schebler.com or click the button below to find a distributor!
