Ventilation systems are crucial in most professional kitchens, but they can be a technical minefield for distributors to pick through. Therefore Catering Insight has separated specification consideration into four key areas: fire safety, cleaning, control and energy efficiency, and asked manufacturer experts to give dealers a clear idea of what to look out for.
This touches on subject areas such as ensuring solid fuel-burning cooking appliances remain safe, plus the benefits of both demand-controlled ventilation and UV canopies. Responding manufacturers comprised: Mansfield Pollard, HVAC Kitchen Ventilation, Halton Foodservice, Corsair Engineering and Britannia.
What fire safety factors should dealers consider when specifying kitchen ventilation systems?
Mansfield Pollard, Scott Donoghue, head of projects and kitchen ventilation: The increasing popularity of catering appliances that use solid fuel as a means of cooking requires a level of ventilation above and beyond that of a standard commercial kitchen extract system.
The updated version of the BESA Specification for Kitchen Ventilation Systems – DW172 launched on 25 January 2018. This includes guidance for ventilating solid fuel burning appliances and it is essential that this document is complied with in its entirety.
Creosote is an oily liquid produced by the distillation of wood tar. In the ventilation system, creosote behaves like grease-laden vapours and has a high flammability risk. It is essential that the following criteria are met when ventilating a wood-burning appliance:
• The appliance(s) shall be located beneath a stand-alone, suitably designed and equipped canopy and ventilation system.
• The canopy must incorporate some form of spark arrestor to discourage any burning embers from the appliance being drawn through the canopy and into the ductwork system where they could start a fire.
• All fans must have the motors out of the airstream and impellers must have metal blades.
• The complete extract duct system shall be manufactured from stainless steel, constructed to DW/144 specification.
HVAC Kitchen Ventilation, Ian Levin, general manager: The main fire safety factors for dealers to consider are construction, materials, grease separation, fan configurations, fire rating of ductwork routes and fire suppression.
Obviously, extract systems are the highest risk because of the contaminants they transport but considerations must also encompass return supply-air to the kitchen space as well. Materials and construction of the ventilation system (canopies and ductwork) are critical as poor manufacture techniques can have a detrimental effect upon the system’s ability to contain fire and to be cleaned.
Grease separators (filters) must be properly sized for the canopy’s specified airflow design such that they are operating within the manufacturer’s stated grease efficiency performance band. If this is not achieved, the grease removal efficiency can be seriously affected and large quantities of grease can pass through the filters and become deposited in the down-stream ductwork and plant. They should also be manufactured from the correct materials (stainless steel).
Halton Foodservice, Craig Gould, customer services director: It is of prime importance that any commercial kitchen ventilation system complies with the requirements of the local authority having jurisdiction. The best way to achieve this is to work within the parameters as set down in the updated BESA specification DW/172:2017. This covers all safety features such as canopy sizing, correct extract flow rates, grease filtration, make-up-air requirements, fire suppression, approved materials, installation etc, and is referred to in other guidelines and legislation, including HSE publications.
Corsair Engineering, Arun Sahajpal, MD: Poor ventilation can have massive fire safety repercussions which could be overlooked when specifying commercial kitchens. There are certain fire safety factors that should always be kept in mind whilst in the specification stage and these should never be overlooked. Dealers should always keep in mind that protecting the area should be forefront when considering a ventilation system. For 24/7 fire protection covering the cooking range and canopy, you should be looking at a fire suppression system. Prevention is always better than the cure. Always look for ways to be preventing a hazard from occurring.
This related to features such as baffle filters that sit inside the canopy. These act as the primary fire prevention as they remove a percentage of grease from entering the extraction system. The main cause of fires in commercial kitchens are caused by a large build-up of grease within the ventilation systems.
Britannia Kitchen Ventilation, Tony Bright: Due to the potential for grease laden deposits, high temperatures and often naked flames or sparks, kitchen extract systems are classified as ‘high risk’ ventilation systems.
When designing the ventilation system the component elements such as canopies should be carefully selected to account for the specific catering equipment to be located underneath it and the individual risks attached to those items.
The Fire Reform Act puts the onus on building owners and/or occupiers to ensure that adequate risk assessments have been compiled, assessed and controls implemented to mitigate or reduce the risk of fire.
The high risk nature of the kitchen extract system will undoubtedly require that controls of some description are implemented, including those for ductwork systems, pro-active, targeted ‘point of entry’, and reactive controls.
How easy or difficult are your ventilation systems to clean?
Scott Donoghue: All our systems are designed and installed to comply with the requirements of the BESA publication TR19 – Internal Cleanliness of Ventilation Systems. In line with this document, access doors are positioned on the side of the ductwork every 3metres and before/after any changes in direction, fans, attenuators, or any other items that may cause an obstruction when cleaning.
Coordination between all trades working on a site is essential to ensure that nothing obstructs the access panels in the ductwork once they are installed and also that future access provisions are considered to facilitate cleaning of the ductwork.
Ian Levin: To make them as easy to clean as possible, all of our kitchen ventilation systems are designed to comply with BESA documents DW172, DW144 and TR19. Reading, understanding and designing to these documents will ensure that any system is as easy-to-clean as practically achievable. There is however, a cost to meeting these standards and it is often difficult to compete with some of the less diligent contractors who take short-cuts in routing ductwork via in-accessible locations and fail to put adequate cleaning hatches at usable points along the duct-runs.
Installation of an in-canopy UV filtration phase can seriously reduce cleaning and maintenance costs and protect the ductwork and down-stream plant from excessive grease deposits by destroying grease molecules before they enter the system, providing that in-turn it is properly maintained. Our own Zephyr canopy ranges are available with our purpose designed Spectrum UV systems and we are told regularly, that cleaning is much easier and less frequent where these are fitted.
Craig Gould: The ease, or otherwise, of kitchen ventilation systems to be kept clean is usually determined by the amount of thought and effort that was applied to the design of the initial installation. Given the relatively accessible nature of the ventilation canopies, these are not difficult to monitor and clean regularly.
However, the problems tend to occur once the exhaust air from the cooking process enters the ductwork system. As no primary grease filter is 100% efficient the ductwork will need a sufficient number of removable access panels spaced at regular intervals throughout the length of the extract duct, from source to discharge. This will give a fighting chance for a reputable duct cleaning company to ensure that the ever-present risk of a fire due to grease-lined kitchen extract ducts is kept to a minimum.
Arun Sahajpal: Our systems are easy to clean as operators will have full access to the system once the filters are removed and the lights above the canopy are also easily removable. Grease is collected in specific drawers that provide an operator with an easy option to empty.
Tony Bright: IMC – Britannia products are designed to be easily cleaned, with all canopies, Ultrastream UV canopies, Mistream canopies and ancillary components such as service distribution units, made from 304 grade stainless steel. Modifications made to the revised Britannia range soon to be launched by IMC will further enhance the ease of cleaning with an improved grease collection and drainage system. Baffle filters are designed to be easily removed and will fit in most commercial dishwashers.
What should dealers consider relating to ventilation system operational control?
Scott Donoghue: It is essential that both extract and supply fans are operated by a common on/off switch to ensure the correct air balance is maintained. Where the calculated extract flow rate is above 2.50metre3/s, consideration should be given to incorporating a demand controlled ventilation system (DCKV) for both cost and energy saving purposes.
Ian Levin: Kitchen ventilation systems once commissioned and set-to-work, should not really be adjusted outside of pre-determined parameters. Extract, and supply fans (often several of each) have to work in harmony with each other to maintain a safe level of ventilation and so having the facility which allows kitchen staff to alter controls without adequate training, has the potential to upset the safe performance of the system.
All speed regulators should ideally be housed in a lockable enclosure having a simple on-off control for operatives – possibly with a programmable seven day timer to accommodate automatic operation. This control panel can also consolidate associated controls such as heater-battery interfaces and gas interlocks, making an installation much tidier and neater by minimising surface mounted conduit and trunking.
Craig Gould: Kitchen ventilation systems should be controlled automatically and not be reliant on a member of kitchen staff turning the system on in the morning and off at night. Nowadays, a relatively inexpensive addition to the system is a demand-controlled ventilation facility. This is where the cooking activity is constantly monitored and the speed of the supply and extract fans are controlled accordingly. It is not unusual for these systems to save as much as 50% of the electrical running costs of the fans, thereby realising a payback period of little more than a year.
Tony Bright: The requirement for gas interlock systems which allow the flow of gas to the appliances only when the extract and supply air systems are proved is well documented, however many companies don’t seem to appreciate the recommendations laid out within HSE catering factsheet 26 – Preventing exposure to carbon monoxide from use of solid fuel appliances in commercial kitchens. HSE factsheet 26 suggests inclusion of audible carbon monoxide detection with accompanying evacuation procedures and processes and carbon dioxide detector which is interlinked to the extract system where possible.
How energy efficient are your ventilation systems?
Scott Donoghue: As a business that considers energy efficiency of paramount importance, we are always looking to develop innovative new products for our customers. As standard, all our canopies include low-energy LED downlight fittings and all our fans are supplied with high-efficiency EC motors.
In addition to this, we offer a demand-based control panel for our kitchen ventilation systems called Eco-Sense. This system monitors increases/decreases in cooking activity and modulates the fan speeds accordingly. The heat load demand of the tempered make-up air system is also modulated relative to the airflow rate to provide further savings.
Ian Levin: HVAC systems are designed to be as energy efficient as possible where client budgets allow. Designing with three phase motors on fans is a simple and low cost way of improving electrical efficiency. We can design systems which utilise EC motors powering the fans which are currently the most efficient type. Other fan motors controlled via frequency inverter speed controls are also significantly more efficient because of the way in which the control starts and stops the motor.
Demand-controlled kitchen ventilation is a point of particular interest at the moment and HVAC can fit demand-based control systems where they can be demonstrated to give reasonable payback. All HVAC Zephyr canopies are compartmentalised to allow efficient operation with demand-based control systems in line with current as well as new guidelines yet to be released – without compromising grease removal performance.
Craig Gould: System efficiency starts with the original design. Plan to extract the correct amount of air based on the cooking appliances, not the size of the kitchen. Ensure that the primary grease filters are high efficiency with a low pressure drop. Size the ductwork properly: small ducts = high velocity = higher pressure = more powerful fans = low efficiency with higher running costs. Proactive, rather than reactive, control is considered more responsive to the fluctuating changes in the cooking process. As an example, Halton’s Marvel demand-based system, a series of modulating volume-control dampers ensures that not only separate canopies, but also separate sections within a canopy, can be controlled based entirely on the real action taking place under it.
Arun Sahajpal: Corsair will always size the fans/plant to DW172, resulting in a highly efficient system. For example EC fans and control strategy to suit cooking methods also offer further efficiency. This will all help to drive the running costs down.
Tony Bright: The Cheetah system when incorporated into the IMC – Britannia canopies works by controlling ventilation fan speeds such that extract rates are matched with cooking demands. This works on the principle of the ‘affinity laws for centrifugal loads’, the result of which is that a fan running at 40% of its normal operating speed will only consume 6% of the energy required to run the fan at 100% of its operating capacity.
Controlling the extract and supply fans together ensures that they run at the lowest speed possible and ramp up only when cooking occurs, minimising energy usage whilst maintaining comfortable and safe conditions.