Recently an article was written about kitchen exhaust fan maintenance and I have received comments about some issues with the article. I thought the article was fairy well written and most likely left out some pertinent information for editorial reasons. (so it did not end up being a novel). The author is correct that the fan is the heart and sole of the kitchen exhaust system and the restaurant cannot operate the cooking appliances without the fan functioning correctly. The sections about wiring issues and rattling are on point and been addressed in some of my previous posts. However, I do have some comments that I would like to share. One of the most common fan failures we see out in the field is the vibration isolators. They are 4 round rubber connectors that hold the wheel and motor framing to the fan housing. They dry out, age, and fail over time and need to be replaced. This is an inexpensive item that most fan and HVAC parts warehouses carry. When they do fail, it can cause the fan housing to slip to one side and cause the fan intake Venturi to rub against the fan wheel causing expensive damages and fan failure. Another point is the recommended use of inline fans. The only time they should be used is with a PCU in place as we have found major leakage issues with these style of fans. They are also very difficult to repair and maintain. The 3rd issue is the comment for the use of down blast fans. While it was stated in the article that these fans should not be used for high grease situations, they actually must NEVER be used for any kind of grease exhaust fan. In fact that is spelled out in both the IMC and NFPA96 standards as the discharge for fans must adhere to certain clearance requirements which down blast fans cannot meet. These style of fans have not been allowed for over a decade. Also, the grease containment systems listed are only a fraction of what is out there. There are at least 2 containment systems, one UL listed and one UTL listed that do not contain any absorbent material in them at all. The systems without absorbents also have the extra benefit of containing the wastewater from the cleaning during the cleaning process. Nothing was mentioned about keeping containment systems off the roof so the roof under them can easily be monitors for grease leakage. The major issue found with Utility Set fans in high grease load situations was not mentioned. With the vertically mounted fan blades, they "Sling" the grease into the air and many times all over the roof instead of impacting it on the fan bowl like the up-blast style fans(sometimes called centrifugal fans due to this phenomenon). Horizontally mounted fans that can take higher static pressures similar to the Supreme or the Captive Air HRE and CBRE fans are a good alternative for the Utility Set Fans. There was a comment about grease leakage happening from fan blades are not running properly or the housing not thoroughly cleaned. This is simply not the facts. In fact, almost all style fans will have some grease leakage by design and thus require some sort of grease containment. The grease buildup on the walls of the fan is continuous and when it rains or snows, the grease is partially washed down to the lowest point. It also leaks down with normal buildup. Fans come with collection devices that are most time adequate for low grease situations, but require additional capacity for medium or high grease uses.
Originally published July 5, 2013 on Tales of the Greaser.