Code is determined by many things, not the least of which is was the exhaust system inspected at the time of original installation? Wasa the inspection done by someone who knew what to look for and did they actually go on the roof and look at the fan. The date of the original installation will also make a difference. The codes do change from time to time.
1. At one time, down blast fans did meet code, possible the one you have is an old one. The reason we do not use down blast fans now is the air movement puts the grease on the roof. Roofers tell me that the grease will ruin the roof. Of course, the day the exhaust system catches fire, the fire will be impinging directly on the grease covered roof.
2. I have had electricians tell me that the NEC allows wiring to run in the exhaust duct. That may be, but it is a bad idea as the heat, grease and the chemical do degrade the wire covering. What I usually see is that the wire is not protected where it comes throught the sheet metal, and is subject to abrasion when the fan is tipped. Guess who tips the fan? and whose fault it is when the wiring insulation is comprimised.
3. NFPA 96-2001 6.2.3 "Grease filters shall be listed and constructed of steel or listed equivalent material. " NFPA 96-2001 6.1.3 . " Mesh filters shall not be used. " Aluminum filters are sold and used. They are cheaper than steel.
The baffles in the duct are an attempt to keep heat in the builing at night when the place is empty. They plug up with grease, do not open or close and are almost impossible to clean. To clean, hold the louvers open with your foot.If you can, make the baffles disappear. I have been know to take them to my shop and put them in my dumpster. If asked, claim the louvers were broken. Just don't tell them the louvers broke when you put your foot on them while cleaning.
Visit your local fire department and building inspector. Ask what they look for when doing inspections. Then discount 90 % of what they say when they tell you how serious they take inspections and how thay want to know of any violations you see. If they want inspection reports, they will tell you. Serious violations should be noted on your invoices.
A copy of NFPA 96 should be in your possesion and used. Even if NFPA 96 is not part of the code in your area, it is the standard most of us use. The day you get your ass hauled into court, the opposing lawyer will ask why you, as a professional, did not use the NFPA 96 . Get a copy of whatever is used for code in your area.
Continue to ask questions. Some questions will make those of us with more experience laugh. And while we are laughing, we are hoping no one will remember when we did not know the answers. One day you will be on the boards, someone will ask a question and you can share the knowledge you have gained.
Douglas Hicks
General Fire Equipment Co of Eastern Oegon, Inc
