ROOF MOUNTED FANS FAQs
Answers to your most frequently asked questions about Greenheck roof mounted fans.
There are numerous reasons why fans fail to perform as specified. But first it is important to understand what defines acceptable performance. According to AMCA Publication 200, a fan installed in a ventilation system should expect a tolerance of /- 7.5% for flow (cfm). In other words, a fan that produces 1,000 cfm in a lab environment should provide a volume flow rate of 925 to 1,075 cfm when installed in a properly designed ventilation system. Volume flow rates falling below this range are typically the result of variances in system static pressure or mechanical problems with the fan.
Common symptoms include:
- Obstructions in the duct system - closed dampers, closed registers, dirty filters, clogged coils
- Obstructions in the fan inlet - elbows to close to the inlet, walls too close to the inlet
- Duct design - improperly designed turning vanes, leaks in supply or exhaust ducts
- Fan related - impeller running backwards, fan speed too low, impeller dirty or clogged, clearances between inlet cone and wheel cone are incorrect.