Sequential start-up of parallel variable-frequency exhaust fans
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The problem is as follows: Due to the very large variations in air volume, it is not easy to choose a variable-frequency fan. Therefore, it was decided to use two variable-frequency exhaust fans in parallel: at low load levels, Fan A is used to stabilize the pressure upstream, and when the upstream load exceeds Fan A’s capacity, Fan B is activated. I understand that when mechanical devices are operated in parallel, it is ideal for them to have identical performance, but since these fans are variable-frequency, their performance levels may differ, making the operation quite complex. When starting fan B, the negative pressure at the inlet of fan A is high, and I feel that fan B might run idle. Is it possible to gradually reduce the speed of fan A after starting fan B, so that the operating frequencies of fans A and B are the same? It seems very difficult to achieve. I would appreciate some advice from everyone, thank you
It is best to start both fans simultaneously, check the relationship between speed and outlet air pressure, and then set the speeds of the two fans to different frequencies while maintaining the same outlet air pressure. This will likely require a PLC to use a relatively complex algorithm; with that approach, there should be no major problems.