Airflow checking

[redif]

Hi,

We are designing a fan and duct system. The rooms should always be ventilated. As per our client's requirement, if there is a reduction in airflow ( due to any fault), it has to be signalled at remote controlled station. There are two ways to send signal to remote station.

1. By providng pressure switch in the duct, so that if there is reduction in airflow, PS will sence the reduction in static pressure and give signal to remote station.

2. By sensing the motor amperage. if there is big fluctuation in amperage it will be signalled to remote station.

Can anybody tell the better system out of two.

Thanks

 

[vzeos]

I don't know if they're any better than what you’re proposing but I have seen sail switches activate equipment in response to airflow from a fan. See attached info.

http://www.electronicaircleaners.com/database/documents/honeywell_s688_product_data.pdf

 

[lilliput1]

I recommend using (2) fans with one as backup. Each fan should have a differential pressure switch, automatic intake damper and automatic discharge damper. The DPS should be between the fan inlet & outlet. I prefer DPS versus current sensors because it will sense belt failure. Some CT can sense belt failure but it must be provided at each phase if motor is 3 phase.