Differential Pressure switch (For auto cleaning in 2.5"H2O) in Raining Weather After start to cleaning don't stop.

can we calibrated cleaning setting point at 3" H2O? Number of filter cartridge is 48(6*8)

 

When did this problem start?

How long has it been since the filters were changed?

Does the inlet filter house have a "rain hood" which tries to prevent rain from impinging on the filters and causing the filter media to become wet and swell and increase the differential pressure across the media?

Have you installed pre-filter "socks" on the filter media?

In general, it should not be necessary to increase the switch setting, however, sometimes site conditions require it. This may, or may not be one of those times.

If the filters are dirty and the combination of dirt and moisture is causing the dp to increase, then that's a problem. Pulsing the self-cleaning system when the filters are dirty and wet doesn't usually work very well. Pulsing usually works best when the filters are dry.

Rain hoods are one method for trying to limit the amount of moisture that can get to the filter elements. But, a lot of sites didn't purchase them originally, and a lot of sites didn't orient the unit to try to limit the entry of rain into the inlet filter.

Pre-filter socks can extend the service life of the main filters, but they can also cause high dp's when not changed regularly, and when the dirt on the socks gets wet, it can also increase the dp. Also, the self-cleaning mechanism doesn't work very well on the dirt captured on pre-filter socks.

Have you considered manually pulsing the self-cleaning system when the filters are dry to try to remove the most dirt? Also, many sites have installed air compressors which can be used when the turbine is not running to provide air to the self-cleaning mechanism. This doesn't work as well as when the unit is running (because the high reverse flows don't occur) but the shock of the pulse can remove some dirt, presuming its a dry contaminant and not combined with an oily residue.

Site conditions and the types of filters, inlet filter house configuration, and the type of contaminant as well as the amount of rain and humidity can all have an impact on how the turbine and auxiliaries are operated. I'm not a fan of increasing the setpoint temporarily because the it's inconvenient to change the filters at this time. Just shut off the self-cleaning control, and don't forget to turn it back on and pulse the system when it's dry again.

 

We are a GE 7FA site with a Donaldson Inlet Filter. The set points are 3.0" to start cleaning and 2.5" to stop. however, we never even reach that so in auto the puffers would never fire. so we decided to put it on timer so that it would at a minimum pulse once a day. You should check the specs of your system.