IPAK dirty filter diff. switch question

[tim fox]

I have a fairly new (aprx. 1 yr old)rtu with a dirty filter alarm. Even with new filters the alarm remains. I read in the IOM that the alarm is triggered at .5 in.w.c. diff. The unit has both 2 " disposable and bag filters so I'd imagine the press drop is high in the best case.I think someone has played with the switch.The alarm will go away if I place the down stream tube out of the door and blow into it so I believe the switch is only in need of adjusting.I am familiar with adjusting other types of static press. or flow proving switches and usually it's some variation of turning the adj. screw one direction until the unit alarms or shuts down and then back off a pre determined number of turns.Can someone tell me the recommended proceedure for adjusting this switch.Also airflow is o.k. per manometer readings and refrig. pressures.

[enart9591]

First check your DP to make sure that it has the range you need. I would expect your DP across filters and bags to be around 1" which means you have to set the switch for around 1.5".

To accurately set the DP up: Tee the high side of a magnehelic to the high side of the DP. Use a pneumatic pump up bulb to apply pressure to the DP/magnehelic. Disconnect the wires to the DP and attach your ohm meter to the terminals and calibrate to where you want it to be.

Caution: Remember, the DP is designed for " of water. You can destroy the DP switch by applying to much pressure.

[tim fox]

Thanks enart.