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Brian HVAC Guy
Brian HVAC Guy, HVAC Technician
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A question for Brian HVAC Guy only. "What would be a "typical"

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A question for Brian HVAC Guy only.

"What would be a "typical" final pressure drop of a bag filter for a very large HVAC system when that filter should be replaced?"

Could it be expressed as fraction of what it new?

Hello,


I'm Gina, and I’m a moderator for this topic. I sent your requested professional, Brian, a message to follow up with you here, when they are back online.

If I can help further, please let me know. Thank you for your continued patience.


Best,

Gina-Moderator
Customer: replied 3 years ago.

Gina, Thank you and I would like to wait for Brian HVAC to get an answer from him please.

Hi, I'm Brian. I'm here to answer your HVAC question to your complete satisfaction!

Thanks for requesting me! As I recall an 85% efficient (other efficiencies should be pretty close) bag filter bank should have an initial pressure drop across it in the range of .25"-.3" Wg with a final resistance somewhere around .75" Wg. I used a Magnehelic 0-2" gauge to measure the pressure drop as I found an analog gauge more friendly to read than a digital one. Here is a link to the gauge that I used:

http://www.coleparmer.com/Product/Dwyer_Magnehelic_Differential_Pressure_Gauge_2002_0_2_0_WC/WU-68062-08
Brian HVAC Guy, HVAC Technician
Category: HVAC
Satisfied Customers: 846
Experience: I have been an HVAC/R mechanic/technician for 30+ years.
Brian HVAC Guy and 4 other HVAC Specialists are ready to help you
Customer: replied 3 years ago.

GREAT JOB Brian! You have provided me exactly what I needed!! It will be of great help to me in a problem that I have been having as a newly-elected member of the Board of a very large housing cooperatoive corporation. And what you have provided supports what I believe will help our chief engineer solve a problem that affects a lot of people.

That's great! Thank you for the kind words! Good luck in your endeavors on the board and if I can help in any way just ask. -Brian
Customer: replied 3 years ago.

Brian, About how much does the pressure gauge you identified cost? An do you do one pressure reading on one side of the filter bag bank and then one on theothersider? Or how is it done?

On that link the guage was like $75 (I think I paid 55 for it about 20 years ago at Grainger) There is also a kit that would help if you want to use it as a portable diagnostic manometer. It comes with a mounting bracket, hoses and case. I will look for that for you and post a link here. The manometer (Magnehelic brand) will have two ports, one labeled hi and one low. If the bag filters are in the return side of the system you would connect a hose to each port and insert the hi pressure hose before the filter and the low pressure hose after the filter. If the filters are in the supply side of the system you would reverse them. You would need to drill a 5/16"-3/8" hole (or so) in the sheet metal filter box or duct before and after the filters to be able to insert the hoses about a 1/2" into the holes. You do not need any sort of static pressure pickups, just insert the hoses into the duct to measure the static pressure.
Here is a link to the portability kit for the Dwyer guage I posted a link to above:

http://www.coleparmer.com/Product/Portability_Kit_for_Magnehelic_Gauges/WU-68462-77
Brian HVAC Guy, HVAC Technician
Category: HVAC
Satisfied Customers: 846
Experience: I have been an HVAC/R mechanic/technician for 30+ years.
Brian HVAC Guy and 4 other HVAC Specialists are ready to help you

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