Pre-Filter for HEPA on DIY air filitration [Archive] - Sawmill Creek Woodworking Community

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Scott A Evans

11-17-2015, 9:06 AM

HEPA'S Lasting about 4 hours of vector/ rastering 1/8" baltic birch plywood. Looking for input on what level of filter is good as pre-filter for HEPA. I have tried the following combinations in order on negative pressure system. HEPA last before jet dust collector.

QTY4 1" merv6 blue/white filter mat, QTY 4 Poly- Sorb carbon filter media, 4" of activated carbon granular, (QTY-2)Rigid VF6000 HEPA Filter. (1 or 2 of HEPA/ blast gates lowering/raising flow as needed) 1.5hp JET DC1100VX-CK dust collector (canister wrapped with carbon filter media)

Also tried this combination:

QTY2 1" merv6 blue/white fiber filter mat, QTY 4 carbon filter media, QTY2 MERV 8 pleated filter 4" of activated carbon granular, (QTY-2)Rigid VF6000 HEPA Filter. (1 or 2 of HEPA/ blast gates lowering/raising flow as needed) 1.5hp JET DC1100VX-CK dust collector (canister wrapped with carbon filter media)

I have plenty of flow until the HEPA's clog at about 4 hours of use, I use blast gates to slow down the airflow when all filters are new and open up as they start to clog up, have slight to mild wood burning smell, we don't see any visible smoke, not loosing air in system.

The HEPA filters are not able to be blown out for reuse, They particles on any of the filter media dont want to come off so I am assuming smoke or resin? I need to find a solution or combination of filters that will give longer use of the air filtration system as the cost of replacing HEPA's is crazy. (been thru 6 in last 4 days) The filter box has strong burnt odor so I might need to go up on the activated carbon.

Any suggestions on improving the setup would be greatly appreciated. Have searched and read Dan's DIY blog but not found info on a good prefilter setup. GLAD we didn't go with the ATMOS dou at this point as those filter costs would be killing me.

Sorry about pic...on IPAD and I can't get it to load in the correct orientation.
Thanks
Scott

Glen Monaghan

11-17-2015, 12:52 PM

I have a 4" thick Diamond Accumulair for the prefilter, then 8" of activated charcoal, and a 4" thick HEPA (all are rectangular, 16"x19"). My current HEPA has been in use for 2 months, which has included well over 20 hours of cutting acrylic and probably something like 12 hours of cutting 1/8" BB. I haven't kept track but might have changed the prefilter twice in that time.

Scott A Evans

11-17-2015, 4:11 PM

Glen, thanks for the response I will rework it tonight and see if I can better our results.

Raphael Weil

11-17-2015, 6:08 PM

Kind of similar to my plan. I was going to go:

-crappy washable prefilter
-2" thick Merc 10 as a prefilter (with room to slide in a second if that doesn't cut it)
-6" activated charcoal
-Merv 15 filter doubling as a HEPA

Glen what kind of charcoal have you found to be the best for this? I'm seeing at least 6 kinds including the pricy coconut stuff (which I'll surely avoid).

Scott A Evans

11-17-2015, 8:49 PM

Glen Monaghan

11-18-2015, 12:26 AM

I dunno what is the best type, but I've been using GC4X8S. Bought a 25Kg bag which has lasted me about 18 months, need to buy more for next change...

Raphael Weil

11-18-2015, 4:52 PM

Take 2 underway. Rework most of the filter box with filters locally available today) Now....1" merv8, 2" merv 11, 2" merv 13, 8" Techsorb TS-201 AC, 2 Rigid VF6000 HEPA then dust collector.

seal/gasketed every crack and crevis...though I dont think that was issue...

I'd be curious to hear from some others if this is overkill or not? By the time you've got those 2 MERV 13's in there, what does the Hepa filter even do? In theory Merv 13-15 is going to get the same particle size right?

Also thanks Glen, that does look like a good price point for the carbon based on the one you quoted.

Scott A Evans

11-18-2015, 10:18 PM

I'd be curious to hear from some others if this is overkill or not? By the time you've got those 2 MERV 13's in there, what does the Hepa filter even do? In theory Merv 13-15 is going to get the same particle size right?

Also thanks Glen, that does look like a good price point for the carbon based on the one you quoted.

sorry my post confused ya...it is QTY (1 )2" merv 11 and merv 13...not 2 each. I believe that merv 13-16 will get approx 75% of .3 micron particles while a HEPA/(Merv 17-20) will capture 99.97% of the same .3 micron paticles.

My HEPA's dont pull through each other.