Stretch said:
...the Envirosept uses a power supply and media,
Yes. Less than 2 watts at 7 kV...
therefore produces o-zone as well high resistance media.
It does not produce ozone. I'm not sure what you mean by the rest.
The electrostatic filters typically used arrestance test for efficiency, which has a large particle size dust for testing.
Here's a basic comparison. "Electrostatic" below means Honeywell types with fine wires with a high voltage and no charged media:
Typical Ambient Particle
Size distribution (in microns) per m^3 Particle Removal Rates
% by % by Electrostatic ESSA
Size (um.) Count count weight ($800-1200) ($200)
10+ 1,000 .005% 28% xxx x 99% 99+% 5-10 35,000 .175% 52% x x 95% 99+% 1-5 264,000 1.32% 17% x x 85% 99+% ..5-1 1,352,000 6.78% 2% xxx 60% 90+% ..01-.5 18,280,000 91.72% 1% xxx 40% 65%
|||||_ bacteria/viruses/spores
||||_ cooking/tobacco smoke
|||_ household dust
||_ pollen/mold/spores
|_ dander/hair
Average synthetic dust weight arrestance: 79%
Single pass efficiency: 33% @0.3 um, 75% @0.5 um, 95% @1 um, 99% @3 um
Pressure drop: 0.05" @150 lfm, 0.1" @225 lfm, 0.15" @300 lfm, 0.22" @375 lfm
ASHRAE dust holding capacity: 20 gm/ft^2
The media filters typically use dust spot test as opposed to arrestance test used by electrostatic filters.
I think we are comparing apples to apples above.
Electrostatic filters don't work well below about 300 Feet per minute air velocity, because they don't develope a charge below that air speed.
I think those "electrostatic filters" are different animals, with no power supplies. The expensive Honeywell types above work better with lower flow rates and longer residence times.
The combination filters like Envirosept and Dynamic are the worst of both worlfs. They have media which has high resistance to air flow needs and replaced periodically $$$, and they produce ozone.
The Envirosept doesn't. IIRC, the filters cost about $1. I wish they made a washable filter. That would be a better worlf.
...you should get a flow hood and a differential pressure gauge and test the results before you recommend them to anyone.
Again, here's the Envirosept spec:
Pressure drop: 0.05" @150 lfm, 0.1" @225 lfm, 0.15" @300 lfm, 0.22" @375 lfm
It's designed to slip into the same space as a passive filter. How do these pressure drops compare to passive filters and typical duct pressure losses?
As an option, put two filter grilles side by side, due to the fan laws, since the velocity is 1/2, the pressure drop will be only 1/4 (the square of the change). Then the Envirosept becomes a more interesting concept.
From the spec above, the fan laws may fit fans better than filters. For instance, 300 lfm is 2X 150, but dP = 3 vs 4X.
And maybe most blowers can handle higher pressures, or the duct and register losses are a lot larger than filter losses, so the filter loss doesn't matter much. I know Envirosept's father Mike Putro, who is one smart cookie, and honest as well. He's been selling these filters for about 10 years. A larger housing might be difficult to make, as well as unnecessary.
...half of the systems that I measure have air flow of 200 CFM/ ton instead of the 400 CFM/ton they should have. Hence my dislike of high efficiency/high resistance filters that reduce air flow another 10% to 20%.
Which bodily orifice produced your 10-20%?
IMO, most modern ACs cool too much and dehum too little, wasting too much electrical energy in the blower and too much heat energy through the walls. A fountain or mister or perspiring human can help distribute coolth to occupied rooms more dynamically, with less heat gain from the outdoors...
Nick
