I am in the process of adding central air to an existing furnace system. The system currently includes a Honeywell electronic air cleaner made in 1976. As part of the addition, I am considering replacing the old Honeywell with an Envirosept Electronic Furnace Filter, which sounds pretty good just from browsing the Net.
My question is, would this new unit be much more effective (or less effective) than the old one? I know the old one is working to some extent, since I can see the dirt come off when it gets cleaned.
Media air filters typically filter the air better than standard fiberglass filters. However they have much more resistance to air flow than standard air filters. Typically, they reduce measured overall air flow by 10% to 20%. If you add an AC coil to your existing furnace, you will be reducing air flow some with it. The electronic air filters usually have low resistance to air flow, I would stick with the existing electronic filter. Electronic filters are usually more effiient than media filters as well.
Typical Ambient Particle Size distribution (in microns) per m^3 Particle Removal Rates % by % by Electrostatic Envirosept 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%
supply and media, therefore produces o-zone as well high resistance media. The electrostatic filters typically used arrestance test for efficiency, which has a large particle size dust for testing.
The media filters typically use dust spot test as opposed to arrestance test used by electrostatic filters. A 95% arrestance rating on an electrostatic filter is about the same as a 15 to 20% atmospheric dust spot test. The tests are completely different, therefore no direct co-relation.
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. Therefore their high resistance to air flow is their own enemy. If you oversize electrostatic filters to reduce resistance to air flow, the velocity drops below the 300 FPM threshold and they loose effectiveness.
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. Nick, you should get a flow hood and a differential pressure gauge and test the results before you recommend them to anyone. The saving grace of the Envirosept is it seems to be a better than average filter, if you have a powerful enough blower to overcome their high resistance to air flow. 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.
Just remember, if you use a high resistance/efficiency filter, your air will be cleaner, but with reduced air flow your AC may not work well and your efficiency will be reduced. (Unless you have a high powered blower or oversized filter.)
Nick, 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% to20%.
It does not produce ozone. I'm not sure what you mean by the rest.
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%
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 Envirosept doesn't. IIRC, the filters cost about $1. I wish they made a washable filter. That would be a better worlf.
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?
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.
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...
For what its worth, after nixing an electronic filter on account of cost, and "sticky" treated filters on account of cost and reduced airflow, my solution is to spray a light coat of cooking oil on the cheapie regular fiberglass filter. My theory is that the oil will retain dust particles better than a plain filter. I get to change the filters more often and thus remove the dust permanent instead of letting it be blown back into the ducts and air. I only did this last month when the weather no longer required the furnace to run. I should know when the weather gets cold again whether there is any problem having cooking oil on the filter for an extended period and whetehr it picks up dust and better.
The fiberglass filters come from the factory with a coating already on the filters. They are called viscous impingement filters. Spraying them with oils not necessary, but will not hurt.
Some clarifications, using industry standard nomenclature, So that we are speaking the same language:
"Here's a basic comparison. "Electrostatic" below means Honeywell types with fine wires with a high voltage and no charged media:"
Nick, The filters that use electricity to charge plates or media are normally called ELECTRONIC AIR FILTERS in the trade. While they don't use much electricity, the power output is usually several thousand to as high as ten thousand volts. It is the high voltage (low current) that produces ozone, due to corona discharge effects. The higher the voltage, the more ozone is produced. Many such filters have ozone reduction options that reduce the output voltage to reduce ozone generation. This also reduces their effectiveness and cleaning power. The ELECTRONIC air cleaners have very low resistance to air flow. If you want a high efficiency air filter, this is the way to go.
ELECTROSTATIC FILTERS are those that use the high velocity of air to put a static charge on plastic media, much like rubbing your shoes on a rug as you walk across a floor. They usually use a couple of different plastics to enhance the effect. ELECTROSTATIC air filters have no power supplies.
The envirosept does not fit neatly into either category, as far as I can see.
Nick, a 20 x 20 fiberglass filter at 800 CFM has a pressure drop of .08"WG. The net opening of that filter is 18" x 18", or 2.25 Sq. Ft..
800 CFM/2.25 Sq. Ft. = 355 linear feet per minute (FPM). Compare this to the Envirosept pressure drop of .22" at 375 FPM. At very close velocities, the Envirosept filter has a pressure drop of just under 3 times that of the fiberglass filter.
The fan laws apply to fans, duct systems and coils. I have also found it to be very close with air filters that I have tested. Nick, I test air flow with a flow hood, a hot wire annemometer and a digital differential pressure gauge. I have been using a flow hood for 17 years. I have been using the other instruments almost as long. I am not pulling these numbers out of any body oriface as you suggest. (Have you been hanging around alt.hvac.group too much?? That kind of language does not belong in an intelligent conversation.)
As to AC systems cooling too much and dehumidifying too little, I agree there. Paying attention to load calculations and proper air flow would help tremendously. Most AC systems dehumidify best at air flows of 350 to 400 Cubic Feet per Minute (CFM) per ton. If systems deliver proper air flow, there would be much less need to oversize them as most contractors do. If the duct systems matched the equipment better, instead of being undersized, there would be more blower capacity for high efficiency filters.
Because so many people now purchase pleated media filters at the home centers, I recommend Variable Speed (VS) blowers when I sell replacement systems. Variable Speed blowers are more efficient than standard blowers. Typically, the SEER goes up at least 1 (12 SEER increases to 13 SEER) when changing from a standard to a VS blower. Also, while most standard blowers will produce rated air flow with a coil installed at .3 to.5 inches water column external static pressure, a VS blower will produce rated air flow at .8 to 1.0 inches water column external static pressure. In addition, the VS blower will speed up as the filter loads up, producing nearly the same air flow at different filter pressure drops. I have measured this in the field, it is not just some marketing balony from manufacturers.
I don't dispute that the Envirosept does a MUCH BETTER job of cleaning the air. My problem with it, and other similiar products is that significantly reduced air flow adversly affects performance of heating and cooling systems already installed and designed to work with standard air filters. That is if any design work was done on them at all.
Just remember that whole house AC systems are a SYSTEM. Anything you do to one part of the system affects the rest of the system.
By the way, I would not recomment using a "mister" or swamp cooler here in South Carolina. Your customer would probably come to blows with you over that. It might work wellin your climate up in Mass though. Remember that this group goes to people all over, what works in your climate may not work in other climates.
My 2 cents worth.... Electronic filters work well if they are properly maintained. Electrostatic filters are not very efficient and cause too much restriction in the airflow and are unsanitary. Fiberglass disposables are worthless
3M Ultra Allergen filters create too much restriction in the airflow and are very expen$ive A good quality pleated filter with a MERV rating of between 8 and 11 will get all the nasty particulates out of the air, and not break the bank. Keep in mind that reguardless of what the label says, (good for up to 3 months), I recommend that they be changed every month. When you write the check for your light bill, use that as a reminder to change the filter....clean filter = better efficiency = lower bills.
Good. The first 3 rules of philosophy are "clarify, clarify, clarify."
I also think "electrostatic precipitator."
Maybe higher. I built one years ago with a 1B3 and a TV flyback transformer.
Except for the price, cleaning task, zappy noises, and ozone... I'm not sure they all produce ozone. The Ionic Breeze doesn't, altho it puts all the dirt on the walls of the room :-) I put one inside a 12" grounded stovepipe with a light bulb below to make some airflow, and it worked as an electrostatic precipitator.
OK.
I wonder how important that is, given some blower overcapacity and the rest of the pressure losses in the duct/register/plenum system. What's a typical total?
Grainger's 5C092 direct drive furnace blower (with a 9.5" 1075 rpm wheel and a 1/4 HP motor) is rated 1529 cfm at 0.3" sp, 1517 at 0.4, 1483 at 0.5,
1416 at 0.6, 1326 at 0.7, 926 at 0.8, and 397 at 0.9. Adding 0.22-0.08 = 0.14" wouldn't make much difference over the low part of that range.
Not the Envirosept, with 3X vs the fan-law 4X pressure drop at 2X flow. We also need to consider the operating point on the blower curve, IMO.
They don't seem unreasonable. If the blower above is working in the middle of its range at 0.6" and 1416 cfm and we add 0.14", the output might drop to 1326-(0.74-0.7)/0.1(1326-926) = 1166 vs 1416 cfm... 18% less.
Seems to me they could dehumidify better and better at lower velocities.
Sounds like a fix for the Perils of Pressure Drop.
I might, in conjuction with a low-flow AC that mainly dehumidifies. You might think of this as an alternative to variable air volume, or "dynamic balancing," with less blower power and duct and house heat losses. Why cool a room if nobody's in it? A little misting can lower the air temp in an occupied room while the rest of the house air is warmer and drier, with less coolth moving out through the walls.
I'm near Phila. We only need home AC for 1-2 weeks per year mostly in our tropical August climate when night temps and RHs stay over 70 F and 70%. Even then, ceiling fans are a good alternative.
The opposite of heat. It's equally ambiguous, since it can mean a flow (heat power in Btu/h) or a quantity of energy (stored heat in Btu). Coolth flows from cooler to warmer objects. Google shows lots of use.
If it's 90 F outdoors with w = 0.012 and 80 F with w = 0.012 indoors and we move 400x60xrho = 2400Rho pounds per hour of air into a room with 0.24 Btu/lb of specific heat and 2400Rhox0.24(80-T) = 12K Btu/h and Rho = 39.38/(460+T) lb/ft^3, T = 53.9 F, with HVAC business as usual.
If we move C cfm of 40 F saturated air with ws = 0.005216 into a room and mist a pound to wr = 0.012, that makes 1000(wr-ws) = 6.78 Btu of coolth. Raising a pound makes 0.24(80-40) = 9.6 Btu. The total is 16.38, and 40 F air weighs 0.07876 lb/ft^3, so 60Cx0.07876x16.38 = 12K Btu/h makes C = 155 vs 400 cfm, with smaller ducts or (400/155)^3 = 17 times less blower power, and...
Please put spaces around your =, +, /, * (operators) Your posts are hard to read and you need to define your terms. Example: I use grains, you use decimal fractions, eg 0.012 vs 84 grains. It would be easier to understand you if you use standard terms and defined what is not standard. For the sake of other people, please define everything.
My concern is when I change the regular furnace filter the dust on it is dry, loose and easily blown back into the ducts. But if there is an oil stain anywhere in the house the dust particles get stuck on the oil stain. Hopefully the dust particles will stick better to an oil coated furnace filter.
An idea that just came to mind is to have a small heated oil reservoir infront of the filter element. The concept is everytime the furnace fires up the heater element will be switched on to vaporize a little oil and deposit a fresh sticky coat. The vapor will be deposited onto the filter by the air drawn into the furnace.
Cooking oil deposits inside the ducting is likely a health and maintenance concern. But what about aromatic oils meant for household use, as in those wall plug-in gizmos? In fact it is easy enough to install several of these vaporizers in the cold air return plenum and tie that to the furnace ON circuit. The vapor may do a double duty of helping to attract dust onto the filter element first before doing its original purpose to make the rooms smell nice.
.22" is a very significant load on a blower in a residential furnace.
You have internal losses of the fan cabinet (air entering the fan),plus a non ducted loss probably 1.25 times the velocity head of the discharge from the fan for a blow through application, the pressure loss of pushing air through a heat exchanger, perhaps 0.25 or more inches through a wet coil and then leaving something some pressure for the ductwork.
The blower on a furnace probably will handle 0.5" of external static. If this filter system is 0.22 inches when clean, it will soon clog up and the pressure drop will increase. Would need an oversized blower to run this filter with central AC on a furnace, filter would eat up pressure normally reserved for the cooling coil,.
It can be argued that reduced airflow gives more dehumidification, but also be aware that in heating reduced airflow results in cycling on high limit and premature failure of heat exchangers.
May work problem free in a climate where required cooling CFM was lower than required heating CFM, say a 75MBH 90% furnace with a 50F ATR and
1.5 to 2 tons of cooling.
I am surprised at your intrest in this POS system when you could just patent "Nick's Idiotic Breeze".
Put an old 14" monitor inside a 20x20 box add a throw away filter and a grainger fan and you will catch more dust than an ionic breeze. Throw in some swedish microfibre cleaning cloths and an access door and you are all set. Installation is easy, just need a duplex receptacle to plug in the blower and monitor.
sayeth the Pineth "If we move C cfm of 40 F saturated air with ws =
0.005216 into a room and mist a pound to wr = 0.012, that makes 1000(wr-ws) = 6.78 Btu of coolth. Raising a pound makes 0.24(80-40) = 9.6 Btu. The total is
16.38, and 40 F air weighs 0.07876 lb/ft^3, so 60Cx0.07876x16.38 = 12K Btu/h makes C = 155 vs 400 cfm, with smaller ducts or (400/155)^3 = 17 times less blower power, and..."
Factor in the pressure drop of the custom built 10 row, 14 fin per inch cooling coil, that will take 80 degree air down to saturated at 40F.
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