furnace filter - in vs out

with the recent weather in the Chicago area being really cold, I've been playing with the furnace filter... forced air - usual setup -

It's the 20x25 slide in kind - using a medium pleated version vs standard fiberglass

Trying to decide between :

A - leaving it in and having more back pressure on fan motor, and also creating less air flow delivery to rooms

B - taking it out & having less back pressure, and creating more air flow to the rooms

I guess this decision works both in the really cold days of winter, and the really hot days of summer -

?????

Reply to
ps56k
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The question is not whether or not you should *remove* the filter (no, you shouldn't) it's more about using the correct filter and keeping it changed and/or clean.

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Reply to
DerbyDad03

The A/C evaporator coil will catch the dust bunnies that are now trapped in the air filter. The coil is supposed to keep itself clean via the condensed humidity running off the fins, but might be overfuzzed. Challenging place to clean.

Reply to
Bryce

On Tue 16 Feb 2010 02:04:09p, ps56k told us...

Heating and/or cooling units were simply not meant to be run without filters in place. If you value your equipment, you won't run it without a proper filter in place.

If you've ever removed a dirty filter and looked at what it collected, imagine that colllecting on the fins of your a/c, or coating the insides of your heat exchanger or air handler.

If you're concdrned about air flow, look for filteres that have less resistance. They may not clean the air as well, butat least it willa be better than nothing.

This not even to mention the dirt that you'rte blowing right back into your rooms if not using a filter.

Where would you get such an idea?

Reply to
Wayne Boatwright

To further this, if you want to use a finer filter and are finding that it is restricting the flow too much, you need to go to a larger version of the filter to compensate for it's greater resistance. Depending on the configuration of your return system this can be easy or difficult to do.

Reply to
Pete C.

My neighbor said he had poor heat so we looked at his furnace and AC coil, he didnt have a filter, we looked at the AC coil it was so clogged shut and caked with years of dust no air could pass, we removed it completely and he said got heat for the first time since buying the place, that spring he power washed it. It doesnt take long and all the dust that bypasses a filter will hit the coil. My filter didnt seal 100% and its a 4" pleated 400$ april air unit, every year or so I have to clean my coils with a 400$ air filter. So dont do it and check the AC coil insted.

Reply to
ransley

If you take it out how will the air be filtered? If you want more air-flow, just leave the blower fan on 24/7.

Reply to
Phisherman

tnx for all the comments.

My main line of thinking was - A - air pressure on fan motor B - air flow capacity & delivery to rooms C - runtime to get room temps up to thermostat turnoff

Had not considered what little bunnies might be gathering on the A-Coil.

Reply to
ps56k

On Tue 16 Feb 2010 03:36:22p, Pete C. told us...

Another thought, too, would be using an electrostatic filter. They often have good air flow, but the electrostatic properties usually have a strong attraction for dust, pollen, etc. Many are permanent, some are disposable.

Reply to
Wayne Boatwright

I don't consider the drop in replacement filters that claim to be "electrostatic" to be legitimate electrostatic filters. The true electrostatic precipitators have a washable metal grid and a power supply unit, and will not fit in place of a standard 1" media filter. The real electrostatic filters work very well as long as you wash them regularly.

Reply to
Pete C.

All of the forced air furnaces that I have seen had the filter on the supply side of the furnace. The fan sucks air through the filter. It does not blow through the filter. Therefore, removing the filter wouldn't change the back pressure on the fan. It would increase flow because there would be no filter losses. I wouldn't do it though because dust and dirt would collect on the heat exchanger and reduce both airflow and heat transfer efficiency.

If you need more airflow you could try playing with the fan pulley sizes to speed up the fan.

Reply to
Reno

On Tue 16 Feb 2010 06:50:23p, Pete C. told us...

If you're talking about electronic air cleaners; e.g., Honeywell, I agree. However, the drop-in electgrostatic filters do have less air resistance and tend to filter better than a simple fiberglass filter, although probably not as well as according shaped media filter.

Reply to
Wayne Boatwright

Hi, I use mounted EAC and coarse metal mesh pre-filter in front of it. Works fine. I have two sets of elements. One is in use. One is cleaned and sits stand-by.

Reply to
Tony Hwang

fan motor - didn't know if blocking off more of the return air flow into the squirrel cage fan housing would cause the motor to work harder or not...

Reply to
ps56k

The furnace is designed to operate with a filter in the return air. It may restrict the airflow slightly, as does the ductwork, but all of that is taken into consideration in the design. That is one reason most furnaces have mulitspeed blower motors-- to allow optimum airflow with vith various amounts of restriction to that airflow. Larry

Reply to
Lp1331 1p1331

The air handlers are designed for a certain amount of back pressure from the ductwork. If there is not enough back pressure and the multi speed motor is set at one of the upper speeds, the airflow will be too high and will result in condensation being blown off the A/C coil instead of flowing down into the condensate pan.

Reply to
Pete C.

Of course the fan motor is going to need more power the more restrictive the filter element is. It doesn't matter if the restriction is after the fan or before it, whatever you do that restricts air flow will increase the work the fan must do to move the air. And that equates to slightly higher operating cost.

However, I don't see why in your original question you made this sound like a seasonal issue. With any reasonable filter that is not clogged up, the house should heat or cool pretty much the same as it would without the filter. Let's look at heating, let's say with a filter the air leaving the furnace gains X degrees. Without the filter, because there is more air flow the air will be slightly cooler, let's say X-1 degrees, but there will be MORE air flowing, so the amount of heat going into your house is about the same. I say about the same, because with a higher temp delta, the furnace becomes slightly less efficient, with a little bit more energy going out the exhaust. But unless you have a clogged filter, it should not be enough that it is even remotely connected to how long it takes to raise your house temp 5 degrees.

Reply to
trader4

I've never heard of that "keeps itself clean". But I have heard of, and seen a lot of very dirty evaporators.

Reply to
Stormin Mormon

I've seen both heat only ,and heat / AC systems really badly clogged by dust. So, the missing filter may provide better heat today. But nwarly guarantees expensive repairs later. I'd leave the filter in. Might try a different brand of filter, though.

Reply to
Stormin Mormon

A filter on the supply side would not protect the furnace. I've never seen a filter on the supply side.

A fan sucking air in through the filter is on the return side.

The dirty filter would starve the fan for air, and reduce the air flow. That creates some other problems.

Reply to
Stormin Mormon

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