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Default Furnace Air Filter Questions

My 95.5% Gas furnace came with a fiberglass air filter
with little restriction and no filtering action.

I substituted a Filtrete allergy reduction filter and went
about my business. Been running that way for 2 years.

In my filter search today, I found a gauge that tells you when
to change the filter by monitoring negative pressure
near the blower inlet. It says it can be calibrated
for 0-.4"WC.

I did some measurements on my system.
With the filter removed and the filter door open,
I measured -0.1"WC.
I measured with my Filtrete installed and with a
lesser MERV9, I think, filter then a washable
permanent electrostatic filter.
All measured -.55"WC.
With the filter access door closed, it goes up
to -0.6"WC.
That's outside the calibration range of the filter
monitor gauge, so it got me thinking.
I don't have a fiberglass filter to compare.

I also measured some temperatures.
With indoor temperature at 65F, the air coming out
of the closest vent stabilizes at 119F. It's about
12' from the furnace and the ducts are insulated,
so it should be somewhere near the furnace output
temperature.

Looks like I'm getting 60F rise across the furnace.
That's near the max claimed in the spec.

Another thing is that I don't heat part of the house.
Three registers are closed. Last time I did the experiment,
heating the whole house cost me almost 50% more in gas.

So,
I don't want to heat the whole house.
I need the better air filters.
Should I worry about overheating the furnace?
Is there anything simple I can to about it?
Like turn up the blower speed?

I do have an electronic filter that's designed to replace
the 1" paper filter. I'd have to cut it down to fit.
Looks like it has about as much material as the original
fiberglass filter, so should have lower pressure drop.

Is that a viable alternative?
It's not clear how they compare at removing pollen.
It's hard to decide based on the vague marketing hype.

Thanks mike.
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Default Furnace Air Filter Questions



mike wrote:
My 95.5% Gas furnace came with a fiberglass air filter
with little restriction and no filtering action.

I substituted a Filtrete allergy reduction filter and went
about my business. Been running that way for 2 years.

In my filter search today, I found a gauge that tells you when
to change the filter by monitoring negative pressure
near the blower inlet. It says it can be calibrated
for 0-.4"WC.

I did some measurements on my system.
With the filter removed and the filter door open,
I measured -0.1"WC.
I measured with my Filtrete installed and with a
lesser MERV9, I think, filter then a washable
permanent electrostatic filter.
All measured -.55"WC.
With the filter access door closed, it goes up
to -0.6"WC.
That's outside the calibration range of the filter
monitor gauge, so it got me thinking.
I don't have a fiberglass filter to compare.

I also measured some temperatures.
With indoor temperature at 65F, the air coming out
of the closest vent stabilizes at 119F. It's about
12' from the furnace and the ducts are insulated,
so it should be somewhere near the furnace output
temperature.

Looks like I'm getting 60F rise across the furnace.
That's near the max claimed in the spec.

Another thing is that I don't heat part of the house.
Three registers are closed. Last time I did the experiment,
heating the whole house cost me almost 50% more in gas.

So,
I don't want to heat the whole house.
I need the better air filters.
Should I worry about overheating the furnace?
Is there anything simple I can to about it?
Like turn up the blower speed?

I do have an electronic filter that's designed to replace
the 1" paper filter. I'd have to cut it down to fit.
Looks like it has about as much material as the original
fiberglass filter, so should have lower pressure drop.

Is that a viable alternative?
It's not clear how they compare at removing pollen.
It's hard to decide based on the vague marketing hype.

Thanks mike.

Hi,
I think you should do the measurement with all the registers open.
I use EAC only on our furnace. I clean the elements twice a year.
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Quote:
Originally Posted by Tony Hwang View Post
mike wrote:
My 95.5% Gas furnace came with a fiberglass air filter
with little restriction and no filtering action.

I substituted a Filtrete allergy reduction filter and went
about my business. Been running that way for 2 years.

In my filter search today, I found a gauge that tells you when
to change the filter by monitoring negative pressure
near the blower inlet. It says it can be calibrated
for 0-.4"WC.

I did some measurements on my system.
With the filter removed and the filter door open,
I measured -0.1"WC.
I measured with my Filtrete installed and with a
lesser MERV9, I think, filter then a washable
permanent electrostatic filter.
All measured -.55"WC.
With the filter access door closed, it goes up
to -0.6"WC.
That's outside the calibration range of the filter
monitor gauge, so it got me thinking.
I don't have a fiberglass filter to compare.

I also measured some temperatures.
With indoor temperature at 65F, the air coming out
of the closest vent stabilizes at 119F. It's about
12' from the furnace and the ducts are insulated,
so it should be somewhere near the furnace output
temperature.

Looks like I'm getting 60F rise across the furnace.
That's near the max claimed in the spec.

Another thing is that I don't heat part of the house.
Three registers are closed. Last time I did the experiment,
heating the whole house cost me almost 50% more in gas.

So,
I don't want to heat the whole house.
I need the better air filters.
Should I worry about overheating the furnace?
Is there anything simple I can to about it?
Like turn up the blower speed?

I do have an electronic filter that's designed to replace
the 1" paper filter. I'd have to cut it down to fit.
Looks like it has about as much material as the original
fiberglass filter, so should have lower pressure drop.

Is that a viable alternative?
It's not clear how they compare at removing pollen.
It's hard to decide based on the vague marketing hype.

Thanks mike.

Hi,
I think you should do the measurement with all the registers open.
I use EAC only on our furnace. I clean the elements twice a year.
I can't really comment on your questions but you've got me thinking. I too use Filtrete filters. I think maybe I should get one of those gauges. Never even occurred to me. Wonder how much I'm wasting.
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Default Furnace Air Filter Questions

On 2/6/2012 5:28 AM, wrote:
On Feb 6, 7:29 am, wrote:
My 95.5% Gas furnace came with a fiberglass air filter
with little restriction and no filtering action.

I substituted a Filtrete allergy reduction filter and went
about my business. Been running that way for 2 years.

In my filter search today, I found a gauge that tells you when
to change the filter by monitoring negative pressure
near the blower inlet. It says it can be calibrated
for 0-.4"WC.

I did some measurements on my system.
With the filter removed and the filter door open,
I measured -0.1"WC.
I measured with my Filtrete installed and with a
lesser MERV9, I think, filter then a washable
permanent electrostatic filter.
All measured -.55"WC.
With the filter access door closed, it goes up
to -0.6"WC.
That's outside the calibration range of the filter
monitor gauge, so it got me thinking.
I don't have a fiberglass filter to compare.

I also measured some temperatures.
With indoor temperature at 65F, the air coming out
of the closest vent stabilizes at 119F. It's about
12' from the furnace and the ducts are insulated,
so it should be somewhere near the furnace output
temperature.

Looks like I'm getting60F rise across the furnace.
That's near the max claimed in the spec.

Another thing is that I don't heat part of the house.
Three registers are closed. Last time I did the experiment,
heating the whole house cost me almost 50% more in gas.

So,
I don't want to heat the whole house.
I need the better air filters.
Should I worry about overheating the furnace?


Rather than saying it's the "max claimed", I'd be
looking at it as the "max allowed".
As long as the temp rise is within the furnace spec,
which you say it is, you're not going to damage the
furnace.


Is there anything simple I can to about it?
Like turn up the blower speed?


Yes, no, maybe. It depends on the furnace. Read
the install manual and see what choices there are.
Some have at least some selection of blower speeds
for heating and cooling. Furnaces with a true variable
speed blower would have the most options which
can be set with dip switches. Then it
also depends if it's already set to the max for heating
or not.....




I do have an electronic filter that's designed to replace
the 1" paper filter. I'd have to cut it down to fit.
Looks like it has about as much material as the original
fiberglass filter, so should have lower pressure drop.


I've never seen a 1" electronic filter.


That's easily remedied.
http://www.cimatec.com/Cimatec-Air-F...creen1000.aspx
Picked it up dirt cheap at a garage sale a few years back.
Only been using it a few days, so the jury is still out.

All the electronic
filters I've seen are more like 4 or 5 inches deep and are
in their own cabinet that sits in the duct next to the
furnace.







Is that a viable alternative?
It's not clear how they compare at removing pollen.
It's hard to decide based on the vague marketing hype.

Thanks mike.


What problem are you trying to solve?


The problem I'm trying to solve is hay fever.
I built a heat recovery ventilator to solve an IAQ
problem caused by sealing up leakage.
Worked great until the pollen hit.
So, I started working on an air filter for it.
That led me to making some efficiency measurements
that side-tracked me onto the air flow in the furnace.

I made more measurements, and determined that the pressure
below the filter is pretty much independent of whatever filter
I tried. It's -.55"WC. With the filter removed, it's still
-.3"WC. That's likely the result of the flexible return pipe
they used to solve a blower noise problem with a new furnace.

It's always easier to get it right the SECOND time you do something. :-(

The airflow you
get is going to be influenced by not only the filter, but by
the duct work. You also say you've got some registers
closed off. That obviously is going to reduce airflow.

I use one of the thick pleated filters that goes into a
seperate filter cabinet. It's about 4 inches thick. By
being deeply pleated it has a lot more surface area and
hence while doing a good filtering job, it presents less
resistance than a thinner filter that would have the same
filtering capability. I think if you want good filtering and
lowest resistance, either one of those or a true electronic
one that's in it's own cabinet is the only way you're going
to get it.


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Default Furnace Air Filter Questions

On 2/10/2012 11:31 AM, radiotom wrote:
Tony Hwang;2799305 Wrote:
mike wrote:-
My 95.5% Gas furnace came with a fiberglass air filter
with little restriction and no filtering action.

I substituted a Filtrete allergy reduction filter and went
about my business. Been running that way for 2 years.

In my filter search today, I found a gauge that tells you when
to change the filter by monitoring negative pressure
near the blower inlet. It says it can be calibrated
for 0-.4"WC.

I did some measurements on my system.
With the filter removed and the filter door open,
I measured -0.1"WC.
I measured with my Filtrete installed and with a
lesser MERV9, I think, filter then a washable
permanent electrostatic filter.
All measured -.55"WC.
With the filter access door closed, it goes up
to -0.6"WC.
That's outside the calibration range of the filter
monitor gauge, so it got me thinking.
I don't have a fiberglass filter to compare.

I also measured some temperatures.
With indoor temperature at 65F, the air coming out
of the closest vent stabilizes at 119F. It's about
12' from the furnace and the ducts are insulated,
so it should be somewhere near the furnace output
temperature.

Looks like I'm getting 60F rise across the furnace.
That's near the max claimed in the spec.

Another thing is that I don't heat part of the house.
Three registers are closed. Last time I did the experiment,
heating the whole house cost me almost 50% more in gas.

So,
I don't want to heat the whole house.
I need the better air filters.
Should I worry about overheating the furnace?
Is there anything simple I can to about it?
Like turn up the blower speed?

I do have an electronic filter that's designed to replace
the 1" paper filter. I'd have to cut it down to fit.
Looks like it has about as much material as the original
fiberglass filter, so should have lower pressure drop.

Is that a viable alternative?
It's not clear how they compare at removing pollen.
It's hard to decide based on the vague marketing hype.

Thanks mike.-
Hi,
I think you should do the measurement with all the registers open.
I use EAC only on our furnace. I clean the elements twice a year.


I can't really comment on your questions but you've got me thinking. I
too use Filtrete filters. I think maybe I should get one of those
gauges. Never even occurred to me. Wonder how much I'm wasting.

Those gauges can be useful for people who don't have a calendar and a
pencil.
You can do the same measurement with some plastic tubing and water.
Google "manometer". Once you figure out how long a filter lasts
in your situation, just mark the calendar to change it.

While there's no question that moving air costs money and friction
adds to that, I've never seen any apples-to apples numbers that
support how much.

In any given situation, you have the ratio of the BTU's in the
gas supply to the BTU's that end up as heat in the dwelling.
For small changes in back pressure, I don't expect that ratio
to change much. The blower may use more power...I'd like to hear
some real numbers on that. Next time I have the cabinet open, I'm gonna
stick a current meter on the blower power and try it with and without
the air filter installed. Just gotta figure out how to read the meter
through the metal door.

The vendors for low restriction filters and gauges use all sorts
of marketing speak and misdirection to induce you to buy their stuff.
They throw the apples and oranges into the mix and claim it's proof.

Here's what I think I know about filters. I'm sure people won't
be shy about correcting my misconceptions.

For a simple, passive filter, the size of the particles that can be
trapped is determined by the pore size of the filter. As the pores
get smaller, you can put more pores in the same space. But the filter
material has some minimum fiber dimension. At some point, you're
down to one fiber width between pores and you can't fit any more in.
And there are significant friction effects as the pores get smaller.

Pressure goes up for smaller pores, so you have to have more surface area.
Pleating is the first thing to do, but even that has it's limits.
You can make the filter as large as will fit in the cabinet, but
that has limits too. Smaller pores plug up faster.

Making the media thicker doesn't help. To reduce pressure, you'd
have to make the pores even bigger and not be able to trap the small stuff.
Thicker filters can accommodate bigger pleats of the thin media
resulting in larger surface area.

The solution to this diminishing returns situation is to use
technology that traps particles in a way unrelated to their size.
Electronic filters use an electric field to force particles to displace
out of the air stream and collect on a plate.
The electric field has little effect on the air stream, so pressure
rise is minimal.
This also has tradeoffs, so you usually end up with a passive filter
for the big stuff and the electric field for the stuff that gets thru.

Now, back to the question that I started in another thread.
There is a technology that uses an electric field that does not require
external power.
I thought the field was created by the triboelectric effect of air
passing through insulating media. The only response to that was
the rude statement that, "my education was faulty," but no real
useful help was provided.
The other theory presented was that the electric field was permanently
installed
at the time of manufacture. That was debunked.

I've looked at my sample and can't find any evidence of an electric field.
I stuck one on my HRV, but can't tell if it's better than an ordinary
filter.
That led me to another quest for a particle counter to measure
actual results.
People who sell passive electrostatic filters say they're terrific.
Technical people seem to think they're snake oil.

Jury is still out on that one.

Are we having fun yet?

mike


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Default Furnace Air Filter Questions

On Fri, 10 Feb 2012 13:41:57 -0800, mike wrote:

On 2/10/2012 11:31 AM, radiotom wrote:
Tony Hwang;2799305 Wrote:
mike wrote:-
My 95.5% Gas furnace came with a fiberglass air filter
with little restriction and no filtering action.

I substituted a Filtrete allergy reduction filter and went
about my business. Been running that way for 2 years.

In my filter search today, I found a gauge that tells you when
to change the filter by monitoring negative pressure
near the blower inlet. It says it can be calibrated
for 0-.4"WC.

I did some measurements on my system.
With the filter removed and the filter door open,
I measured -0.1"WC.
I measured with my Filtrete installed and with a
lesser MERV9, I think, filter then a washable
permanent electrostatic filter.
All measured -.55"WC.
With the filter access door closed, it goes up
to -0.6"WC.
That's outside the calibration range of the filter
monitor gauge, so it got me thinking.
I don't have a fiberglass filter to compare.

I also measured some temperatures.
With indoor temperature at 65F, the air coming out
of the closest vent stabilizes at 119F. It's about
12' from the furnace and the ducts are insulated,
so it should be somewhere near the furnace output
temperature.

Looks like I'm getting 60F rise across the furnace.
That's near the max claimed in the spec.

Another thing is that I don't heat part of the house.
Three registers are closed. Last time I did the experiment,
heating the whole house cost me almost 50% more in gas.

So,
I don't want to heat the whole house.
I need the better air filters.
Should I worry about overheating the furnace?
Is there anything simple I can to about it?
Like turn up the blower speed?

I do have an electronic filter that's designed to replace
the 1" paper filter. I'd have to cut it down to fit.
Looks like it has about as much material as the original
fiberglass filter, so should have lower pressure drop.

Is that a viable alternative?
It's not clear how they compare at removing pollen.
It's hard to decide based on the vague marketing hype.

Thanks mike.-
Hi,
I think you should do the measurement with all the registers open.
I use EAC only on our furnace. I clean the elements twice a year.


I can't really comment on your questions but you've got me thinking. I
too use Filtrete filters. I think maybe I should get one of those
gauges. Never even occurred to me. Wonder how much I'm wasting.

Those gauges can be useful for people who don't have a calendar and a
pencil.
You can do the same measurement with some plastic tubing and water.
Google "manometer". Once you figure out how long a filter lasts
in your situation, just mark the calendar to change it.

While there's no question that moving air costs money and friction
adds to that, I've never seen any apples-to apples numbers that
support how much.

In any given situation, you have the ratio of the BTU's in the
gas supply to the BTU's that end up as heat in the dwelling.
For small changes in back pressure, I don't expect that ratio
to change much. The blower may use more power...I'd like to hear
some real numbers on that. Next time I have the cabinet open, I'm gonna
stick a current meter on the blower power and try it with and without
the air filter installed. Just gotta figure out how to read the meter
through the metal door.

The vendors for low restriction filters and gauges use all sorts
of marketing speak and misdirection to induce you to buy their stuff.
They throw the apples and oranges into the mix and claim it's proof.

Here's what I think I know about filters. I'm sure people won't
be shy about correcting my misconceptions.

For a simple, passive filter, the size of the particles that can be
trapped is determined by the pore size of the filter. As the pores
get smaller, you can put more pores in the same space. But the filter
material has some minimum fiber dimension. At some point, you're
down to one fiber width between pores and you can't fit any more in.
And there are significant friction effects as the pores get smaller.

Pressure goes up for smaller pores, so you have to have more surface area.
Pleating is the first thing to do, but even that has it's limits.
You can make the filter as large as will fit in the cabinet, but
that has limits too. Smaller pores plug up faster.

Making the media thicker doesn't help. To reduce pressure, you'd
have to make the pores even bigger and not be able to trap the small stuff.
Thicker filters can accommodate bigger pleats of the thin media
resulting in larger surface area.

The solution to this diminishing returns situation is to use
technology that traps particles in a way unrelated to their size.
Electronic filters use an electric field to force particles to displace
out of the air stream and collect on a plate.
The electric field has little effect on the air stream, so pressure
rise is minimal.
This also has tradeoffs, so you usually end up with a passive filter
for the big stuff and the electric field for the stuff that gets thru.

Now, back to the question that I started in another thread.
There is a technology that uses an electric field that does not require
external power.
I thought the field was created by the triboelectric effect of air
passing through insulating media. The only response to that was
the rude statement that, "my education was faulty," but no real
useful help was provided.
The other theory presented was that the electric field was permanently
installed
at the time of manufacture. That was debunked.


They are called ELECTROSTATIC filters. They are not electronic - and
they DO work on the electrostatic charge built up by the air flowing
through them.. Don't know if triboelectric is the correct term or not
- but the darn things work pretty well and are quite low resistance.
And they fit directly in place of the 1 inch cheap folded paper or the
even cheaper tangled string filters.

I've looked at my sample and can't find any evidence of an electric field.
I stuck one on my HRV, but can't tell if it's better than an ordinary
filter.
That led me to another quest for a particle counter to measure
actual results.
People who sell passive electrostatic filters say they're terrific.
Technical people seem to think they're snake oil.


I don't sell them, and I've used the real electronic "dust zappers"
as well as pleated and fiber filters - The electrostatics are MUCH
more effective than the fiber or paper, perhaps not quite as good as
the expensive electronic units.

I've also found "treated" fiber filters work pretty good. I used to
have a can of spray that made the fiber ones act like an
electrostatic. But the darn stuff wasn't cheap, and you could not wash
and re-use the filters like you can the electrostatic.

Jury is still out on that one.

Are we having fun yet?

mike


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Default Furnace Air Filter Questions

On 2/10/2012 6:23 PM, wrote:
On Fri, 10 Feb 2012 13:41:57 -0800, wrote:

On 2/10/2012 11:31 AM, radiotom wrote:
Tony Hwang;2799305 Wrote:
mike wrote:-
My 95.5% Gas furnace came with a fiberglass air filter
with little restriction and no filtering action.

I substituted a Filtrete allergy reduction filter and went
about my business. Been running that way for 2 years.

In my filter search today, I found a gauge that tells you when
to change the filter by monitoring negative pressure
near the blower inlet. It says it can be calibrated
for 0-.4"WC.

I did some measurements on my system.
With the filter removed and the filter door open,
I measured -0.1"WC.
I measured with my Filtrete installed and with a
lesser MERV9, I think, filter then a washable
permanent electrostatic filter.
All measured -.55"WC.
With the filter access door closed, it goes up
to -0.6"WC.
That's outside the calibration range of the filter
monitor gauge, so it got me thinking.
I don't have a fiberglass filter to compare.

I also measured some temperatures.
With indoor temperature at 65F, the air coming out
of the closest vent stabilizes at 119F. It's about
12' from the furnace and the ducts are insulated,
so it should be somewhere near the furnace output
temperature.

Looks like I'm getting 60F rise across the furnace.
That's near the max claimed in the spec.

Another thing is that I don't heat part of the house.
Three registers are closed. Last time I did the experiment,
heating the whole house cost me almost 50% more in gas.

So,
I don't want to heat the whole house.
I need the better air filters.
Should I worry about overheating the furnace?
Is there anything simple I can to about it?
Like turn up the blower speed?

I do have an electronic filter that's designed to replace
the 1" paper filter. I'd have to cut it down to fit.
Looks like it has about as much material as the original
fiberglass filter, so should have lower pressure drop.

Is that a viable alternative?
It's not clear how they compare at removing pollen.
It's hard to decide based on the vague marketing hype.

Thanks mike.-
Hi,
I think you should do the measurement with all the registers open.
I use EAC only on our furnace. I clean the elements twice a year.

I can't really comment on your questions but you've got me thinking. I
too use Filtrete filters. I think maybe I should get one of those
gauges. Never even occurred to me. Wonder how much I'm wasting.

Those gauges can be useful for people who don't have a calendar and a
pencil.
You can do the same measurement with some plastic tubing and water.
Google "manometer". Once you figure out how long a filter lasts
in your situation, just mark the calendar to change it.

While there's no question that moving air costs money and friction
adds to that, I've never seen any apples-to apples numbers that
support how much.

In any given situation, you have the ratio of the BTU's in the
gas supply to the BTU's that end up as heat in the dwelling.
For small changes in back pressure, I don't expect that ratio
to change much. The blower may use more power...I'd like to hear
some real numbers on that. Next time I have the cabinet open, I'm gonna
stick a current meter on the blower power and try it with and without
the air filter installed. Just gotta figure out how to read the meter
through the metal door.

The vendors for low restriction filters and gauges use all sorts
of marketing speak and misdirection to induce you to buy their stuff.
They throw the apples and oranges into the mix and claim it's proof.

Here's what I think I know about filters. I'm sure people won't
be shy about correcting my misconceptions.

For a simple, passive filter, the size of the particles that can be
trapped is determined by the pore size of the filter. As the pores
get smaller, you can put more pores in the same space. But the filter
material has some minimum fiber dimension. At some point, you're
down to one fiber width between pores and you can't fit any more in.
And there are significant friction effects as the pores get smaller.

Pressure goes up for smaller pores, so you have to have more surface area.
Pleating is the first thing to do, but even that has it's limits.
You can make the filter as large as will fit in the cabinet, but
that has limits too. Smaller pores plug up faster.

Making the media thicker doesn't help. To reduce pressure, you'd
have to make the pores even bigger and not be able to trap the small stuff.
Thicker filters can accommodate bigger pleats of the thin media
resulting in larger surface area.

The solution to this diminishing returns situation is to use
technology that traps particles in a way unrelated to their size.
Electronic filters use an electric field to force particles to displace
out of the air stream and collect on a plate.
The electric field has little effect on the air stream, so pressure
rise is minimal.
This also has tradeoffs, so you usually end up with a passive filter
for the big stuff and the electric field for the stuff that gets thru.

Now, back to the question that I started in another thread.
There is a technology that uses an electric field that does not require
external power.
I thought the field was created by the triboelectric effect of air
passing through insulating media. The only response to that was
the rude statement that, "my education was faulty," but no real
useful help was provided.
The other theory presented was that the electric field was permanently
installed
at the time of manufacture. That was debunked.


They are called ELECTROSTATIC filters. They are not electronic - and
they DO work on the electrostatic charge built up by the air flowing
through them.. Don't know if triboelectric is the correct term or not
- but the darn things work pretty well and are quite low resistance.
And they fit directly in place of the 1 inch cheap folded paper or the
even cheaper tangled string filters.


What measurement techniques did you use to determine that "they work
pretty well"? I'm interested in pollen capture.
I cut one down to 64 square inches and stuck it on an experimental Heat
recovery ventilator. Put about 20 CFM through it. Velocity is pretty low,
so I'd like some info on performance vs air velocity that's creating the
electrostatic field. Also wonder how humidity affects it.
If you have any links to actual, unbiased engineering tests, I'd like
them. If there's an electric field in there, I should be able to detect it.
So far, I've not been able to do that. Exactly where is the field
supposed to be?

A particle counter ought to be able to verify performance instantly.
If that could show that they work, you'd think the vendors would publish
that video alongside their flashy videos of marketing speak.

We've been having rain lately, so the pollen count has gone down.
I have no idea whether the filter is doing its job in my application.

I've looked at my sample and can't find any evidence of an electric field.
I stuck one on my HRV, but can't tell if it's better than an ordinary
filter.
That led me to another quest for a particle counter to measure
actual results.
People who sell passive electrostatic filters say they're terrific.
Technical people seem to think they're snake oil.


I don't sell them, and I've used the real electronic "dust zappers"
as well as pleated and fiber filters - The electrostatics are MUCH
more effective than the fiber or paper, perhaps not quite as good as
the expensive electronic units.


The people who sell 'em make wild claims that their electronics
are WAY superior to anything else.
https://www.toxbox.ca/why-toxbox/

I've also found "treated" fiber filters work pretty good. I used to
have a can of spray that made the fiber ones act like an
electrostatic. But the darn stuff wasn't cheap, and you could not wash
and re-use the filters like you can the electrostatic.

Jury is still out on that one.

Are we having fun yet?

mike



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Default Furnace Air Filter Questions

On Fri, 10 Feb 2012 21:07:17 -0800, mike wrote:

On 2/10/2012 6:23 PM, wrote:
On Fri, 10 Feb 2012 13:41:57 -0800, wrote:

On 2/10/2012 11:31 AM, radiotom wrote:
Tony Hwang;2799305 Wrote:
mike wrote:-
My 95.5% Gas furnace came with a fiberglass air filter
with little restriction and no filtering action.

I substituted a Filtrete allergy reduction filter and went
about my business. Been running that way for 2 years.

In my filter search today, I found a gauge that tells you when
to change the filter by monitoring negative pressure
near the blower inlet. It says it can be calibrated
for 0-.4"WC.

I did some measurements on my system.
With the filter removed and the filter door open,
I measured -0.1"WC.
I measured with my Filtrete installed and with a
lesser MERV9, I think, filter then a washable
permanent electrostatic filter.
All measured -.55"WC.
With the filter access door closed, it goes up
to -0.6"WC.
That's outside the calibration range of the filter
monitor gauge, so it got me thinking.
I don't have a fiberglass filter to compare.

I also measured some temperatures.
With indoor temperature at 65F, the air coming out
of the closest vent stabilizes at 119F. It's about
12' from the furnace and the ducts are insulated,
so it should be somewhere near the furnace output
temperature.

Looks like I'm getting 60F rise across the furnace.
That's near the max claimed in the spec.

Another thing is that I don't heat part of the house.
Three registers are closed. Last time I did the experiment,
heating the whole house cost me almost 50% more in gas.

So,
I don't want to heat the whole house.
I need the better air filters.
Should I worry about overheating the furnace?
Is there anything simple I can to about it?
Like turn up the blower speed?

I do have an electronic filter that's designed to replace
the 1" paper filter. I'd have to cut it down to fit.
Looks like it has about as much material as the original
fiberglass filter, so should have lower pressure drop.

Is that a viable alternative?
It's not clear how they compare at removing pollen.
It's hard to decide based on the vague marketing hype.

Thanks mike.-
Hi,
I think you should do the measurement with all the registers open.
I use EAC only on our furnace. I clean the elements twice a year.

I can't really comment on your questions but you've got me thinking. I
too use Filtrete filters. I think maybe I should get one of those
gauges. Never even occurred to me. Wonder how much I'm wasting.

Those gauges can be useful for people who don't have a calendar and a
pencil.
You can do the same measurement with some plastic tubing and water.
Google "manometer". Once you figure out how long a filter lasts
in your situation, just mark the calendar to change it.

While there's no question that moving air costs money and friction
adds to that, I've never seen any apples-to apples numbers that
support how much.

In any given situation, you have the ratio of the BTU's in the
gas supply to the BTU's that end up as heat in the dwelling.
For small changes in back pressure, I don't expect that ratio
to change much. The blower may use more power...I'd like to hear
some real numbers on that. Next time I have the cabinet open, I'm gonna
stick a current meter on the blower power and try it with and without
the air filter installed. Just gotta figure out how to read the meter
through the metal door.

The vendors for low restriction filters and gauges use all sorts
of marketing speak and misdirection to induce you to buy their stuff.
They throw the apples and oranges into the mix and claim it's proof.

Here's what I think I know about filters. I'm sure people won't
be shy about correcting my misconceptions.

For a simple, passive filter, the size of the particles that can be
trapped is determined by the pore size of the filter. As the pores
get smaller, you can put more pores in the same space. But the filter
material has some minimum fiber dimension. At some point, you're
down to one fiber width between pores and you can't fit any more in.
And there are significant friction effects as the pores get smaller.

Pressure goes up for smaller pores, so you have to have more surface area.
Pleating is the first thing to do, but even that has it's limits.
You can make the filter as large as will fit in the cabinet, but
that has limits too. Smaller pores plug up faster.

Making the media thicker doesn't help. To reduce pressure, you'd
have to make the pores even bigger and not be able to trap the small stuff.
Thicker filters can accommodate bigger pleats of the thin media
resulting in larger surface area.

The solution to this diminishing returns situation is to use
technology that traps particles in a way unrelated to their size.
Electronic filters use an electric field to force particles to displace
out of the air stream and collect on a plate.
The electric field has little effect on the air stream, so pressure
rise is minimal.
This also has tradeoffs, so you usually end up with a passive filter
for the big stuff and the electric field for the stuff that gets thru.

Now, back to the question that I started in another thread.
There is a technology that uses an electric field that does not require
external power.
I thought the field was created by the triboelectric effect of air
passing through insulating media. The only response to that was
the rude statement that, "my education was faulty," but no real
useful help was provided.
The other theory presented was that the electric field was permanently
installed
at the time of manufacture. That was debunked.


They are called ELECTROSTATIC filters. They are not electronic - and
they DO work on the electrostatic charge built up by the air flowing
through them.. Don't know if triboelectric is the correct term or not
- but the darn things work pretty well and are quite low resistance.
And they fit directly in place of the 1 inch cheap folded paper or the
even cheaper tangled string filters.


What measurement techniques did you use to determine that "they work
pretty well"? I'm interested in pollen capture.
I cut one down to 64 square inches and stuck it on an experimental Heat
recovery ventilator. Put about 20 CFM through it. Velocity is pretty low,
so I'd like some info on performance vs air velocity that's creating the
electrostatic field. Also wonder how humidity affects it.
If you have any links to actual, unbiased engineering tests, I'd like
them. If there's an electric field in there, I should be able to detect it.
So far, I've not been able to do that. Exactly where is the field
supposed to be?

A particle counter ought to be able to verify performance instantly.
If that could show that they work, you'd think the vendors would publish
that video alongside their flashy videos of marketing speak.

I can't give you any quantitative data, but there is a LOT less fine
dust in the house and I hardly ever need my athsma medication any
more.. When I wash the filter there is a lot of REAL FINE dirt.
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Default Furnace Air Filter Questions

On Feb 10, 2:41*pm, mike wrote:
...snip...
Now, back to the question that I started in another thread.
There is a technology that uses an electric field that does not require
external power.
I thought the field was created by the triboelectric effect of air
passing through insulating media. *The only response to that was
the rude statement that, "my education was faulty," but no real
useful help was provided.
The other theory presented was that the electric field was permanently
installed
at the time of manufacture. *That was debunked.

I've looked at my sample and can't find any evidence of an electric field..
I stuck one on my HRV, but can't tell if it's better than an ordinary
filter.
That led me to another quest for a particle counter to measure
actual results.
People who sell passive electrostatic filters say they're terrific.
Technical people seem to think they're snake oil.

Jury is still out on that one.

Are we having fun yet?

mike


Yes, term is electrostatic.

Triboelectric is the garranteed charge distribution that is caused by
forcibly separating dissimilar materials with different electron work
functions. Examples are wool to rubber, hair to comb, almost
everything some more than others.

Electrostatic filters REQUIRE air movement to work.

Yes, they work. ...and I'm technical. To be equivalent to electronic
air cleaners requires a bit of volume in comparison.

From memory, I thought it possible/plausible to create a 'built-in'
field during manufacturing, but know that charges would quickly
accumulate to null the fields out. You say it was debunked. Was the
'ability' to "...install..." the charge debunked? Or, rather whether
it was done by electrostatic filter manufacturers at all?

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Default Furnace Air Filter Questions

On 2/11/2012 5:17 AM, Robert Macy wrote:
On Feb 10, 2:41 pm, wrote:
...snip...
Now, back to the question that I started in another thread.
There is a technology that uses an electric field that does not require
external power.
I thought the field was created by the triboelectric effect of air
passing through insulating media. The only response to that was
the rude statement that, "my education was faulty," but no real
useful help was provided.
The other theory presented was that the electric field was permanently
installed
at the time of manufacture. That was debunked.

I've looked at my sample and can't find any evidence of an electric field.
I stuck one on my HRV, but can't tell if it's better than an ordinary
filter.
That led me to another quest for a particle counter to measure
actual results.
People who sell passive electrostatic filters say they're terrific.
Technical people seem to think they're snake oil.

Jury is still out on that one.

Are we having fun yet?

mike


Yes, term is electrostatic.

Triboelectric is the garranteed charge distribution that is caused by
forcibly separating dissimilar materials with different electron work
functions. Examples are wool to rubber, hair to comb, almost
everything some more than others.

Electrostatic filters REQUIRE air movement to work.

Yes, they work. ...and I'm technical. To be equivalent to electronic
air cleaners requires a bit of volume in comparison.

From memory, I thought it possible/plausible to create a 'built-in'
field during manufacturing, but know that charges would quickly
accumulate to null the fields out. You say it was debunked. Was the
'ability' to "...install..." the charge debunked? Or, rather whether
it was done by electrostatic filter manufacturers at all?

The electronic filter creates several kilovolts across about a
centimeter or so.
I believe you can create a fixed electrostatic field by solidifying a
polar polymer in the presence of a strong electric field.
Since the distance is tiny, you might even convince yourself that you
have similar kilovolts/cm. But does that do any good in a filter
application.
Wouldn't a dust particle have to actually bang into that molecule
to experience any field at all?
So, if the electrostatic had any permanent electric field, where is it
in the material stack and how would one measure it?

I don't have much air volume, so the electrostatic may not work for me
even if it does work in a furnace. Might as well build another
electronic one and be done with it.

A particle counter would settle the question rather easily.
I considered buying one of the $10 Sharp optical counter modules, but
it looks like what I want to measure would be down in the noise level
for that module. The projects built on that module have lots of
glitz, but no real numbers. Anybody can detect a cloud of smoke.
Optically detecting small amounts of pollen is quite another matter.


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On Feb 6, 7:29*am, mike wrote:
My 95.5% Gas furnace came with a fiberglass air filter
with little restriction and no filtering action.

I substituted a Filtrete allergy reduction filter and went
about my business. *Been running that way for 2 years.

In my filter search today, I found a gauge that tells you when
to change the filter by monitoring negative pressure
near the blower inlet. *It says it can be calibrated
for 0-.4"WC.

I did some measurements on my system.
With the filter removed and the filter door open,
I measured -0.1"WC.
I measured with my Filtrete installed and with a
lesser MERV9, I think, filter then a washable
permanent electrostatic filter.
All measured -.55"WC.
With the filter access door closed, it goes up
to -0.6"WC.
That's outside the calibration range of the filter
monitor gauge, so it got me thinking.
I don't have a fiberglass filter to compare.

I also measured some temperatures.
With indoor temperature at 65F, the air coming out
of the closest vent stabilizes at 119F. *It's about
12' from the furnace and the ducts are insulated,
so it should be somewhere near the furnace output
temperature.

Looks like I'm getting 60F rise across the furnace.
That's near the max claimed in the spec.

Another thing is that I don't heat part of the house.
Three registers are closed. *Last time I did the experiment,
heating the whole house cost me almost 50% more in gas.

So,
I don't want to heat the whole house.
I need the better air filters.
Should I worry about overheating the furnace?
Is there anything simple I can to about it?
Like turn up the blower speed?

I do have an electronic filter that's designed to replace
the 1" paper filter. *I'd have to cut it down to fit.
Looks like it has about as much material as the original
fiberglass filter, so should have lower pressure drop.

Is that a viable alternative?
It's not clear how they compare at removing pollen.
It's hard to decide based on the vague marketing hype.

Thanks mike.


I spray my fiberglass filters with WD40 then set them in the sun to
dry so I dont get wd40 in my coils. You just won't believe how ell
this works until you try it.

Jimmie
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Default Furnace Air Filter Questions

On Feb 6, 7:29*am, mike wrote:
My 95.5% Gas furnace came with a fiberglass air filter
with little restriction and no filtering action.

I substituted a Filtrete allergy reduction filter and went
about my business. *Been running that way for 2 years.

In my filter search today, I found a gauge that tells you when
to change the filter by monitoring negative pressure
near the blower inlet. *It says it can be calibrated
for 0-.4"WC.

I did some measurements on my system.
With the filter removed and the filter door open,
I measured -0.1"WC.
I measured with my Filtrete installed and with a
lesser MERV9, I think, filter then a washable
permanent electrostatic filter.
All measured -.55"WC.
With the filter access door closed, it goes up
to -0.6"WC.
That's outside the calibration range of the filter
monitor gauge, so it got me thinking.
I don't have a fiberglass filter to compare.

I also measured some temperatures.
With indoor temperature at 65F, the air coming out
of the closest vent stabilizes at 119F. *It's about
12' from the furnace and the ducts are insulated,
so it should be somewhere near the furnace output
temperature.

Looks like I'm getting 60F rise across the furnace.
That's near the max claimed in the spec.

Another thing is that I don't heat part of the house.
Three registers are closed. *Last time I did the experiment,
heating the whole house cost me almost 50% more in gas.

So,
I don't want to heat the whole house.
I need the better air filters.
Should I worry about overheating the furnace?
Is there anything simple I can to about it?
Like turn up the blower speed?

I do have an electronic filter that's designed to replace
the 1" paper filter. *I'd have to cut it down to fit.
Looks like it has about as much material as the original
fiberglass filter, so should have lower pressure drop.

Is that a viable alternative?
It's not clear how they compare at removing pollen.
It's hard to decide based on the vague marketing hype.

Thanks mike.


Use the filter the manufacturer recommended for your furnace. Spray it
with WD40 before installing, preferably a day before installing so the
volatile parts can evaporate. What will be left on the filter is a
sticky wax that greatly improve the ability of the filter to do its
job. Works unbelievably great. Alternatively you can buy a can of
filter coat, much more expensive and in my opinion doesn't work as
well.

Jimmie
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Default Furnace Air Filter Questions

mike wrote:
On 2/10/2012 11:31 AM, radiotom wrote:
Tony Hwang;2799305 Wrote:
mike wrote:-
My 95.5% Gas furnace came with a fiberglass air filter
with little restriction and no filtering action.

I substituted a Filtrete allergy reduction filter and went
about my business. Been running that way for 2 years.

In my filter search today, I found a gauge that tells you when
to change the filter by monitoring negative pressure
near the blower inlet. It says it can be calibrated
for 0-.4"WC.

I did some measurements on my system.
With the filter removed and the filter door open,
I measured -0.1"WC.
I measured with my Filtrete installed and with a
lesser MERV9, I think, filter then a washable
permanent electrostatic filter.
All measured -.55"WC.
With the filter access door closed, it goes up
to -0.6"WC.
That's outside the calibration range of the filter
monitor gauge, so it got me thinking.
I don't have a fiberglass filter to compare.

I also measured some temperatures.
With indoor temperature at 65F, the air coming out
of the closest vent stabilizes at 119F. It's about
12' from the furnace and the ducts are insulated,
so it should be somewhere near the furnace output
temperature.

Looks like I'm getting 60F rise across the furnace.
That's near the max claimed in the spec.

Another thing is that I don't heat part of the house.
Three registers are closed. Last time I did the experiment,
heating the whole house cost me almost 50% more in gas.

So,
I don't want to heat the whole house.
I need the better air filters.
Should I worry about overheating the furnace?
Is there anything simple I can to about it?
Like turn up the blower speed?

I do have an electronic filter that's designed to replace
the 1" paper filter. I'd have to cut it down to fit.
Looks like it has about as much material as the original
fiberglass filter, so should have lower pressure drop.

Is that a viable alternative?
It's not clear how they compare at removing pollen.
It's hard to decide based on the vague marketing hype.

Thanks mike.-
Hi,
I think you should do the measurement with all the registers open.
I use EAC only on our furnace. I clean the elements twice a year.


I can't really comment on your questions but you've got me thinking. I
too use Filtrete filters. I think maybe I should get one of those
gauges. Never even occurred to me. Wonder how much I'm wasting.

Those gauges can be useful for people who don't have a calendar and a pencil.
You can do the same measurement with some plastic tubing and water.
Google "manometer". Once you figure out how long a filter lasts
in your situation, just mark the calendar to change it.

While there's no question that moving air costs money and friction
adds to that, I've never seen any apples-to apples numbers that
support how much.

In any given situation, you have the ratio of the BTU's in the
gas supply to the BTU's that end up as heat in the dwelling.
For small changes in back pressure, I don't expect that ratio
to change much. The blower may use more power...I'd like to hear
some real numbers on that. Next time I have the cabinet open, I'm gonna
stick a current meter on the blower power and try it with and without
the air filter installed. Just gotta figure out how to read the meter
through the metal door.


The blower being restricted will start to use less power. It will tend to
speed up because the air just tumbles. I was wondering if my furnace had a
air speed sensor, which could detect flow, being a variable rate fan.

Greg


The vendors for low restriction filters and gauges use all sorts
of marketing speak and misdirection to induce you to buy their stuff.
They throw the apples and oranges into the mix and claim it's proof.

Here's what I think I know about filters. I'm sure people won't
be shy about correcting my misconceptions.

For a simple, passive filter, the size of the particles that can be
trapped is determined by the pore size of the filter. As the pores
get smaller, you can put more pores in the same space. But the filter
material has some minimum fiber dimension. At some point, you're
down to one fiber width between pores and you can't fit any more in.
And there are significant friction effects as the pores get smaller.

Pressure goes up for smaller pores, so you have to have more surface area.
Pleating is the first thing to do, but even that has it's limits.
You can make the filter as large as will fit in the cabinet, but
that has limits too. Smaller pores plug up faster.

Making the media thicker doesn't help. To reduce pressure, you'd
have to make the pores even bigger and not be able to trap the small stuff.
Thicker filters can accommodate bigger pleats of the thin media
resulting in larger surface area.

The solution to this diminishing returns situation is to use
technology that traps particles in a way unrelated to their size.
Electronic filters use an electric field to force particles to displace
out of the air stream and collect on a plate.
The electric field has little effect on the air stream, so pressure
rise is minimal.
This also has tradeoffs, so you usually end up with a passive filter
for the big stuff and the electric field for the stuff that gets thru.

Now, back to the question that I started in another thread.
There is a technology that uses an electric field that does not require
external power.
I thought the field was created by the triboelectric effect of air
passing through insulating media. The only response to that was
the rude statement that, "my education was faulty," but no real
useful help was provided.
The other theory presented was that the electric field was permanently installed
at the time of manufacture. That was debunked.

I've looked at my sample and can't find any evidence of an electric field.
I stuck one on my HRV, but can't tell if it's better than an ordinary filter.
That led me to another quest for a particle counter to measure
actual results.
People who sell passive electrostatic filters say they're terrific.
Technical people seem to think they're snake oil.

Jury is still out on that one.

Are we having fun yet?

mike

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On 2/11/2012 10:44 AM, gregz wrote:
wrote:



The blower being restricted will start to use less power. It will tend to
speed up because the air just tumbles. I was wondering if my furnace had a
air speed sensor, which could detect flow, being a variable rate fan.

Greg


You're absolutely right.
I had it in my head that the power went up, then headed down
as the airfoil stalled.
Not so.
Just measured an axial fan and a squirrel cage blower.
Both powers headed down immediately with restriction.
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I'm guessing when you say it's been running like that for two years that you've replaced the filter since then? I use the Filtrete allergen filters because I have dust allergies. If you close off the registers in certain rooms, you may want to think about getting baffles to close off the vent runs to make it even more efficient.
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