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