On Tue, 12 Feb 2019 14:14:45 GMT, (Scott Lurndal)
wrote:

Clare Snyder writes:
On Mon, 11 Feb 2019 16:35:25 -0500, Tekkie®
wrote:

Clare Snyder posted for all of us...



On Wed, 6 Feb 2019 14:02:53 -0500, Tekkie® wrote:

Frank posted for all of us...



On 2/4/2019 7:23 PM, Ed Pawlowski wrote:
For the first time in 53 years of owning homes, my new house has a
furnace and uses filters.* It takes a 1" filter.

I see prices can vary considerably but is a MERV 8 and MERV 8 regardless
of the brand?* Should I use MERV 8 or MERV 11?* We have no pets.

I see filters with MERV 11 rating from $9.95 ($7.45ea by a dozen) to
$14.50. Any real difference if they have the same rating?

Discount filters seems cheapest.

I use air filters and had never heard the term MERV so looked up your
question:

https://airexpertsnj.com/knowledge/e...erv-11-filters

Prompted me to look at the filters I'm using and now see that they are
MERV 11. Don't know about price difference but sometimes filter may
collapse somewhat and more expensive filter might be sturdier.

I am no filter expert but IIRC if the MERV number is increased then possibly
the blower motor can overload. Research the info on your system to determine
the suitability.
Restricting airflow does NOT overload a blower motor. Restricted
filters restrict the amount of air moved REDUCING load on the blower
motor. Youknew that and forgot - right "tekkie"?

If I am wrong then teach me. I have always been willing to listen.
Plug your vacuum hose and listen to the pitch of the motor. It speeds
up. Power is consumed by moving air. Block the filter and you move
less air, therefore using less power. It's not like a positive
displacement pump like a compressoe - where you WOULD be correct.

One problem with blocked air filters and plugged vacuums (without a
bypass motor) is overheating because less air moves across the motor
to cool it. It overheats not from overloading but undercooling.

I hope that "clare"ifies things for you.

Don't take my word for it.
look at
https://www.cagi.org/news/HowInletCo...pressors. pdf
look at the intake pressure section on page 3 - just after figure 2.

I thought we were discussing furnace filters. What does an
air compressor have to do with it?

The facts are that the air handler in the furnace needs to work _harder_
when the filter gets dirty. Working _harder_ requires more current.
No - you are wrong. The squirrel cage blower of a furnace IS an "air
compressor" - and not a positive displacement one. Power consumption
is rependant and the mass of air moved, and a furnace blower draws
LESS current with a blocked filter. It draws more current per cu ft
(or lb) of air moved, but the decrease in air moved is much larger
than the "efficiency" in watts per cu ft, so the blower draws less
current.
The effect is less than in a "turbine" type blower - but it is VERY
real.


here are some actual measurements gleaned from other sources:

Dirty filters drop the amps - Less airflow equals less amperage.
Here ya go info on a squirrel cage
Low speed
filter quality amps
none n/a 7.4
panel clean 7.05
pleated clean 6.75
pleated dirty 5.4

High speed
none - n/a 13.10
panel - clean 12.92
pleat - clean 12.77
pleat - a bit dirty 12.70
pleat - dirty 12.30
pleat ~90%; blocked 12.20

Notice that on low speed with no filter the blower drew 7.4 amps, and
with a dirty pleated filter that dropped to 5.4 - a drop of 2 amps -
or 37%

On high speed the fan with no filter drew 13.1 amps and with a 90%
blocked filter that dropped to 12.2 - a drop of .9 amps - 0r about
6.9%

At high speed the percentage drop in air flow was less than at low
speed - but still significant - and more significant - the current
DROPPED in both cases with restricted filters.