HVAC guys, advice on filters please chime in!

[CDX825]

see you even confused me

So you are saying its ok to run a 1" filter.. wouldnt that be vastly more restrictive than a 4"? How is that ok?

Most furnaces run a 1 inch filter without issue. Yes the 4 inch will have less restriction but Joe homeowner doesn't care about that. The selling point of the 4 inch filter has always been longer service life. They say that you can get 6 months to a year out of the 4 inch filter. Obviously under optimum conditions. Where as the 1 inch filter if you get 3 months out of it your doing good. But a lot of people don't want to pay the money for the 4 inch filter so carrier gave them the option of being able to use a 1 inch.

 

[KJSmith]

are too restrictive which puts necessary strain on the fan.

How will it put more "strain" on the fan?

 

[KJSmith]

If that was my setup, I would put a 1" poly in front as a pre filter for the 4".

 

[PWMDMD]

How will it put more "strain" on the fan?

It creates negative pressure and the fan motor must work against that suction to move air. Air handlers are designed to move a specific volume of air per unit time. If the ductwork was designed for a 4" then that means they should have taken static pressure readings to determine proper airflow with a 4" in place. If you change it to 1" all of that will change.

 

[Zee09]

Most furnaces run a 1 inch filter without issue. Yes the 4 inch will have less restriction but Joe homeowner doesn't care about that. The selling point of the 4 inch filter has always been longer service life. They say that you can get 6 months to a year out of the 4 inch filter. Obviously under optimum conditions. Where as the 1 inch filter if you get 3 months out of it your doing good. But a lot of people don't want to pay the money for the 4 inch filter so carrier gave them the option of being able to use a 1 inch.

Right...Lennox have a 5" but have a slot to run one 1" filter instead.
The 5" last a year.
16x25 x5 or 16x25x1

 

[KJSmith]

It creates negative pressure and the fan motor must work against that suction to move air. Air handlers are designed to move a specific volume of air per unit time. If the ductwork was designed for a 4" then that means they should have taken static pressure readings to determine proper airflow with a 4" in place. If you change it to 1" all of that will change.

Lots of people get this wrong...so have you.

Restricting the airflow decreases the amount of work the fan motor can do.
Amperage is the measurement of work done.

Restrict the airflow and amperage will go down.
Remove all filters...or the blower door and amperage will shoot up.

Same happens with an electric water pump (except if you restrict suction you cavitate the pump) restrict the head, pump does less work, amps go down.