Goodman Furnaces and air filters

[Lew]

I had the 6 year old Goodman serviced this winter and weas told to only use the cheap spun glass air filters and also to install them on the diagonal in the cold air return box. These filters compared to the 3M ones I had ben using are useless. Anyone know why I should do this?

[mtnman1100]

Well I'm new to the HVAC trade, but what the installer might have been getting at is if you put more resrticting filters on the system the way it is set will cause less air to flow over the evap coil. Which would not allow the superheat to build to the mfg's recommendation (flood the coil). A possible solution with a more restricting filter would be to increase the blower fan speed to put more air over the evap coil. You should have 400cfm over the evap coil per ton. This should have been tested and set at start up.
Have you tried calling the installer's service manager? He might be able to explain.

[gear junkie]

Well I'm new to the HVAC trade, but what the installer might have been getting at is if you put more resrticting filters on the system the way it is set will cause less air to flow over the evap coil. Which would not allow the superheat to build to the mfg's recommendation (flood the coil). A possible solution with a more restricting filter would be to increase the blower fan speed to put more air over the evap coil. You should have 400cfm over the evap coil per ton. This should have been tested and set at start up.
Have you tried calling the installer's service manager? He might be able to explain.
In laymans terms; better filters restrict air causing your indoor unit (evaporator) to freeze up unless the unit was designed for it.

[OkieBill]

So that service tech can come out and clean your evap coil this summer when you freeze up because that rock catcher filter is worthless :eek:

400 CFM is a rule of thumb that should be forgotten (it is not good for anything)... Like they say 500sqft per ton...Always use manufactures specifications:)

If you have not had any problems with your system (Evaporator Freezing up or the furnace going out on limit due to lack of airflow) I would keep using the good filters.

[gear junkie]

So that service tech can come out and clean your evap coil this summer when you freeze up because that rock catcher filter is worthless :eek:


Yep, even freeze up new units. Especially when a manual j and d isn't done on changeout and you're working with old duct system. I think than an electronic air cleaner coupled with the cheap filters that are changed once a month are more effective that a super hepa filter.

[OkieBill]

I have never been a fan of the electronic air cleaners... The electrostatic plates while being good for airflow are really not that good at filtration after the first few days of operation.

That being said I have not seen a residential system that could handle a true HEPA filter (99.7% of all particles down to .3 micron) The products that are being marketed as HEPA in Vacuum cleaners and Furnace filters use the term very liberally.

I have yet to run into a residential system that could not handle a good 2020 filter though I have had to bump up the blower speed on a few older systems.

:)