I have a Carrier AC Air Handler Model #FC4DNF060. The filter access panel is blocked as shown in the photo (at bottom of unit). Has anyone had a similar situation or advice on how I might be able to access in order to change the filter? Thank you.
Carrier AC Air Handler Model #FC4DNF060 Filter Access Panel
air-filtercarrierhvac
Related Solutions
There is a set of connections in the air handler that usually includes the "C" terminal, and it should be labelled (though it may be hard to read depending on the location of the control board and/or wiring/etc in the way).
One way to tell for sure is that while the furnace is not running, using a multi-meter you can measure between the "C" and "R" (or Rh or Rc terminals) and you should see 24VAC. R (or Rh and Rc) will already be going to the thermostat.
As an example, on your furnace, from the manual:
The colors may match, but don't count on it. The sure-fire way is to check using a multi-meter as I said above.
What you’re describing sounds like a combination of negative pressure in the compartment that the drain pan connected to and an incorrectly sized p-trap on the condensate drain.
The depth of the t-prap has to be greater than the negative pressure in inches of water column of the compartment where the drain is connected to. A t-prap with insufficient depth, will prevent the condensate from overcoming the negative pressure which prevents draining until the fan stops.
Further information on sizing of p-traps for condensate can be found in this pdf article: Condensate Traps by Ronald F. Brusha.
Best Answer
Are you sure there is a filter there? Is there a return-air vent somewhere else in the house/office? The situation you show is common, but typically the filter has been relocated somewhere else in the return-air ductwork system.