I've been lurking here the last couple of months to learn more in preparation for the inevitable failure of my (then) limping system. I'm not an HVAC-savvy person, just a customer.
My old system finally failed so I just had a new one installed. The condenser, furnace and coils were replaced along with one of the line sets.
There's a few things that concern me that I'd like to follow up with the installer but was curious into seeing what some of you experts thought.
First, the new furnace/coil unit was roughly 8 inches taller than my old unit and the tech was not able to wrestle it into my AC closet without removing the filter base. He assured me that a filter grille would be an adequate substitute for this install. The area under the furnace is unfinished space and the tech sealed it with some kind of poly foam, caulked the furnace base and any holes for the line set or wires. The grill was installed and caulked. I'm attaching some photos. The water damage seen underneath there is years old and happened when the old unit had a clogged drain line. My main concern is that the return air going back into the furnace isn't as clean as it would be using a base-mounted filter.
Another concern is also related to the filter grille. It uses a 12x24 filter. My old system was 2.5 tons and used a 16x25 filter. The new unit is a 3 ton system. Is this filter too small for this application?
I'm also experiencing a weird harmonic hum that sounds like its coming from the coil. It only happens when the thermostat is set to cool. The fan setting can be either "On" or "Auto". Even when the compressor is off outside, the harmonic hum is still there. I noticed this when the tech was working on the outside unit and had the condenser safety disconnect pulled. The inside unit was on and humming noticeably even with the compressor off. The service company has contacted the manufacturer and will follow up but I was wondering if anyone here has seen this before.
Again, I'm not very handy when it comes to these sorts of things so please forgive any descriptive errors. If more photos or information is needed, I can update this post. I did read the site rules but if this post is inappropriate in any way, please let me know.