Am. Std. 4TEE3F - Unsafe Condition?

[ferd1942]

This is a "40B" fan coil unit installed horizontally with outlet roughly 12"W x 24"H. About 12" of the outlet height is blanked off to connect to existing ductwork (using Thermopan, no less).

About 3" of the inlet width is also blanked off.

As a great friend used to say "I don't make this stuff up".

What kind of problems can be expected if this 1-1/2 year old installation is left as is?

Many thanks!

PS: DIP switches are set for 1,200 CFM cooling airflow with a 2-1/2 ton heat pump.

[motoguy128]

Try setting the dip switches correctly to 2.5 tons (1000CFM) and then measure the static pressure. You might even run it a little lower, around 350CFM per ton with ductwork restriction. Then check the charge after you set the airflow.

The biggest problem you could run into is uneven flow across the coil. It should have a transition for that reason. IF airflow is lower across part of the coil, that section could ice up. Althohg since it's a 3 ton air handler, you have some margin for error.

[ferd1942]

Thank you.

"uneven airflow across the coil" prompts another question: Could it be pulling moisture off the coil and discharging it into the supply duct? I ask because there's what appears to be mold (black) and mineral deposits (white) on the interior duct surfaces adjacent to the unit outlet connection.

I'd been operating under the assumption the discolorations predated the install (this was a replacement of 16 year old equipment, retaining the old duct system "as is"). Is there a chance they're new, as a result of the install? The duct surfaces were dry to the touch when checked recently.

Again, thanks.