On Friday, March 3, 2017 at 10:35:06 AM UTC-6, wrote:
On Fri, 3 Mar 2017 07:04:55 -0800 (PST), Uncle Monster wrote:

On Friday, March 3, 2017 at 7:17:16 AM UTC-6, Cental VA wrote:
I have what is a simple question I hope. For a horizontally installed heat pump system what is the proper orientation of the A-coil () relative to the airflow?

1. supply return
2. supply return

My new system is a 2., and I am wondering if this could have something to do with the coil not drying properly between cycles when in AC causing musty smell.

Thanks for any input.

The A-coil should be situated with the top of the A pointing up because the condensation drips down the sides to the drip pan. The direction of air flow really doesn't matter. What can often happen is crud can build up in the drip pan surrounding the sides of the A-coil and cause the water to drip into the air handler/furnace. You can get coil cleaner from Home Depot, Lowe's, Amazon and even Walmart. Sometime the coil is so dirty that it must be removed from the housing to clean it. Depends or your setup. ?(?)?

http://www.homedepot.com/p/Web-AC-Fl...WACF/202319836

https://www.lowes.com/pd/WEB-Cleans-...ls/1000024695#

https://www.amazon.com/Evaporator-Co...i l%20Cleaner

https://www.walmart.com/ip/Aerosol-E...Rinse/39088018

https://www.youtube.com/results?sear...clean+ac+coils

[8~{} Uncle Dirty Monster

On an air handler designed to be mounted horizontally the A coil is
really a coil pointing in the direction of the air flow. I would
suggest that the fan is not running long enough after the compressor
turns off. He may have the wrong thermostat or it may be installed or
adjusted wrong.
RTFM

Oh hell, I forgot about those because most of the horizontal flow systems I worked on were commercial systems with a flat evap coil standing upright. Come to think of it some were slanted but it was rare for me to see an A-coil on its side. He still needs to clean it. ヽ(ヅ)ノ

[8~{} Uncle Slanted Monster