Hi Jim~

It's not that important…It will just sweat more without it…As long as it drips into the pan (and from your description of ends of coil it should) and then the drain is clear to drain it…Just slightly more condensate production is all….

Steve~

Just leave it alone 

Follow-up question:

The air handler in question is open on all sides to the ambient air in the cabin. The intake grill is fairly well closed off so that air is routed through it by way of a wooden frame that fits around the grill and is faced with trim ply. My question is whether or not it would be beneficial to go on the backside of the unit, and build some sort of enclosure so that the only air that goes to the cooling fins of the grill would come from the front. As it is, the black mastic still seems to be covering any gaps around the back, so I don't think ambient air is getting from the back of the unit to the cooling fins, but can't be sure without pulling it out of the cabinet. It would be fairly easy to fabricate a more air-tight enclosure with insulation board…would there be any benefit to doing so?

I like that answer.

If you ever open an East coast branch, I want to be on your customer list!