Installed Fantastic fan in kitchen and guess what?

[Eaglehead]

Dave you were right, JD confirmed that is the cold air return. I'll leave the cardboard for now as it is an advantage in hot weather to not draw air from the storage area. Dave, check the partition that blocks off where the plumbing and the furnace is and at least on my camper you will find that it is not sealed off, it only goes up to the frame for the floor above it and not to the floor itself.

[Aeromech]

Turned on the fan and felt air coming from under the butler cabinet, that's what I call it , so I pulled out the drawers and found a HUGE opening to the area where all the plumbing and duct work is located which would defeat the purpose of running the fan to remove heat build up as it would allow it to draw air from outside the boundaries of the living space. Here a couple pics of before and after. I just used cardboard to block off the opening which is about 95% effective.Attachment 781Attachment 782

It is for heater return. We have the same on our Solitude. If you turn on ANY vent fan it has to get what's called "make up" air from outside to make up for what's going out the vent. This is usually drawn in through any cracks around doors and windows etc. and is either hot or cold unfiltered air. The pass through is climate controlled to prevent freezing water lines in winter. It also stay relatively cooler in the summer underneath. I would rather have it this way as it has a chance to "buffer" the incoming make up air a little so the interior doesn't heat up quite as fast when you turn a vent on.

[mageorge]

I might as well pull my drawers out in a couple days and see what's there. I just repaired one drawer because the bottom plywood wasn't attached with staples on the back - so it bowed with the goods inside and fell out. Gorilla Glue and clamps to the rescue!