Master SR Moisture Issue

[JLR]

Okay - so this is on the other boat but I look to the experts here for some help.When using the air conditioning in the master with the door closed on a hot day, there is so much moisture/humidity in the room that water actually forms on the mirrors and hard surfaces. Has anybody experienced this or know had to remedy this situation? I can buy a small dehumidifier but that should not be necessary. Thanks.

Does this sound like a drain pan clog issue, a dirty filter issue or what. In a nutshell, the air is being cooled but no moisture is being removed. In fact, it almost appears as if it is being created.

 

[Reefgeorge]

If you have access to a humidity meter, does the RH change from before AC to after AC with condensation? You may just be lowering the dewpoint of a very humid room abd making fog or you may be producing moisture. Do you have access to the drain hose to see if the evap coil can drain its condensate?

Is it possible that some of the duct work may be leaking and bringing in outside moist air.


George

 

[Pascal]

It doesn’t sound to me like clogged condensate drains would cause this. I ve had clogs many time as it seems that most boat builders live in a fantasy world where water flows uphill...

What size is the air con? I have heard that units that are too large cycle on and off too quickly to dehumidify the trim.

Check the location of the air handler and see if it could be pulling warm moist bilge air. Some builders don’t seal the air handler spac so instead of pulling return air from the room it pulls warm humid air from the bilges

 

[Reefgeorge]

My wife and I have bad allergies so a quality AC unit is important in home, vehicles and boat. When my boat was first built I modified the AC system as follows:

Fabricated dedicated aluminum returns so that all return air to the unit comes from the room and not the bilge or ER (as Pascal pointed out).

Installed a good filtration mesh at that return grill point.

Put a sensor in the cabin space instead in front of the evaporator and changed the unit to intermittent fan

Lowered the evap fan motor low speed setting (not too much or the coil will freeze).

Sealed all return ducts very well, especially the ones that route outside the conditioned space.

This was a s ton of work but the result is really clean air and a conditioned space with RH that is at least 15% lower than the factory install. We routinely get ubder 40% RH in the peak of the summer when the system runs a lot. When I go on other boats, they are freezing, damp and smell like diesel oil/fumes. Ours has not of that. We also never get any mold in the furniture, carpet, towels, etc - all problems in cold and damp boats as I have owned in the past.

George

 

[JLR]

I checked the drain line and it did not appear clogged. However, the inside of the drain pan appears to have some sort of built in foam all around, even over the drain line. So, not sure how that foam impedes draining. I also took a hard look at the return. The return is located inside a closet with another return vent on the outside of the closet so that it can suck in air from the master. However, it appears to me that the inside of the closet( the floor to be precise) does permit some air to be sucked in from under the master bed and perhaps even the bilge. We drain the hot water heater in the winter and some small amount of water does remain under the master bed in a semi sealed area. So, I guess the question is whether I need to buy a manometer to see if there is too much pressure in the master with the door shut and whether this might be creating the excessive humidity problem.