DE HUMIDFIER for aft cabin ?

[Al B]

Boat is 30 ft ,
2 cabin , main area , aft cabin
Aft cabin is Considered bedroom ,
Has two small windows , port & starboard , limited circulation
Aft cabin is a waste of valuable space , used for storage
9.5 wide , apx 5 ft wide , can not stand , crawling on knees too get around
a/c unit for boat is located within this aft cabin enclosed in a cabinet mounted too ceiling. Water run off dumps into bilge
Manufacturer never installed a a/c vent into aft cabin , only one main vent that blows into main cabin , Main cabin is very cold , 10,000 btu is too large for area cooled , , I guess they figured cool air would work into aft cabin but not the case , Gets so cold most time have too raise thermostat

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A/C unit is 1997 , 10,000 BTU , 30 amp , old type Freon
I don't let it run when were not there ,
Until recently I used a way too big home dehumidifier , Sat in bathroom ,
Door open , run off drains into shower sump pump
When we open cabin door that funky mildew smell hits you , heat from dehumidifier feels like its 100
Other day I am in aft cabin, figuring will wipe down everything hoping too rid that mildew smell , and everything felt moist ,
I know its the best too run a/c all the time , but until I purchase a new unit I am babying this older AIIIRRRR Marine unit ,
I am planning installing a vent into aft cabin but until this is done I need too correct the moisture aft cabin ,
Main cabin does not feel moist only aft cabin ,
What would you knowledge folks recommend ?
two units ? one for aft one for main cabin

[Sailmonkey]

I’m having a little problem following your question.

But if what you’re asking is “do I need a second dehumidifier on a 30’ boat?” My answer is no.

We use a small compressor based dehumidifier on our 32’ boat. No smells or moisture present.

If you’ve got a desiccant dehumidifier, ditch it and get a compressor unit.

Maybe try a fan pointing into the aft cabin from the main cabin.

If your aft cabin stays damp and smelly, you’ve got leaks or standing water that need to be fixed.

[Dsanduril]

It sounds like the condensate from the AC drains to the bilge in the aft cabin. I would suspect this is the root of the problem (even if you have a decent bilge pump setup). If the AC unit is mounted high enough (sounds like it might be) find a way to drain the condensate overboard without letting it into the boat. If you can’t get it overboard by gravity, install a pump and small, sealed sump on the end of the condensate drain line so the water doesn’t meander through the bilge.

And put a vent in the aft cabin. If the AC unit is there, and the outlet is in the main cabin is there a duct between the two? Or is it a split system? Ducted, just cut a hole and put in a damper. Split, run a fan to circulate air into the aft cabin.