A/C vs Humidity

[Hensch42]

2024 R27 OBLE - Wabasto unit Have docked @ several marinas withe same result.
Running the A/C while cooling, the humidity is brought down as expected, but during off cycles, the fans continues to run and humidity increases to around 80% . Then after some time, the a/c activates and humidity goes down. Upon awakening, the humidity readings are in the 80’s.. used the Humidity setting & didn’t notice much of an improvement, maybe didn’t run it long enough. At least I have not noticed any accumulation of moisture. I keep a dehumidifier on board while at home port or in storage.
Just wondering if any one else has had this experience and how they’ve handled it it..

 

[Rode Trip]

I don't understand the problem. That's what air conditioners do, they remove heat and humidity. All that water flowing out of the condensate drain from the pan of your air conditioner is humidity being removed from the air and drained (hopefully overboard, but often into the bilge). When the compressor is not running and the coils are not cold, no humidity is being removed. If you need more humidity removed, set the temperature lower and the compressor will run longer.

 

[Hensch42]

Sure thank you for responding, It’s not that’s what they do, it’s the introduction of so much humidity while in between cycles. The condensate runs into the sump pump an the humidity is lowered as expected, but I believe that because the fans are always running, the air blowing thru the a-coil as the coil warms up, is what’s introducing the humidity back into the cabin. The level in the cabin reads in the 80+%, while outside is in the 60’s. Maybe if fan would stop in between cycles, that would make a big difference. Setting the temp lower just makes the cabin so much colder until it cycles off and then the problem. Hope all this makes sense.

 

[Rauguthj]

We have experienced similar spikes in humidity, most notable in the morning in the vberth area (R31 CB). We added small dehumidifiers in the vberth ( https://www.amazon.com/dp/B0C9ZV4GJ5?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_2&th=1(and head, and a larger dehumidifier (https://www.amazon.com/dp/B0BVZ62Y3M?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1). The large unit fits in the helm area, and has a drain hose that we use when away from the boat.

Fans to circulate air help as well. We installed hardwired Caframo fans in both vberth and salon. We also use a clip on Caframo fans above the vberth door to push/pull air in or out.

Between the dehumidifiers and fans humidity in the boat stays around 40-50%. We still see fluctuations but we are overall happy with our solution.

 

[Hensch42]

Sure appreciate your info.. the smaller unit sure is a winner, should have thought of that, rather than trying to solve an A/C problem which may not have the ability to turn off fans on off cycles.. I have fans & I will certainly consider using them. I already use a humidifier with drain hose when boat in not in use, which maintains the humidity 45 to 50.
Thx for sharing..
Henry & Brenda

 

[Rode Trip]

Yea, that's a strange one. I don't understand how the humidity in the boat can rise above the humidity outside.

 

[Rednuke1]

I don't understand the problem. That's what air conditioners do, they remove heat and humidity. All that water flowing out of the condensate drain from the pan of your air conditioner is humidity being removed from the air and drained (hopefully overboard, but often into the bilge). When the compressor is not running and the coils are not cold, no humidity is being removed. If you need more humidity removed, set the temperature lower and the compressor will run longer

There should be a setting on your AC Control board which allows you to set the fan so that it only runs when the compressor does. When the compressor shuts off, it can ice over, or cover itself in condensation. With the fan still running over the coils, it will blow that condensation in the form of humidity into the duct system and then throughout the boat. We have ours set to shut off when the compressor isn’t running. Problem solved.

 

[Rednuke1]

You should have a setting on your AC control panel that will allow you to set the fan so that it only runs when the compressor unit does, and shuts off when the compressor is not operating instead of the fan running continuously. When the compressor shuts down after reaching the temperature setting, the coils can become covered in ice, or a lot of condensation. If the fan is running continuously, it will blow that condensation in the form of very humid air into the ductwork, and then throughout the boat. We set our fan to run only when the compressor does, and shuts off when the compressor does. Problem solved

 

[Hensch42]

We have a Webasto A/C unit.. I have scanned thru the manual looking for the ability to set fan so it does not run on off cycles.. on each mode, there is a mention “ if set temperature is higher than room temperature, then only the fan will run”. This to me tells me that fan runs regardless of mode setting. The DEHUMIDIFY setting is the closest since it runs in short cycles, 6 min ON CYCLE and 4 min OFF CYCLE & fan runs in low speed. Unless I’m missing something, I don’t have the choice of fan running only when compressor does. Sure appreciative of all your ideas & responses..

 

[Rode Trip]

The more I think about it, there still has to be something else wrong. A little bit of left over condensation on the coils isn't going to raise the humidity of the boat significantly. I think the only way that could be happening is if the coils are icing over. That can be from a low refrigerant level, blocked air intake (sometimes clogged filter), or blocked air ducts. I would get in there and take a look at the coils after the unit has cooled down and see if it's icing.

 

[Hensch42]

Good point !! I kind of agree with you, they are pretty significant amount of humidity level. Right now I have the boat on trailer, it needs to be on the water to run A/C.. we are away visiting grand kids, so when I return I will put it on my slip and have someone check it out.. the unit is underneath the helm seat, this issue will give me the opportunity to check the filters as well.. I only have 42 hrs on this vessel, but anything can happen. This boat has been ridden with warranty issues, not very serious ones, but workmanship items. Ex. The propane sensor, located bell the stove, had the barcode sticker still on the sensor blocking the sensor input, causing an annoying periodic alarm..