AC Issues

[Osprey69]

Even though our BTUs were adequate, ducting was not. So if you increase BTUs have look at the ducting capacity. I cut into the over-air conditioned master ducting below the salon and put an active fan driven vent in the floor to suck it up. Made a world of difference.

 

[PhilPB]

Even though our BTUs were adequate, ducting was not. So if you increase BTUs have look at the ducting capacity. I cut into the over-air conditioned master ducting below the salon and put an active fan driven vent in the floor to suck it up. Made a world of difference.

Adding additional ductwork would be rather easy on our boat. When I rebuilt the salon I took the bottom curve out of the lower 24" wall, framed and installed a teak wall. I have room for ductwork behind that. When I replaced the plumbing I ran the main line from the freshwater tanks in that space too,resulting in the removal of all water lines out of the hot engine room.

 

[PhilPB]

Today I was at the boat taking measurements to see about adding an additional duct to the current system. While there I had the ac on and decided to cover the vent in the stateroom as well as close the solar vent in the galley to see if there would be an improvement in the salon, and there was. Unfortunately, today's temperature was only 89°f and when I thought I had a problem with cooling it was 93-95°f, so the data isn't optimal.

I figure even if I install a larger 16k btu unit to replace the current 12k btu system I would also add an additional vent to the other end of the salon anyways so there is nothing to lose adding the vent and probably a duct fan booster to the current configuration. I think I will add the ducting, vent and booster to see if there is any improvement.

Does anyone else think this plan sounds reasonable?

 

[PhilPB]

I straightened the ducts and even removed about 4 feet of extra slacked flexible hose. Still the system doesn't cool the cabin well enough. The humidity does drop to 40% but on a 90°f day, the temp won't go below 87°f insid3. Only options left are either wait for cooler weather or bite the bullet and install another larger system

 

[Action]

Thanks for posting.

The system is either undersized or not functioning to the original design.
Since you have owned the boat, has the AC worked to an acceptable level?

Given that the system is 40 years old and may have been repaired at least once in the past, it might be the time to bite the bullet. The AC technology has advanced a lot in the last 4 decades. At least in land based systems and automotive systems. I would assume marine systems as well.

If replacing, know that sizing becomes critial. Too big is nearly as bad as too small.

 

[PhilPB]

Thanks for posting.

The system is either undersized or not functioning to the original design.
Since you have owned the boat, has the AC worked to an acceptable level?

Given that the system is 40 years old and may have been repaired at least once in the past, it might be the time to bite the bullet. The AC technology has advanced a lot in the last 4 decades. At least in land based systems and automotive systems. I would assume marine systems as well.

If replacing, know that sizing becomes critial. Too big is nearly as bad as too small.

After researching the compressor, it appears to be 12k btu and is 10 years old (mfg 06/12/2013). The wall control appears to be original.

On a 90-98°f day, the system, in its entirety is bad. If I restrict the airflow to the salon, the vee-berth, with the door closed and with its 4" vent, gets very cool. Conversely, if I close off the vee-berth ventilation, the salon still doesn't get very cool.

The ac has only worked well in cooler weather (mid to high 70's at night). As another experiment , I left the unit on when I left the boat and returned at 10am the following day and the temp was 75°f inside and humidity was 37%. A bit after noon, and after opening the sliding door a couple times to enter or exit during that time, the temp climbed to 84° and continued to heat up rather quickly as the day went on.