Air Conditioner Expectations

J

John Powell

New Member
Feb 15, 2022
14
Boat Info
1993 330 Sundancer.
Engines
(2) 454 Inboards
5kw Quicksilver Generator
Hello,
I just bought a 1993 330 Sundancer with a 15k Dometic. Outside temp was 88 in a humid coastal environment (Texas) & boat is Not in the shade.

-During the day, Tstat went down to 77. It ran continuously but was dry and comfortable.
-At night, Tstat read 68. Cold and very comfortable. Not sure of outside temp at night.

Is that normal? Are you all with 1 AC unit or the same set up getting better results?

Just wondering how it will be on hotter days...

Thank you,
 
John Powell said:
Hello,
I just bought a 1993 330 Sundancer with a 15k Dometic. Outside temp was 88 in a humid coastal environment (Texas) & boat is Not in the shade.

-During the day, Tstat went down to 77. It ran continuously but was dry and comfortable.
-At night, Tstat read 68. Cold and very comfortable. Not sure of outside temp at night.

Is that normal? Are you all with 1 AC unit or the same set up getting better results?

Just wondering how it will be on hotter days...

Thank you,
Click to expand...

that seems reasonable especially for the age. You might also try a standalone thermometer to see how accurate the AC is reading, they’re not always the best.

it also depends a bit on the water temp I believe, though someone might have to confirm that. I know it does for heating mode but maybe not for cooling
 
As I tell my wife on the boat, the number reading (either set point or temperature) doesn't matter. Just make it comfortable for you.

Boats are not thermally insulated like our houses are. If the T-stat is on an exterior wall down below, there is only a small air gap then the hull between it and the outside. It sounds as if your system is functioning properly. If you want to "check" the readings, buy a digital thermometer that you can place in the cabin. But at the end of the day your answer will be whether or not your feel comfortable.

Jaybeaux
 
Yes, water temp does have something to do with operation. Older units are just not that efficient. We have replaced our with Webasto units. Yesterday, temps high 80s pretty humid, I turned ours on and in 15 minutes it was satisfied at 71 degrees. We used to have the same situation you are having. On the good side, you might be low on freon or have a have a dirty condenser.
 
I had a 99 340 with a single AC unit. Even on the hottest must humid days it would not run "continuously". It might be worth having an AC guy come out and see if she needs a recharge? Though I guess I don't know if you can even service the older rigs with real freon in them...:)
 
John Powell said:
Hello,
I just bought a 1993 330 Sundancer with a 15k Dometic. Outside temp was 88 in a humid coastal environment (Texas) & boat is Not in the shade.

-During the day, Tstat went down to 77. It ran continuously but was dry and comfortable.
-At night, Tstat read 68. Cold and very comfortable. Not sure of outside temp at night.

Is that normal? Are you all with 1 AC unit or the same set up getting better results?

Just wondering how it will be on hotter days...

Thank you,
Click to expand...
The temp on my thermostat never seems to match reality. I think the sensor is in the compartment between the hull and the air conditioned space. If you have bow rails and want to cheaply reduce the temp, hang a canvas across the rails so that the cabin is shaded from the sun.
 
All good info! Thank you for the help!
 
John Powell said:
Hello,
I just bought a 1993 330 Sundancer with a 15k Dometic. Outside temp was 88 in a humid coastal environment (Texas) & boat is Not in the shade.

-During the day, Tstat went down to 77. It ran continuously but was dry and comfortable.
-At night, Tstat read 68. Cold and very comfortable. Not sure of outside temp at night.

Is that normal? Are you all with 1 AC unit or the same set up getting better results?

Just wondering how it will be on hotter days...

Thank you,
Click to expand...
Sounds reasonable to me. "Ran continuously" do you mean the AC/Compressor or the fan? If the fan that is normal.
 
Both fan was on high 6 and compressor ran continuously...
 
jmauld said:
The temp on my thermostat never seems to match reality. I think the sensor is in the compartment between the hull and the air conditioned space. If you have bow rails and want to cheaply reduce the temp, hang a canvas across the rails so that the cabin is shaded from the sun.
Click to expand...

You should have a few extra feet on the sensor line - relocate it to a better spot.
 
All good... Not sure when it was last flushed. Bought the boat about 3 months ago. It was on Lake Travis and I moved it to salt water about 2 months ago... I cleaned the strainer & air filters. I will be getting it flushed/clean the coils asap. Thank you
 
John Powell said:
All good... Not sure when it was last flushed. Bought the boat about 3 months ago. It was on Lake Travis and I moved it to salt water about 2 months ago... I cleaned the strainer & air filters. I will be getting it flushed/clean the coils asap. Thank you
Click to expand...

If there are flow issues with the water a bromine tablet will often kill biological growth inside the system. I keep one in mind at all times throughout the summer.

I have never had a boat air conditioner that would not keep the cabin at least 65° most days of the summer.
 
I had 12k btu Cruisair on a 26’ it was overkill. Some mornings there was frost on the hull. Sometimes bigger is not better. It was literally a fight to keep a good balance between not enough and freezing cold.
As said upthread, it’s a heat pump, only as efficient as the water temperature.
 
I agree with Pirate, we had a 16k in the salon and had to replace with a 12k because 16s were backordered. So I figured I would take a chance. The 12k does a better job than the older 16k.
 
6k on my 26' couldn't keep up...the 8k I upgraded to was perfect!
 
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