[FONT="]I have this 12,000 BTU Dometic model in my 33' boat. My boat did not originally come with it from the factory...I had installed as an after-market add-on. I purchased the unit via the factory so I knew it was the exact same model they used and so I didn't have to figure out all the necessary ducting components, grills, bits, etc. that I needed. [/FONT]
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[FONT="]Having been on other boats in this size-class with A/C, I thought my new Dometic unit was reasonably "quiet" in comparison. While the installer fastened the a/c unit's feet to the boat using rubber grommets to help dampen vibration, I still wanted better. I found, on-line the "optional compressor cover" and installed it (quite a bit of work and cutting for me). It helped a lot, but I wanted better still. Note that the text on this cover says "reduces the COMPRESSOR noise by 50%". While it may do exactly this (i.e. reduce COMPRESSOR noise by 50%), it does not reduce the overall a/c noise by 50%. It seems the main noise culprit is not the a/c unit itself, but rather, the vibration & echo it can cause. If it’s installed under/behind cabinetry, for example, the vibration can be amplified. If you think about it, it’s not much different than the physics and operation of a sub-woofer speaker. Vibration is THE enemy.[/FONT]
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[FONT="]While I don’t have any before & after db numbers to share here, I can tell you that my efforts did make a BIG difference. On my boat, this unit is installed under a storage cabinet just on the outside of my forward stateroom wall. If we want to sleep at night with the a/c on, it’s no problem. Yes, you can hear the humming of the a/c, but it’s not objectionable.[/FONT]
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[FONT="]You mention that your old unit is 16,000 BTU and the link you give to the new unit refers to 12,000 BTU (with 16,000 available). My only comment here is that, if I had to do this project over on my boat, I would seriously consider the 16,000 BTU unit, space & power permitting. 12,000 BTU has been just fine for 99% of my cruising in northern Europe in the summers, Now, however, I use my boat in the Mediterranean and 12,000 BTU helps – but it is not really enough.[/FONT]
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[FONT="]So, in summary, I strongly recommend the following:[/FONT]
[FONT="]1) Make sure to use some sort of rubberized mounting grommets to try to prevent transmission of vibration to the boat structure[/FONT]
[FONT="]2) Install the optional compressor sound cover at the same time you install the a/c system, as it takes a fair amount of extra space and it might be more difficult to get it on later[/FONT]
[FONT="]3) Line the "plenum" area that encloses a/c unit with 1"++ foil-backed engine room insulation. Tape joints. No cracks![/FONT]
[FONT="]4) Check all screws in surrounding cabinetry/joinery (if any) for tightness. Consider adding a very thin layer of rubber between any bits of wood that are screwed together and making noise.[/FONT]
[FONT="]5) Avoid any sharp turns in the output ducting[/FONT]
[FONT="]6) Make sure no engine room air can get sucked into the a/c unit return-air “plenum”. (risk of unpleasant odors being quickly distributed throughout the boat)[/FONT]
[FONT="]7) Absolutely DO get the smart start, unless you have an inverter system with a power-assist feature. While the power draw of these units is very reasonable when running, the heavy starting load can be the thing that will have you forever stepping ashore to re-set circuit breakers.[/FONT]