Originally Posted by a64pilot
Vacuum it down if you can and put 9 oz in it and see.
Many people undersize an AC because they don’t understand the heat load, many boats deck
can get quite hot in the sun and you can feel the heat on the underside, plus the R value of fiberglass
isn’t all that good. Plus they go on the theory that they want the compressor running 100% of the time cause it dehumidifies better
I oversized mine, which to means I run them at their lowest fan speed and the noise
isn’t so bad, but they are still noisier than a home unit of course.
I'm replacing the aged (25 years), obsolete, non-working, environmentally unfriendly (r22) 16K unit on my C30 with a new 14K unit from Marinaire. I used their numbers to select this size.
My old 16K unit (according to PO's logs) always had issues. Then again, it was installed by an idiot. The ductwork was a joke - with a 6" outlet immediately stepped down to 4", then through a 90° elbow
, into a "T", more 90"s, and only two outlets - one at the end of a 12' long winding duct. Needless to say the airflow was anemic.
Even here on Lake Ponchartrain, most guys with similar size boats are happily running 12K units. I've had some other owners say "I wouldn't go less than 16K!"
We'll see how the 14K does. I think with the better location and proper ducting I will install, it will shine.
Factory recommends strongly against oversizing, at it will shut off before properly dehumidifying. They endorse undersizing A BIT to ensure efficiency, dehumidification, and longer life due to less frequent cycling.
BTW, I could have had the 16K for only $90 more and the same physical size. So the extra couple of BTU wasn't prohibitive. I'm pretty sure a proper installation
will make all the difference.
Another BTW - even though I work
for a master A/C technician who was more than willing to work
on the soon-to-be phased out R22 system - I just didn't feel like putting a couplea hundred bucks into a system that has served it's time, led a hard life, has never worked properly, could break again in 2 months, and won't even be "legal" to service
in less than two years.
On my boat as I write this, gonna unload the new A/C from my truck right now!