[C320-list] Seacock question / AC Install

[Onat Dogruer]

Hi Jack,

It is a very user specific choice and depends on how we enjoy our boats &
being on the water. Having said that, some installers oversell the BTU
because in the eyes of their customer, if they undersize the A/C the
customer may be disappointed... so they oversell to be on the safe side
with the view that when you get to your boat, you turn on the A/C and it
will cool it down in 15 min or less ('fast cool'). What this does is,
creating a very rough work environment for the A/C compressor. A/C
Compressors are much more efficient if they can cycle up and down gradually
in steps - with a longer cooling cycle.  Otherwise, oversized A/Cs will
keep working very hard for very short bursts of time (5-7 min at a time),
starting & stopping frequently; hence the increased start power demands
with all these capacitor controllers and increased risk of breakdowns.

15F temperature difference between two spaces (outside & inside) will
effectively make our body to start feel cool. Cooling capacity of marine
air conditioners are simply dependent on water temperature and excellent
air flow through the evaporator.  By the way, 16,000 BTU is 1 1/3 tons of
cooling capacity (roughly 650 SQ/FT residential living space). Granted
there is a lot of thermal loss in boats but not like that.  It sounds like
you have addressed that with your shading as well.

Again, it is a very personal choice but if you ask for my opinion, I think
for a 320, 9000-10000BTU is enough for 'fast cool' on the dock side...
Especially if you have been already using a 5000 BTU window unit..  If you
want to stay with VAC air conditioners, Mermaid Manufacturing in FL makes
decent units.
On our 320, I am using a very efficient 3700BTU (compressor rating per
ABYC) unit and sleep comfortably at night at anchor.

Also, make sure there is a sump pump installed that captures the
condensation with a proper overboard discharge. I don't think it is a
complete installation if there is no sump pump installed - condensation
simply goes to the bilge and continues to add humidity - hence overworking
A/C again. I would also stay away from 'reverse cycle' models.

My thoughts..hope it is helpful.



On Fri, Jul 16, 2021 at 2:07 PM Jack Brennan <jackbrennan at bellsouth.net>
wrote:

> Hi Onat:
>
> I’m kicking over the question of how large a unit to get and the ducting.
> I keep hearing 16,000 BTU and multiple ducts, but I just don’t see it.
>
> This summer, we’ve been getting by with a 5,000 BTU window unit when we
> stay on the boat. Well, on July 4, with temperatures into the mid 90s and
> high humidity in western Florida, it kept the cabin comfortable all day and
> damn near froze us out at night in the aft cabin until we turned it down to
> low.
>
> Window units are notoriously inefficient because they draw in hot, wet air
> – and all AC was coming from the cockpit entry – so I’m thinking that
> 10,000 BTU with one duct will work just fine.
>
> We have a large Bimini and dodger that cover a third of the boat, and our
> ports and hatches are tinted, so we don’t lose as much heat as some. The
> inside liner also provides some insulation. In addition, I have blinds I
> can hang to cover the ports.
>
> Anyone have thoughts on this?
>
> Jack Brennan
> Sonas, 1998 Catalina 320
> Tierra Verde, Fl.
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> Sent from Mail for Windows 10
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