New AC system

[krush]

Resistance coils are useless, unless you have tons of shore power. With 40-50 deg water, you probably will get 3x the heat from a reverse cycle. If you want resistance heat, get a bunch of space heaters lol.

If you have a webasto boiler, then I would be going hydronic heat/chilled water system.

[q240z]

We use three oil-filled radiators and a couple of Rug Buddies on our 42' Commander. The Roamer's got a lot more insulation and will have a much more robust barrier between the hull envelope and the interior than the Commander, though it is a bigger boat.

It's my understanding that reverse cycle starts losing it's efficiency edge at 50°F. It's not just the cost of the power but the wear and tear on the compressor, apparently. Most of the manufacturers I've looked at recommend shut-down at 45. In the Mid-Atantic, we're looking at 2 months or so per year of reverse cycle heat, then it's all resistance or boiler. And let's not forget that $4/gal diesel was a reality during the time I've been doing this refit. I don't want to make the mistake of assuming economic conditions today will be here tomorrow.

[Pascal]

I can't help with heat .

For AC I can say that the chiller system i install r so far has been the best money I ve spent on this boat besides the new factory reman Cummins and new ZF but since they re still sitting in a warehouse...

Personally i think self contained belong on small boats... sub 40/45. There is a reason why nowadays even 50/55 footers use chillers.

I just love the redundancy of the chillers. On the 84 i run if we re at a dock with iffy shorepower I can just turn off one chiller and people barely notice especially in the evening when we use a ton of power for cooking etc.

Is it cheap? Nothing is... how much does a 16k split cost these days? $4 to $5k? Times five is $20/25k. True you need to run thick hoses plus add an expansion tank and pump etc. but it s not that much more. The only way patching up an older split system work is if some of it work allowing you to defer the expenses by doing a condenser every year or air handler...

[q240z]

I'm glad you chimed in, Pascal.

I don't think 'cheap' is a word that really fits in this discussion. For example, a brand new 36kbtu self-contained Flagship unit just ended unsold on ebay for $2800. That's not chump change....it's also a lot of cold air. I assume that a 36kbtu chiller with three evap units would be somewhat--and maybe even significantly--more. But that ebay unit only needed ducting and a thermostat (since I've already got a whopper of a raw water pump and strainer).

One challenge is that pricing isn't readily available, which makes it a PITA to do a proper 'bang-for-the-buck' comparison across all options. It looks like your system ran $20k for two chillers and five evap units, controllers, etc. And you're on an FRP production boat, which is going to be a bit different from mine. I'm spending an absurd amount of time insulating the backside of cabinetry and making a continuous barrier between the hull envelope and the living space. Plus, you're down south. So you might need quite a bit more AC than I do. Still, I don't want to find myself roasting if we cast off and head to Miami.

That said, unless I'm missing something big, I think I could pull off similar cooling with one small and one big self-contained unit (all things considered) for ~1/4 of your new system...and that's without even considering the hillbilly converted window shaker option!!! lol

Maybe if I knew more about the benefits of chilled systems over self-contained, the benefits would be more apparent. I've read the material...I'm just not seeing bang for the buck on smaller, well insulated boats.

[Boatsb]

Q.

I bet if you do proper heat load calculations you will find your a.c. needs are quite a bit lower than similar sized fro boat without insulation.

I'd bet your 20% lower than before you insulated.

Remember the size of the unit needs to be matched to the area to properly control humidity.

[Walter P]

Very important to have size of unit match the space to be cooled. Enough is good, too much is very bad as Scott said. When you install an oversize air conditioning unit in any space it doesn't work hard enough or long enough to remove the humidity. Years ago one of our roof top compressors at my office gave up the ghost and I hired a close friend who was in the HVAC business to replace the system. He installed a system that was greatly oversized because he was able to get a "deal" on it. Well he didn't do me any favors because it was so humid in our office that even copy machine paper was limp. We had it removed and replaced with a proper size unit and all was well. I like multiple smaller units in a boat as they can be turned on or off as the need for more cooling presents itself.

Walt

[q240z]

Using West Marine's sizing system, I get 3600 for the V, 16200 for the salon/galley, and 10800 for the aft stateroom. Using Flagship's system using the lowest recommended cooling factors, I get 3900, 17640, and 11700.

[Boatsb]

How are you calculating the heat load with those systems?

Do they take the insulation level into account? What about your window exposures?

[q240z]

Here's the Flagship method: http://flagshipmarine.com/sizeboat.html

None of them that I've seen account for insulation specifically.

[Boatsb]

What's your ceiling insulation?

That's a large factor in heat loss (or gain for ac.)

What's the window area? How is it protected or is it in direct sunlight? Is it tinted?