Help us settle the Air Conditioner debate

[CatNewBee]

AFAIK it's a CRUISAIR 44000 BTU 220 Volt...

[Dockhead]

Originally Posted by CatNewBee

I just wonder how good an AC can heat up a catamaran in the autumn / winter - do one need a diesel furnace on top or can the AC do the job with the gen set in temperatures around 0°C?

Why would you want to run the genset just for heat, even if you can?

Reverse cycle heat is great at the dock AND if the water is not too cold -- because it is more efficient than resistance heat (if the water is not too cold) and you can get a lot of heat out of it without overloading a normal shore power connection -- if the water is not too cold.

But who wants to run the genset at anchor for heat? That will be inefficient, noisy, plus put a lot of unnecessary hours on the machinery . . .

If you're going to be out much in temps of less than 10C, and especially in temps approaching freezing, you want diesel heat, and lots of it. Either hydronic with radiators or a couple-three forced air units, at least one per hull.

That way you can heat the boat without running the genset all night :ugh:

[Tortuga's Lie]

is that 44,000 BTU one unit? How is the duct run for both hulls? I would think you would want two units for a cat.

[john61ct]

Get factory A/C if it's reasonably priced, dropping in a Webasto for heat aftermarket is much easier

[captstu]

At 0 degrees C a reverse cycle AC is useless. The cold side of the AC would freeze the water which would probably be in the 10 to 15° range, damaging the unit unless it was protected by its internal devices.

I ran to portable electric heaters and the oven gas all day while wishing for a diesel heater. Remember the whole of the boat is against the cold water while the rest is against the cold air and cats are notoriously poorly insulated.

[valhalla360]

Originally Posted by Dockhead

Why would you want to run the genset just for heat, even if you can?

On our prior boat the air/con had heating coils (nor reverse cycle). Usually we used it at dock but occasionally we did use it at anchor.

If it's occasional, it's a lot cheaper to burn $5-10/yr in generator fuel rather than buy, install and maintain a separate diesel heater, which the boat didn't have.

[Dockhead]

Originally Posted by valhalla360

On our prior boat the air/con had heating coils (nor reverse cycle). Usually we used it at dock but occasionally we did use it at anchor.

If it's occasional, it's a lot cheaper to burn $5-10/yr in generator fuel rather than buy, install and maintain a separate diesel heater, which the boat didn't have.

True. I faced the same question when thinking about putting in heat exchangers to put waste heat from engine and generator into my hydronic system and realized I would never recover the cost from running the Eber less.

But it really depends on what "occasional" is, doesn't it? Three or four nights a year is one thing, but three or four weeks a year something rather different. The hourly cost of using a generator is not that trivial -- fuel is just one part of it. I figure using mine costs me maybe 4 Pounds Sterling an hour, including amortization. And COST is not the only consideration, either -- who wants to hear the generator running all night.

[BandB]

Originally Posted by valhalla360

On our prior boat the air/con had heating coils (nor reverse cycle). Usually we used it at dock but occasionally we did use it at anchor.

If it's occasional, it's a lot cheaper to burn $5-10/yr in generator fuel rather than buy, install and maintain a separate diesel heater, which the boat didn't have.

All good points. The buyer needs to look at their needs, the 95% of the time needs plus the other 5%. For the other 5% then a less than ideal system might be fine. If I boated regularly in freezing temperatures then I'd have diesel. If I occasionally boated in freezing weather then I'd have coils. And if I never boated in freezing temperatures but occasionally needed heat in 40-60 degree F temperatures then reverse cycle works fine.

There's no universal "best". It's what is best for your use.

[Cheechako]

3 years in the Caribe and no AC. The only time I needed AC was when living aboard while the boat was being worked on in the yard. Yes some nights were stuffy, but fans did well enough.

[Colin A]

I have used reverse cycle AC heaters on a Motor Yacht when the outside temp was about 10f air temp Water temp was some where in the 30's (ice forming in the coves) it worked but wouldn't bring cabin temp above about 58 degrees. In 40 F weather it worked great.

I think reverse cycle is great if you don't use it alot on the gen.

[valhalla360]

Originally Posted by BandB

All good points. The buyer needs to look at their needs, the 95% of the time needs plus the other 5%. For the other 5% then a less than ideal system might be fine. If I boated regularly in freezing temperatures then I'd have diesel. If I occasionally boated in freezing weather then I'd have coils. And if I never boated in freezing temperatures but occasionally needed heat in 40-60 degree F temperatures then reverse cycle works fine.

There's no universal "best". It's what is best for your use.

If you boat year round in the North Sea, get a diesel heater.

But for most cruisers, when the temps drop below 40-50F, they are either heading south of moving back to land, so only occasionally being at anchor and using the heat is fairly common situation.

One key point with reverse cycle is the water temp is often much warmer than the air temps, so assuming it's using water (typical) rather than air as the heat sink, you may get a 10-20F air temps and the reverse cycle works just fine because the water may still be 40-60F.

[Taichungman]

Originally Posted by Holly3785n

Our plan is to buy a new boat and cast off in a couple years. We are strongly considering the FP Helia 44. My husband is a simple sailor and wants to go green on as much as possible and ditch the air conditioner and generator drama. His logic is that we could buy a portable for the berth if we need to and save the cost. I'm thinking by the time I reach 50 the AC may not be considered optional equipment if you know what I mean but it would be nice to spend the money on something else. But going down that path is a slippery slope because that probably means no washer either. We will be following the sun so heat will be a way of life generally. I mean, that's the whole idea.

These are good problems to have but any strong opinions?

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Holly, have the 146 opinions/posts/replies help settle the debate yet?

[captstu]

My family and I spent two weeks on 2 FP 44s on charter.

They were lovely boats and I'm sure you will enjoy every moment of it.

Even in cooler weather we ran the Air Conditioning solidly. The boats are designed for many things, and do many things well but ventilation is not among them.

One night one of the generators went out because of a clogged water inlet and it led to a new mutiny until we clean the inlet and got the air conditioning running again. This was all relatively cool evening.

You will not easily be able to resell the boat without air-conditioning. It is a small part of the ritual per purchase price.

I would urge you to get the factory generator and factory air conditioners and if your husband wants to sell simple just don't turn them on . I'll bet the price of the first nice diesel fuel that only last a week.

[CatNewBee]

Originally Posted by Tortuga's Lie

is that 44,000 BTU one unit? How is the duct run for both hulls? I would think you would want two units for a cat.

I had the chance to inspect the cat lately. There are 4 independent units consuming a lot of space under the double beds in the cabins + one compartment in the salon under the bench. There is also a 9kW generator under the bench in the cockpit to fire them up underway. (It's a owners version with 3 berths)

If you run them simultaneously on shore power in the marina, they blow up the breaker in the power distribution. Not sure what it was - I guess 16A on 220V.

[Simi 60]

Its all pretty simple.
Pick the right boat for tropical cruising grounds.

Plenty of ventilation
Large overhangs
Shade covering the roof - ours are covered in solar panels with 50mm air gap.