Originally Posted by malbert73
I am hearing about the issue with AC ductwork melting or getting brittle, and that makes sense as it is higher volume, lower temperature design. I am also hearing a concern about reverse flow through AC unit- I would make a damper valve of sorts if I were to do this.
1. If I were to replace my AC ducting with more heat resistant ducting- other than cost, would there be a drawback? Is it too big in diameter since it is higher airflow system?
2. Does anyone think I am stupid for thinking of this? I really don't want to devote more locker space to a second set of ducts, and I suppose I can run the genset to heat the boat... I imagine once I factor in the price of components and value my time, i could probably replace most parts on my generator.
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I think it could be done if you can find a valve that would stop the hot air from leaking out through your AC unit(s). Maybe even a manually operated shutoff would be OK since you'd normally be using either heat or AC, but not both on the same day. If you replaced the AC ducting downstream from the shutoff valve with heat resistant ducting, that should solve that problem and you wouldn't have to replace all the AC ducting, just that portion that's downstream from your shutoff valve. To avoid condensation
related issues when you are using that same ducting for AC, you'd want to insulate it if it didn't come that way. Maybe you can buy heat resistant, insulated ducting? Even though the AC ducting is larger diameter than diesel heater normally is, as long as it's sealed tightly at all the joints, the airflow at the outlets will be unaffected. I use 3" wide metal tape to make sure I have no leaks
at any of the intersections in the ducting. I like it because, unlike duct tape, it's easier to remove and doesn't leave such a sticky residue, plus it doesn't get brittle over time and you can squeeze it tightly around oddly shaped objects such as hose clamps so it makes a good seal.
One comfort issue is that normally, AC outlets are located high in the living space but you'd really prefer to have your heat outlets located as low as possible so your toes can enjoy the heat too.
For sailing in cold climates, a diesel heater is such a big upgrade from reverse cycle AC which requires running the genset!
Even on very cold days I turn it off at night but the first person awake in the morning can turn it back on to take the edge off without waking everyone else aboard.
If you're leaving your boat during a hot day and expect to return late at night when it will be much cooler, to avoid that damp, cool feeling when you return, if your heater is on a thermostat, you can leave it set so it will come on when the boat cools in the early evening.
you can leave it on so no matter how cold and damp it is while on watch on deck
, the inside of the boat is a warm, dry haven no matter how nasty it is on deck
. If you did that with a genset and reverse cycle combo, you'd use a lot more diesel and the noise
of the genset would eventually get on some peoples nerves, especially if you are under sail rather than motoring. I wouldn't worry about putting hours on your genset though because they are made to run almost continuously. It's the short cycles where it doesn't get thoroughly warmed up that kills gensets prematurely. Running it all day while offshore
is better for it than running it for a short time just for a quick shot of heat in the morning.
If you have a heat outlet in your shower
area, you can use it as a drying hanging locker where the off watch hangs their foulies so when it's once again their turn to go back out on deck they can don warm, dry clothing
instead of the same clammy feeling clothing
they removed hours ago. It makes a huge difference in attitude and comfort. Also, with a heat duct in your shower
area, before showering you can make it 80 degrees in that small area so there's no temptation to waste hot water
just trying to get warm. 65 or 70 degree air is fine when you are dry and dressed, but when you're wet and naked, it feels COLD!
I think it's an interesting problem and if you decide to go ahead with it, would enjoy seeing a diagram of your system and what you use for ducting and shutoff valves. I don't think it would work on my boat because I have two AC units located at opposite ends of the boat but if your one set of ducting is set up so it reaches everywhere you want heat, it might work. I can appreciate your reluctance to undertake the installation
of a separate set of ducting when you already have ducts, but the heat ducting is much smaller diameter and I find that I can usually locate it in a locker fastened against the top of it so most people never notice it's there and it doesn't steal hardly any usable space.