Heating
A properly sized and installed hydronic heating system can extend the cruising season into the chilly winter months.
In this interview, our head of the Mechanical Department at Townsend Bay Marine discusses using marine heaters to stay warm and cozy all winter long.
Types of Heating Systems
There are many different brands of heating systems that you can buy for your yacht. For the most part, they tend to be hydronic, but occasionally you will come across a forced air system. A hydronic system uses a diesel furnace to heat the water, then the hot water is circulated throughout the boat to the point of use. Hydronic systems typically use heat exchangers with fans (fan coils) to distribute the heat into individual spaces like a stateroom or salon. Just like in a house you can have multiple "zones," each with its own thermostat. With hydronic it is easy to control the air flow, so if there are any rooms that you wish to exclude, the heat won’t be wasted. With controls for fan speed, you can adjust both the temperature and the noise level as well. Some systems use radiant heat, with exposed radiators. The advantage of this is you're not using electricity to power fans, and of course there's no fan noise. These radiant systems are less practical for retro fit due to the difficulty of finding places for the radiators. Fan coils, on the other hand, which can be located in lockers, can provide a lot of BTUs in a small footprint.
Noise
Early hydronic systems used diesel furnaces that could be pretty noisy. Many were adapted from heaters for locomotives or buses. Newer systems have made good progress in reducing the noise level of the hydronic furnace. Even so, they still make noise. Putting the furnace in a remote location, like a lazarette or engine room that already has some sound-proofing, can help a lot, as can mufflers on the exhaust.
Hydronic
You can plumb your hydronic system so that the engine heats the water when it's running without using the furnace. You can also use the heating system as a block heater for the engine. The Hurricane system has an AC element, so when you're on shorepower you could use it to keep the engine warm and keep the chill off the boat, again without firing up the furnace.
Retrofitting
When retrofitting a boat for a heating system, you have to solve three problems: first, locating the furnace. Second, locating the fan coils. Third, and sometimes the most challenging: finding the routes through the boat for the hydronic tubing.
Frequently the biggest issue when locating the furnace is figuring out how the get the exhaust safely out of the boat. The furnace commonly gets located in the lazarette or the engine room, either of which creates challenges. Newer boats with wing tanks prevent you from exiting through the side. The exhaust is hot, smelly, and need to be above the water line. You have to put in an anti-siphon loop if the furnace is located below the water line to prevent flooding. Consider also whether the exhaust might interfere with rafting up to other boats if it's exiting from the side instead of the transom.
Modifications
On Selenes, for example, we fabricated a stainless steel loop for the exhaust to prevent flooding and put it behind access panels in the bulwarks. Some people might want to glass it in, but it's safe to assume you'll need to access it someday, for maintenance, so having a hatch makes it easier.
Tubing
There are two approaches that you can take when considering the tubing for the system: traditional heater hose or PEX (cross-linked polyethylene) tubing. For example, if you choose heater hose, the installation will be fairly quick because of its flexibility, but it won't last forever. In 10 years or so you will have to replace it. PEX, on the other hand, is designed for radiant heating systems where it's buried in concrete, so it will probably outlast the boat. Installation will take slightly longer because it's a lot stiffer than heater hose, but the durability and overall life is much longer.
When routing the tubing, you have to make a complete loop to return the water to the furnace. You have to find a route through the interior where you make appropriate tradeoffs between ease of installation, location of the fan coils, and loss of storage space. In some cases you can mount the fan coil some distance away from the actual heater outlet.
Pricing
When configuring the heating system, it is best to take a close look at the zones where the outlets should go. You can get the fan coils in different BTU outputs, so you want to spread the heat around the boat so you get the right amount where it's needed. You have to take into consideration the volume of the space to be heated (cubic feet) in order to calculate the total BTUs required. For example, in a large salon, you might use one large capacity fan coil or two smaller ones to distribute the heat more evenly. In a pilot house, you might need half of the unit as a defroster and the other half for simply keeping warm, yet they are to be controlled separately and might have different style fans.
Costs
The total cost of a heating system must take into consideration how many heaters you may wish to install, as well as the brand that you choose. Naturally, you want to have the installation performed by people who are highly skilled, because it is slightly complicated. A poor installation job can eventually lead to a problem, and like most things on a boat you tend to discover these problems at really inconvenient times, and often when you're not in a position to do much about it.
Air Conditioning
Although some air conditioning systems have a reverse cycle to provide heat, for the most part, air conditioning and heating are two separate systems. You can't use the same fan coils for both heat and cold because where the hydronic system has water in the plumbing the A/C system will have refrigerant. Some people want the extra insurance of installing an air conditioning with a reverse system as well as a heating system, but it really isn’t a necessity to do so.
Time Commitment
Installation is a fairly large time commitment, even if it is a small boat, which can easily take 100 hours until completion. Getting into the larger boats can reach into 300 hours and up, depending in size and complexity. In the end though, it is well worth it because you can enjoy your time and watch the world go by in your nice comfy boat.