Heating a 33ft sailboat

[CarinaPDX]

If you are just dealing with staying warm at the marina then buy electric radiator heaters - they are quiet and very effective. Add computer fans for air circulation as needed. For the spring and fall definitely buy a proper dehumidifier, which will of course dry out the boat but also heat it (400W). Moisture is a big part of the problem as bodies give off moisture and cooking does as well. Do not close up the boat completely as it will become a sauna ("rainforest" as Ann says). You need to keep dry exterior air coming in and being heated, while some warm, moist air is vented, so don't skimp on heaters. A 33ft boat in Maryland should be able to be heated by two 1500W heaters, but note that it will require most of a 30A circuit - no room for an electric water heater.

If you want to put a heater in that will work at anchor, or will work if the marina loses power, then the best solution is probably one of the Chinese knock-off diesel forced air heaters. It will take a bit of work to install but at less than $150 it is a bargain. If you are concerned about reliability then buy two and keep one as a spare. No way could I justify a Webasto or Espar with those prices (these are both product lines made for trucks, buses, tractors, etc, and are sold into the marine market at a ridiculous markup). Because the forced air heaters cycle on and off there is no problem with having a large enough heater for really cold weather and still be able to take the chill off of a cool fall evening. The only downside with these heaters is that they take a bit of electricity, which is no problem at the dock and still manageable otherwise, and the vent hoses take up space. For just a few dollars more than a kit you can buy a heater installed in a metal case, with a fuel tank, which could be run outside and the hot air run inside with hose.

Diesel pot-burner heaters work great - I have one - and use little or no electricity (fan, maybe fuel pump). They just need a bit of bulkhead to mount on. But the minimum heat output is about half of the maximum output, and they run continuously, so a heater sized for cold weather is too much for simply cool weather. Some of these can be fitted with copper coils and can heat water, which can be used for a water heater or for radiators. With the cheap Chinese forced air systems available it is hard to argue for these.

The absolute best onboard system is a diesel boiler, where the hot water is pumped through radiators and the hot water heater (and sometimes the engine). Hurricane is one marine brand that is highly thought of. I think both Webasto and Espar make them as well. IIRC there is another brand( or two) that is made for marine use. This makes for a very flexible system, works under way or on the hook, and takes up less space than a forced air system - and is also the most expensive.

Your choice.

Greg

[FionaJC]

I have had three heaters. The first was a 4Kw Eberspacher which was very picky on voltage. It had a problem so I bought a cheap 5Kw Chinese desil. I have had it for five years and its been perfect. The other one heats my Office at hop and thats been running on paraffin daily each winter for 10 hours a day five days a week. I figure that I can buy seven cheap chinese heaters for 1 Eberspacher. I have replaced one glow plug on the baiot and it too an eberspacher one for £30. There is a page about these on facebook in the UK, hundreds of people use them. 5Kw - toasty. I have also connected the boat to my phone and they come with remote controls too.

[c.K.]

I have had a woodstove, forced air propane heater, espar and webasto, right now I have a planar russian forced air
Best one so far, the problem with most of the forced air heaters they foul up and the parts are expensive
Planar I got was too big for my boat and running this one at too low will cause fouling over time so I run it full blast for hour or so
Cleaning the ingnition screen is quite simple as well, use a small torch and glow it out
Cost of this part very reasonable, tricky to install ask the dealer how
Good service too and reasonable price around $1200 can for the biggest planar

[hpeer]

33’ steel cutter has an Espar D4 and is plenty. Very adequate even in ice.

44’ steel cutter has an Espar D4 and it heats the saloon fine, I then keep all other cabins closed off. If I needed more heat I would add a second heater for the aft cabin. That way there is at least one available should one fail.

Main advantage of diesel forced air is you can sail with it running. That is a great advantage when in cold waters.

I have no experience but hear wonderful things about Planar as a cost conscious alternative to Espar.

There are some simple maintence items to have aboard.

[Lepke]

Your best heating is a diesel stove or heater that uses inside air. Changing the inside air is important. Otherwise all the moisture from your breath, showers and cooking stays in the boat. If you don't change the air, you end up with damp bedding and clothes.
Electric heaters don't change the air. They give you warm moist air. Propane heaters that aren't vented add to the moisture problem. Most wood stoves small enough for a sailboat won't hold enough wood to burn all night.
I run a stove all winter in the PNW. My boat's inside humidity runs below 50% even when it's raining.

[Carriage Boy]

The tool used by engineers and HVAC guys to understand the relationship between changes in temperature, humidity and water content of air at sea level is a graph called a Psychrometric Chart. I've attached and marked up one version below from Wikipedia (By ArthurOgawa - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2803863)

Some of these charts can be wonky and complex but if you ignore all the extraneous stuff the 3 underlying relationships are pretty simple and intuitive after looking at them for a minute.

The air temperature is plotted along the horizontal axis. That's the temperature you would read on a thermometer.

The amount of water vapor per amount of air is plotted along the right side vertical axis. That is the weight of water vapor contained per specified volume or weight of dry air. (Yes, dry air has a weight-- a 1 square inch column of it all the way to the top of the atmosphere weighs 14.7 pounds).

You can't practically measure this weight ratio on a boat but think of the general concept of adding (breathing, cooking) or taking away (dehumidifying) water vapor from your cabin. The graph and all but the last example below assume the "same" air, i.e., no mixing or replacing of the air in the cabin with outside air. Just changes in temperature or water content.

The relative humidity is the series of swooping magenta colored lines, with the left-most line being the 100% humidity, condensing (Amazon Rain forest) level. Note that all the humidity lines from 0 to 100% are represented for every temperature.

You can see there is no part of the graph to the left of or above that left-most 100% line, the air can only hold up to 100% humidity. If environmental conditions try to push the air to a point that would be further to the left or above the 100% line, the "excess" water simply condenses out into drops and you are left with both liquid water and 100% humidity air.


Those three factors are dependent on each other. For example, if you know the temperature and humidity, you find the intersection of those two lines on the chart and then read across to the right axis how much the water vapor weighs. If you looked at a pair of temp/humidity points, you could calculate how many grams of water per volume of air would be removed as you changed the temperature or humidity between those two points. That number with a little math would let someone theoretically size a dehumidifier.

Think about an unmanned shrink wrapped (air tight) boat, sitting on a nice day at 25C and 50% humidity, (the red dot on the graph). Folks come aboard and start breathing, cooking and taking showers which adds water vapor to the air (moving up along line "A") and increases the humidity. In a sealed boat, when the amount of moisture in the air approximately doubled, it would be at 100% humidity and start condensing water drops even thought the temperature didn't change from 25C. Conversely, if you ran a dehumidifier on that boat with the messy humans on board, the humidity level could even be driven below the 50% level at roughly the same 25C temperature.


Back to the 25C/50% red dot point again, if the sealed, unoccupied boat dropped in temperature from 25C down to about 13C (moving along line "B"), the humidity in the boat would again reach 100% and begin to sweat, even though no one was aboard.
An additional way of looking at the line "B" model is to not think of changing the temperature but rather think of the temperature axis as mimicking the temperature profile from the center of the heated cabin to one cabin wall on a cold day. Even if the middle of the cabin is a comfortable 25C and 50% humidity, the cold hull can reduce the temperature of that same 50% humidity cabin air immediately adjacent to it down to the point it begins to condense water. Thats the same thing that causes cold glasses of your favorite beverage to sweat in a humid environment.

The big advantage of poking a hole in your shrink wrap then inducting and heating fresh air in cold weather can be seen from following line "C". If you suck in 5C, 90% humidity air (blue dot) from your PNW anchorage and heat it up to your 25C cabin temperature, that now warm incoming air has a humidity of just above 20% simply because it is now warmer.

Mix that relatively dry incoming air with your moist cabin air also at the same temperature fast enough and you get a blended nice humidity level that can sustain folks breathing and cooking. That's what makes forced air heaters so comfy and dry. A few cracked open hatches, fans and some heaters can do the same thing if you get the balance of all those items right.

Anything that simply heats cabin air in a relatively sealed boat without removing any accumulating water vapor will be like my first example above. The humidity level will continue to rise with breathing and cooking and after the first few days will reach equilibrium and begin condensing water on the cabin walls at the same rate that new water vapor is being introduced.

[Cpt Mark]

I had a reverse cycle heat pump which worked awesome except in the dead of winter here on the Columbia River in Portland Oregon. The issue was the water temp was so low it couldn't be used. If you go this route, check the manuals.

Got rid of that and went with a Chinese knock off 5 KW. In the dead of winter on medium low it heats my 35 foot catamaran. Uses little fuel. You Tuber "John Mck" out of Australia has a ton of videos on these things.

I paid $115 for mine on Ebay. Just know that all the hose clamps and stuff are not SS. I also bought much higher quality exhaust pipe/tubing, SS exhaust clamps, SS muffler (that was a waste of money btw. They are so quiet) and you need a proper SS Marine exhaust vent. So your $115 all parts for installation included will cost a few hundred dollars more in upgrading the parts to be marine safe.

One issue people have is that they get soot build up which means take it apart and clean it. Ugly job. Easy but messy and this could be said for all diesel heaters of this type so make sure when you install it you design it to easily come back out/in. What I do is right before shut down or at least once a day in the winter is turn it up max heat for about 15 minutes to burn any soot off. Seems to have solved the problem.

For instructions on how to use the controller look at UK Preppers videos. He gives you the code and shows you what else you can do.

[laird]

The cheap Chinese heaters work great, you can buy a self contained unit that has the tank and the heater , the fuel pipes are a bit useless so it is best to change them ,there's plenty of yt videos on them , there's an Aussie guy who has done a lot of research on them and there's a couple of vids of them being fitted to yachts

One thing to be careful of us the stainless steel.exhaust ,it's not good enough for the salty environment , some people purchase an additional exhaust and with it with a heat bandage ,you can get dedicated through hull fittings for them.

The pump can be irritating with a clicking noise ,they burn about 1 gallon of diesel every 30 to 40 hours

[Obrien1234]

Thank you all for your advice! The boat is a Hans Christian. I do already have a propane force 10 heater installed - but when I used it in the early fall last year (in VT) it produced a very wet heat - really just around the ceiling near the heater. Now I'm thinking though that if I used that paired with a good dehumidifier paired with an electric ceramic heater I may be okay. My fear with electric heat is that I've heard so many stories of marina fires being started by electric heaters. I'll be connected to shore power most of the winter. Any advice on electric heater brands and advice (specifically about the safety aspect)?

Thanks again!!!

[CarinaPDX]

Ideally electric heaters should have a circuit breaker, usually in the plug, and a tip-over switch. I think some have overheat cut-off but not certain about that. I think a significant risk is the quality of the boat wiring as a 1500W heater draws about 12A, so if you have 2 heaters they need to be on separate branch circuits. Any corrosion, especially at the incoming power receptacle, can cause dangerous heating. While the male blades can be cleaned the female side is best just replaced. When running high loads (heaters or A/C) feel the connections for temperature: they may be a bit warm but if they are hot then replace them.

Greg

[Celestialsailor]

Originally Posted by CarinaPDX

Ideally electric heaters should have a circuit breaker, usually in the plug, and a tip-over switch. I think some have overheat cut-off but not certain about that. I think a significant risk is the quality of the boat wiring as a 1500W heater draws about 12A, so if you have 2 heaters they need to be on separate branch circuits. Any corrosion, especially at the incoming power receptacle, can cause dangerous heating. While the male blades can be cleaned the female side is best just replaced. When running high loads (heaters or A/C) feel the connections for temperature: they may be a bit warm but if they are hot then replace them.

Greg

Really good information Greg. In the past year I have seen around 3 listings for sailboats, cheap, all due to fires started from space heaters in some way or other.

[gonesail]

i run a 1200 watt oil filled heater on a 30a circuit. i check the plug which may get warm but not hot. i also run a dehumidifier. in addition i have a vented propane heater when things really get cold. the electric heater has its own circuit breaker and i am confident enough to leave it on while i am gone from the boat but on the 600 or 900 watt setting.

[zengirl]

I've had two and three running 24/7 for 5 winters and never a fire problem. If they tip over they shut off. You'll be fine. Just be smart about it and don't have any clothes can fall on top of them. Keep them free and clear of anything, a no brainer.

[Dolphins]

OB!!!


I have advocated ceramic, but seeing the photo of the Little Cod or Sardine woodstove reminded me of when I fantasized about installing one of those in the nav desk area. Downside: Giving up a lot of real estate for something that will only be used rarely. Upside: THE most gorgeous and romantic interior EVER, even when you are not using the stove. Just seeing it there emanates the feeling of home and coziness.


I've heard that a kitten is a reliable source of heat, though you have to put up with the purring. :-)


Good luck with deciding on your best option.


-Matty Black

[StoneCrab]

I lived on board my boat through many Chicago winters without difficulty.

If you are planning on being at anchor or moving throughout the winter the diesel heater may be OK but if you plan on being at a dock, just use ceramic electric heaters. Get the ones with thermostats and tip over safety shut down switches. The ceramic heaters are small, quiet and work very well.

I was on a 38' sailboat and one heater would keep the cabin at room temperature down to 45 degrees F, two would keep me toasty down to freezing. Below freezing, I'd be running three and also threw an incandescent lamp into the engine room for added safety. I was using a "trouble lamp" - the old school type that a mechanic used to use before LED's. A 60 watt bulb puts out quite a bit of heat. I put the lamp below the thru-hulls which are all in the same area. This kept the engine room warm. It doesn't normally receive air from the cabin, so I felt this was a good precaution.

My only other suggestion is to get some rolls of the mylar bubble insulation and line the inside of your lockers with it to prevent condensation and to keep your clothes from freezing to the hull if condensation does develop.

I showered at a healthclub, never on-board during the winter. I did cook every day and never had a problem with condensation. Being a small space, it doesn't take that much heat to keep the cabin at a good temperature.

I did do a shrink wrap dome over the boat for the winter, mast up. The cover sheds the snow quite well, so having a cover also eliminated the need to "shovel" the deck, but I did it mostly for the added storage that it provides. I took all the sails and runnning rigging down and stored it on-deck under the shrink wrap cover. For fun, one year I took patio door shrink plastic - the clear kind that you use over a patio door in a home for added winter protection - This plastic was put across the stern of the boat like a big picture window. I really didn't expect it to last the winter, but it did and in the process provided quite a bit of light and a nice view of the city skyline.

Don't be afraid of staying on board over winter. It was a lot of fun and I discovered a new group of hardy soles who, like me inhabited the marina over the winter months. We became good friends, sharing many activities and resources.