A Thought About Heat

[atoll]

Originally Posted by Dockhead

For heat storage, I was thinking something like a large hot water tank.

1 liter of water can hold 60 watt/hours of energy over 40C range of temperature (say 80 to 40), so 100 liters is 6kW/h. 200 liters would be 12kW/h which seems to me like maybe a useful amount of heat.

So if you had an extra-large domestic hot water tank, well insulated, and ran your hydronic loop through it, it seems to me like you could get 3 or 4 hours of moderate heat out of it, after you shut the main engine down.

It would be even more useful with the generator. In moderate weather where you need just a bit of heat, it seems to me that you might be able to largely avoid using the diesel furnace at all.

I wonder if anyone has tried something like this.

As a bonus you would have super deluxe inexhaustible domestic hot water. We do love our hot showers.


As to how much heat is required to stay warm -- a lot, notwithstanding your friends' experience. My boat is pretty well insulated and doesn't suffer from much condensation, but I'm using 3.5kW of electrical heat (100% efficient) right now, and it barely keeps the salon and aft cabin at 18C in this weather (2 to 8C, not that cold). One probably I have is really good ventilation, which sucks the heat right out of the boat when the wind blows.

I have a 10kW Eber and it cannot get the boat to 20C when the temperature is below freezing. That might be a limitation of my distribution capacity, however, as I have rather crappy fan coils, but I think I would want about 15kW of total capacity on the new boat.

we only heat the pilot house which is about 4.5mx6m space with a 1kw oil filled heater and only wear a tshirt!
if it gets really cold we run a 1kw fan heater as well,sounds like you have too much ventilation.

[minaret]

Originally Posted by Dockhead

Thanks for reminding me; I'll have another look.

The most obvious disadvantage of this furnace is that it is HUGE compared to the ordinary marine hydronic furnaces. It weighs 100kg! It's the size of a small generator. I guess it would be much easier to service, however -- just like what you have at home.

My OL60 probably does weigh quite a bit, but huge it ain't. About 2' x 2'. Installed in the same space the Webasto forced air unit was in. Actually took less space because no massive ducts coming off it.

[deblen]

Originally Posted by atoll

first thing to do if you are building the boat from scratch is to plan to have 3-4 inches of insulation throughout,including under the floors,with double glazed hatches and windscreens.

2nd is to place your radiators at the lowest level possible,ie floor level if using a hydronic system with passive radiators.

this system should also include a loop in to the engines cooling system,so you can heat the boat when running the engine.

this I would back up with a blown air system in the pilot house for instant heat,and a 4kw woodburner in the main living area or gravity fed diesel with a loop into the radiators.

you also need to plan to have ventilation otherwise condensation can be a problem

Excellent suggestion-in floor hot water heating is very popular in new Canadian homes-either in the poured concrete floor or thru the floor joists.
PEX type plastic pipe can be used-inexpensive & doesn't corrode,but must be properly supported to prevent chafing. Hot water can be piped to an area like a pilothouse as part of this system. If your "floors" are warm,you are warm. Electric zone valves & circulating pumps with wall thermostats are used to control heat levels in different areas. Study up on this type of home system & adapt for your boat.
http://www.thisoldhouse.com/toh/arti...548320,00.html

For source of heat-check out Refleks 61MSF with hot water coil. Refleks makes the most trouble free diesel heater as long as you install them properly with their insulated stovepipe.They don't require a fan for draft & can be left running unattended indefinitely.Ask any northern fishing boat.

Maintenance of above is simple.Keep stove burner pot clean & filter the diesel. Keep a spare circulator pump & zone valve aboard.
You can even heat your domestic HW with it.

You may be able to plumb your engine HW into this system but I think you may need a "heat exchanger tank" as you would not want to run stove heated water thru your engine.Not sure on that point.

Cheers/ Len

[TrentePieds]

Go have a chat with Willy Occam. Better still, go here:

Boat Heaters - Dickinson Marine | Fisheries Supply

and have a chat with Mr. Dickinson :-)

Dickinson diesel-fuelled heaters and fireplaces have been the standard on this cold (and wet) coast for eons.

I take it that by "hydronic" you mean "hot water circulating through radiators". As you will see from the above link Mr. Dickinson will be glad to oblige. You can even have the radiators motivated by that nifty bulkhead-mounted "fireplace" with the deekie little window that lets you see the flames.

Prolly the best new year's eve I've ever spent was in a snug cabin with a solid fueled Dickinson fireplace while anchored in Campbell Bay with snow on deck — snug enuff to permit a rather delectable little pierhead jump to strip down to her party rig :-)

Cheers!

TrentePieds

[Cheechako]

just a couple comments.
-If you run a forced air type like a Webasto on Kerosene it is far less maintenance.
- on a big boat two smaller webasto types might make more sense, less ducting etc.
- Hydronic systems are complicated and require a lot of installation. One boat I bought had it, granted it was an old system, but very complicated and took up a lot of room in storage areas. It was removed within a year.
-The heat "soaks" into surrounding space rather slowly. If you come in from the cold, you don't have the option of "sitting in front of the warm air" like you do with forced air.

[poiu]

I have done a lot of work designing domestic property and one thing I have learned is that it is how effective insulation and draught proofing can be. There are plenty of zero carbon homes around and even more near zero carbon homes. Passivhaus is a leader in this. Heat recovery systems in a ducted ventilation system are a key element. This can be routed via a central boiler in the engine room and can be part of or in addition to your heating system. It is not hard to achieve near zero heat requirements and for a liveaboard full time I am sure it is economically viable in the savings of fuel alone. This could be a starting point and make compromises away from the base. Low energy loss and low draughts are essential for comfort as well as economy.

Look also at domestic oil fired combi boilers. Very cheap to buy and reliable. With a combi boiler you need no water tank or complicated heat exchanger systems as it heats water on demand. Also, consider condensing boilers, which use maybe 5-6% less oil than a conventional boiler. You can still add in heat recovery from the engine if the boiler is in the engine room reasonably easily if you wish.

You can purchase a whole boiler in spare parts (other than the combustion chamber and frame), which will take very little space and cost little. It will give you all the redundancy you might reasonably need. If you need two systems for true redundancy, then you will have to give up a bit of space, but you may have saved that space in the water tank anyway.

The combi boiler probably not less efficient as without a water tank you are not losing heat continually. Anyway, the energy saved from having engine heated domestic water for showers will be pretty small I believe as to be unexciting. You surely don't have your engine or genset on much do you? A quick beer mat calculation gives me the cost of two showers a day at $146 per annum when burning $0.9/lt cost diesel. If you run the engine/genset one day in three then it's only $50/yr you save on shower water from having a tank. It will cost more in depreciation/maintenance.

I can see an argument that engine heat recovery for space heating is wanted as it might be your emergency heating system as well as it being a more effective cost saving measure than for domestic hot water.

If It was my choice, I'd be somewhere warmer .

[Juho]

I'll describe briefly what kind of a system I might build. Currently our engine heats our isolated hot water tank (alternatively shore power can be used). The tank is quite small, but that system already gives us quite "inexhaustible" source of hot water (not for hot showers, but yes for anything else).

Since you want a water based system, I'll continue from the system described above. If you don't mind some extra weight, I would add another larger isolated hot water tank after the first one (hot water has priority and needs higher temperatures than heating).

If you use your motor or generator reasonably often, I would absolutely connect them in the same water based heating system. Our motor heats the hot water very quickly. After that all the generated heat is lost to the sea. It would make sense to catch also that heat (and not use some other burner to do the same and use double amount of fuel). Also this supports the idea of a large isolated hot water tank.

That water should be very hot, reducing the required size of the tank considerably. The system should have two heat levels, one for water stored in the tanks and one for water circulating in the radiators. This system would allow the water to be heated only occasionally (when running the motor or when using the furnace), not continuously. You could even have a proper fireplace for burning driftwood (generating lots of heat in short time).

I think one furnace should be enough in principle. If there are no efficient enough models available, then you must have two, but otherwise I don't see the need. If you want redundancy, you can get it also by connecting your motor and generator to the system, or by adding e.g. some simple air based heater.

I note also that our 32' boat has an air based heating system with 5 vents (one for every "room"). Air hoses are of course wider than water pipes are, but there's always some space in all the corners, and it should not be too difficult to install such a system also in a larger boat. But since you want a water based system, just forget this comment. Transferring heat from hot water (e.g. from the motor) to air would anyway require one additional device to be installed.

Good isolation was already mentioned. That's important. I'd install also a heat exchanger for the incoming and outgoing air. You mentioned that your ventilation causes loss of heat. This way you can take most of it back. I'd thus definitely install an air heat exchanger if I could fit that in the boat architecture.

If you plan to go the Arctic or towards it, get a pilothouse too, so you (and not only the boat) will be warm all the time.

[northwestsailor]

I fews ago I installed a truck type hydronic heater by Proheat sold by Sure Marine in Seattle. I used pex pipe throughout the boat to the domestic water heater and several air handlers (also sold by Sure Marine). I have a high capacity heat heat exchanger to get take heat out of the engine when running. There is also a five gallon coolant storage tank.

I have install a thermostat like in a house to control the temps automatically. In addition I wired up the air handlers to go on only when the coolant is about 140 degrees F.

All in all couldn't be happier. Doing it yourself is the way to go because you could not pay and installer enough to spend the time to run the pex exactly where to want it to heat up closets etc.

The boat did come with a Taylor drip diesel stove which we kept in place as a backup or additional heat should it become necessary.

[Pete7]

Originally Posted by Dockhead

Thanks for reminding me; I'll have another look.

The most obvious disadvantage of this furnace is that it is HUGE compared to the ordinary marine hydronic furnaces. It weighs 100kg! It's the size of a small generator. I guess it would be much easier to service, however -- just like what you have at home.

How much heat does 100kg of steel hold when really hot? our wood burner at home (90kg) can still be warmish the following morning so it has been giving out heat all night.

Pete

[Juho]

Originally Posted by Pete7

How much heat does 100kg of steel hold when really hot? our wood burner at home (90kg) can still be warmish the following morning so it has been giving out heat all night.

Pete

Some heat capacity values:
Steel 0.466 J/g/K
Brick 0.84 J/g/K
Water 4.1813 J/g/K

This means that water is very good at storing heat, and that bricks in a stove can be more important than the steel parts (per weight). The heat storage capacity of water is limited by its boiling temperature, but water is ok if you don't plan to go that high.

I have played also with the idea of using paraffin wax. Its heat capacity is "only" 2.5 J/g/K, but it has a nice melting temperature at around 46°C - 68°C, giving it some extra boost.

[Dockhead]

Originally Posted by Pete7

How much heat does 100kg of steel hold when really hot? our wood burner at home (90kg) can still be warmish the following morning so it has been giving out heat all night.

Pete

About the same as 11 liters of water.

The specific heat of water is about 9 times greater than steel.

I thought it might be cool to use the lead keel for heat storage, but lead has very low specific heat of 33x (!) less than water.

[dannc]

Originally Posted by Dockhead

For heat storage, I was thinking something like a large hot water tank.
...

When we were designing our house we knew we would want the primary heat to be wood. We have lots of woods and mother nature is constantly killing trees that have to be cleaned up, so burning the wood is a no brainer.

Our question was to put in just a wood burning stove(s), use an outdoor wood burner or andindoor wood furnace.

Outdoor wood burners are quite large and the old ones can burn quite a bit of wood. However, the burner is often choked down to burn slowly so the load will burn overnight and not overheat the house. This can make the burner generate huge amounts of smoke especially if wet wood is used.

Some of these units do use water to transfer the heat into the house.

The indoor wood furnace we studied was very efficient. It burnt cleanly, very little smoke, and used very small amounts of wood but this meant the heat was only available in short bursts of time. To compensate, a huge water tank was used to store the heat from the short burn times. I think the water tank was at least 1,000 gallons depending on heating needs. That took up lots of space and one needed to be concerned about the weight of the water. The water was circulated in the house and fires burned as needed.

We were gong to put under floor heating using PEX with solar heated water but when looking at the numbers it did not make sense for us to install the systems. This is the right decision for 11 months of the year but I doubt myself for those few weeks when it really gets cold. Like right now.

We could use a second wood stove during the really bad cold spells but it is just not worth the money and installation issues.

This is a long winded way of saying that heat storage systems are out there and they do make sense for some.

PEX is pretty reliable and tough piping. It's only issue is having the correct fitting and tool to set the fittings. The tool used to be expensive but I think they have dropped in price.

For a boat with multiple ways to heat water a heated water storage system could make a great deal of sense. The real question is how much would it cost to build, how much water will have to be stored aka how much space/weight is used, and how much will it cost to maintain?

We have an 80 gallon hot water heater in the house. Tis pretty big because it is well insulated but there would be space for it on a large boat. We bought this water heater to make sure we had enough hot water and it is actually cheaper to operate than smaller, cheaper, but less well insulated units. We have a well for water and if we loose power, we do not have water but an 80 gallon water tank will give us plenty of drinking water until we can work around the power outage. Thankfully, never had to tap it that way.

Later,
Dan

[wrwakefield]

Originally Posted by Dockhead

I've thinking about heating systems for my hypothetical new boat.

I sail in cold places and plan to sail in even colder places, so heat is mission-critical and even a life safety issue.

In my opinion diesel-fired hydronic systems are functionally superior to other types of heat, but they have a big disadvantage in that the furnaces are not easily user serviceable, and they do need service from time to time.

So I thought to back up the hydronic system with a pot-type heater with coils, maybe in the pilot house. Something which would allow you to see the flames, which would be cozy.

One reason why the hydronic furnaces coke up and require service is running with light loads. It occurred to me that two birds might be killed with one stone by installing TWO of them in series, a small one and a larger one. You could run both when you need max heat -- initial warming of the boat, or really cold weather. Then shut one down and continue on the small one for maintenance heat. There would be two of them, so if one stopped working while cruising in a remote place, you'd still have the other. No special control system would be required. Just have two control panels and do it manually. I wish you could get a readout of what heat stage each furnace is using -- they do Low, Medium, High, and Power, and I wish to hades that I could see which at any given time.

If complexity were not object (it always is an object, so this is purely hypothetical), other things on my dream wish list:

1. Engine and generator cooling circuits spliced in with plate-type heat exchangers.

2. Some kind of heat storage so that the engine or generator waste heat could be stored.

3. Separate kerosene (paraffin) tank to supply the heaters periodically, to burn off carbon and extend the service interval.

4. Radiators instead of fan coils wherever possible for zero power consumption and noise. Maybe supplemented with fan coils for when high output is needed.


I would think that this would be robust enough for remote area polar cruising. You could carry parts, diagnostic harness, and even a complete spare furnace, if you wanted to.

Hi Dockhead,

You bring up a topic near and dear to my heart after living and boating in Alaska for over 30 years now...

I can offer some feedback from both living on land and boats in cold climates.

Your numbered points are spot on, and I think you will need both radiant [passive] and fan forced capability at your heat dissemination zones. [zoned, thermostatically controlled radiators and fan forced heat exchangers- based upon experience elaborated upon below.]

Also consider radiant heat under the sole where applicable- in addition to radiators and fan forced exchangers. Amazingly efficient and silent... [I installed this under the framed floors in my home in Fairbanks...]

RE: Heat storage: Install the largest, best insulated, heat exchanger capable water tank you can fit [or more than one... I believe the IsoTemp SPA line is very cost effective, but may not be large enough for your application if you had only one... Here is my blog post about ours...]

Also use the engine(s) as a heat sync plumbed into the hydronic loop. [more below...]

I'll briefly outline experience and expand on what I would consider doing if I were building a new boat...

First, I agree that hydronic is the way to go for fast BTUs in cold climates. [I had a Webasto hydronic (I don't recall which model) on a Tayana 47 and loved it.]

The current boat came with a forced air Espar installed, and we dedicated a tank that only holds [untreated] #1 fuel oil for it- drastically reducing maintenance requirements.

Before we go further north with our current boat, I will add hydronic, and keep the forced air to mitigate running one or the other at low settings- the same reason you outlined with two hydronic units in series. [I have no where to install a drip heater without extensive remodel effort...]

Both offer the advantage of choosing where to run the ducts/hoses. e.g., You can heat select lockers and stowage areas; attach hydronic hose [heater hose and/or pex tubing] runs under seating/berth areas to heat the seats/mattresses, etc.

Ventilation: I am always harping on people to do as you mention and keep the ventilation open on their boat- especially in winter- for all the reasons we are already familiar with.

However, having lived on a Valiant Esprit 37 for a few winters [and many summers...] in Prince William Sound, Alaska, [where it would reach -28C several times each winter] I can attest to the fortitude it takes to keep the ventilation going when you can't keep the boat as comfortable you would like.

[Side note: I installed a very reliable, double vented Sigmar drip stove (separate intake and exhaust vents to prevent blow-outs from back-pressure during high wind gusts...) Nothing like a sooted cabin and no heat during a cold windy night at anchor...]

How to solve the issue of fresh air exchange without loosing too much heat?

In our homes in interior Alaska [and many other cold climates around the world] we use Heat Recovery Ventilators. [HRVs; not to be confused with ERVs used in hot climates...]

e.g., I installed a Canadian made Venmar 3000 in my home in Fairbanks and wouldn't hesitate to put on on my boat... That particular unit is not sheet metal, but rotomolded polyethylene. The only metal is the [AC] fan motor. It is very compact, lightweight, quiet, and offers HEPA air filtration. At 84% efficiency, that will keep your boat dry with lots of fresh, clean air when you are in cold Wx without dumping your heat.

An HRV makes a huge difference in quality of life in a climate where we have snow on the ground over half of each year...

This will resolve mold and allergen issues and allow you to seal up your normal ventilation during cold Wx- preserving heat and actually improving air quality.

Ducting requirements: Run discharge ducts as high up as possible, and in as many cabins as convenient. A single return duct is all you need, near the headliner, and in the main living area if possible (to draw all the air discharged into the cabins to this area...)

If you did this, you could also consider a forced air heater to supplement your existing hydronic heater and cover your needs for redundant heat and balancing use of the heat plants based upon need and to keep them running on high for reduced maintenance.

RE: Hydronic plumbing considerations:

1) Do plan to plumb in any coolant loops from engines so you can pre-heat them and/or use them as heat syncs and of course, run your hydronic heating off the engine when motoring...

i.e., Why let the main engine cool down when it is a centralized radiator? Alternatively, reduce the amount of heat the engines receive, but keep them warm to reduce cold wx related maintenance and condensation.

I did this on the Tayana 47 and it was marvelous since both engines were centrally located in an island of cabinetry amidships.

2) Bleeding hydronic loops, following is an excerpt from one of my blog posts regarding heating systems on boats: [Several of those posts will link back to discussions on this forum...]

Bleeding air from hydronic loops can be quite a chore as the top of each loop is not always conveniently accessible. [I know ours aren't...]

To make this easy, we use small, cheap, automatic air bleeders used in home boiler heating systems. Typically we install a T at the top of each hydronic core and install the air bleeder in the highest port of the T. [i.e., Where the coolant return line to the engine exits the core.] Basically, air bleeders need to be installed at a high point in each coolant loop.

I'm happy to elaborate on any of these points further if that would be helpful.

Best wishes planning your new vessel!

Cheers!

Bill

[wrwakefield]

Dockhead,

Just for reference, here is the link to the specification sheet for the Venmar HEPA 3000 HRV I mentioned in my previous post.

There may be even smaller units available that are worth considering. This just happens to be the model I have personal experience with. [Since 2002]

FYI

Bill