Finally -- Bus Heater Install!

[Stu Jackson]

KISS:


https://c34.org/wikiwp/?rdp_we_resou...3DCabin_Heater

[Juho]

Originally Posted by Dockhead

So you would need a well-insulated tank. Maybe could double as a water ballast tank.

Yes, having two supporting arguments / use cases could make it feasible.

[Dockhead]

Originally Posted by Juho

Yes, having two supporting arguments / use cases could make it feasible.

I would love to have water ballast. 500 liters is like 6 or 7 guys on the rail.


I think in a new build it should not be that hard to accomodate such tanks, but insulating them would be a trick.

[Juho]

Originally Posted by Dockhead

I would love to have water ballast. 500 liters is like 6 or 7 guys on the rail.


I think in a new build it should not be that hard to accomodate such tanks, but insulating them would be a trick.

Few more notes.

Insulation can be built, but especially with long tanks (close to the toe rail) that insulation takes some considerable amount of space. Tanks could be also non-insulated towards the cabin, if their heat content will always be used for heating right away (during next 24h).

I guess ballast tanks will contain sea water. Maybe it should be possible to open and clean them. One could also filter the incoming sea water.

It should be possible to use the same system for cooling the boat. The hot motor can then be isolated from the rest of the system. For cooling one would use a heat pump, and maybe also cool sea water directly.

In principle it would be best to divide large heat storages in compartments since that would make it possible to first heat only one compartment properly, then the next etc. But in the ballast tanks water will be pumped anyway from one side to the other, so it may be easier to treat them just as one big unit.

Also a ballast tank might benefit of internal compartments to avoid water moving continuously from one end of the tank to the other. Or maybe those tanks will be always either full or empty, or small enough not to cause any harm.

If the complexity of the pumping and heat management system grows (multiple tanks, ballast movement, emergency bilge pump), its valves could be controlled by a computer.

[Dockhead]

Originally Posted by Juho

. . . If the complexity of the pumping and heat management system grows (multiple tanks, ballast movement, emergency bilge pump), its valves could be controlled by a computer.

I would want to avoid complexity as much as possible.


Ballast tank functions can be managed like in Dashew's boats -- reversible pumps, level gauges, and solenoid valves -- simple.


Heat storage function would also be really simple -- I think you just put coils in the tanks and run your hydronic system through it. I don't think you even need any valves at all. If there is water in the tank, the coil will heat the tank when heat is present in the system. When heat is not present in the system but present in the tank, then you will get heat transfer in the other direction.


Simple.

[Bill O]

Originally Posted by Dockhead

I would love to have water ballast. 500 liters is like 6 or 7 guys on the rail.

Some older Chuck Paine designs (Apogee 50, Bougainvillea 62) that we've looked at had non-insulated fresh water ballast tanks. The idea was good, but many didn't really grasp onto it and don't know of any new boats that now install them. They did take up quite a bit of potential storage room, but for short handed performance sailing IMO it was worth it. Probably could spray foam them and create an insulated heat sink.



There is a Bougainvillea 62 ketch in your neck of the world for sale.

[Juho]

Originally Posted by Dockhead

I would want to avoid complexity as much as possible.


Ballast tank functions can be managed like in Dashew's boats -- reversible pumps, level gauges, and solenoid valves -- simple.


Heat storage function would also be really simple -- I think you just put coils in the tanks and run your hydronic system through it. I don't think you even need any valves at all. If there is water in the tank, the coil will heat the tank when heat is present in the system. When heat is not present in the system but present in the tank, then you will get heat transfer in the other direction.


Simple.

I agree with having simplicity as one key target and requirement.

[wsmurdoch]

I'm not sure that storing hot water for overnight boat heating is too practical.

Let's say you have a 100 gallon water tank for heat storage. Your engine has 160F coolant, and you can heat the tank to 150F. Your bus heater produces air 20F cooler than the water, so with 160F coolant the air is 140F, and the metal register on the bus heater will almost burn you if touched. If fed 120F water the outlet air would be 100F (about as warm as your exhaled breath) and getting marginal for heating a boat with the bus heater. The water in the tank can thus cycle over a useful 30F temperature difference. If the tank held 100 gal of water or 832 lb of water, it could store 25,000 BTU. If that heat were used over a 10 hr evening, that would supply 2,500 BTU/hr or about half the output of a 1500 W electric heater.

Bill

[Dockhead]

Originally Posted by wsmurdoch

I'm not sure that storing hot water for overnight boat heating is too practical.

Let's say you have a 100 gallon water tank for heat storage. Your engine has 160F coolant, and you can heat the tank to 150F. Your bus heater produces air 20F cooler than the water, so with 160F coolant the air is 140F, and the metal register on the bus heater will almost burn you if touched. If fed 120F water the outlet air would be 100F (about as warm as your exhaled breath) and getting marginal for heating a boat with the bus heater. The water in the tank can thus cycle over a useful 30F temperature difference. If the tank held 100 gal of water or 832 lb of water, it could store 25,000 BTU. If that heat were used over a 10 hr evening, that would supply 2,500 BTU/hr or about half the output of a 1500 W electric heater.

Bill

Your BTUs and degrees F make my head hurt!


500 liters heated to 80C will give up 27kWh by the time it's cooled down to 30C. Call it 20kWh. That's 2kW continuously over 10 hours -- a decent amount of heat.



I picked 500 liters because I have 2x of those as water tanks now and imagine it wouldn't be hard to tuck those up under the rail as ballast tanks.


If you had two of them, which you filled up specially to take the heat, then you'd have double that. So 4kW continously over 10 hours.



Seems like a reasonable amount of heat to me. Not enough to get you through an Arctic night below freezing, but more than enough for a 10C night.


As it is, I don't normally heat at night off grid anyway. I will run the Eberspacher during the evening and get the chill off, then shut it down when I go to bed and rely on my down comforter. Can be hard in the morning to crawl out from under it, though, if the overnight temps are in single digits.

[a64pilot]

I think if you run the numbers and especially if you consider simplicity and expense, running a diesel heater will be far more effective.
Using heat stored in the water heater and opening the engine compt to keep the interior warm is a trick for us guys who sail in 80F water but a cold front moves through and it’s a little chilly tonight, it’s not for “real” heat like you guys way up in higher Latitudes see.
Because we don’t have Diesel heaters.

Heating your drinking water may cause more “stuff” to grow in those tanks, and who wants to drink piss warm water? I did enough of that in the Desert.

[wsmurdoch]

Silly French units. Silly, silly. Proper English units... When we lived in Hartlepool, a grocer in Sunderland was taken to court for selling bananas by the pound. Travesty.

Your tank is a little bigger than mine.
Your engine coolant temperature is hotter than mine.
The stored water must be cooler than the engine coolant. Maybe 5-10C.
The air from the air heater must be cooler than the water. Maybe 10C.
The final exit air must be warmer than the space that is being heated. Maybe 10+C.

We are great fans of a 12V bunk warmer made for use in the sleeping compartment of a semi truck (articulated lorry). ElectroWarmth 12-Volt Bunk Warmer at RoadTrucker.com

Bill

[Juho]

Originally Posted by wsmurdoch

I'm not sure that storing hot water for overnight boat heating is too practical.

Let's say you have a 100 gallon water tank for heat storage. Your engine has 160F coolant, and you can heat the tank to 150F. Your bus heater produces air 20F cooler than the water, so with 160F coolant the air is 140F, and the metal register on the bus heater will almost burn you if touched. If fed 120F water the outlet air would be 100F (about as warm as your exhaled breath) and getting marginal for heating a boat with the bus heater. The water in the tank can thus cycle over a useful 30F temperature difference. If the tank held 100 gal of water or 832 lb of water, it could store 25,000 BTU. If that heat were used over a 10 hr evening, that would supply 2,500 BTU/hr or about half the output of a 1500 W electric heater.

Bill

Yes, there will be heat losses in all the phases. One should however note that part of those heat losses will leak into the cabin.

The heat storage tanks could have intentionally relatively poor insulation towards the cabin. If that is the case, one will need less additional heat from the active heating system (e.g. bus heater, Eberspächer). The leaks will thus be a positive phenomenon here.

One way to calculate the heat losses is to say that all the heat (above the initial remaining temperature of the tanks) stored in the water tanks inside the boat will help keeping the boat warm. Usually insulation in boats is quite poor. It is weak especially close to the roof (ceiling, windows, companionway). It would make sense to pay special attention to improving the insulation of the boat. Also a heat exchange based ventilation system would be really good. Those tricks would reduce the heating (and cooling) requirements quite a lot.

[Dockhead]

Originally Posted by a64pilot

I think if you run the numbers and especially if you consider simplicity and expense, running a diesel heater will be far more effective.
Using heat stored in the water heater and opening the engine compt to keep the interior warm is a trick for us guys who sail in 80F water but a cold front moves through and it’s a little chilly tonight, it’s not for “real” heat like you guys way up in higher Latitudes see.
Because we don’t have Diesel heaters.

Heating your drinking water may cause more “stuff” to grow in those tanks, and who wants to drink piss warm water? I did enough of that in the Desert.

It's always a question whether any of this is worth it compared to just running the furnace a little more. Certainly not worth retrofitting, which is why I have not. I have not installed heat exchangers to put waste heat into my hydronic circuit for this very reason.


I also agree that I would never heat my drinking water. The idea here is to heat sea water in tanks which would double as water ballast tanks. Now this I think might very well be worthwhile as there is no complexity at all other than a couple of coils and some insulation. I mean, if you're going to have the water ballast tanks in the first place, which I definitely would in a new build.


Such a heat sink might also help use the hydronic furnace in a more efficient regime -- they coke up running on low for hours. You could run it on high for a few hours and then "coast" on the heated tank.


Sort of like batteries for your heating system.

[Dockhead]

Originally Posted by Juho

. . . Usually insulation in boats is quite poor. It is weak especially close to the roof (ceiling, windows, companionway). It would make sense to pay special attention to improving the insulation of the boat. Also a heat exchange based ventilation system would be really good. Those tricks would reduce the heating (and cooling) requirements quite a lot.

This is a pet peeve of mine. Our previous boat had a lot of exposed uncored fiberglass hull inside, and it was condensation city in cold weather.


This one is vastly better -- there is no exposed hull at all, the hull is fully cored, and there is insulation between the hull and the interior panels.


But the single-glazed windows and hatches are a problem. If you were new-building a boat for high latitudes you would definitely want double glazing of some kind or another.


As to heat recover ventilation -- it would be great, but I'm not sure how you would do it. A micro heat exchanger in each dorade? Doesn't seem feasible to me. Cold air whips through my dorade vents (6x big ones) in the winter but I've always regarded that as the price of having a well-ventilated and so fresh smelling boat.

[artisanmach]

https://encrypted-tbn0.gstatic.com/i...Amu4r&usqp=CAU