Using Waste Heat

[Dockhead]

Originally Posted by wooden head

Sounds like a good plan. I have one last request in modifying any water heating system please make sure all loops are over presure protected. RE; t&p valve on waterheater, presure vent cap on engine loop etc. When adding valves keep in mind every heating source must not be valved off from relief. Explosion hazzard if you're lucky no one gets hurt you just blow a hole in the hull.

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Thanks -- good advice!

Another advantage to this layout is that there are no extra loops. Just the engine main loop where there's a normal radiator cap. And the calorifier which already has the temperature/pressure relief thing, plumbed overboard in the original build.

[Dockhead]

Originally Posted by Lepke

I have a hydronic system based on an oil fired boiler and baseboard type radiators. It was installed when diesel was about 20¢/gallon. I am in the process of replacing the baseboards with marine heaters similar to the ones in other replies. I found the forced air heated a cold boat much faster than the baseboards. 30 minutes vs several hours. None of the original circulation lines were insulated and I had a large heat loss from the boiler to distant heaters. Insulation makes a big difference.
As to waste heat - my boiler has a copper coil in the top of the boiler that heats a 50 gallon electric hot water tank if the boiler is hot. Both mains were modified to send 175° engine water thru the boiler by turning a few valves. Most engines have a in and out port that can be used for a heater. Mains and generators of mine have these. By diverting the water with valves into the circulation system the engine fresh water pump pushes enough water thru the boiler to heat it to about 170°. I don't need an auxiliary pump. Each new heater is a zone with a valve controlled by a thermostat. The zone valves are closed unless there is a call for heat. The engine water just goes thru the boiler unless there is a heat call. Then the boiler circulation pump also pushes water. It works better having the engine water enter the boiler top and return from the bottom. Opposite normal circulation. But this way I get heat as soon as the engine is warm and hot water will flow to the heaters even if the boiler is still cold. I only have 1 engine heating the boiler at a time in case of some plumbing accident. I don't want both mains w/o water.
I also have a pellet stove with a coil that heats the boiler and a diesel stove with a coil that can heat the hot water tank. Most of the time I have the boiler oil burner disconnected, but use the control circuit for the thermostats. In the winter I use the pellet stove to heat the whole boat via the boiler.
I had to redo the fresh water plumbing and added a return line and small pump that allows me to get hot water to a remote sink or shower without dumping fresh water down the drain. The cool water in the supply line is returned to the hot water tank where normally incoming cold water replaces hot water being used.
With a little thought, all of this can be controlled with solenoid valves and relays.

That sounds like a good system. It sounds like domestic heating systems in Germany where a domestic hot water tank is used as the main boiler.

I also like your pellet stove -- I wish I had some way of using solid fuel on board.

I guess if I were building a boat from scratch for cold climates, it would be set up something like that. A pellet stove in the main salon (or pilothouse!) with a glass door so you can watch the cheery fire, and a circulation loop in it. Maybe even with a pot burner as a backup source of oil heat, in case the Eberspaecher goes down in Patagonia or somewhere without service.

Concerning baseboard heat or passive radiators -- these sound great in theory -- no power, no noise -- but I have also found passive convection heat sources to be less than useful on boats. Even oil-filled electric radiators. Decent fan coils are essential, IMHO. I don't like mine because they seem to be of low capacity, and they run constantly -- no thermostatic control. I'm going to have a pro look at them soon.

[Dockhead]

Originally Posted by tanglewood

I designed (with a lot of help) a diesel fired hydronic heating system for our boat. It includes a heat exchanger like you are contemplating. The engine coolant loop that circulates through the hot water tank also passes through a heat exchanger. In the heat exchanger, it imparts heat into the hydronic heat loops. The controls have a selector switch for Diesel heat (the boiler) or engine heat. I know, both are diesel powered, but I think you get what the position mean. In the engine heat position, all the controls and circulator pump operate as normal, but the boiler is locked out and all heat is drawn off the main engine. It is all waste heat otherwise destine to dump in the ocean, so there is truely zero fuel cost to heat the boat this way. So far it works great, but I think the coldest we have been in while cruising is about 40F.

Could you post diagrams/other design documents from your system? This sounds really good, and you were smart enough to get professional help, while the rest of us fumble around trying to figure it out for ourselves.

[Boatyarddog]

Originally Posted by carstenb

Dockhead - why make this so complicated?



You already have an engine waste heat exchanger - it is called a hot water heater.



Simply buy another hot water heater (a 40 liter costs maybe £300) and plumb it in just like your current water heater.



Now take the fresh water outlet and plumb that to your towel rack (and perhaps a small radiator or two somewhere else).



now plumb the fresh water coming back from the towel rack into the inlet side of the water heater so you have a closed loop system.



If you also hook the electric heater side up to your inverter, then you have warm towels even when your engine hasn't been running for several days.



Finally you could (quite simply and at very little cost) rig a set of electrically operated valves in front and back of this supplementary water heater so you could shunt the hot water into your regular hot water system (this way the gals would have a lot more hot water to shower in - extra brownie points)



For a low () hourly wage, I will plumb this system up for you

You guys are tooooo funny!


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[Dockhead]

Originally Posted by carstenb

Dockhead - why make this so complicated?

You already have an engine waste heat exchanger - it is called a hot water heater.

Simply buy another hot water heater (a 40 liter costs maybe £300) and plumb it in just like your current water heater.

Now take the fresh water outlet and plumb that to your towel rack (and perhaps a small radiator or two somewhere else).

now plumb the fresh water coming back from the towel rack into the inlet side of the water heater so you have a closed loop system.

If you also hook the electric heater side up to your inverter, then you have warm towels even when your engine hasn't been running for several days.

Finally you could (quite simply and at very little cost) rig a set of electrically operated valves in front and back of this supplementary water heater so you could shunt the hot water into your regular hot water system (this way the gals would have a lot more hot water to shower in - extra brownie points)

For a low () hourly wage, I will plumb this system up for you

I didn't see this when it was posted, for some reason.

This is actually a pretty good idea (except for connecting the immersion heater to the inverter ). I remember when hydronic heating systems in the U.S. used to be configured like this.

The second calorifier could have two loops, like the first one, only this one would be connected to engine and generator, instead of engine and furnace.

The only problem is I don't really have any place to put it. I have a whole empty bay under my salon table which is intended for watermaker and watermaker day tank -- which I don't have yet. Otherwise, there's just no place at all for it -- that's the problem.

[carstenb]

Originally Posted by Dockhead

I didn't see this when it was posted, for some reason.

This is actually a pretty good idea (except for connecting the immersion heater to the inverter ). I remember when hydronic heating systems in the U.S. used to be configured like this.

The second calorifier could have two loops, like the first one, only this one would be connected to engine and generator, instead of engine and furnace.

The only problem is I don't really have any place to put it. I have a whole empty bay under my salon table which is intended for watermaker and watermaker day tank -- which I don't have yet. Otherwise, there's just no place at all for it -- that's the problem.

Dockhead - having been on your boat - I think we can find a space

[Dockhead]

Originally Posted by carstenb

Dockhead - having been on your boat - I think we can find a space

Ha! When you're on board in May, you can look, but I think you have an exaggerated idea about available space on board! There's never enough space on any sailboat, that I've ever been on.


I just spent the night a couple of days ago on a friend's 60 meter (!) motor yacht, a former expedition vessel. He just bought it and was only spending the second night himself. You may recall that I was asking for advice on here about finding such a vessel -- same guy. Now THAT has space on board for any kind of installation you could ever want (including a helicopter hangar, which he is having installed).

But there is a hell of a difference between 60 and 16 meters