heat exchanger to sea water

[p.hammar]

Right, more plumbing questions...

Is it at all possible to connect a heat exchanger for my cabin heating circuit to an engine that is entirely sea water cooled?

The facts:
I have a warm water circuit in my boat that heats four radiators and, shortly, also a five gallon water heater.
Connected to this circuit is a kerosene heater that does a fine job warming the boat.
For convenience, it would be lovely to also have the circuit heated from the engine since kerosene is messy and expensive and awkward to store.
The engine is a 1976 Yanmar YSB8G with no fresh water cooling.
The water that comes out of the engine goes via an anti siphon to the exhaust.
Installing fresh water cooling on the engine would be one solution, but I want to avoid this for other reasons.
Buying a new engine with pre installed intake/outtake for heating would be lovely, but expensive.

So, is there anything that stops me from letting the sea water (warm) that comes out of the engine pass through a heat exchanger and add some heat to my system? I'm assuming it would be just before it goes into the exhaust pipe.

Kindly

Per Runhammar

[Dockhead]

I don't know if it helps, but people do make hot water with sea water cooled engines. I believe it should work, although you will get less heat from it because of the lower operating temperature of such engines.

Maybe someone has some actual experience and can give you more exact information.

[p.hammar]

Thank you anyway.
For clarifying; I have my boat in fresh water, save for an annual turn in brackish Baltic Sea. This is why I hesitate to convert to fresh water cooling, plus I do not like to depend on electrical pumps for engine cooling.

Per

[mrm]

I don't think it will work very well as the temperature of water going to the mixing elbow is rather low. Perhaps confirm that with some sort of cheap thermometer probe while motoring?

As for the electric pump - what gave you the idea such pump is needed?

Originally Posted by p.hammar

Thank you anyway.
For clarifying; I have my boat in fresh water, save for an annual turn in brackish Baltic Sea. This is why I hesitate to convert to fresh water cooling, plus I do not like to depend on electrical pumps for engine cooling.

Per

[gjordan]

Since your boat is in fresh water it would be easy to change your thermostat to 180 degrees for most of the year and do a quick swap back to the lower temp for your yearly trip to the Baltic. I think your engine would run better and last longer at the higher temp. Just my opinion. Grant.

[p.hammar]

If I want to convert my engine to fresh water cooling, I need a pump to circulate the cooling water circuit between heat exchanger and engine, won't I?

Anyway, my main question is whether it is possible to use the heat from a sea water coooled engine for cabin heat and water heater. True that the water ight not be hot enough to give any effect, but do I run any risks by letting the water out of the engine through an exchanger? Would be fun to try.

[mrm]

Originally Posted by p.hammar

If I want to convert my engine to fresh water cooling, I need a pump to circulate the cooling water circuit between heat exchanger and engine, won't I?

True, but why electric? You want it to run when engine runs, so why not a simple, belt driven one like in a car?

Have you seen this thread? http://www.cruisersforum.com/forums/...em-122461.html

[a64pilot]

You can get quite a lot of heat from a bus heater, even from the lower temp of a raw water cooled engine. Bus heaters are inexpensive and readily available
I would leave the factory thermostat in place

[guyrj33]

yes what your proposing is entirely possible. Before converting to Fresh Water Cooling my Atomic 4 was Raw Water Cooled (RWC) and was used to make domestic hot water. The engine cooling water's last use was running through the heat exchanger in the water heater before being injected into the exhaust. The 140 degree thermostat in the Atomic 4 produced plenty of hot water.

[Dave22q]

Rout your hot salt water coolant through a standard marine heat exchanger on its way to the exhaust. You then need to extend your existing closed hot water system to include your new heater. Setting up flow controls might get complicated but it seems doable to me.

[p.hammar]

Lovely! Thank you for your replies!
I conclude that I run no risk by trying other than that of spending time and money with little effect. This I have been doing for years and feel quite at home.

[Djarraluda]

The YSE8 is a very small engine, 8HP, single cylinder. You may be asking a lot of the standard pump.
My last boat had the same engine, the water outlet, head to the exhaust elbow is short and small bore. Make certain you increase the size of the pipe before adding any length to it. If the pump has to cope with increase to resistance, the flow will reduce despite the positive displacement pump, so be aware and limit that resistance by using larger bore pipe.
The last "risk" is that you overcool the discharge water. This will lower the temp in the exhaust injection point and may increase the build-up of corrosion and possibly the glass like obstruction that forms there. Not significant, but the elbow will need maintenance more than before, be aware!
Roger

[Bor the Wolf]

A problem with using the engine is that the expansion tank may be too small.

I added a boiler that uses either shore power or the engine's cooling circuit. When the coolant heats up it expands and the expansion tank captures the coolant that wants to leave the circuit. After the circuit was expanded the volume of water that wanted to leave the circuit increased to the extend that the expansion tank started to overflow. So I needed to add yet another expansion tank to prevent the system from draining its coolant.

Next I needed to add a one way valve after I noticed that, while on shore power, the boiler started to warm up the engine by natural convection. Hot water tends to rise up and pushes the cold water in from the bottom through the (closed) engine's cooling circuit. After a couple of hours I had a hot engine and the (coin operated) shore power had gone in no time.

They are not big problems but something to keep in mind.

[Lepke]

Hydronic heating systems usually have a closed expansion tank. You shouldn't need one because any expansion goes out the exhaust.
Boiler circulating systems run under pressure so a higher heat can be set w/o making steam. Mine runs at 250°F @ 15psi. They have to have an expansion tank and usually air ejectors.

[Sputnik]

What make is your current water heater? Most will work on diesel as well as kero....use engine fuel to drive the water heater?
When you buy your diesel you can purchase at the lower heating rate, or at least a certain %.
Neil