plumbing FW water cooled engines for hot water heater

[gfatula]

I am considering adding a couple of Y valves to the heat exchanger plumbing I have in my Islander 28 so I can circulate the contents of my FW tank through the heat exchanger instead of sea water when I so choose. We cruise the Maine coast and are not troubled with hot weather. We don't drink the water from our holding tank as a cold beverage. Having a little stored heat inside the hull may prove to be a comfort on most days "down east". We try to extend our season when we can and have sailed all winter in the past. We do not have an electric water heater.

What would be the problems I might create if I had two Y valves connected to the heat exchanger's raw water lines? Would the exhaust just get too hot to be safe? (I expect so). Would circulating the warming FW water create an un-managable engine temperature issue. I certainly don't want to risk over heating the engine ( I do have a temperature and oil pressure alarm installed). I wonder how warm I could expect to raise the temperature of the fresh water in the holding tank before I needed to switch back to the raw Gulf of Maine coolant. I do have a bypass valve on the engine's cooling lines. I could monitor it and switch back to raw water at what ever point the FW was keeping the engine from cooling properly. I wonder if it would be worth it to try?

I would expect to turn off the raw water and introduce FW briefly while still having the raw water return (now FW from the tank) emptying into the muffler. Then switch that Y valve to return the FW to the holding tank. Perhaps a second heat exchanger is a better idea?

George

[msauntry]

Not sure I grasp what your at... Running your fresh water tanks through the engine will only contaminate your fresh water if its returning back to the tank. Running your fresh water tanks though the engine and out the exhaust only wastes water, so why bother?

If you're after heat, why not install a little heater core and blower for the cabin? They're about $200. Plum your raw water exhaust through it. It works just like the heater in your car, using otherwise wasted engine heat.

[gfatula]

Hi, msauntry

I have a heat exchanger now that is cooled by the raw water pump's flow. There is a second pump that circulates antifreeze through the engine and back through the heat exchanger on the coolant side. What I was trying to explain was the possibility of switching from running raw water through my existing heat exchanger to running my FW tank's contents through the same heat exchanger. The only loss would be briefly at the switch over to flush the raw water out of the heat exchanger so the water tank's contents would not become too brackish.

Your idea if installing a small coil heater is a good one. I could tap the heat from the exiting heated raw water with no impact on the engine. It would heat the air and that is a plus.

I might install a second heat exchanger between the engine's heat exchanger and the water lift muffler to heat water we could use for showers, etc.

I might buy a bigger boat, too. Ha!

Thanks,

George

[Bob.Griffin]

I'm a bit confused too! The sea water that circulates through the heat exchanger in your FWC should exit into the muffler or water lift and out through the exhaust at your stern. If you use your fresh water holding tank as the soource of coolant for the heat exchanger, you need a closed system, else you'll empty your holding tank. With a closed system, water no longer exits via the exhaust system, meaning the exhaust will overheat. The only solution is a second heat exchanger before the sea water coolant enters the exhaust system.

I played with the same idea on my C&C Corvette (31ft), but gave it up in preference to a solar heater. I use a low capacity pump attached to a 10 gal water container painted black, it's surprising how much the water heats up on a sunny day. Then the pump runs the warm water to a shower head, either attached to the boom above the cockpit or to the head if the missus wants privacy!!

Bob (s/v Saga, Kingston, Ontario)

[msauntry]

I just had a crazy idea of running tubing through the floors like they do in houses! Imagine walking around your cabin sole in bare feet. Even better, have them under the cockpit sole and seats. Now that would be luxury!

Shock other sailors when you brag about your heated seats!

[msauntry]

George,
Should be pretty easy to find space for this unit.

http://www.defender.com/product.jsp?path=-1|406|1066337|714835&id=48295

[gfatula]

msauntry,

That is a nice unit, thanks. I will go aboard with an eye to its plumbing and installation.

George