making hot water

[BadaBing]

About 8 years back I installed an electric water heater powered by my batteries/ alternator and an inverter. It has worked well, especially since adding a 100 amp alt.
This all worked well, if the batteries were well charged, with the new alt., We would have a tank full of how water in a half hour of running time.
I'm planning to add refrigeration to our newly insulated icebox for the 2016 season. We have some extended trips planned. To reduce some of the electric load I want to add a heat exchanger to capture some of the engine heat vs. dumping.it.overboard.
I would appreciate some thoughts on making hot water via a heat exchanger. I will be using the existing electric water as a hot water holding tank as well as a heater when necessary.
I have a small atomic 4 (cooling) heat exchanger and I'm thinking.of using it for the making.of hot water and using a small electric pump as a circulato.
Thanks
Bill

[Al Schober]

Bill,
I take it your water heater doesn't have a coil for engine coolant.
You scheme should work fine. The engine won't see it as any different from adding a conventional water heater. The pump and added heat exchanger will take up additional space and need some extra plumbing.
Be aware of the scalding hazard - your hot water can get up to engine temperatures. A tempering valve is a good precaution.
Enjoy the holidays!

[BadaBing]

Thanks Al
The water heater is actually a small domestic 110v type. So no , no engine coolant coil.
Thanks for the input.
Merry Christmas
Bill

[JOHN COOKSON]

A while back I saw in the forum somebody had coiled tubing around the exhaust hot section. I don't remember it was to cool the exhaust or heat water. Maybe something like this would work in your set up to preheat the water?

TRUE GRIT

[BadaBing]

John.
I thought of that idea as well when that picture was posted. Also thought it was a cool way to cool down a hot section. The only difficulty would be, for me, to wrap 20'(?) Of 3/8 soft copper cooling around the hot section (1'long section) & keep it tight and not linking it. A large in diameter coil 6"dia plus would be doable, off the boat and.my knees but I don't know if I could pull it off on a 1.5" pipe in that tight space.
But thanks for the cool idea, it's worth considering.

Merry Christmas!

[romantic comedy]

The coil around the exhaust was probably mine. It was to cool the exhaust. I have yet to run water thru it, so cant say how it could work. Just it being there has been enough to protect the cabinetry.

You would have plenty of heat from the engine coolant. It should be easy to plumb also.

[JOHN COOKSON]

John.
to wrap 20'(?) Of 3/8 soft copper cooling around the hot section (1'long section) & keep it tight and not linking it.
Merry Christmas!

Copper and iron would make a great battery. That said I don't know if there would be enough electrolysis between the two metals to be of concern.*
I guess RC is blazing the trail along these lines. I'm sure he will report back and let us know how well it works and if there is any major electrolysis as time goes on.
* How far apart the two metals are on the galvanic scale - or what ever it is called.

TRUE GRIT

[ndutton]

John, please see the new thread in the Standards section for answers to your nobility scale question.

Bill, what type of circulation pump are you considering? I ask because of a previous pump failure of my own due to not paying close enough attention to temperature specifications.

[joe_db]

I am not sure I understand this. Copper is an excellent conductor of heat. My exhaust is wrapped in 2-3 layers of lagging and I can touch it when it is at full throttle. Copper would give me a bad burn IMHO.

The coil around the exhaust was probably mine. It was to cool the exhaust. I have yet to run water thru it, so cant say how it could work. Just it being there has been enough to protect the cabinetry.

You would have plenty of heat from the engine coolant. It should be easy to plumb also.

[BadaBing]

Bill, what type of circulation pump are you considering? I ask because of a previous pump failure of my own due to not paying close enough attention to temperature specifications.[/QUOTE]

Neil.
I'm thinking of a Johnson cm3 , I have an extra and it moves alot of water with min amps.

I woke up rethinking the idea after drawing it up last night.
The A4 HE will require cutting into the discharge water, not a problem but another place for a problem in the future.

R C s tubing wrap is interesting but I am thinking with all that available heat off a 3-400 degree hot section I would make much too hot water.
Thinking instead of doing just 3-4 wraps around the outside of the insulation wrap on the hot section. Possibly with a wrap of tape over the New money still coil. With the pump.running whenever the engine is running
Bill

[ndutton]

Bill, are you FWC? Somehow I think you are as a few comments hint at it. If yes, I don't understand why you'd be messing with 'discharge' (raw?) water.

Could you post your drawing?

[hanleyclifford]

Bill - I understand that you would like to keep your present tank, but in all honesty and considering your new FWC status, the real solution is a new hot water tank with an exchanger coil for engine antifreeze built right in. You could spend a lot of money, energy, and engine room space doing the "work around" and not have a satisfactory product. FWIW

[romantic comedy]

This is what I did. Not sure it was the best idea. I should probably have just made the air flow better. But I like to have fun, so this is what I did. So far the copper has kept it cooler.

[BadaBing]

Last winter, when I rebuilt.the exhaust, replaced the stand pipe, and rebuilt.the top end of the engine I converted to FWC.
However, I was not satisfied with my engine temp. While using fwc, antifreeze in engine, he, an d raw water with the Johnson electric pump I couldn't get my temp, after running und e r power for a trip across the bay, under 190.
To test if my fears were unfounded, before taking a long cruise, we did a 2 day trip to Atlantic City and made 4 transits of the Absecon inlet. At least 2 inlet transits were against the 2-4 knot tide.
Half an hour under full power, against a tide load drove the temp over 200. Almost to boiling the antifreeze. After dropping anchor, if I shut her right down, she hisses like a big snake.
We wanted to do some cruising! And I was tired of cooling experiments. After returning from that early season trip, I pulled the HE and pump and went back to raw water cooling.
For the rest of the season, with no thermostat, I never saw above 140 again.
FWC is wonderful, but this A4 preformed well for 40 years with raw water. Who am I to question her preference? ( I know some.May think, push on,, don't give up till it works BUT, I own the boat to sail it)

So the HE I have to work with, for now, is the one I had tried to use for FWC and would use hot raw water from the Thach discharged manifold, into t the HE and out to the standpipe.

Bill

[BadaBing]

One more thought.
The raw water discharge is hot but not so hot that I can not put my hand in it as it exits the boat.
Knowing that 140 is well below best temp performance wise I intend to install a thermostat to bring the engine and water temp up to 160 + or - when I recommissioned her in the spring. That, a hot water coil and EI wrap up my engine plans for this season. Refrigeration and new bottom paint should get us to splash.