As you may remember, I have had propane tankless hot water heaters for many
years and have they work well every day.
Norm
S/V Bandersnatch
Lying Julington Creek FL
----- Original Message -----
From: Lee Haefele
To: [email protected]
Sent: 11/21/2007 11:48:48 AM
Subject: [Liveaboard] Hot water project
I would like hot water for showers and dish washing without running the engine.
Would also like to improve time the engine takes to heat water.
I have an Attwood 11 gallon heater, it seems to have ~1/2" of fiberglass
insulation, at least on the front where I can see. I have new Westerbeke 44B
motors, the antifreeze circulates from below the thermostat, to the water
heater and back to the water pump. The previous Westerbeke 42B engine tapped
water with a restricting double "T" that was inline to the heat exchanger.
Neither arrangement would heat water at idle, both took 1-2hrs at cruise speed.
There is an expansion tank plumbed in the antifreeze output line of the
heater, it is such that all water flows through, it holds about a gallon and
takes about 5 minutes to heat after the hoses are very hot. So I think flow is
less than 1 quart/minute. I am going to replumb this so that the hot water
flows directly back to the engine and the tank is on a "T". Doubt this will
make much difference. The exit water is colder than the entry water, possibly
by 30 degrees, but it is hard to get a good reading on a rubber hose. !
Other boaters heat water in less than 1/2 hour, why is mine slower and what
can I do to improve it? Is there a better place to tap hot antifreeze?
I have 4 120W solar panels and usually have some excess energy, however, I have
a Blue Sky MPPT controller that does not switch excess power to a load.
Possibilities: Foam insulate existing heater (What to use? Great Stuff brand?)
and use either a 12V heating element or a 240V element run on 120V from the
inverter (This will give 1/4 wattage), combined with a wind up timer switch.
Automatic operation would be much better, is there any way I could use a Blue
Seas adjustable battery combiner for this? Any other ideas?
Big $$ idea: Replace heater with Isotherm model 40DS, ~$800?, this has foam
insulation, a double loop in the exchanger tube and this model has 2 exchanger
loops. Could I plumb a solar water collector in to the second loop? This
could be as simple as a coil of black pipe, but would need a pump and controls.
I have heard of some mini solar pumps, what I find is expensive. I could plumb
a coil of hose in line with the shower, but I normally shower not at times of
hot sun. It seems silly to have tropical sun and no hot water.
Lee Haefele
Leopard 38 cat Alesto 2
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