Hot Water -- Dumb Idea?
 

I'll be doing some extended cruising next year in places remote enough
that shoreside shower opportunities may be few and far between, and
the water pretty cold in August, let alone October, so I am
considering an engine heated hot water system.

The dumb idea is: "How about just diverting some engine jacket water
straight to my cold water shower fixture." I'm in fresh water, and
anywhere I would want to use it would be pretty clean fresh water.
Even with a heater tank I would probably use lake water in the system.
Comments?

Assuming that really is a dumb idea, how about recommendations and
caveats for installing a hot water system? How big a tank do you need
to get a satisfactory shower? Does running the engine while showering
extend that capacity a lot?

Thanks,

Rick

Ryk wrote:
I'll be doing some extended cruising next year in places remote enough
that shoreside shower opportunities may be few and far between, and
the water pretty cold in August, let alone October, so I am
considering an engine heated hot water system.

The dumb idea is: "How about just diverting some engine jacket water
straight to my cold water shower fixture." I'm in fresh water, and
anywhere I would want to use it would be pretty clean fresh water.
Even with a heater tank I would probably use lake water in the system.
Comments?

Doesn't that get mixed with the exhaust? ANd isn't the volume pretty
small at low rpm?


Assuming that really is a dumb idea, how about recommendations and
caveats for installing a hot water system? How big a tank do you need
to get a satisfactory shower? Does running the engine while showering
extend that capacity a lot?

Our boat normally comes with a 5 or 6 gallon tank; we opted for the 11.
THe month after it was "sealed in" practical Sailor did a review
which said that ours (Sealand?) was so bad at retaining heat they
couldn't even show it on the chart. However, it will take some major
work to get it out, so we're stuck with it for a while.

Even so, it holds enough heat for 24 hours so we can still take two
showers a day after running the engines, though they will be getting
down towards luke warn rather than hot. When we're sitting at anchor
for a long time I often take a shower while charging the batteries.
That way I'll have all the heat I need, and the heater ends up fully
charged. Running the engine for about 20 minutes is enough to generate
hot water. Running under low load, such has charging batteries, will
take a bit longer and doesn't get it quite as hot as powering at WOT,
which will generate the most heat.

Of course, we're talking about "navy showers" here. You get a little
wet, turn off the water, use a little soap, then try to rinse with a
pint of water. We probably use more like a gallon or so, but you can't
take a 20 minute steaming hot shower on a small boat.




Thanks,

Rick

On Mon, 15 Nov 2004 11:59:47 -0500, Ryk
wrote:
Assuming that really is a dumb idea, how about recommendations and
caveats for installing a hot water system? How big a tank do you need
to get a satisfactory shower? Does running the engine while showering
extend that capacity a lot?
==================================

Showering with engine water? It might work out OK but there's at
least some risk of getting rust and scale in your plumbing system, and
temperature regulation might be problematic as your engine thermostat
regulates itself. You will also be unable to turn the shower off or
regulate the flow rate. The flow constriction may even cause your
engine to overheat.

I think most people would opt for a conventional water tank with a
heating loop just for esthetic reasons. A 5 gallon tank is enough for
one or two brief showers, and yes, running the engine will extend your
shower time. My last boat had a 10 gallon tank and that was more than
enough with 2 people on board.

Jeff,
Could you wrap the heater with an insulating blanket like a house unit? If
you have room, might help.
MMC
"Jeff Morris" wrote in message
...

Our boat normally comes with a 5 or 6 gallon tank; we opted for the 11.
THe month after it was "sealed in" practical Sailor did a review which
said that ours (Sealand?) was so bad at retaining heat they couldn't even
show it on the chart. However, it will take some major work to get it
out, so we're stuck with it for a while.

I suppose wrapping would reduce the loses some, but it is a rather tight
fit in the locker and 3 sides probably can't be insulated. Actually the
inner cylinder is wrapped and contained in a larger box. Unfortunately,
because we opted for the larger it will take a saw to get it out for
replacement.

Frankly, we haven't had much of a problem since we normally vacation in
"heat wave" weather, and the need for a "hot hot" shower is minimal.
Although the temp is diminished, there is usually enough warm water in
the morning (16 hours after running) to shower, including the dog who
likes to swim. However, if we were to add more solar power to reduce
the number of times we run the engine for juice, we could have a problem
- I'd probably get one of those "black bag" heaters and rig it in the
shower so there would always be a reserve.

The one year we traveled in a nasty early winter we tended to stay at
marinas a lot so we could run electric heaters and have the water heated
electrically. Also, I suppose one could heat electrically with a genset
since they only draw about 1.2 kW and its a simple resistive load.

All that said, were I doing it over, I would review the Practical Sailor
result (Jan '99?) before choosing a water heater


MMC wrote:
Jeff,
Could you wrap the heater with an insulating blanket like a house unit? If
you have room, might help.
MMC
"Jeff Morris" wrote in message
...


Our boat normally comes with a 5 or 6 gallon tank; we opted for the 11.
THe month after it was "sealed in" practical Sailor did a review which
said that ours (Sealand?) was so bad at retaining heat they couldn't even
show it on the chart. However, it will take some major work to get it
out, so we're stuck with it for a while.

In article ,
Wayne.B wrote:

Showering with engine water? It might work out OK but there's at
least some risk of getting rust and scale in your plumbing system, and
temperature regulation might be problematic as your engine thermostat
regulates itself. You will also be unable to turn the shower off or
regulate the flow rate. The flow constriction may even cause your
engine to overheat.

I think most people would opt for a conventional water tank with a
heating loop just for esthetic reasons. A 5 gallon tank is enough for
one or two brief showers, and yes, running the engine will extend your
shower time. My last boat had a 10 gallon tank and that was more than
enough with 2 people on board.

One thing that might be considered here is to use the engine cooling
water, in a closed secondary cooling loop, thru the Hot water tank.
We use this type of system for heating water for remote cabins in
alaska. You would run the engine to heat the water in the domestic
hot water tank, via a secondary engine cooling loop. I have a really
nice Onan 3kw Genset that provides power for my Remote Cabin. It
was originally a Marine Genset with water cooling thru a heat exhanger.
I scrapped the Raw Water Wet Exhaust, and added two Radiators with
electric fans, (one inside the cabin) to the Primary cooling loop, and
run the Secondary cooling loop thru a 20 turn 6" diameter 3/4" copper
pipe that is inside the domestic Hot Water Tank for the cabin. The
Generator powers a 2.6Kw Inverter/Barttery system for power, and heats
the cabin interior via one Radiator/electric fan, until the cabins
interior temp comes up to 72F, then the fan shuts off and the heat
goes thru the heat exchanger to the secondary loop to the Hot water
tank until it comes up to 160F. Then the electric fan on the exterior
radiator turns on and dumps the heat to the outside air. Usually takes
about two hours to heat the cabin from atmospheric cold, and bring the
domestic hot water tank up to temp. this is very close to the amount
of time for the inverter to rechage the Battery bank back to 90%, as
well. Very efficent system.

Bruce in alaska
--
add a 2 before @

I've always been of the impression that heat exchanger type
water heaters don;t work well with raw water cooled engines.
The raw water doesn't get all that hot in its short trip through the
engine.

Doug
s/v Callista

"Bruce in Alaska" wrote in message
...
In article ,
Wayne.B wrote:

Showering with engine water? It might work out OK but there's at
least some risk of getting rust and scale in your plumbing system, and
temperature regulation might be problematic as your engine thermostat
regulates itself. You will also be unable to turn the shower off or
regulate the flow rate. The flow constriction may even cause your
engine to overheat.

I think most people would opt for a conventional water tank with a
heating loop just for esthetic reasons. A 5 gallon tank is enough for
one or two brief showers, and yes, running the engine will extend your
shower time. My last boat had a 10 gallon tank and that was more than
enough with 2 people on board.

One thing that might be considered here is to use the engine cooling
water, in a closed secondary cooling loop, thru the Hot water tank.
We use this type of system for heating water for remote cabins in
alaska. You would run the engine to heat the water in the domestic
hot water tank, via a secondary engine cooling loop. I have a really
nice Onan 3kw Genset that provides power for my Remote Cabin. It
was originally a Marine Genset with water cooling thru a heat exhanger.
I scrapped the Raw Water Wet Exhaust, and added two Radiators with
electric fans, (one inside the cabin) to the Primary cooling loop, and
run the Secondary cooling loop thru a 20 turn 6" diameter 3/4" copper
pipe that is inside the domestic Hot Water Tank for the cabin. The
Generator powers a 2.6Kw Inverter/Barttery system for power, and heats
the cabin interior via one Radiator/electric fan, until the cabins
interior temp comes up to 72F, then the fan shuts off and the heat
goes thru the heat exchanger to the secondary loop to the Hot water
tank until it comes up to 160F. Then the electric fan on the exterior
radiator turns on and dumps the heat to the outside air. Usually takes
about two hours to heat the cabin from atmospheric cold, and bring the
domestic hot water tank up to temp. this is very close to the amount
of time for the inverter to rechage the Battery bank back to 90%, as
well. Very efficent system.

Bruce in alaska
--
add a 2 before @

On Tue, 16 Nov 2004 16:58:32 -0500, "Doug Dotson"
wrote:

I've always been of the impression that heat exchanger type
water heaters don;t work well with raw water cooled engines.
The raw water doesn't get all that hot in its short trip through the
engine.

Thanks Doug. The jacket water temperature indicator on my Atomic 4
shows 150 F (how accurate that is I don't know). I would expect that
to be able to get a tank up to respectable domestic hot water temps.
Does anybody have direct experience on this one?

Ryk

In article ,
"Doug Dotson" wrote:

I've always been of the impression that heat exchanger type
water heaters don;t work well with raw water cooled engines.
The raw water doesn't get all that hot in its short trip through the
engine.

Doug
s/v Callista

Depends on the setup, i would suppose. Most of the commercial
units I have used have a two loop design with a heat exchanger
between the loops, and the raw water running thru the secondary
loop. They have a thermostat in the Primary loop, that sets
the temp for that loop and the engine. Typically these are 180F
and can be as high as 200F. The secondary loop only has to remove
the total energy being dumped by the primary loop and can run at any
temp that allows removal of the heat energy being produced. In my
cabin heating system design, the primary loop is designed to:
1. heat the airspace in the cabin.
2. heat the domestic hot water.
3. when all the other energy needs are met, dump the waste heat
to the outside air.

The primary loop runs at 180F which is thermostat regulated.


Bruce in alaska
--
add a 2 before @