The AC element on my hot water heater is 1250 watts.

Can you safely draw from an inverter while the engine is running? If
I put in a 1500 watt inverter and used it carefully to only run the
water heater (which would also be getting waste heat from the cooling
water coil) and was sure that my other 12 V loads were minimal at the
time, could I get my hot water tank heated up in the 5 - 10 minutes
that I do with shore power? (It takes motoring half a day to do it
with the waste heat alone from my 20 hp diesel).

Or, will this burn up my little 35 amp alternator? I have a 55 I can
put in but it needs a different voltage regulator.

I would never try to make hot water from the batteries through the
inverter for obvious reasons.

--

Roger Long

Roger Long wrote:

(It takes motoring half a day to do it
with the waste heat alone from my 20 hp diesel).

Something may be wrong with your setup, Roger. IIRC, you have a very
similar engine to my Yanmar 2GM20FC. I run the coolant through an 11
gal heater, and it get quites hot in well under an hour, maybe even 30
minutes. Actually for a few years the engine was running a tad hot
(180 degrees) but after cleaning out the heat exchanger its normally
at 165-170, which probably slows the heating a bit. Even if all I do
is run the engine for a little while to set an engine, it usually
heats enough for showers for the day. When I run for charging, the
engine never gets above 160, so in that case after an hour run its
still not quite as hot as when we're pushing hard.

If you had a large alternator (like my 110 Amp) then by putting a
large load on it you might be able to raise the engine temp enough to
heat the water faster!

The heat exchanger in your set up is the key. Simple raw water
systems like mine run way too cool for best diesel engine operation.

As described in my response to Tom's Atomic 4 cooling question down
below, I'm looking into a keel cooler to get the operating temperature
up.

I'm glad to hear that your engine does put out that much heat. That
means that the keel cooler setup, which would cost about the same as a
big inverter, would give me hot water in more reasonable time.

--

Roger Long



"Jeff" wrote in message
...
Roger Long wrote:

(It takes motoring half a day to do it with the waste heat alone
from my 20 hp diesel).

Something may be wrong with your setup, Roger. IIRC, you have a
very similar engine to my Yanmar 2GM20FC. I run the coolant through
an 11 gal heater, and it get quites hot in well under an hour, maybe
even 30 minutes. Actually for a few years the engine was running a
tad hot (180 degrees) but after cleaning out the heat exchanger its
normally at 165-170, which probably slows the heating a bit. Even
if all I do is run the engine for a little while to set an engine,
it usually heats enough for showers for the day. When I run for
charging, the engine never gets above 160, so in that case after an
hour run its still not quite as hot as when we're pushing hard.

If you had a large alternator (like my 110 Amp) then by putting a
large load on it you might be able to raise the engine temp enough
to heat the water faster!

Hi Roger,

Roger Long wrote:
The heat exchanger in your set up is the key. Simple raw water
systems like mine run way too cool for best diesel engine operation.

Whether an engine is raw-water cooled or cooled through a heat
exchanger should have nothing to do with the temperature
it operates at.

Somewhere in the system should be a thermostat which prevents
new coolant from being pumped into the engine until the
coolant in the block has come up to the proper temperature.
This will work whether the coolant is an antifreeze mixture
pumped through a heat exchanger, or raw water drawn through a
water intake.

Is your thermostat possibly stuck open, or missing? Or am I
missing something here?

Don W.

Don W wrote:
Hi Roger,

Roger Long wrote:

The heat exchanger in your set up is the key. Simple raw water
systems like mine run way too cool for best diesel engine operation.


Whether an engine is raw-water cooled or cooled through a heat
exchanger should have nothing to do with the temperature
it operates at.

Somewhere in the system should be a thermostat which prevents
new coolant from being pumped into the engine until the
coolant in the block has come up to the proper temperature.
This will work whether the coolant is an antifreeze mixture
pumped through a heat exchanger, or raw water drawn through a
water intake.

Is your thermostat possibly stuck open, or missing? Or am I
missing something here?


Yes, Yanmar (and other manufacturers) use a much lower temp for raw
water cooled engines. I believe it is to reduce precipitation of
salts. The thermostat and alarm are set to much lower temps - the
alarm is at 145 instead of 185 as on fresh water engines.

Don W wrote in news:Xp_Rf.1452
:

Somewhere in the system should be a thermostat which prevents
new coolant from being pumped into the engine until the
coolant in the block has come up to the proper temperature.
This will work whether the coolant is an antifreeze mixture
pumped through a heat exchanger, or raw water drawn through a
water intake.

Is your thermostat possibly stuck open, or missing? Or am I
missing something here?



I think what's missing is the directly cooled engine has GOT to bypass
water around the engine/thermostat into the hot exhaust to cool it long
before that thermostat ever opens. This means his hose-to-the-exhaust has
COLD water in it before the thermostat opens to cool the exhaust (and the
hot water tank). The amount of water through a thermostat that had bypass
water flowing around it would be miniscule. Outboard motors are like this,
somewhat. The exhaust hardly gets warm, certainly never warm enough to
melt the paint on it....or to heat water in a tank.

Larry wrote:

Don W wrote in news:Xp_Rf.1452
:


Somewhere in the system should be a thermostat which prevents
new coolant from being pumped into the engine until the
coolant in the block has come up to the proper temperature.
This will work whether the coolant is an antifreeze mixture
pumped through a heat exchanger, or raw water drawn through a
water intake.

Is your thermostat possibly stuck open, or missing? Or am I
missing something here?




I think what's missing is the directly cooled engine has GOT to bypass
water around the engine/thermostat into the hot exhaust to cool it long
before that thermostat ever opens. This means his hose-to-the-exhaust has
COLD water in it before the thermostat opens to cool the exhaust (and the
hot water tank). The amount of water through a thermostat that had bypass
water flowing around it would be miniscule. Outboard motors are like this,
somewhat. The exhaust hardly gets warm, certainly never warm enough to
melt the paint on it....or to heat water in a tank.

Hmm...

You are right about the exhaust manifold cooling of course, however
there should also be a hose coming directly from the engine block
which could be used as a source of HOT water to heat the hot
water heater. Perhaps it is just a matter of which hose is
connected to the hot water heater, or possibly putting in a
new fitting to allow the hot water from the block to flow
through the heater before re-entering circulation.

I think there has got to be a way to make it work like its
supposed to--even with raw water cooling.

Also, Jeff's comment about the use of lower temp thermostats
in raw water cooled engines makes sense to me, although my
5.7L Mercruiser runs around 160F, and it has raw water cooling.
However, even 145F water should be plenty hot to heat the hot
water tank, although it might take a bit longer. I think that
Roger's problem is that he is not getting 145 degree water.

Don W.

Sorry, I was thinking you had fresh water cooling. The thermostat on
your raw water system is set much lower than mine (140 degrees?)
making it real hard to get the hot water tank up to the 155-160
degrees that you'd like to see in order to have hot showers the next
day. You may even want to research the thermostat a bit - I've heard
conflicting setpoints, 125 or even lower.

Of course, you could always take a dip in ocean

Roger Long wrote:
The heat exchanger in your set up is the key. Simple raw water
systems like mine run way too cool for best diesel engine operation.

As described in my response to Tom's Atomic 4 cooling question down
below, I'm looking into a keel cooler to get the operating temperature
up.

I'm glad to hear that your engine does put out that much heat. That
means that the keel cooler setup, which would cost about the same as a
big inverter, would give me hot water in more reasonable time.

If your engine is running too cool anyway, why
don't you just decrease the cooling water flow?
That would give you a higher engine operating
temperature and hotter raw water for your heat
exchanger.

Chris wrote:
If your engine is running too cool anyway, why
don't you just decrease the cooling water flow?
That would give you a higher engine operating
temperature and hotter raw water for your heat
exchanger.

It will burn out the impellor. Ask me how I know.