Hot water question for Larry
 

"Roger Long" wrote in news:xkWRf.18096$jf2.9960
@twister.nyroc.rr.com:

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


Ok, let's do the arithmetic.

Power = Volts X Amps
So, screwing that around, at 1,250 watts at 14V (charging full), let's
see, carry the 2, push this button, turn the calculator right side up and
we get....Wow! damned close to 90 Amps! The inverter, not a perfect
device but fair, would probably draw 95A at 14VDC to run the water
heater. Hmm...The alternator will put out 35A so we won't ever see
"charging" if this inverter is on....nope. We'll see DISCHARGING! So,
our voltage is a smidgen high in the calculation if we
discharging....Let's say 12.2V if the batteries are up, at least for a
while. 1,250 watts at 12.2V, carry the 2, push this button, rotate the
calculator around so we can see the display and it reads......WOW! 102
AMPS NOW round that up to 110 from the inverter! 35A coming from the
tiny alternator running wide open (it won't destroy it, by the way, it
puts out what it can)...and the ol' house batteries are gonna need to
supply 110A minus 35A = SEVENTY FIVE AMPS! How big did you say those
house batteries were?!! Ouch! PHooey....This isn't gonna work, is it?

You'd be makin' hot water from the house batteries, even WITH the engine
running full throttle....(sigh).

(Calculator to off)....

I saw on a previous post about cooling water heating so slow......

Question: I assume this Atomic 4 is direct seawater cooled, right, as
you say the cooling seawater is heating the hot water tank on its way to
the exhaust....right? Doesn't these seawater systems cooling the engine
have to run lots of water through them to cool the exhaust so it doesn't
burn the exhaust hoses? I can see that water never gets "hot", like a
car running without a thermostat. I've never been around an Atomic 4 so
don't know what the cooling system loop looks like, so I'm asking.

If it DOES have a restrictive thermostat, no water heating in the hot
water tank would happen until that thermostat opened. Wouldn't a
seawater cooled engine have to have a seawater bypass into the exhaust
around this thermostat-controlled engine to force lots of water into the
exhaust before the exhaust hoses melt before the thermostat opens? If
that's the way it works, isn't your plumbing forcing COLD seawater,
bypassed around the engine, through the hot water tank...before the
engine thermostat makes it warm....on its way into the exhaust??

Coolant looped systems with a seawater heat exchanger, I can see, would
heat water much better as the coolant is really hot, like your car, with
its thermostat actually pressurizing the water through the hot water
tank's exchanger. Lionheart's Perkins 4-108 heated water at sea produces
a LOT faster recovery in the little 6-gallon tank than the 115VAC at the
dock does. A whole lot of us can shower, making the whole crew MUCH more
socially acceptable in the process, during the battery charging phase
under Perkins Power. It only takes it a few minutes to recover and scald
the next victim in the head....or on the deck if no women object.

The Atomic 4 should make a LOT of great heat to heat the water tank. Why
do I suspect we're not actually forcing the heat through the water tank's
heat exchanger right?? The gas engine is more inefficient than diesels.

??????

Hot water question for Larry
 

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.

Hot water question for Larry
 

"Roger Long" wrote in news:adXRf.9323$Da7.2373
@twister.nyroc.rr.com:

OK Larry, you don't need to chime in and make me feel even more
foolish. I did something wrong in my head with that calculation.

Damn, where is that calculator?



Oops...sorry. Didn't read this before I posted your answer....(blush)...

Just don't make those calc errors on the shape of the next trawler hull!...
(c;

Hot water question for Larry
 

Roger Long wrote:
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.

For those boats which have Eberspacher and similar heating systems, you can
now buy a heat exchanger which will give you virtually instant hot water
within 5 minutes of the diesel-fired heater coming on in the morning, or
whenever. Why bother with all this imersion heater/inverter crap?

DP

Hot water question for Larry
 

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.

Hot water question for Larry
 

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.

Hot water question for Larry
 

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.

Hot water question for Larry
 

Don W wrote in news:QbfSf.39468
:

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



Another point that needs investigating is the water pressure differentials
around this system the hot water hoses are hooked to.

If the supply hose can be connected to the high side of the thermostat, the
thermostat will provide pressure to drive water through the water tank.
However, if you look at the water inlets to the exhaust, you'll see it's
not just pouring every available gallon of water into the waterbox to flood
it. There are "jets" built into the manifold that keep the water from
swamping into the exhaust and flooding back into the open exhaust
valves/ports. They're like spray nozzles. If the outlet of the hot water
heater is hooked to the plumbing supplying these nozzles, there is
considerable back pressure fighting against driving the water through the
water heater's heat exchanger, which is counterproductive. I bet it's a
bypass through the water heater, not a full-flow system, like the heater in
your car.

Hot water question for Larry
 

Gary wrote in news:XTmSf.149826$sa3.13759@pd7tw1no:

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



I'd bet that didn't happen within rowing distance of the dock or trailer,
either, right?...(c;

Hot water question for Larry
 

How is the heat exchanger plumbed in to the system?

Is it simply taking the cooling water as it is returned to the exhaust
system, if so it may be very slow as this water is a mixture of hot from the
"Block" and cold from the thermostat bypass.

Or is it taking from a take off ports on the engine "Block". This is usually
better but on small engines like the Volvo and Bukh for rapid heat up a
separate 12v pump is needed to assist flow. It can have a thermostat if this
gives better control of heat.

Alec


"Roger Long" wrote in message
...
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