GBM wrote:
"Rich Hampel" wrote in message
...

The water temperature will soon reach a steady state once the heater
temperature 'equilibrates'. Typically such a heater will come up to
temp quite fast. My 7 gallon heater will heat to 'hot' water from the
engine loop in about 10-15 minutes. Was the same with an Atomic 4 as
it is with my 3QM30. Actually the cooler the water in the manifold is
actualy better ... less carbonate (salting) deposition.... and heat
transfer is regulated by the 'log mean temperature difference' - the
cooler the inlet water the better the overal heat transfer.



Thanks Rich - I think I will try it - It seems such an easy way to get some
hot water without a closed circuit system. Got to order the heater first!

GBM


I'll be curious about the results. From what I've heard,the raw water
systems don't heat the water enough to really heat up a water tank.

My system has an 11 gallon tank on a 2GM20FC (fresh water). When
running hard, the engine water temp gets up to 170+ and the hot water
tank gets fully heated in under 30 minutes. However, when used for
battery charging, the temp barely gets to 160, and the hot water tank
takes the full hour to heat up, and even then its not as hot as when
running hard.

As near as I can tell, the target for the hot water tank is about 160
degrees. IIRC, the PS test heated to 160, and then measured to
cooldown rate - the goal was to have hot water the morning after a run.

I think the tstat on the Yanmar raw water systems is set at 140, but
I've also heard 125 degrees. I don't know if that implies that the
loop you speak of is reduced to this lower temp. Of course, if all
you did was heat the tank to 120 degrees, that would be a big step up
from cold - it just means that you can't count on much heat left a day
later.