Uninstalling and analyzing this heater is a good thing. Further
inspection may just exonerate the design. If you look closely at the
bottom tubes in this picture,
http://sports.webshots.com/photo/291...97509592UoBucA
you'll notice that they enter the tank through two very loose sleeves.
Check out the ample clearance between the coil ends and the sleeves
they pass through. I need to find a way to determine if what appears to
be an exageration of sloppy pipe fitting is in fact a clever design
intended to drain any chemicals away from contact with fresh water
should the tubing leak for any reason. It is possible that the design
is a tube inside a tube, with the outter tube being an non-pressure
path out of the unit. If that's the case, I can see why the hot water
heat is so slow to come up to temperature, but the added safety feature
would be worth the wait.
As an experiment, I'm thinking of suspending the tank with the tank
face parallel to the floor, so that any drop of water in the tank will
drip from the boiler drain. Then, I would feed a stream of water into
the sleeve and see if it eventually begins to flow from the other side.
If it does, and if it never flows from the boiler drain, then I can
conclude that there exists an isolating compartment, which is vented to
atmosphere, between the anti-freeze filled tubing the fresh water tank.

If I find that to be true, I'll connect to the engine again without
losing sleep.
Scout



Jeff wrote:
I think Seaward made two versions, SS and Aluminum.

I have a galvanic isolator, and use the non-toxic anti-freeze.

Scout wrote:
How many here have a hot water heater that works with the engine's
coolant system as a heat source?

It is a very thin line separating that toxic material from your drinking
water supply. The closed engine coolant loop may reach 15 psi when hot,
and could easily outmatch the force in the fresh water system,
especially if you run dry or turn off your on-demand pump for any
reason. A pin hole or a crack in the hw heat exchanger could have deadly
results.

In my work as a boiler tech, we were never permitted to use toxic
anti-freeze in boilers that produced domestic hot water (summer-winter
boiler packages). I've replaced tens of those coils due to leakage!

Just a thought, but Bart's recent comment about galvanic isolation got
me thinking.

Maybe I'll get that RedDot heater that Ole Thom has mentioned, remove
the anti-freeze loop from my fresh water supply, and use those lines to
supply aux heat in the cabin.

Scout