On Sat, 18 Feb 2006 09:58:43 -0800, Grant Erwin
wrote:

I have a 10 year old hydronic heating system in my home. There is a boiler and
it leads to a special tank which holds the heated water, which is circulated on
demand through wall registers. The thing that makes this tank special is that it
also holds potable water, i.e. a hot water tank. The heating and potable water
never mix, ever.

My tank has developed a pinhole leak right up on the domed top. I cannot imagine
that there wasn't a manufacturing defect, but the warranty says that if the
house is sold the warranty ends at 5 years. Before I buy a new tank at a
whopping $1200, I want to at least try to fix the pinhole. My heating system guy
shook his head and said "it would never hold" but I don't see how I have much to
lose. There is almost certainly some kind of liner which I'd have to worry
about, so I'd want to use minimum heat.

If it's a lined tank you are probably going to have to stick with
non-heat methods - the lining can be "Glass" (porcelain) or some sort
of epoxy or blown-in-place polyethylene. Either way, the application
of welding or soldering heat is going to be a problem.

And consider what will happen if that patch pops big-time, and you
have a half-inch gusher flowing your water main full out into the room
- is this tank somewhere you'll have huge water damage problems?

I'd try an external epoxy patch as a stop-gap to either buy a few
weeks or get through this winter, and I'd try to work some epoxy
inside the hole to act as a mushroom plug of sorts. If it's a
flexible lining you could use a mechanical seal like the 'boiler patch
bolt' with a big neoprene washer under the head. But if it's a rigid
lining (porcelain) you could crack a big chunk off on the inside and
accelerate the deterioration.

And now the "r.c.m Monster Garage" question: Is it possible to
split up the systems and save a lot of dough in the long run?

Instead of spending $1,200 for that special heat-exchanger tank you
install a plain old electric DHW water heater for $300, and a plain
hot-water storage tank (or a second electric water heater) for the
boiler for roughly the same, and an external water-water heat
exchanger and a pair of wet-rotor circulation pumps to heat the DHW
from the boiler side.

You leave the electric heating elements turned off for normal use,
and if the boiler or the heat exchanger dies, you can fire up the
electric elements as an "Oh, Sh*t" backup heat system.

The storage tanks they sell for solar systems are nothing more than
an electric water heater with no wiring, elements or thermostats
installed. You can even remove the access hatches and see the plugs
in the element holes.

There are other dodges to this, but what fuels do you have available
at the house?

If you have natural gas or propane available, substitute the
appropriate gas water heaters for the storage tanks. (And plug off
the vent flues when not in use to prevent heat loss.) And then you
have the option to switch over if fuel oil prices spike higher than
propane or natural gas, or vice versa.

This is where having a 'Plan B' shines. I have accounts with big
condo buildings with two or three Raypak gas fired hot-water boilers
for DHW in a tankless pipe-circulation system, one of the buildings
has them all in the same room - but plumbed as totally separate
systems. No "Oh Sh*t" valves to tie two sections together for a few
days in case one of the boilers fails. The hot water might get
lukewarm during the "morning rush" but if the residents know, they can
adjust.

-- Bruce --

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
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