"jamesgang" wrote in message
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On Monday, February 4, 2013 2:56:03 PM UTC-5, TomR wrote:
PrecisionmachinisT wrote: "Existential Angst"
wrote in message ...
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A friend has a house that came with two identical water heaters
hooked up in parallel. He doesn't need all the capacity, so we turned
one of them off and turned off the water going into it. This was
several years ago. The water heater was about 4 years old at the time,
it's now 7 years old. Given that a tank has already had some
service, what would you guys do to try to keep the spare tank
available for as long as possible? Leave it full of water?
Drain it? My thought was that draining it would be worse,
because allowing air in, it would rust....... Fill it
with water, add a rust inhibitor? As an aside, shouldn't two water
heaters be hooked up in series? Been meaning to post that to the group.
The rcm peeple should have some insights into both Qs. Having a
second tank that's unpowered, uninsulated, and plumbed in series so that
cold water passes through it first will reduce summertime AC and water
heating costs by naturally warming the inlet water up to room temp. I am
not sure, but I think that technically speaking that approach won't save
any money on energy costs. The reason is that for the water in the first
tank to be brought up to room temperature, it needs to draw its heat
energy from the room. So, it will cost that much more to heat the room
because some of the room heat is going toward heating the water in the
first tank. In other words, there is no free heat -- it either gets its
heat from being heated by at working hot water tank, or it gets its heat
from the room and that heat energy needs to be replaced by the heating
system for the room.

I believe he said "reduce summer time costs". And it does do that since
ground water and city water are usually a lot cooler than summer air temps.

I run two wh in series with the 1st one on a 30amp switch in the hall. When
I anticipate guests or otherwise needing extra hw I just turn it on.
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Staged water heating.... what a neat idear!!
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EA