On 2005-10-28, Bob wrote:

More likely, the pressurized water is the cold water supply to the
water heater. The other way, the shower temp would change as the
pipes warmed up, etc, and special plumbing to the shower would be
required.

I'm intending to just run the cold water supply to the shower through
the heat exchanger. This is easier than running the entire cold water
supply to the hot water heater through the heat exchanger. I don't
really want to have the pressure drop for all the hot water outlets,
as well.

As to the shower temperature increasing as the heat exchanger heats
up, that is true. Of course, it is already the case that the shower
temp slowly increases as the hot water pipes heat up and the stale hot
water is drained out. If it becomes a problem, I will either switch
to a thermostatic shower valve, or I'll put a mixing valve into the
cold water supply to the shower, mixing preheated cold water with hot
water to, say, 90 degrees.

How does a thermostatic mixing valve behave if the set temperature is
above the temperature of both inlets, or below the temperature of both
inlets?

Thanks, Wayne