Passing my heater this morning, I grabbed the inlet and the outlet pipes on
the water tank to see the temperature differential. They were both hot.
There is a valid reason for this. I'll post the answer later for anyone that
cannot figure it out.
Run the hot water for a second and the cold pipe will get cold. Heat
rises and a sitting tank is bound to have hot water rise in the cold
pipe by convection. Also the pipe inside the tank that brings the cold
water to the bottom of the tank may be broken off.
Normally, the outlet is hot when running water and the inlet is made cold by
hte incoking water. This is, though, an indirect fired water tank.
Having used enough hot water to trip the thermostat, the heating sycle
started so water was passing through the heat exchanger and back into the
storage tank, already heated. Only during the actual heating cycle do you
have both pipes hot.
What are you talking about? The heat exchanger on an indirect is a loop into
the boiler, not the potable water. The only way your scenario would be true,
is if the potable water went through a coil in the boiler before it went to
the domestic cold inlet on the indirect. Without anyone knowing what type of
system you have and how it's set up, any answer could only be a wag.
Your answer is a wag. A wrong wag. True that some indirect fired systems
have an internal coil for exchange in the tank, but mine has an external
plate exchanger on the boiler. As stated, both top pipes are hot when using
and making hot water. That was the "mystery" compared to a regular stand
alone heater. There is a third pipe at the bottom of the tank too to
complete the loop.
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