In some systems, outdoor reset control can vary the supply
water temperature from a relatively high design temperature down to just above room temperature.
When floor heating
and domestic water heating occurred at the same time, I discovered there was no
flow through the heat exchanger in the indirect tank.
An installer was
asked by a client to use both a ground source heat pump and a boiler as
alternative heat sources in a zoned, low-temperature hydronic distribution
system.
An installer uses a 4-way
motorized mixing valve to interface between a conventional gas-fired cast-iron
boiler and a low temperature radiant panel system.