RBM (remove this) wrote:
The heat exchanger is a tank with a coil in it and uses two circulators. One
circulator moves dirty boiler water through the coil in the tank and back,
that one would get clogged if there was to much sludge. The other circulator
moves the heat exchanger tank water through the heating pipes and back into
the tank


I had something different. I had a Weil Mclein steam boiler, that had a
spot to insert a coil to make hot water. The coil ( or heat exchanger)
is in direct contact with the boiler water. There was an inlet and an
outlet on this coil. Only this was not used for domestic hot water, it
was used for hydronic baseboard. We just attached a circulator, a
regulator valve for the water supply, and an aquastat. It was just one
circulator, not 2. so this is why I asked how sludge can be an issue
because the actual boiler water never comes in contact with baseboard
water in my set-up. But I have seen the setup you are describing in
other houses.