I bought this house recently and I have Gas Water Heater and Weil McLein Water Boiler for heating. There is an expansion tank installed on the Hot Water side (where heated water comes out of boiler) of the boiler. And there is no expansion tank installed around the Water Heater. Is this configuration OK? I get this doubt becuase I have read in many posts that Expansion Tank must be installed on the cold water side of the Water Heater.

In my boiler I have Pressure/Temperature gauges in two places.
1. One where the heater water comes out of boiler
2. and another one is installed on the return water pipe taht enters boiler.

1st gauge reads 30 psi and 180 farenheit. 2nd gauge reads 25 psi and 170 farenheit. Why is my return water so hot? Shouldn't it be cold? Is this a problem?

Thanks for your help.

- Vasan