Freddy wrote: In my opinion it's a necessity. Allowing the boiler to drop below 140* is not a good thing. The last thing a boiler wants to do is expand, contract, expand contact. It won't bother a steel boiler too much, but it can be bad for a cast iron boiler. Also, dropping below 140 can allow condensation to occur in the exhaust & that's a bad thing too. That might be more of an oil thing than a coal thing, but physics is physics.
My thoughts exactly. Cold return water killing the temps is not good at all. You could have vastly better heat with some changes.Probably save quite a bit of fuel also.