Cement lined chimney will low stack temp be a problem

Blackoakbob

We had a new burner installed for better dependability replacing a 40 + year old power burner but the new one has a stack temp at <350 degrees F at the breaching and the cement lined chimney goes up 40 ft thru a cold garage. My concern is possible condensing in the boiler or enough condensing in the chimney to detiorate the lining until it fails  the boiler is a fire tube scotch type cica 1965 low pressure steam 
Any thoughts, thank you

Big Ed_4

A chimney running up though the garage is not bad . North standing outside chimney really is the worse , A liner could not hurt . Size it to the new equipment would be best . A way to see if you really need a liner , on a cool day check the condensate leaving the chimney . There should be a space between the chimney and the condensate ..

STEVEusaPA

Are you sure you’re not underfired?

EBEBRATT-Ed

If your net stack temp stays above 330 you should be ok.

Big Ed_4

Scotch Marine boiler is very efficient ... The original owner knew and paid for it .

Blackoakbob

It is in a commercial  building and a commercial grade prefab chimney  sorry I  didn't  elaborate  more and a wet back scotch style boiler 

Blackoakbob

This new burner is the type that tunes it's  combustion by O2 varying gas and combustion air independently and modulates from high to low output by steam pressure my concern is too efficient (83%) for the old equipment chimney and boiler

EBEBRATT-Ed

@Blackoakbob 83% should be fine in a normal chimney especially with steam

Big Ed_4

Do you mean the burner controls the proper O2 for level of combustion ? That's cool