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Indirect Water Heater & Old Boiler

Good Afternoon Heating Help!

We recently bough a home (built in 1979) that currently has gas baseboard heat (4 zone) and a standard gas chimney vented water heater. The water heater is about to go so I have had a few plumbers in to price out options. All of them have recommended I go with a indirect water heater fed off of our existing boiler. The existing boiler (Utica Model No. 200 AGB) is original to the home and my concern is that this will add more stress to an already old boiler. All of the plumbers have said this is not an issue and that the boiler is better served running all year than sitting dormant for 6-7 months a year. We are not currently in a position to replace the boiler. Now I would love the indirect because when we plan on replacing the boiler (hopefully in 2-3 years) I think they will complement each other from an effecenty standpoint. However I am tempted to just go with a standard water heater to not stress out the system as we cannot afford an emergency replacement.

Do the experts here agree that adding an indirect to an old boiler should not cause it to fail sooner? I have attached a photo of the tag on the boiler.



  • Bob Bona_4Bob Bona_4 Posts: 2,083Member
    Listen to your plumbers, I agree with them. You're not going to stress out the boiler, in fact, it will be better off being run all year.
  • HatterasguyHatterasguy Posts: 6,058Member
    There is no "stress" on a cast iron boiler. If they don't corrode, they last forever. The burner's components will wear a bit more but they can easily be replaced if they fail.

    The indirect makes the most sense in your situation.

    However, you want the indirect installed with a large differential (preferably 25-30 degrees) so that it only fires the boiler infrequently. If they install it with a typical 7 degree differential to keep the tank temperature in a narrow range, the boiler is going to run 10 times a day and the efficiency is going to be in the toilet.

    To set it up that way will require the use of a tempering valve (at additional cost) but it's mandatory for any kind of efficiency out of the indirect.
  • DP1982DP1982 Posts: 14Member
    Thank you Bob/Hatterasguy,

    As always great information to put me in the right direction!
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