Indirect Off Steam Boiler or Condensing High Efficiency Gas Water Tank

okgnyc

Hi.



I recently purchased a late 1880s Brownstone in Brooklyn NY. It is a two family house of approximately 3600 square feet. The existing setup is a steam boiler ( 250k BTU oversized!), and two AO Smith 40 gallon gas fired water tanks in parallel.



I'm looking to modernize the system. Most likely I'll stick with steam, albeit with a properly sized boiler.



My question pertains to maximizing the efficiency of the domestic hot water system. To maximize efficiency is the best course of action to get a well insulated indirect tank, or to get a separate high efficiency condensing unit such as the AO Smith Vertex? The indirect seems efficient for the winter months, but is it less than ideal to fire a large boiler in the summer months just to heat domestic water?



Also, if I end up going with a hot water system, in lieu of steam, does this equation completely change?



Thanks in advance for all the help!

Steamhead

First off, keep the steam

and use thermostatic radiator valves in the tenant space to give them some means of control.



A coil-type indirect off the steam boiler will work well as long as all of the coil is below the boiler's water line, and as long as you don't want to bill the tenants' hot water separately. If the tenants have their own gas meter, they should pay for their own hot water. Whether to use a standard tank-type heater or some other type will depend on how much gas the incoming service and meter will handle, also whether there is a safe place to sidewall-vent a unit that cannot use a standard chimney.