Approaches to replacing (+/-) 20-year old natural gas hot boiler

brucewo1b

http://www.heatinghelp.com/heating_howcome1.cfm

Gary_19

Different Approaches to NG Boiler Replacement

Our early 1900s home has a closed gravity hot water heating system whose system of cast iron radiators are supplied by a (+/-) 20-year old natural gas boiler (American Standard Gas Boiler, model G26DPG, A.G.A. ratings: input 150,000 Btuh/output 120,000 Btuh). The boiler operates at 165 degrees F with a maximum water pressure of 30 PSI. Three inch hot water outflow and cool water return flow pipes connect to the boiler. Based on the Equivalent Direct Radiation (EDR) method the heat emitted by the seven existing radiators is estimated at about 78,000 BTUs.

We would like to replace the existing low efficiency boiler with a new high efficiency natural gas boiler (ex. comparable to the Dunkirk Quantum 90-200 or even a Dunkirk Q95-200M – both with 1-1/4” plumbing connections). From what we have read a recirculation pump would be required as part of any new boiler installation, because the operation of the pump is integral to the boiler’s efficiency.

To date we have received preliminary information from potential contractors that offer markedly different approaches to replacing this boiler.

Since the gravity operation of the radiators supplied by the existing hot water discharge and cool water return system is functioning perfectly, which course would be the best for us to follow (and any significant advantages or disadvantages to each on initial investment and annual operating costs). (1) Simply replace the existing natural gas boiler with a new high efficiency one, installing the recirculation pump, and connecting this new boiler directly to the existing distribution plumbing supplying the radiators (adding either a boiler or system bypass, as appropriate). (2) Install a relatively small (10-15 gallon) insulated storage tank between the new boiler and the existing distribution system (connect the new boiler and its recirculation pump so the boiler heats the water in the tank, while a gravity system - supplied by hot water in the tank – operates through the existing distribution system. (3) Other options are also welcome.