[WannaBePlummah]

Here's my situation. I have an American Standard 'Arcoliner' boiler with the original 'Arcoflame' burner that came with the house that we bought a few years ago. The boiler is original to the house and still runs at about 85% efficiency. The house is heated by hot water baseboard (one zone) off one side of the boiler and our domestic hot water runs directly off the boiler with no tank. So the boiler has to run all the time in order to keep the water hot for the domestic. So, to conserve oil, we've resorted to turning the boiler off whenever we don't need the hot water, turning it on about 15 minutes before we need it again (showers, laundry, etc). I'm sure this isn't the best thing to be doing for our boiler so we'd like to buy an electric or gas tankless hw heater and bypass the domestic hw side of the boiler. How do I cap off the domestic side of the boiler without causing damage to it? Do I have to loop the cold input to the hot output, thereby just closing the loop closer to the boiler? Or does there still need to be a cold water input for the heater part of the boiler? Connecting the new tankless will be relatively easy. I just don't want to cause any damage to the existing boiler since it's still in really good shape. Any help would be GREATLY appreciated. Thanks in advance