Noticed that grapeview is thinking on the TC-500. I'm in a similar situatioin. Got a smaller old house. Not much room in the way of water storage, but I also have cast iron radiators- about 9 of them. I seem to think that I wouldn't want anything over 100K BTU/HR. I wonder if the 125 gallons of water storage on the TC-500 is going to help. But is this boiler too big?