Any suggestions with this one?

cab02149

I had a natural gas, Burnham 204 installed to replace an old Oil fired boiler. Trouble is the boiler and the radiators rarely heat up beyond 110 to 120F to satisfy the thermostat. I want a higher temperature to protect the boiler or have the capability to get there. I don't want to replace the boiler. I have old cast iron radiators and mains. The boiler has a system bypass to raise the boiler temperature. That bypass has little affect. I use globe valves to slow the supply flow and make more water flow through the bypass but to make any difference I must almost completely throttle down the flow of hot water to the radiators. I have received opposite suggestions: Smaller circulator , larger circulator. Boiler by pass-system bypass. Use a thermic valve. Use primary/secondary piping. The boiler was sized to the radiators and I suspect it is too large. The apartment is well insulated and tight for an old house (1892). The living room is uncomfortable when the winter sun goes down The heating systen does not respond fast enough. So I want more heating capacity without incurring a big expense. I also suspect I am buring more gas than I should.