Am planning a conversion from oil to N.gas. Have a 6" SS lined chimney in the Northeast and finned element radiators. At the current gas price, I'd only be savings less than a hundred dollars a year with condensing efficiencies (even if they could be achieved, without adding 70% more radiator length to accept 130F water temps). So, I'm looking at heat only non-condensing gas boilers.
I've only found one manufacturer of a modulating non-condensing gas boiler so far. Space heat loss is 70k BTU/h and already have a 41 gal. indirect tank heater and my shower useage at only 2GPM (hot only) would indicate DHW load of at least 100k-120k output needed. That's the boiler output I have now and the DHW is acceptable. Unfortunately the two smallest of three space zones are BOTH only 14k each. Without a modulating firing rate, a typical 130k output boiler would be short cycling a lot delivering only 14k.
What other brands are out there that installers like installing.