In getting quotes I'm getting different recommendations. IBC has been the most recommended. Any feedback?
We have a 1800 sq ft house, two full baths and live in Vermont. Is Takagi really sized for heating? We have one for on-demand hot water and it's served us well.
Is this a combi boiler, or just a tankless?
If just a tankless, Rinnai (the largest manufacturer of gas fired appliances in the world) is an easy call, provided the is decent local support (usually is.) When Takagi was bought out a handful of years ago word on the street is that their overall robustness fell a notch with the newer models, but I can't confirm that. IBC is a much smaller player, but may have good support in your area.
If it's a combi boiler you need to
do some napkin math on the zone radiation first to properly specify it. Low mass combi boilers are usually only a good fit for homes with unusually high heat loads and low to moderate hot water loads. With 2 baths you'll need a 199KBTU/hr tankless to deliver reasonable hot water service, but the minimum fire output of 199K combi boilers is more than half the typical 99% design heat load of an 1800' house, and way oversized for the radiation, to the point that it's prone to short cycling on zone calls if operating at high efficiency condensing temperatures.
If you have a heating history on the place it's also worth running a
fuel-use based heat load calculation , which in combination with your radiation numbers allows to estimate your heating water temp requirements and properly size the boiler's minimum firing rate.
