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I'm about to replace my nearly 30 year old WM250 boiler with something more appropriate to my now fully insulated home in Long Island NY. In addition, I'm planning on ditching my separate gas DHW and getting an indirect tank.
Several years ago I reconstructed the house and put in 6" of foam into all walls and 10" under the roof. Performing a manual j calculation I get a need for a 100K BTU unit. This is corroborated by a gas usage vs degree heating days analysis for the past several years.
The home today has 9 zones of radiant and 5 Zones of high temp 2 are backup heat in ac coils put in just in case the radiant did not provide sufficient heat (it does). 1 is connected to radiators in two bedrooms and 1 is connected to a length of baseboard in 4 bedroom while the last goes to radiators in the basement (also not needed). Everything else is radiant with each room on it's own thermostat, all connected to Tekmar controls.
So, I'm looking for a new boiler which I can control the modulation with the Tekmar control which supplies a 0-10v signal. Many of the unit's I've looked at don't even have the ability to be externally modulated as they expect that their control is all that's installed.
Right now, I'm circling around the Lochinvar KBN-151 which is a tad too big but the next smaller size seems a tad too small. I'm contemplating adding a 30 gallon buffer tank to prevent short cycling.
My ears are open