Jeff_G
New Member
It's time to replace my 35 year-old natural gas boiler. I've had two contractors come over so far and both wanted to know how many feet of baseboard I have. Neither cared at all about the heat load calculations I spent hours on. They said it doesn't matter. Feet of baseboard is what matters.
Even if my heat load calculations are correct, is there any reason why feet of baseboard might matter? Does X feet of baseboard require a minimum boiler size of Y to run properly?
My house has 200 feet of baseboard with 5 zones (plus a 6th zone for the basement, which we never heat, that has 45 feet of baseboard). Based on this the contractor wants to install a 140K BTU (input) boiler.
I did six heat load calculations and most were between 70K and 80K BTU (DOE output).
So if I buy an 83% efficient cast-iron boiler, it seems like a 100K BTU input boiler should be enough???
Or is that too small for 245 feet of baseboard or a house that is 3700 sqft?
* We had the attic sealed and insulated in 2013, which reduced nat gas use by 20%. Heat load before this was about 100K BTU. The house was built in 1982. Location is NYC metro area. I used a 99% outdoor design temperature of 12 degrees F.
Should I listen to the contractors and go bigger? Or should I insist on a boiler size based on heat load calculations???
Even if my heat load calculations are correct, is there any reason why feet of baseboard might matter? Does X feet of baseboard require a minimum boiler size of Y to run properly?
My house has 200 feet of baseboard with 5 zones (plus a 6th zone for the basement, which we never heat, that has 45 feet of baseboard). Based on this the contractor wants to install a 140K BTU (input) boiler.
I did six heat load calculations and most were between 70K and 80K BTU (DOE output).
So if I buy an 83% efficient cast-iron boiler, it seems like a 100K BTU input boiler should be enough???
Or is that too small for 245 feet of baseboard or a house that is 3700 sqft?
* We had the attic sealed and insulated in 2013, which reduced nat gas use by 20%. Heat load before this was about 100K BTU. The house was built in 1982. Location is NYC metro area. I used a 99% outdoor design temperature of 12 degrees F.
Should I listen to the contractors and go bigger? Or should I insist on a boiler size based on heat load calculations???