Choosing correct boiler size

[jamesander]

I am in the process of buying a new boiler (I posted a few days back). I had 3 different contractors come up with the same sized boiler in their bids. I have done a couple of heat loss calculations and came up with a figure of 60,000 BTU heat loss. Program used sq feet of each room plus exterior wall area, window and door area, with general categories of insulation and window. I'm not sure if this is correct. All contractors chose a boiler with a range of about 60-110BTU (IBR net rating), which is the second smallest available. I also explained that I wanted to eventually refinish my basement (which is currently unheated. I don't think any of the contractors did a heat loss calc, although the one I am going with offerred to.

Does this sound like the correct size boiler? Thanks.

[Bob]

A LOT depends on if you're going to heat domestic water with the boiler.

[jamesander]

Yes, I will be using an indirect hot water tank.

[Bob]

With an indirect water heater, you can go with the smallest boiler possible to heat your home, but I'd strongly advise against installing a three section cast iron boiler (of any brand) because the rear fire wall is too close to the burner nozzle and end cone, causing all kinds of problems. I don't really understand your original post. First you say, "I had 3 different contractors come up with the same sized boiler in their bids." Then you say, "All contractors chose a boiler with a range of about

60-110BTU". There's a big difference between 60MBH and 110MBH. Finishing your basement adds very little heat loss to your home unless the basement is above ground and has standard windows and doors.

[Edwin Pawlowski]

None of us have a clue what size house and what type of construction or if you live in North Dakota or South Carolina so no one can say it is right or wrong. What size do you have now? You probably want to be close to that, assuming it is heating properly. Finishing the basement with insulation will have a small affect on what the total needs are. Keep in mind, smaller is not cheaper to operate.