Heating Help Pros,
We just bought a big old fixer upper from 1911 last year. We were told that the boiler was on it's last leg and sure enough, come March, it breathed it's last breath. I've been shopping around different contractors and have been receiving all sorts of information and all sorts of pricing. Some contractors are quoting a boiler near the size of the old one that's in there (which I believe is WAY oversized), others, are quoting boiler sizes based on the amount of BTUh radiation needed, while still others are doing a flat sq/ft floor measurements and only one did a very rudimentary heat loss calculation.
So, in reading (for hours) all the posts on this forum, I decided to get as much information as possible and ask all of you pros what your thoughts on my current situation and hopefully get some advice on a size for a boiler replacement that makes sense without costing me a fortune (since we're pretty house-poor now :)
- Weil McClain Model EGH-85 - Natural Gas - 350,000 BTU Input - 280,000 BYU Output - Net I.B.R. Output Water - 243.5.
- Basement has no radiators, but original big/think black cast iron pipes (3-4 in") that transition into more modern copper (1.5") near the boiler. I mention this because I didn't count the basement into my heat loss calculation. The supply sides are wrapped in good-old asbestos insulation. We've had some friable stuff removed, the remainder is in ok shape, so we're keeping for now (after all, it IS a great insulator)
- The system has two zones.. one for all of the house, and another for what we call the "Family Room" which was added in 1944 - basically they enclosed a once open exterior porch.
- The house throughout has traditional cast iron radiators in all room EXCEPT for the added family room where there is some sort of Convector? radiators (picture attached).
- Mod/Con boiler with indirect DHW tank (to replace an incredibly inefficient electric one we inherited).
- I'm looking specifically at the Lochinvar Knight line with stainless steel heat exchangers, but have also heard/read good things about the Buderus model GB142 with aluminum heat exchangers.
- I guess I would plan on keeping the same zone layout for now, using just the two circ pumps (no valves). EVENTUALLY, I might pull a 3rd zone and make a 1st floor loop in the basement, so I'd have 1st Floor zone, 2nd & 3rd Floor zone, and Family room zone, but that's WAY down the road - just mention it in case it matters.
WHAT I'VE DONE:
Calculated Total Radiation:
- I did a count of all the current radiators and calculated total square feet of radiation. I've attached a PDF of my results. I think it's all pretty accurate, except I found no mention of these odd-ball "convector" radiators in the family room, so on my radiation summary, I used the sq/ft model for the big family room only. - Came up with numbers around 220,500 BTU @ 170deg and 238,000 BTY at 180deg water? Possibly?
Calculated Total Square Footage
- I also counted up square footage of the house room my room with my new nifty laser measuring tool. The HEATED area of the house is attached broken down my room (not including basement or walk-in, unheated attic space from the 3rd floor). Total Square footage method showed 4,306 sq.ft.. Looks like I should use at MOST 42BTU/sq.ft so I'm getting about 180,852 BTU needed from that method.
Calculated Heat Loss
- Using the Slant/Fin mobile too, I did (what I think to be the most accurate heat loss calculation). We've replaced all the windows except for 1 on the 2nd and 3rd floors, and I'm adding insulation where I can to bathrooms we're re-doing and blown-in in the crawl-space above the 3rd floor. I used 180F water temp, 70F Indoor Temp and 14F outdoor temp as my variables, and was conservative if anything... In many instances I put 2 courses of brick instead of the probable 3 that's in there. The total Heat Loss for the house came to 149,000 BTU/HR from the program, but again, that doesn't include the basement as I wasn't sure what to do with that.
So you can see, My methods show ranges from 149,000 BTU through 238,000 BTU, but certainly not the old boiler's output of 280,000.
As I mentioned above, I am looking to integrate an indirect hot water tank into this system too, but my understanding is that doesn't really affect the BTU required to heat the house as there is DHW priority mode which will quickly heat the tank as needed, then the boiler will focus on the house heating.. right?
I just want to be sure that we're paying for the correct size boiler, and want to take advantage of the Mod/Con's "steady" mode rather than have an over-sized boiler short cycling/etc.
Any thoughts would be VERY much appreciated.. We have to bite the bullet before next heating season!