New Buderus Size

Zman500

I am getting ready to replace my old Burnham v-14 with a new boiler. I got two quotes, both from reputable contractors in this area. Both recommended the Buderus G115 WS with a Riello burner. One recommended the WS/4 at 95,000 Net BTU without doing any load measurements or going anywhere other than the basement. The next one first recommended the WS/5 at 119,000 Net BTU. When I questioned him about the size, he said it was because it is what I currently have and has worked for all these years. Then he suggested a load test and said he would probably be able to recommend a smaller one if he did that (don't ask me why he didn't just do that in the first place). So he measured all the rooms and windows, came up with a load of about 66,000 BTU, and then recommended the WS/3 at 74,000 Net BTU. My house is about 1700 sq ft (heating area), 50 years old. I've upgraded the attic insulation and will be replacing the windows this spring. I did my own load evaluation using a form I found on the web and came up with a similar load requirement, so I guess the WS/3 is OK, but I am concerned because it is so much smaller than my current one at 119,000 Gross BTU (I don't know the net). Does this sound OK? Also he recommends the Logamatic. Any thoughts on that? Thanks much.

Robert O'Brien

You did

the heat loss,why question your own numbers? Get the right size boiler with ODR,you won't regret it, paid an oil bill lately?

Jean-David Beyer

Why question my own heat loss too?

My former contractor walked around the east and north sides of my house (outside), counting his paces. From that he decided I needed a 105,000 BTU/hr boiler. My existing 60 year old oil boiler had a 1/2 gallon/hour nozzle in it and a replacement Beckett oil burner that with a nozzle like that took in only 70,000 BTU/hour. It always provided enough heat for over 30 years. By that time I had found this site and read John Siegenthaler's second edition hydronic heating book, so I realized the need for a real heat loss calculation. I knew that 70,000 BTU/hour was the upper bound on the amount of heat required, especially since the new boiler would be a lot more efficient than the old one.



I first calculated the heat loss using a booklet by Weil-McLain (who made the new boiler I would be getting) and I forget what it came up with, but was less than 40,000 BTU/hour. I did not like calculating the heat loss this way because it involved a lot of tables describing the construction of my house, and none of them matched my house very well. I never figured out whether I should calculate the heat loss of my slab because it provides heat (radiant) that way, so actually there is a heat gain from it, not a loss. I know there is loss out  beneath, but it does not want to know the conductivity of the ground below or how far down the water table is.



I then got the Slant/Fin program and calculated my heat loss that way. I think that is the most accurate of my estimates, But it is off for many reasons too. The house is a Cape Cod, so the upstairs (2) rooms have very different floor areas from their ceiling areas. I used the floor area to get the wall area, and the ceiling area for that. But this leaves the diagonal parts of the walls. To make matters worse, the ceiling has about 10 inches of fiberglass insulation above it, the diagonals have a 2x4 thick fiberglass (3 inches?), and the vertical walls (upstairs) have about 6" of fiberglass. Downstairs, there is a 2x4 thick urea-formaldehyde foam. I do not know what the corners are like. I do not know if there is any insulation under or around the slab (but I doubt it). So even if I did the math right, there are an awful lot of approximations in here. That calculated out to about 30,000 BTU/hour.



Now the smallest W-M Ultra was 80,000 BTU/hour (input), so I got that. I did insist that the outdoor reset be connected up. Contractor did not think it mattered. Former contractor. It is pretty clear that even this boiler is oversized, but the outdoor reset helps a lot until it gets so warm out that it cannot modulate low enough. I am really glad I did not get the 105,000 BTU/hr unit.



I do not know how professional contractors do heat load calculations. I doubt it matters how the calculations are done -- pencil and paper, computer, etc. But the problem of Garbage in: Garbage out has to be dealt with, and that is not easy unless you saw the building being built. And I assume that is rare.

carl_nh

Consider the Buderus G125BE

ZMan,



You should seriously consider the Buderus G125BE-21 - Blue Flame 72000 BTU  boiler if you are looking at Buderus. If your contractor doesnt install them then find one that will.



We have had ours for 2 yrs now - just over 1600 hrs of operation and used 500 gal oil per year vs 900 before - in a 2800 SF Cape style house with cathedral ceilings. By the way, I did my heat loss calculator too @ 5* F outside temp and came up with 65,000 BTU loss, then my contractor did his also @ 0*F and came up with 70,000 BTU loss.

 

The unit is 90.7% efficient so you get back $1500 in fed tax credits too, which offsets the cost of the unit. They come with the Logimatic, outdoor reset, and ultra filter as standard equipment. Then coupled with the oil savings its a very good ROI,



By far one of the better if not the best oil boilers out there today,

meplumber

I agree with carl to a point.

The BE burner must be installed by a contractor that has been trained by buderus to install this particular boiler.  The wholesalers are not supposed to sell them otherwise, but it happens.



They are great boilers/burners, but must be specifically installed and setup.  Contact buderus for a list of contractors in your area that are trained.



Good Luck.

Zman500

Thanks

Thanks, Carl, for the advice about the Buderus 125BE. I did read some about that. I ended up going with the G115WS with the Logamatic. My main concern was that the maintenance on the 125 needs to be done by a certified person. My contractor is certified, but I felt more comfortable having more of a standard unit that most anyone could work on. Also, the tax credit is not $1500 anymore, now it is $150. The G115 is much more efficient than my old unit, so hopefully I'll be happy with it. Was just installed yesterday and seems to be ok. Thanks again.