Oil to Propane Conversion

FPEngineer

My house is a 3 bedroom, 2.5 bath split entry cape in southern New Hampshire.  It is approximately 1700 sq ft  and we plan to finish another 500 sq ft in the basement.  It is currently heated by a ~25 year old 120k BTU Burnham oil boiler with fin tube baseboard throughout the house.  We also supplement with a Morso wood stove located on the 1st floor of the house.  DHW is provided by an indirect 41 gallon BoilerMate.



As part of the basement renovation, I've convinced my wife that we should upgrade our heating system.  We have propane at the house for a gas cooktop and I've decided that it makes sense to convert the boiler to propane to gain space in the basement and increase the overall efficiency of the heating system.  We will keep the BoilerMate for DHW since it is newer than the existing boiler and in good shape.



I've downloaded and installed the Slant Fin heat loss software and input the necessary information into the program.  The exterior of the house is framed with 2x6s and it is insulated.  Windows are single glazed with storms (to be upgraded eventually).  The attic has 6" of insulation.  I came up with 37k BTU for a heat loss with a design temperature of 0F.



Based on my heat loss, I am considering the following boilers.



Viessmann Vitodens 200W (53k BTU)

Triangle Tube Solo 60 Prestige (47k BTU)

Lochinvar Knight (63k BTU)

Buderus GB142 (75k BTU)



All of these are oversized based on my heat loss calculation, but I am leaning more toward the Viessmann or Triangle Tube.



The 1st contractor (same one that did the LP tank and gas line for cooktop) that I had to the house suggested I install the Buderus and said it should be sized based on 40 BTU/sq ft to be heated.  He said that this is a general "rule of thumb" that he uses to size boilers in our area.  This did not give me a great feeling about the contractor.  I am an engineer and would prefer someone more technical to design my new heating system.  It also made me question the accuracy of my heat loss calculation since my calculation indicates the boiler should be roughly half the size that he is recommending.



Does a 37k BTU seem out of line for a house my size?  There are no contractors listed for New Hampshire on the "Find a Contractor" section of this website.  Can anyone recommend someone who does work on the NH seacoast?

FPEngineer

More info

I forgot to mention in my original post that we plan to replace the existing fin tube baseboard on the 1st floor because the covers are old and scratched/dented.  When I used the Slant Fin heat loss calculator, I entered a water temperature of 140F and will use the amount of Multipak 80 indicated by the calculator.  The new basement area will be radiant floor and I install it using Warmboard Radiant Subfloor per their recommendations (rigid foam insulation over existing concrete slab).



Not sure if any of this would effect which boiler I choose...

CMadatMe

Heat Loss

Call Hydronic Alternatives in Springfield Mass, he's the Viessmann rep and can find you a reputable qualified contractor. After doing thousands of heat losses, I'd say your pretty close with your heat loss, may be a little light but 40 btu/hr no way.



Like your boiler choices. My vote would be the Vitodens for two reasons. Heat exchanger has a much better warranty and Lamda Pro Combustion.

kcopp

I am in Dover.....

is that anywhere near you?

FPEngineer

Location

Yes,Dover is close to me.  I am in Hampton, NH.



I've also attached a PDF of the Slant Fin heat loss output.

FPEngineer

Thanks Chris

It's good to know that I'm in the ballpark on the heat loss.  Even if I am a little light, the smallest boiler I'm considering is 10k BTU/hr larger than my calculation.