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Posted by John on August 25, 2007 at 16:13:43:
Here's my situation.
Our boiler's coil is in need of replacement. The boiler is 30 years old.
A representative from the heating oil company that services our boiler (we buy oil from them also) came up with the following proposals which includes installation and equipment.
1) Replace hot water coil. There is a risk that any one of the studs may snap off because they're badly rusted. [cost = $932]
2) Install a Phase III Smart-40 36-gallon Indirect Hot water heater off of existing boiler. [cost = $2400]
3) Replace boiler with a Burnham RSA 85 with a domestic hot water coil and Becket AFG oil burner. [cost = $5,500]
4) Replace boiler with Burnham V83 with wet base cast iron boiler with a domestic hot water coil and Becket AFG oil burner. [cost = $6100]
5) Replace boiler with Burnham MPO 147 Triple Pass Heat Only Cast Iron Boiler with a Beckett Burner (don't know what model burner?). Also, install a Smart-40 36-gallon Indirect Hot water heater. [cost = $7,675]
I live in Connecticut with my family (four of us) and plan on living in the house for another 20 years. We use on average about 710 gallons of heating oil annually (over the last 6 years).
I've analyzed the proposals as best I can. Here's what I've learned.
According to Burnhams boiler literature I can figure out my annual savings due to improved AFUE using the following equation.
Existing Boiler AFUE
-------------------- x Annual Fuel Bill = new fuel bill
New Boiler AFUE
So let's say I'm paying $2.50 per gallon and I use 710 gallons annually with my existing boiler my cost per year is 710 x $2.50 = $1,775.
If I use the most efficient proposal above (MPO 147, AFUE = 87%) just in terms of the boiler's AFUE and not the fact that is uses an indirect water heater I end up with the following.
82
--- x $1,775 = $1,673 or a savings of $102 per year.
87
That's not much savings. It'll take more than 20 years to make back the difference of $7,675 - $5,500 or $2,175.
Given the above I can't justify spending the extra money to purchase a more efficient boiler. Is my analysis flawed?
I hear that the indirect hot water heater is much more efficient than using a hot water coil. How much more efficient? Would I realize a greater savings with an indirect hot water heater than the savings realized by a better AFUE as outlined above?
If you tell the pay back period of spending the extra money on the indirect hot water tank is long (say 10 years or more) I may be tempted to buy a kit (according to Burnham literature) that improves the efficiency of the RSA 85 and go with that proposal. Or maybe the V83 proposal if the AFUE = 86% instead of 82.6%. According to literature there are two AFUE's.
What do you think?
Thanks for listening.