DOE Heating Capacity Maximum

It's a lot easier and less trouble to compare your EDR (which should be in square feet rather than BTUh) to the boiler square foot rating for steam than to start converting stuff to BTUh…

Not really.

Its just math.

And that leads to people thinking the boiler is too small because it doesn't quite support enough EDR which is because the number had the 33% built into it. So a boiler that's 30% over the required output gets up sized again.

61,000 * 1.15 to 1.33 = 70,000 to 80,000.

And no one ever makes a mistake when it comes to math

note that most systems need far less than a 30% pickup factor

I don't get why you need to convert the EDR to BTU, then determine if you need the select Input of 105,000 BTU(0.75 x 140,000/gal rated fuel, or 92,000 BTU DOE capacity, or NET AHRI 69,000 BTU output. Only to get back to a boiler that has a rating of 288 SqFt NET Steam rating.

If you want to get fancy and dial in the firing rate to 0.66 GPH by using a 0.50 nozzle at 175 PSI. You will need a combustion analyzer to properly tune the burner with this specification, but it will work.  Ask me how I know?

If you like to do math and hope you didn't make a mistake carrying the 1 to the next column, then calculating the difference between the actual input rating of the nozzle and the higher pressure adjustment of the fuel pump. Here is the equation:

The relationship is proportional to the square root of the pressure ratio because the flow through a nozzle is governed by orifice flow principles. Once that math is done and you get the actual firing rate of the burner, then measure all the combustion parameters in order to provide proper combustion for at least one season until you can return for the annual maintenance for the next season. You must also determine if the lower firing rate of the boiler will impact the exhaust temperature adversely.  Once you have done that you can now use the actual 0.66 GPH x 140,000 BTU fuel = 92,400 BTU Gross Input.

That would make the 92,400 BTU gross Input convert to about DOE Heating capacity of 81,000 BTU.  That 81,000 DOE would convert to AHRI NET rating of 60,750 BTU.  That 60,750 AHRI NET would convert to AHRI 253 NET Sq Ft steam.  

After all those calculations were completed which will have taken some time you can then do this magical math related prediction:

1. Pick a number between one (1) and ten (10)  not including one or ten. 
2. Multiply that number by 9
3. Now you have a 2 digit number correct?
4. Add the two digits together
5. Now subtract 5 from your number answer.
6. Using the alphabet as a cipher where 1 = A and 2 = B and so on… select the letter in the alphabet that corresponds to your number 
7. Think of a European country that begins with that letter.
8. What was the last letter of that country?
9. Think of an animal that begins with that letter