"Most Outdoor Boilers Have Not Been Tested For Btu Output"!

If an outdoor boiler does not specify a Btu output value
it likely has not been tested or the manufacturer is too embarrassed to post the results!

This is why some manufacturers only state "this appliance will heat up up to XXXX square feet"
because they have not actually tested or verified their products performance!

Next if the manufacturer has the Btu value listed:
a) is it a tested output Btu value or an estimated Btu value?

b) if it is not a tested value, is it an estimated input or an output value?
Btu output is determined by multiplying the Btu of the fuel input into the appliance by the tested
efficiency of the appliance, this can be a huge difference if the appliance is only 60% efficient!

c) what type and quality of fuel is the Btu value (input or output) based on, as this is effected by
the Btu factor (value) of the product being burned. (Btu values are typically based on high
Btu value fuel, not the fuel the average consumer will actually be burning in their appliance)

d) is the tested Btu based on a constant sustainable draw over an extended period of time?

e) or is it a "temporary" maximum draw based on the "tested" appliance Btu output and the
stored Btu (1Btu = 1 degree Fahrenheit per pound of water) in the water jacket of the boiler?

Stored Btu example: a 300 US gallon boiler with fluid of 180 degrees Fahrenheit can effectively
store up to (300/.12*(180-32))=370,000 Btu providing heat down to the freezing point
(great for a shop, warehouse, etc.) but would only provide a practical residential heat storage
(based on room temperature of 70 degrees) of (300/.12*(180-70))=275,000 Btu.

Hence the problem with determining the actual Btu output for an outdoor boiler.