What is difference between BTU and MBH for house furnaces?
BTU is how much heat is produced at one instant, BTU/hr is the amount of heat produced in an hour. MBH is 1000 BTU/hr. However, BTU is sometimes used as an equivalent to BTU/hr, so the conversion might work. Wikipedia has an article that might clear things up.

1 MBH = 1000 BTU/hr. Thousand BTUs per Hour (MBH).

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