Question 1

What is BTU/hr and when is it used?

Accepted Answer

BTU/hr (British Thermal Units per hour) measures heating/cooling power in HVAC. 1 BTU/hr = 0.293 watts. A typical home AC is 12,000-24,000 BTU/hr (1-2 tons).

Question 2

How do I size an air conditioner?

Accepted Answer

Rule of thumb: 20 BTU per sq ft. 500 sq ft room = 10,000 BTU. Adjust for sunlight (+10%), kitchen (+4,000 BTU), or extra occupants (+600 BTU each).

Question 3

What's the difference between mechanical and electrical horsepower?

Accepted Answer

Mechanical HP (550 ft·lb/s) = 745.7W. Electrical HP = 746W. Metric HP (PS) = 735.5W. Boiler HP = 9810W. Different industries defined their own standards.

Question 4

How do I size a motor or generator?

Accepted Answer

Calculate peak power needs, add 20-25% safety margin. Consider duty cycle - continuous vs intermittent use affects sizing differently.

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