Q. How do you calculate the required BTU’s for heating on air handling equipment?
A. You take the CFM x the air temperature rise ( delta T ) x 1.08. Example 5000 cfm x a 90 degree rise ( entering air at 10 and leaving air at 100 = 90 ) x1.08 = 486,000 btu’s output required. If you use an indirect heating method you need to divide the efficiency into that total to get the input btu’s required for your selection. Example an 80% efficient heater you would take 486,000 divided by .80 = 607,500 btu’s input required.
Q. How many btu’s are in a ton of air conditioning?
A. 12,000.
Q. How do you calculate your cooling load requirements for air conditioning?
A. You would use the same formula as you do for heating only divide your total btu’s by 12,000 to get the tonnage of cooling needed. Example 5000 cfm x delta T ( 95 degrees down to 60 degrees = 35 ) x1.08 divided by 12,000 = 15.75 tons. This is a sensible load only.
Q: How do I calculate the heat transfer in a heat exchanger?
A: BTUH = GPM x Temp Diff. x 500 e.g. to heat 200 gpm from 160F to 180F would require 2,000,000 BTU’s per hour ( 200 x 20 x 500)
Q: What does the term “pump head” mean?
A: Pump head is a term used to describe the force the circulator develops to overcome pressure drop (pipe, fittings and valves). In a closed system, “pump head” has nothing to do with the height of the building. Height, as far as the circulator is concerned, doesn’t exist.
Q: What information do I need to order pump parts?
A: 1. Pump serial number (if available)
2. Pump model number (if available)
3. Casting number from volute
Q: Should I pump into my boiler or away from my boiler?
A: Always pump away from the boiler if possible. Pumping into the boiler can cause the boiler to exceed its pressure rating and can also create cavitation in the pump. It is mandatory in commercial installations with high head pumps to pump away from the boiler. In residential installations with small head circulators, it is common to pump into the boiler with no ill effects.
Q: What causes the level of water in my compression tank to rise ?
A: There are only two things that can add more water to a compression tank. First, there’s the feed water valve. Open it and you’ll bring in more city water. Since the system is already filled, the extra water must go into the tank. The other thing that can add water is heat. Water heated from 40 to 180 degrees will expand about 5% and will move into the compression tank. Although the pump is often blamed for adding water to the tank, it is innocent since it does not control the feed water valve or the heat in the system.