How to calculate ventilation requirements for removing heat from a kiln room

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How to calculate ventilation requirements for removing heat from a kiln room

To calculate how many CFM of air ventilation you need moving through a kiln room

  1. Look up the amount of BTU/Hour that your kiln kill give off. You can find the various tables for this here.
  2. Use the BTU/Hour figure based on the maximum temperature you will be firing to. You can extrapolate these numbers. For instance you can pick a BTU/Hour number between the column for 2000°F and 2350°F for Cone 6 firing.
  3. Assume the maximum temperature you want in the room is 120°F. This is below the safe limitation of the control and is probably as hot as you will want it to be in the room anyway.
  4. Figure what your typical hottest day is. You may decide not to fire your kiln, for instance, when it is 105°F outside and that you will use something like 100°F as this design temperature.
  5. This gives you a Delta T (temperature differential) of 20°F in this example.
  6. Divide the BTU/Hour that you want to remove from the room by the product of 1.085 x the Delta T.

The Formula

(BTU per Hour) / (1.085 X DELTA T) = CFM


 Calculate the ventilation CFM required for an e23T-3 kiln firing at Cone 6 with an outside temperature of 100°F.

  1. Look up the BTU/Hour heat loss for an e23T-3 firing at Cone 6.
  2. See that the heat loss at 2000°F is 12444 BTU/Hour.
  3. See that the heat loss as 2350°F is 15439 BTU/Hour.
  4. Extrapolate between these two numbers for Cone 6 (around 2280°F) and come up with approximately 14,500 BTU/Hour.
  5. From above we have a Delta T of 20°F
  6. 14,500/ (1.085 X 20) = 668 CFM
  7. Size your ventilation fan for something above that number.
  8. Make sure you have the ability to have make up air get into the room (i.e. an air inlet into the room, open door or window). This will keep the static pressure to a minimum. An increase in static pressure will downrate the rated CFM of a given fan.