Example:

Twice an hour the production line requires 8 GPM of hot DI water for 10 minutes. After this, the system remains off for 20 minutes before beginning the cycle again. Incoming water is 60^oF and desired outlet temperature is 120^oF. Power available is 480 Volt, 3 Phase.

Step 1
Solve for the variables:

Step 3
Select the D120 because the storage capacity of the D120 is the closest match to the value solved for in Step 2.
Step 4
10 x .80 = 8.0 + 20 =  28
Step 5
 120 ÷ 28 = 4.3 GPM
Step 6
Select the 40 KW size at a 60^oF rise.
Specify Model: D120-0-40SST4
Note: In comparison, an instantaneous heater for this application would have to be 70 KW.

1. Hot water flow
2. Time On
3. Time Off
4. Incoming Cold Water
5. Outgoing Hot Water

8 GPM
10 Minutes
20 Minutes
60^oF

120^oF

Step 2
8 x 10 = 80 ÷ 70 = 114