If two condenser water pumps run in parallel and one pump is throttled, what is the effect on total flow to the condenser?

• A. Decrease
• B. Increase
• C. Remain the Same
• D. Oscillate

Answer: (A)

In a parallel pump setup, the total flow to the condenser is the sum of what each pump delivers at the system head. When one pump is throttled, its discharge decreases, while the other pump continues at roughly its normal output. The combined flow becomes the reduced flow from the throttled pump plus the steady flow from the second pump, which is less than the original combined flow when both were fully open. So the total flow to the condenser decreases. The other options—increase, remain the same, or oscillate—don’t fit because throttling one branch in parallel doesn’t automatically boost or stabilize the total flow; it simply lowers it unless the second pump somehow increases to compensate, which isn’t typically the case.