If a vacuum pump in a vacuum steam heating system burns out, a common cause is which of the following?

• A. Backward rotation
• B. A failed steam trap
• C. Incorrect voltage to the pump
• D. A failed vacuum breaker

Answer: (B)

In a vacuum steam heating system, removing condensate efficiently is essential. The steam trap is responsible for draining condensate from the steam lines and heat exchangers while preserving the vacuum. When the trap fails, condensate starts to accumulate in the line and on the suction side of the vacuum pump. The pump is built to handle vapor, not a heavy liquid load, so this extra liquid increases suction head, reduces the effective vacuum, and forces the pump to work harder to remove liquid. That added workload quickly leads to overheating and, over time, burnout of the pump motor.

Other failure modes tend to show different symptoms: backward rotation points to a mechanical or wiring issue with the drive, incorrect voltage stresses the motor electrical system directly, and a failed vacuum breaker mainly causes loss of vacuum but doesn't impose the same heavy liquid load on the pump. The condensate buildup from a failed steam trap is the most common and direct path to burning out the pump in this system.