I have a nursing home that has heat pumps in every room and a heat exchanger in the mechanical room tied to the heat pump loop and the cooling tower. The cooling tower pump keeps loosing its prime and the system shuts down. The strainers are clean and the pump will not pull the water from the tower.The tower is not piped properly, the suction comes out of the pump and goes up five feet and outside and down five feet to the tower.We thought the water was flowing back to the tower when the power went out and the pump would lose its prime but I found a check valve in the suction pipe yesterday so it was not flowing back and the power did not go out yet it still went down.I got it to run yesterday by removing the check valve and running the main pump (5 hp B&G) and the 7.5 hp back up at the same time. This got the system up and running but the pump is still cavitating(I can hear it).
The tower is an open BAC and the sump is full so I am pretty confident that I have a full column to the pump.
My question is will scaled plates on the heat exchanger cause my pump to cavitate. The water goes from the pump to the exchanger to the tower and back to the pump.The building is three years old, there is chemical in the system. The system has done this in the past maybe three times before this summer,(maintenance guy keeps great records)but this summer it has gone down maybe ten or fifteen times so something is wrong.
Sorry so long but want to giv e as much info as possible. Thanks for all replies