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Why Booster Sets don't turn off


We often get asked by our clients to identify why a booster set doesn't turn off. Cold water booster sets are designed to only run when there is demand for water, and switch off automatically. This can be hard to verify in normal hours, as most buildings have a reasonably constant demand for water throughout the day, and demand often only stops overnight.


However, a simple way to test whether a booster set turns off is to close the valve on the outlet (discharge) of the booster set to simulate the demand for water stopping, and watch to see if all the pumps turn off. If they don't then you may have an issue.


Booster sets that do not turn off consume a lot of energy unnecessarily, can cause overheating as the water continues to churn in the pump rather than flow away, and can cause premature failure of the pumps.


The three main causes of booster sets failing to switch off are as follows:


1) The pressure setpoint is set too high.

Any pump will have a maximum pressure it can attain (normally this is written on the dataplate of the pump). If the booster set is programmed to maintain a pressure higher than that maximum, then the pump will run continuously and never maintain the pressure it is being asked to meet. We recommend setting the setpoint no higher than 90% of the maximum head of the pump plus the inlet pressure to the booster set


2) Failed non-return valve

On a multi-pump booster set it is important that each pump has a functioning non-return valve (also known as a 'check valve'). This is so that if only one of the pumps is running, the water cannot recirculate back through the other pump(s). Sometimes this can be identified by a pump spinning even when it is switched off.


3) Electrical controls not set up correctly

We often see on variable speed booster sets (and sometimes fixed speed booster sets) that a programming issue on the controls means that the pump never goes into 'standby' mode. This is commonly on inverters that are not designed specifically for pump control. This will normally require the control panel designer/manufacturer to adjust the program


If you are experiencing problems with a water booster set not switching off automatically, then please get in touch.