Holdfast Training Services Trial Blog

This blog post summarises the unintended consequence of an energy optimisation measure and explains the chosen method to solve the issue.

Pool water recirculation pumps make up about 50% of the pools electrical energy demand, interrogating a pools recirculation rate can reveal unecessarily high turnover rates set during commissioning. Through the use of inverters (or the use of electronically commutated variable speed motors) it is possible reduce the frequency and speed of the pump allowing reductions in the power drawn thus enabling energy savings.

However, as was the case with the pool in question, a reduction in the recirculation rate affected the pool makeupwater control strategy i.e the pool water level dropped below its setpoint. Due to spatial restrictions this pools balancing tank is set lower than the height of the pool and a separate makeupwater tank could not be installed. Usually a makeupwater tank is separate to the balancing tank and is set at the level of the pool water. This balancing tank has been used for two purposes, the first to allow for ‘spill’ whereby swimmers enter the pool and increase the height of the swimming pool water and the second to allow for makeupwater injection.

The flow diagram below explains sequentially the consequences of reducing the pool recirculation rate to realise energy savings.

The chosen solution has been to seal the balancing tank and install an automatic air vent thus creating a closed loop system. There is an existing ‘siphon’ pipe (seen below) connected to the pool which shows the true level of the pool water, therefore a new float level switch is to be installed in this siphon pipe that will control the injection of makeupwater into the balancing tank via the solenoid valve based on the actual pool water level.

As far as allowing for ‘spill’ from swimmers goes (the function of the balancing tank), it was calculated that even if 12 120kg swimmers (Maximum pool occupancy is 4) entered the pool the water level would only raise by 14mm, this is well below the limits of both the siphon pipe and the pools perimeter construction.