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Spa +  Pool Pump Heating Control
CLIENT: Sun Pacific Villa's - Mount Maunganui
PROJECT: Spa + Pool Pumps - Heating Valve Control


The customers current spa and pool heating systems needed to be replaced. The existing controllers and valves were poorly configured and had been exhibiting erratic noise and pool  temperatures periodically during extreme conditions. After a through inspection  of both  installations we found that the heating control valves and controllers had been wired up to perform a very crude operation of the heating control valves in an effort to  regulate the temperatures of both the spa and pool. The heating  control valves could only operate at a fully open or fully closed position. This resulted in the heating control valves "hammering" open and "hammering" closed repeatedly in an effort to maintain pool temperatures. The heating valve controllers were also crudely configured to require a one degree deficit in pool temperature before calling for heat. In other words, the spa and pool water temperatures were consistently  having to loose and entire degree of water before the  controller would call for more "water heat" and the cycle would resume. This explained the constant "hammering" of the heating valves in and effort to fully open and then fully close and then repeat. This equated to very poor energy conservation, uneconomical heating of the pool water and uneconomical plant longevity due to the strain placed on the heating control valves to operate in this fashion.

Schneider Zelio Smart Relay PLC SR3B101BD and SR3B261BD

Schneider Zelio PLC Spa + Pool Controllers

siemens mxg Heating Control Valves

Siemens MXV Heating Control Valves


We identified that it would be possible to automate the existing heating control valves correctly, however both heating control valves had suffered from the effects of the "valve hammering" so we decided to replace them with identical new units. By using two  of our Schneider Zelio PLC's with one of our custom spa and pool heating control programs which output a 0-10V analog signal to allow "on the fly" valve adjustments in 10% increments.


This would enable the heating control valves to operate as intended, i.e. very smoothly to maintain a setpoint without any noticeable deficit. Simply put, if the swimming pool Zelio is set at 28oC, then the swimming pool heating control valve will maintain a consistent pool temp of 28oC. And if the spa pool Zelio is set at 37oC, then the spa pool heating control valve will maintain an consistent pool temp of 37oC...without any temperature deficits.


We added end user HMI screens to the Zelio's so that the staff could monitor the systems and alarms along with making easy  adjustments to  the temperature setpoints to suit the different seasons throughout the year if required. We recycled the existing (but now redundant)  Carel IR33 controller as a spa safety back-up high temperature alarm, should the Zelio ever fail.



2 x Schneider Zelio SR3B261BD PLC modules  with analog extension cards.

 2x Siemens MX Magnetic Actuator Heating Control Valves.

Zelio Spa and pool controller demo

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