Pool Pumps
ENERGY SAVING MULTI SPEED POOL PUMPS - MYTHS EXPOSED

 

There are many wild and varied claims being made about energy saving multi speed pool pumps mostly by people wanting to sell them. I thought it prudent to throw my years of engineering and pool experience into the mix to expose some of the myths, mistakes, half-truths and lies.

 

I will start by saying that in most cases an energy saving pump is beneficial but the savings are often exaggerated and they will not work for everyone.

 

When selecting a pump for a pool filtration system there are several criteria that need to be met. The first is that it will circulate the water through the filter at a high enough rate to turn the pool water volume over at least once per day (turn over rate prescribed by AS3633). This needs to take into account how adequately the pool plumbing has been designed and installed. The second most important criteria if the pool uses a sand (or other media) filter is that the pump provides a high enough flow rate to backwash the filter properly. An automatic suction pool cleaner also has a minimum flow rate requirement and will affect the efficiency and performance of a pool pump, sometimes very significantly.

 

Ideally a pump is selected to match the pool, a filter to match the pump and then other equipment such as salt chlorinators, pool cleaners, chemical dosing systems and fountains matched and added. The effect of the additional equipment should then be fed back into the pump and filter selection process.

 

The same criterion applies to multi speed pumps with the difference being that the pump has two, three or more available speeds. The lower the speed that the pump can be operated to turn over the water for filtration the better the savings, however this is often affected by the need to adequately ‘fill’ a salt chlorination cell and operate a pool cleaner. The highest speed is usually used to backwash the sand filter and most pumps only have the capacity to backwash up to a 700mm (28”) filter.
 

 
Now, for what I will give the benefit of calling the common mistakes made with specifying systems or calculating savings:

 

  • The flow rate from a pump on low speed is typically about half to two thirds of the full speed flow. To achieve adequate water turnover the pump may need to run 1-1/2 to 2 times the previous time. The power saving is often quoted at 70% but if the pump needs to be run twice the amount of time then the saving is closer to 40%. This is still significant but be careful of what is being claimed.

 

  • If an automatic suction pool cleaner is connected into the skimmer box then not only will the flow be further restricted but the pump may need to run at a higher speed to make the pool cleaner operate properly. This will further erode the savings. The best solution to this is using a robotic cleaner that runs entirely independent to the filtration system. The pool will skim and filter better, you will maximise your power savings and your pool will be cleaner.

 

  • It is a serious mistake to fit a multispeed pump to a filter that is too large for the pump. If there is insufficient water flow to lift the media bed and wash it thoroughly during the backwash cycle then the filter will build up with debris and it will not operate properly.

 

  • Mismatched salt chlorinators can also be an issue although in many cases where undersized salt chlorinators have been fitted the extra run time makes them right sized. This is where the real savings are achieved with multi speed pumps because often pumps need to run far longer than required for water turnover reasons to provide sufficient chlorine production from the salt chlorinator.

 

  • Some chlorinators will not run a multispeed pump and in fact some chlorinators will be damaged by a multispeed pump and vice versa. It is important to verify that the multi speed pump that you choose is compatible with your salt chlorinator or chemical dosing system.

 

  • Some solar controllers will not run a multi speed pump properly. I cannot understand why anyone would want to run a multispeed pump for solar but sometimes the solar controller controls the filtration pump as well. A fix is available for some controllers.

There are two particularly opportune times to think about fitting a multispeed pump. The best time is when the pool filtration system is being designed and specified at the time of installing a new pool or a filtration system replacement. This allows all of the equipment to be properly matched. The other time that you should consider this option is when you are replacing a pool pump that has failed. Replacing a pool pump though is a bit like paying a speeding fine, you begrudge the expense and there is a time limit to getting it sorted out. A working pool pump can be replaced but the pay back period will be longer than if you were looking at the price difference over a standard pool pump. A multispeed pump is typically $300 to $500 more expensive than a standard pool pump.

 

Another way of achieving the power saving without replacing the pump with a multi speed pump is to fit an inverter type multi speed controller. This controls the speed of your existing pump by altering the frequency of the power supply. Very good robust controllers are available that have advantages over multi speed pumps and if taking into account the lack of installation cost the price is very comparable.

 

Mr Stoves Pool World will provide an honest and well-informed proposal to best match your pool equipment and situation, will make the entire process easy for you, carries a selection of multi speed pumps in stock and if required offers finance options.