Swimming Pool Blog


Optimizing Variable Speed Pump Savings

Increasing Variable Speed Pump Savings
Rob Cox, March 7, 2018

variable speed pool pump savings

The best thing about Variable Speed Pumps, besides quiet operation and a long lifespan, is the energy savings. The Intelliflo offers up to 90%* savings over traditional pumps, according to Pentair, and same goes for the Hayward Ecostar.

But there's an asterisk next to the 90% because of the many variables that lead to that number.


"Actual savings may vary based on local utility rates, pool size, pump run time, pump speed (rpm), plumbing size and length, and other hydraulic factors."

WHERE'S THE SAVINGS?!?

It reminds me of a story about a customer, I'll call him Jim. Jim bought a brand new variable speed pump, and after a flawless installation began to monitor his electrical consumption. After finding the sweet spot of motor speed and daily run time, he was discouraged to find his actual savings of only 48%.

He had followed the manual closely to set the pump speed and run time, and other variables within his control, to optimize savings with a variable speed pump, but had only achieved two-thirds of his expected savings.

Pentair IntelliFlo Variable Speed PumpJim sent pictures to me by email, and I saw a tired looking filter system. A small sand filter with a multiport on top, and all 1.5" PVC plumbing, old rusty pool heater, and a shiny new Intelliflo pump. The plumbing was small, and used a lot of hard 90° degree fittings, and I noticed what looked like an old salt system, and also two valves on the return side - old and new. Jim's pool is an in-ground gunite pool of about 24,500 gallons.

PRESSURE LOSS

All pools have resistance in the system, caused by the friction of running through pipes, pumps, filters, and valves. This resistance reduces water flow and increases system pressure. When I asked Jim what his filter pressure was reading, I was not too surprised to hear it started out clean at 22 psi, and he normally backwashed at 29-30 psi. I asked about the heater and was told it had not worked in a few years.

2 inch Deep Socket Sweep ElbowsHere was a case of too much resistance in the system, especially on the return side (after the filter). I told Jim to replumb the return side from the filter valve, all the way until the pipe goes into the ground. Bypass the heater, and run all new 2 inch pipe without a valve on the line (no need for it).
And, I told him to use
1.5"x2" reducers to connect on each end, and use as few bends as possible. And when a bend is needed, use (deep socket) Sweep Elbows, not regular hard 90's."

Jim said he would follow the advice and I figured that was the end of it.

SYSTEM LOSS

I was glad to hear from Jim about a month later. He told me that he had done what I had suggested, and replumbed the return side (also known as pressure side) to get rid of the old heater and valves, and he did it using 2 inch PVC. Jim reported that the pressure had gone down on the filter pressure gauge - now reading 18 psi after cleaning the filter (with his VS pump on high speed). Then I received the revised report on the variable speed pump energy savings. Savings had now improved from 48% to 58% compared to what he used to pay with the old single speed pump.

Then the question came again. Jim wanted more savings and was clearly not stopping at 58% when 90% had been the initial expectation.

We started talking about the sand filter, and I asked about the age of the filter and the last time the sand was changed. Age is not really the issue however; it's the size of the filter and valve. Smaller filters are simply more restrictive. And multiport valves are extremely restrictive—so much in fact, that California has approved
legislation to discourage the use of 1.5" multiport valves on pools. The internal design of Push-Pull valves, also known as Slide Valves, are much less restrictive than a Multiport Valve, so they create much less system head or pressure.

But what's even less restrictive than a slide valve? No valve at all. Cartridge filters for pools and spas do not require any external valve because they are not backwashed. For this reason, most cartridge pool filters produce much less system head resistance, when properly sized, as compared to sand or D.E. pool filters, even when a push-pull valve is used.

Pump Sweep Elbow, 2 inchHere was a case of a very restrictive filter and valve, and I suggested replacing his filter with a larger sand filter and slide valve, to see system pressure reduce further. To reduce filter resistance to the lowest level however, go with a
Jandy Large Cartridge Filter, Hayward Super Star Clear or Pentair Clean & Clear Plus, the new generation of super-sized cartridge filters, that run at very low pressure and can go an entire season between cleanings. And - be sure to use all 2 inch plumbing from pump to filter, using 2" pump sweep elbows.

Jim said he would follow the advice and I figured that was the end of it.

SUCTION LOSS

Clean & Clear Plus filter by PentairA month later, Jim informed me that he went with the 420 SF Clean & Clear Plus Cartridge Filter, which is a nice size for his pool. He sounded excited and I could hear that he was pleased with his purchase.

He said that filter pressure had dropped all the way to 8 psi, and that his variable speed pump energy consumption was down again; energy savings were now at 72%, a large jump from 58%, but still not enough.

He asked again what else he could do, so I suggested that he replumb the suction side, in 2 inch PVC and use 2.5" large Jandy 3-way valves on the three lines (main drain and two skimmers). I also advised him to be sure to leave at least 10 inches of clear pipe between the pump and any valves or bends to avoid turbulence in this area, and to use only Sweep Elbows.

The existing suction pipes were all still 1.5 inch, and everything else above ground was now 2 inches. Enlarging the suction side pipes would help reduce vacuum pressure, and balance flow more evenly on both sides of the pump.

Jim said he would follow the advice and I figured that was the end of it.

PIPE RUN LOSS

Pump UnionThis time only 2 or 3 weeks went by and Jim reported that he went ahead and purchased a 2" pump union, a pump sweep elbow, several deep socket sweep elbows and three 1.5" to 2" SxS reducers, to connect the 2 inch pipe at ground level. Jim said that the pressure gauge reading was now 2 psi higher than before, the pump sounded a bit quieter, and that he was now happily saving 78% over his previous pump!

I jokingly asked Jim if he wanted to know what else he could do, but he already knew the answer. Not much, unless you want to replace all of the underground pipes with 2 inch pipe, or move the filter system closer to the pool. Not something he should want to attempt, I warned.

Jim said he would follow the advice and that was the end of it.



I suspect that a true 90% energy reduction may be elusive, unless you currently have a very unnecessarily large pump running 24/7. But even if your filter and pipes are large and close to the pool, for a low-level Total Dynamic Head, there are still days when you need to run the filter longer than one complete turnover, such as after spring openings, rain storms, heavy pool use, or to clear up algae or other water conditions. And during the hotter summer months, many pools will need to increase the number of daily hours that the pump runs on higher speeds to avoid cloudy water and algae.

Perhaps above ground pools can come close to 90% savings with simple filter systems located right next to the pool wall, just in and out - very little resistance, very low Total Dynamic Head. In the real world, if you just slap a variable speed pump on an existing filter system, you can expect between
50% to 75% savings over a single speed pump, according to a 2012 Department of Energy report on Variable Speed Pumps.

Factors Affecting Energy Savings with Variable Speed Pumps

  •     Pentair SuperFlo Variable Speed PumpsRestrictive pipe size diameter and long pipe runs
  •     Restrictive pipe valves and filter multiport valves
  •     Restrictive pool filter, heater or other equipment
  •     Restrictive 90° fittings, perhaps some unneeded
  •     Size of the pool and the size of the pump
  •     Ambient temperature, season and weather
  •     Overall circulation and cleanliness of pool


Ways to Optimize Energy Savings with Variable Speed Pumps

  •     Use 2" or 2.5" plumbing and valves above the ground
  •     Use Sweep Elbows to replace all hard 90° fittings, Eliminate bends where possible
  •     Leave 10" of space between pump inlet and first valve, Tee or Sweep elbows
  •     Use the Large 3-Way Jandy Valves in 2"-2.5" or 2.5"-3" sizes, for less restriction
  •     Program VS pumps to turnover all pool water each 18-24 hours, depending on season
  •     Use one of our Large Cartridge Filters, or a large DE or Sand Filter with a Slide valve
  •     Remove unused equipment or valves, or unnecessary PVC fittings and reducers.
  •     Use a correctly sized Variable Speed Pump, just big enough to do the job, don't oversize it

Give our call center a call if you need help selecting from our variable speed pool pumps. Be an early adopter! By July 21, 2021, Federal Minimum Efficiency Standards, issued by the Department of Energy, will require a variable speed pump on all new or replacement pool pump installations!
 

 

 

- Rob