‘Smart pump' is a new term in the world of pumps. But what is it? Well, that depends on whom you talk to. To some manufacturers it's a very specific type of pump that features an electronically commutated motor (ECM) with an integrated control that varies the speed of the pump according to temperature or pressure.
To other manufacturers, it's just another name for anything that's not a ‘dumb' or steady state pump. "On the residential end, when people talk about smart pumps they are generally talking about variable speed circulators," remarked John Barba, contractor training and trade program manager for Taco, Cranston, Rhode Island.
Pumps like the Wilo Stratos, Grundfos Alpha or Magna, Bell & Gossett Eco Circ and Taco's Bumble Bee or 00-VDT integrate the controls into the pump. They sense what is going on in the system and automatically adjust flow rates according to system requirements with or without external sensors. Depending on the model, they can operate independently or be tied into the building control system.
Grundfos calls this technology "Auto Adapt." At Bell & Gossett, it's "pipe and play." The technician installs the pump with its pre-set factory settings and over time it analyzes system operation and adjusts itself accordingly.
With an ECM motor controlled by internal circuit board, the result is smooth or "stepless" variable speed control, remarked Bill Hooper, market development manager for ITT Residential and Commercial Water, Quispamsis, N.B. There's no "slip" in an ECM motor, he adds. The power out is a lot closer to the power in than it is with a conventional AC induction motor pump. ITT recently bought the Laing Pump Co. and is incorporating its smart technology into its product line.
Features vary depending on the model. The Wilo Stratos, for example, can be tied into a laptop computer. It includes self-diagnostics, a 40-year memory so the technical can look at the operation history, see the pump curve and make set point changes.
That being said, a lot can be achieved without ECM motors, remarked Eugene Fina, commercial product manager for Taco.
"You can do a lot of things with efficient motors, variable speed drives and feedback systems that have nothing to do with ECM motor technology, especially on higher horsepower pumps."
Sheldon Schiffner, vice president of sales for Wilo Canada Inc., in Calgary agrees, but only to a point. In addition to the added complexity, a conventional variable speed pump with smart controls won't be as efficient as an ECM smart pump at lower pumping speeds, he advises.
A bunch of Wilo Stratos smart pumps adds up to significant energy savings.
Different pump modes
A smart pump is controlled either by Delta-P (pressure) or Delta-T (temperature). Generally, in residential applications Delta-T pumps are used while on the commercial side, it can go either way, notes Fina. "It has more to do with how you arrange your piping and valving, pressure drops and the pressure differences between primary loops and secondary loops."
On the Delta-P pump the technician could set it for 20 feet of head and it will maintain that regardless of what's happening in the system. The pump curve is a straight line from lower left to the upper right, with, using the former example, max pressure would be 20 feet of head, but zero on the curve would be 10 ft. "A smart pump only gives you as much flow and head as you need to overcome the system head pressure," says Schiffner.
Delta-T pumps are more common in hydronic heating applications.
Where you are dealing with zone valves, radiant floor heating, manifold actuators, etc., a Delta T pump makes more sense because it's going to vary its speed based on the temperature going in and the temperature coming back, "which is a true indication of how many Btu's are being removed from the system at any given point in time," said Barba.
"The Delta T is the thing that we can monitor that tells us how many zones are calling at any given time, how cold it is outside at any given time and how many Btu's are being taken out of the fluid," said Barba.
A Delta T pump can be set to maintain a certain temperature in a secondary loop. In a condensing boiler system, for example, a sensor on the return side keeps the water temperature as low as possible to maximize condensation. "You maximize the efficiency of the boiler plus your system efficiency goes way up," said Schiffner.
And this is where things get interesting. The electrical savings, particularly in a residential application, may not justify the additional cost of a smart pump, which is usually about double that of a conventional pump. However, the fuel savings from more efficient operation of the boiler can be significant. Thirty percent is not unusual, while at the same time building occupants enjoy a higher level of comfort, said Barba.
Bell & Gossett's Eco Circ - "pipe and play" in a residential heating application.
Designing with smart pumps
A smart pump takes a lot of guesswork out of designing a system. Steady state pumps are typically oversized – given a certain safety factor to ensure adequate pressure or flow. With a smart pump, if the parameters the plumber dials in prove incorrect, either it will automatically adjust or he can come back later and dial in the required change.
However, using smart pumps in a residential hydronic heating system requires some thought during the design process. Don't think: "It's smart so therefore I don't have to be," said Barba. "You still have to apply the thing properly. Know what you are doing. It doesn't free you from understanding the fundamentals of hydronics."
"Any time you install a pump, you need to have a good understanding of how it's interacting in the system," added Fina. This becomes even more critical with variable speed pumps and electronic controls.
Installing a smart pump
On the job site, installing a smart pump is basically the same as installing a "dumb" pump, says Schiffner. "It just bolts in like any other pump would."
However, depending on the brand and model, the installing mechanic might have to choose which operating mode he wants – Delta T, Delta P, etc. and then dial in the required temperature or head pressure.
A Delta P pump is a little more complicated. "You have to make sure all of your zones are of similar length and similar pressure drop when you design them," said Barba. The designer must calculate the maximum head out to a reasonable point.
ECM motor technology along with matching pump speed to demand means that smart pumps consume considerably less electricity than conventional pumps (Please see sidebar). Is it enough to justify the additional cost? If one is looking at it strictly for electrical savings, it really depends on the application. The savings can add up in systems with multiple pumps.
However, smart pumps justify their cost not just in electrical energy savings, but in making building systems more efficient. And as a premium product, the profit margins for contractors are higher, remarked Hooper.
Reduced energy costs and improved comfort levels for the customer along with a little more money for the green savvy contractor make smart pumps worth considering.
How much energy do smart pumps save?
It's a given that the ECM motors in today's smart pumps use less electricity than a conventional single-speed pump, but how much less?
B.C. Hydro wanted to know. In 2007 they sponsored a study by Prism Engineering Ltd. of Burnaby. B.C. For a test building, Prism selected Rosewood Towers in Richmond, B.C., a complex made up of two essentially identical high-rise apartment buildings.
A Wilo Stratos Model 3.0x3-40 smart pump was installed in the perimeter heating system of one building while the other retained its 1.5 horsepower single-speed pump, rated at 162 U.S. GPM at 18 feet of head. The Stratos has an ECM motor and integral variable speed drive.
The test took place from December, 2008 to May of 2009. This covered most of the heating season in what turned out to be an unusually cold winter. Prism measured and logged three-phase voltage, three phase amps, power consumption and power factor. Based on the 140 days of metering, Prism projected annual power consumption.
The results were impressive. The existing pump used 9,582 kWh per year versus 2,252 kWh for the smart pump, for a savings of 76 percent. The power factor for the existing pump was measured at 56 to 60 percent versus 96 to 98 percent for the Stratos.
This type of power reduction can up to significant savings on the electrical bill.
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