Case
Optimizing Domestic Water Pressure Boosting System Cuts Energy Use by 86% at Seattle Office Building
SEATTLE — Confronted by a failing domestic water booster pump at one of the downtown commercial properties managed by Martin Selig Real Estate, Chief Engineer Phil Boyd began searching for options to repair the existing tri-plex boosting pump system.
The booster station serves the 43-story commercial office building at 1000 2nd Ave., located blocks from the Puget Sound waterway. Such high-rise buildings—including hotels, multifamily, office and other institutional applications—require pressure boosting equipment to raise incoming municipal water pressure to serve upper floors. Demand for water in such multi-story buildings can vary significantly throughout the day, and this unpredictable flow places extraordinary demands on pumping equipment.
Boyd planned to repair the pumping station until Corey Rasmussen, Grundfos Sales Manager, suggested that the property management’s investment would be better spent on a new, more efficient water boosting system. To support this recommendation, Rasmussen advocated an independent energy audit to determine the building’s actual pressure requirements, given the condition of the existing 27-year-old pumps.
“We had absolutely no doubt that we could significantly lower the operating costs of the existing unit by using intelligent, demand-based pump technology,” recalls Rasmussen, who nonetheless provided Boyd the $17,000 repair quote. “The problem, however, was convincing a price-conscious customer to invest in new technology instead of rebuilding the decades-old pressure boosting pumps and motor drives.”
Unknown to Boyd, Rasmussen already had a solution in mind. His trump card was the Grundfos Hydro MPC BoosterpaQ, an integrated pressure boosting system that would deliver the exact pressure necessary to achieve optimal performance — all without direct human intervention. Ideal for water supply systems, as well as municipal boosting, water transfer, and industrial applications, these integrated pumping systems utilize an advanced controller to adjust pump speed and stage additional pumps as necessary to meet specific pressure demand.
“Initially, Martin Selig was looking at the possibility of rebuilding the existing pump station. After looking into the costs, we realized it made better sense financially to upgrade to a more energy efficient system,” says Boyd.
Energy Audit
Anxious to demonstrate the value of replacing rather than repairing the pressure boosting system, Rasmussen contacted Grundfos colleague Roger Weldon, C.E.M., LEED AP, Energy Optimization Engineer, to arrange a pump audit. Weldon has extensive experience with this type of application and traveled to the site to install the pump audit equipment (flow, power, pressure meter/loggers) onto the existing pressure boosting system. The pump audit equipment recorded performance data for a two-week period.
According to Weldon, “The data derived from the pump audit allows us to select the optimum replacement system that is often substantially smaller and less costly to purchase and operate. Additionally, the data we collect is used to apply for utility incentives, which help to boost the company’s return on this capital investment.”
The Current System
The pumping station employed a pressure boosting system that was installed when the building was constructed in 1987.
“The building’s existing pressure boosting system, which consisted of one 20 horsepower (hp) and two 30 hp vertical turbine pumps, ran at full speed and the pressure was controlled by pressure regulating valves that significantly reduce the system’s overall efficiency, and would require scheduled annual maintenance,” recalls Boyd.
Due to the simplistic control technology employed, one of the pumps ran 24 hours a day regardless of flow demands, which are significantly lower during overnight and weekend periods when the building is unoccupied. The current control scheme not only wastes electricity but also decreases the equipment’s life expectancy from the excessive heat and hydraulic forces generated from operating when there is no flow demand.
One way to leverage the savings realized by moving from a constant-speed pumping system to a variable-speed, demand-based platform is to apply for a utility incentive. Weldon worked with the local utility, Seattle City Light, a publicly owned electric power utility, to secure a large power reduction incentive for the property management customer. Like many utilities, Seattle City Light's Energy Smart Services program, offers financial incentives to help medium and large businesses reduce electricity use, save money and shorten the payback on energy-efficient investments.
“After the new Hydro MPC BoosterpaQ was installed, the Utility’s technical metering team monitored the power consumption of the pressure boosting equipment over a two-week period starting at the end of August 2014 to account for changes in load demand, and compared this data against the estimated power consumption of the new unit,” explains Lisa Frasene, Energy Management Analyst, Seattle City Light.
Notes Frasene, “Incentives are based on total annual kilowatt hour (kWh) savings over the first year of the project. Combined rebates from all utilities may not exceed 70 percent of project costs and the incentive amount is capped to a minimum payback period of six months.” Seattle City Light is currently offering an incentive rate of $.27 per kWh reduction in the first year of operation for this type of project.
| Equipment | Motor | Speed Control |
Average Annual Consuption |
Annual Operating Cost* |
Annual Maintenance† |
|---|---|---|---|---|---|
| Original vertical turbines |
2@30HP 1@20HP |
Constant Speed |
131,400 kWh | $12,220 | $900 |
| Grundfos Hydro MPC BoosterpaQ |
4@7.5HP | Variable Speed |
18,078 kWh | $1,681 | $100 |
| Savings | - | - | 113,322 | $10,539 | $800 |
| % Reduction |
- | - | 86% | 86% | 89% |
* based on $0.093 per kWh
† Annual maintenance is based on general industry rules of thumb.
Pump 1 (20HP) is out of service and the repair estimate is between $15-20K.
It goes without saying that all the parties were thrilled to learn that the projected energy savings—and the resulting utility incentive —would make the shift to newer technology very attractive.
Office Complex Located at 1000 2nd Ave.
First year costs projected from the audit are:
- System cost — $61,521
- Utility Incentive — +$29,328
- Annual cost/energy savings — +$7,604 (86% reduction – savings of 108,624 kWh per year)
- Repair costs avoided - $17,000
- Total 1st year cost $4,024
“With an annual estimated energy savings of 108,624 kWh, or $7,604, the high efficiency pressure boosting system would qualify for a one-time incentive payment in the amount of $29,328,” continues Frasene. “Simple payback is estimated to be 5.1 years, and each year thereafter, the business will save an estimated $7,600 in reduced electric bills.”
The financial returns on this project were outstanding, as is often the case in the Seattle/Tacoma/Bellevue area due to the generous incentives being offered by the utilities, explains Weldon.
“The energy savings from the Grundfos pumps were impressive,” recalls Boyd. “The new ‘right-sized’ water booster system has a lower initial cost than a ‘like-sized’ system, costs less to operate and the utility incentive would pay for nearly half of the system.”
Matching Output with Demand
The replacement Hydro MPC BoosterpaQ system is a state-of-the-art pressure boosting system. The unit is equipped with the extremely efficient and reliable Grundfos CR vertical multi-stage centrifugal pumps. Each of the pumps is coupled to a 7.5 hp Grundfos MLE integrated variable-speed drive and motor.
The Multi-Pump Controller (MPC) does an extremely good job of managing VFD controlled pumps in parallel fashion. The pump performance curves are loaded into the controller on the Hydro MPC BoosterpaQ, which selects the most efficient combination of pumps and pump speeds to precisely match the flow and pressure demand.
“In recent years, variable frequency drive technology has become more affordable and critical in bringing intelligent speed control to a number of commercial pumping applications, including domestic water boosting,” explains Rasmussen. “The ability to adjust the pumping system output based on system demand was the primary reason we knew we could significantly reduce energy consumption for this building.”
In the end, the final numbers were more than impressive: a $7,604 per year reduction in energy savings; approximately $2,500 per year reduction in maintenance costs; and an average 86 percent reduction in energy use.
“The replacement BoosterpaQ system has performed very well; it is very quiet and maintenance-free,” says Boyd. “We are saving money in maintenance and energy costs.”
Success Leads to Similar Upgrades
Due to the success of the booster pump retrofit at the 1000 2nd Avenue location, Boyd got the green light to make similar upgrades at two more downtown office buildings.
The second retrofit was located at 2101 4th Avenue, which is also known as the Fourth and Blanchard building. The facility is a 25-story office building in downtown Seattle. The existing system was a tri-plex boosting system equipped with one 15 hp and two 25 hp fixed-speed pumps.
The team recommended replacing the existing system with a Grundfos Hydro MPC pressure boosting system utilizing three CRE 10-6 pumps. Each is controlled by a 5 hp variable-speed pump.
Office Complex Located at 2101 4th Avenue
First year costs projected from the audit indicate:
- System cost — $63,183
- Utility Incentives — +$17,009
- Energy savings — +$5,055 per year (84% reduction – savings of 63,000 kWh per year)
- Total 1st year cost = $41,119
The results from the Fourth and Blanchard building were similar to the 1000 2nd Avenue project, except the utility incentive was lower because the building is not as tall and the pump system is smaller, thus consuming less energy.
Following these two successful retrofits, Rasmussen and Weldon completed an energy audit on a third commercial property managed by Martin Selig. The audit for a 12-story high-rise, located at 2401 2nd street (Fourth and Battery), examined the building’s existing duplex pressure boosting system with full-speed 5 hp end-suction pumps.
The power reduction in this third application yielded an impressive 94 percent energy savings, but due to the system’s size, the kWh savings are less than the first two buildings and therefore the utility incentive is less.
The proposed replacement system is a Grundfos Hydro MPC BoosterpaQ equipped with two variable-speed 1.5 hp CRE pumps.
Office Complex Located at 2401 2nd street
The summary data for the project is as follows:
- System cost — $ 47,383
- Utility Incentives — +$6,700
- Energy savings — +$2,000 per year
- Total 1st year cost = $38,683
By replacing the pressure boosting system in these three commercial properties Martin Selig Real Estate has:
- Lowered the power consumption in each building
- Improved the reliability of the pressure boosting systems and almost eliminated the annual maintenance costs associated with each system
- Avoided costly repairs of obsolete systems
- Increased the value of their property
Grundfos was able to provide a total turnkey solution for Martin Selig Real Estate, which means they only had one vendor to deal with, making life simpler and easier for their staff. “Martin Selig did not even consider purchasing another pumping system because the Grundfos team demonstrated its ability to take a project from evaluation to installation,” concludes Boyd.