Baseline Description: Typical hot and small chilled water pumps
Baseline Energy Use: 1 kWh per year per square foot

Assume that a 1 hp fixed speed motor is used to circulate hot or chilled water for a 2,000 sf area.  The pump drive motor is assumed to operate at a 75% load factor and have an efficiency at its load point of 83% (Note: Federal efficiency standards have been passed for small single-phase motors that are in effect in 2015.  For a 4-pole motor, the full-load efficiency standard is 82.6% for a 1 hp motor.  As this measure is for new construction, this efficiency will be assumed for a baseload, fixed-speed motor).  The pump is assumed to operate for 3,047 hours annually (58.6 hours per week for office buildings, (CADMUS, 2009 Pg Table C-SC2)).  Annual energy use is thus 1 hp x 0.746 kW/hp x 0.75 x (1/0.83) x 3,047 = 2,053 kWh/year.  This is equivalent to approximately 1.0 kWh/sf-year.

"Typical" Savings: 80%

Taco claims that its Viridian hot and chilled water circulating pump ECPM motor saves up to 80% of the electrical energy compared to conventional pumps. Grundfos and Wilo also claim up to 80% savings on their ECPM motor-driven pumps.

"Typical" Savings: 75%
Low and High Energy Savings: 20% to 80%
Energy Savings Reliability: 5 - Comprehensive Analysis

Comments:

Assuming 45% efficiency for the existing motor and 80% efficiency for the ECPM unit, the energy savings are equal to the original energy use multiplied by (1 - E1/E2), where E1 and E2 are the efficiencies of the standard and ECPM motors at their load points, respectively. The expected energy savings percentage just for this motor upgrade is (1 - 0.45/0.8) x 100% = 44%.

Energy savings also result from the variable speed capability of the new ECPM motor, which is actually responsible for the bulk of the energy savings. Assuming an average speed reduction of 37%, the total energy savings would be equal to about 75% of the baseline energy use.

Actual savings will depend on the site-specific operating load profile.

Prism Engineering investigated the energy savings with ECPM pumps for BC Hydro, publishing the findings in a report, “New Pump Technology Pilot Project,” dated May 2009. The study compares two nearly identical high-rise residential towers in Richmond, B.C. Each building originally had a 1.5 hp constant-speed pump to serve all perimeter heating needs. In one of the buildings, this pump was replaced with a Wilo Stratos variable speed pump. Metering was installed in both buildings to measure electricity consumption for pumping. Measured power draw for the existing pump averaged 1.1 kW throughout the test period, while power consumption for the Wilo Stratos pump averaged 0.45 kW in the winter months and 0.3 kW in the spring. The researchers projected annual energy savings of 76% (Wilson, 2010).

This technology applies to new  applications in commercial buildings with chilled water systems when the pump is less than 7.5 hp. Retrofits are known to not be cost-effective due to requirements to replace existing 3-way valves with two-way valves.  Estimates are based on preliminary updated numbers from the 2013 update to the Commercial Building Stock Assessment (CBSA) using the estimates for 2014.  Using market shares from the CBSA (CADMUS, 2009) – the percentage of commercial space that is conditioned (85%) and served by chilled water systems (19%).   The CBSA estimates the commercial building stock will grow by approximately 1% over the next 20 years. To account for additions to the building stock, use 10 years of growth to account for the potential, which is 10% of the existing housing stock.   Estimates are further reduced by 75% to include only chilled water systems with motors 7.5 hp and below.

Using the market shares above results in a total potential of 3,118,000,000 sf x 0.1 x 0.85 x 0.19 * 0.25 = 12,588,925 sf.

Installed first cost per: square foot
Emerging Technology Unit Cost (Equipment Only): $1.00
Baseline Technology Unit Cost (Equipment Only): $0.50

Comments:

The Grundfos Magna commercial circulator pumps cost about 50% more than standard circulators. Wilo indicates that the Stratos and Stratos ECO pumps cost 200% to 250% more than standard circulators. The simple payback for these pumps (assuming electricity savings only) can range from eight months to about three years in new construction (Wilson, 2010). Note that the pump and motor are sold as an integrated unit, and the variable speed drive must obtain a feedback signal from a sensor, be pre-programmed, or be equipped with smart programming to fully utilize its variable speed capabilities.

ECPM motor-driven circulating pumps should be considered during new construction of circulating hot and chilled water systems that utilize pumps of 5 hp or less.  VSD-driven pumps are already required by code for larger systems. Retrofits are not cost-effective as the three-way valve that diverts hot or chilled water from a supply line to a coil must be replaced by a two-way valve.  Without this modification, pressures would not build up in the supply line to give a signal to the pump VSD to reduce speed.  The cost of each “hose kit” consisting of a new valve, strainer, and pressure transmitter port is about $1,000.  This requirement for valve replacements results in the simple payback for a retrofit being well over 100 years.

For new construction, costs depend on whether a cast iron or stainless steel pump is installed, and varies depending on developed head and flow. An Armstrong Compass has a power range of 5W to 45W with a first cost of $266. A 1/6 hp Magna costs $546; a 1/3 hp pump costs $1,463; and a 1 hp pump cost about $2,025 (Internet prices, March 2015). Assuming that  a 1 hp pump can serve about 2000 sf of floor area, the cost is about $1/sf.  Flange options can be sold separately.

Cost Effectiveness:

Simple payback, new construction (years): 7.4

Simple payback, retrofit (years): N/A