half an hour after installation, the shaft voltage was measured again. This time, the reading was only 380 millivolts (peak-to-peak). For years, VFD-induced bearing
failure was often misdiagnosed, until repair shops and testing consultants proved that the high peak voltages, fast voltage rise times and non-sinusoidal shaft currents associated with typical pulse-width- modulated VFDs lead to the cumulative erosion of ball bearings and race walls. For motors already in service, the
ring can be retrofitted on any NEMA or IEC motor, regardless of shaft size, horsepower or end-bell protrusion. Key to the ring’s success are conductive microfibers that line the entire inner circumference of the ring in two rows, completely surrounding the motor shaft. Once installed, the ring requires no maintenance and lasts for the life of the motor, regardless of rpm. Baldor Electric Company recently NEMA
introduced its Super-E® Premium®
line of inverter-ready 1–
The tape was removed from one joint of the ring, allowing it to be opened, to fit over the motor’s shaft without the need to de-couple and realign the motor to the pump.
50 HP general-purpose motors with AEGIS grounding rings factory installed inside the motor housing. Customers can choose a totally enclosed fan-cooled (TEFC) or open drip-proof (ODP) configuration. Operations and maintenance costs
can account for 60 – 80% of a building’s life-cycle costs. When
equipment does not have to be repaired or replaced as often, that percentage drops significantly. The university’s maintenance department is aggressively promoting the AEGIS SGR bearing protection ring as a way of safeguarding energy savings and realizing the full cost-saving potential and ROI of VFDs. l
More AERCO high-efficiency water heaters
83
Specifications: • 5 sizes support up to 90 GPM water flow • Brazed plate single-wall design • Plate and frame double-wall design • 2- or 3-way valve operation • Compact footprint 29 1/2"W x 48"L • Stainless steel heat exchanger
• Potable water side surfaces are stainless steel, copper or copper alloy • Max. DHW side pressure drop is 5 PSIG • Max. boiler water pressure drop is 10 PSIG • Max. DHW pressure & temp is 150 PSIG @ 180°F • Max. boiler water pressure & temp is 150 PSIG @ 220°F
KC1000 Gas-Fired Water Heaters • Market Proven for 22 Years • 1 Million BTU/hr. • 20:1 Turndown • 93%-99% Efficiency • ±4°F Temperature Control • 78"H x 22"W x 57"D • Natural Gas or Propane • Optional Low NOx Burner • 6" Vent Size
WaterWizard Helitherm Heaters • Self-Descaling Hx Design • ±4°F Temperature Control • 90-99% Thermal Efficiency • Impervious to Thermal Shock • No Traps or Tanks Required • <4 ft2
Footprint • Pneumatic or Electronic Controls
• Family of Steam-to-Water & Water-to-Water Units
• 20-Year Pressure Vessel Warranty
To learn more visit
www.aerco.com/sp8 e Circle 46 on reader reply card
Heat You Can Bank On Copyright 2009 AERCO International, Inc.
U-Tube Double Wall Heaters
• UL Listed Steam-to-Water & Water-to-Water Heaters
• ±4°F Temperature Control • <4 ft2
Footprint
• Pneumatic or Electronic Controls
• 20-Year Pressure Vessel Warranty
phc may 2011
www.phcnews.com
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