Dave KoestererDir. of Eng. Performance Systems

Furnace Updates

Topics

• 95% With ECM Blower Motor• Residential Furnace Product Improvements

• New Trap• Pressure Switches• Probe Access Terminals• Cabinet Leakage Improvements

• Blower/Motor Failure – Case Study

*G7SD/MGCSD

• Up to 95% AFUE• Single Stage• Inputs– 38 kbtuh– 54 kbtuh– 108 kbtuh– 120 kbtuh

• ECM Motors – Constant Torque

• Orientation– Upflow– Horizontal Left– Horizontal Right

• Availability – Q4 2015

New PVC Trap with Cleanout

• Vent Trap with Cleanout

• 2” slip x ½” slip x 3/8” NPT

• Implemented - 8/31/15

Inducer Pressure Switch Changes

• New inducer switch opening pressures identified• More reliable operation• Current switches do NOT impose a safety issue• Implementation in Q4, 2015

Model Old Switch Setting New Switch Setting

*G7SA 108C-35C1 632636 0.85 632488 0.75

*G7SA 126C-45D1 632636 0.85 632488 0.75

*G7SC 054D-24B1 632487 0.90 632495 0.80

*G7SL 120D-45D1 632487 0.90 632493 0.60*G7SM 118D-45D1 632571 1.30 632495 0.80

*G7TC 060D-VB1 632515 0.73/0.43 632514 0.63/0.43

*G7TC 100D-VC1 632548 0.80/0.50 632555 0.70/0.50

*G7TC 120D-VD1 632516 0.80/0.40 632614 0.70/0.40

New Style Pressure Switches

Current Future

• Phase-in over next 2 years• Increased Accuracy• Wider Setting Range (0.1 to 5.0”)• Slimmer Profile

Probe Access Terminals

• Probe Access Terminals – Power input Line (L) &

Neutral (N)– Limit Switches– Pressure Switches

Air Leakage Improvements

• 80% Upflow Models– Added seals around the lower

blower door.– Implemented 6/19/15

• All Upflow Models– Add seal to lower corners between

Heat Exchanger, Blower Deck and Wrapper.

– Implement in September, 2015

Loose Blower Wheels – 1 HP PSC Motors

• Field reports of Blower Wheels working loose

• Requested failed blower assemblies from customers• 1 HP PSC Motor 622300• 11 x 10 Wheel 667280

• Root Cause Analysis• Set Screw

• Sampled production models• Torqued within proper range• Set Screw is correct length

• Motor Shaft• Proper hardness• Dimensionally correct

Failed Blower Wheel

• Set Screw Loose• Hub Separated from Blades

Failed Blower Wheel

Internal Hub Wear

Vibration Testing of Motor and Blower

Swaying Mode Movement of the motor and wheel as one body relative to the blower housing.

The natural frequency is 17 Hz and should not be excited in transit.

Rocking Mode Wheel rocking mode vibration involves the movement of the blades relative to the center plate, or the movement of the center plate with respect to the hub.

The response frequency is 28 Hz, far above the maximum operating speed (1050 rpm, 17.5 Hz) of the motor and should not be excited.

Vibration Testing of Motor and Blower

Torsional Mode (Wheel-Shaft-Rotor) This mode involves the relative torsional movement between the wheel and the motor rotor, while the shaft acts like a torsional spring.

Types of Failures (Torsional Mode)• Blade – Center Plate separation• Hub – Center Plate• setscrew loosening• Motor shaft gouging• Excessive noise

Vibration Testing of Motor and Blower

The excitations are the 120 Hz and 240 Hz motor torque pulsations generated by a PSC motor with a 60 Hz line frequency.

If a system is near resonance, the motor torque pulsation forces will be amplified and transmitted to the blower wheel.

The natural frequency of this system was measured to be 168.5 Hz. This is not close to 120/240 Hz torque pulsations. However, the forces were high.

The solution• Move the motor closer to the wheel hub 0.75”• Shift resonance from 168.5 to 185 Hz• Reduce force amplitude by 25%

Vibration Testing of Motor and Blower

700 750 800 850 900 950 1000 1050 1100 115040

50

60

70

80

90

100

185 Hz168.5 Hz

RPM

Peak

Tor

que

Loose Blower Wheel Solution

• TB15-106RA 622300-904860 1 HP Motors-667280R Blower Wheels was issued 4/15/15

• Effective 3/20/15 Motors were repositioned in production.

Furnace Updates

Thank you!

Questions?