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Publication Date: 2014-Sep-25
Document File: 3 page(s) / 42K

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The Prior Art Database

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Alexander Barber: AUTHOR [+3]


A mechanism for initiating a defrost cycle for heat pumps to melt ice from fan blades and orifice rings is described. A vibration sensor is used to detect ice formation on a fan blade or ring by detecting the change in motion of the fan blade due to the chance in weight distribution. Once detected the sensor sends a signal to a controller which initiates a defrost cycle at the heat pump.

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Alexander Barber

Eric Berg

Lennox Industries



[0001]                           Heat pumps operate in a wide range of temperatures and conditions. In some cases ice can form on the fan blades, orifice rings or other components.  Ice buildup on fan blades or other components can result in noise, which can be a nuisance, or can result in the fan freezing in position making the unit inoperable.  While there are methods to attempt to defrost fan blades and other components of heat pumps, those methods may be unreliable or limited to narrow temperature ranges or conditions.


[0002]                           This paper describes a new mechanism for initiating a defrost cycle for heat pumps that will melt ice from fan blades and orifice rings.  The algorithm provides a means for detecting ice buildup and triggering the defrost routine.

[0003]                           The algorithm detects ice buildup using a tilt or vibration sensor.  When ice forms on the fan blades or orifice ring of a heat pump, it changes weight distribution and balance of the components and causes the blades or ring to vibrate.  This vibration is detected by the tilt or vibration sensor which detects the motion of the unbalanced fan.  Once detected, the vibration causes a set of contacts in the sensor to open, thereby sending a signal to a controller.  The controller monitors the sensor and is programmed to react when the sensor output goes below or beyond a programmed threshold.  The sensor can be installed in series with the system low pressure switch.

[0004]                           Once the threshold is passed the controller initiates a defrost cycle to melt the ice that has formed on the fan blades or orifice ring.  Existing defrost control routines will normally initiate a defrost cycle when the low pressure switch has opened twice within one heating demand.  By placing the vibration sensor in series with the low pressure switch, existing defrost control routines can be used as the control routine would see the opening of the vibration switch as an opening of the low pressure switch.  Two triggering of the vibration switch would result in t...