Variable speed fan motor control for forced air heating/cooling system

• US 6,684,944 B1
• Filed: 05/15/2000
• Issued: 02/03/2004
• Est. Priority Date: 02/18/1997
• Status: Expired due to Fees

• Current Assignee: Hoffman Controls Corp.
• Original Assignee: Hoffman Controls Corp.
• Inventors: Byrnes, Howard P., Steffen, Daniel B.
• Primary Examiner(s): Ford, John K.
• Application Number:
  US09/570,880
• Time in Patent Office: 1,359 Days
• Field of Search: 236/11, 236/91.F, 236/78.D, 236/49.3, 236/38, 236/DIG.9, 165/293, 165/244, 165/247, 237/8.R, 126/110.A, 126/110.E, 621/57, 621/80, 621/86, 622/31, 318/439, 318/471, 318/806
• US Class Current: 165/247
• CPC Class Codes: F04D 27/00 Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
• CPC Class Codes: F24F 11/77 by controlling the speed of ventilators
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
• CPC Class Codes: Y10S 236/09 Fan control

Abstract

A forced air heating and/or cooling system utilizing an induction type fan motor is controlled by a controller circuit which is operable to continuously vary the speed of the fan motor during a start-up phase and a shut-down phase of the heating and/or cooling cycle. The controller circuit includes terminals for connection to the source of electrical energy for the heating and/or cooling system and for connection to the system controls without altering the control function or circuitry thereof. The controller circuit includes temperature sensors which are operable to control start-up and shutdown of the fan motor over continuously variable speed operating cycles in response to sensed temperature of the air being circulated by the fan.

Claims

1. A method for controlling a fan motor of a forced air heating and cooling system for controlling the flow of air through said heating and cooling system, said heating and cooling, system including a first controller having a temperature sensor in an air conduit of said heating and cooling system for controlling operation of said motor during at least one of heating and cooling of a space, said method comprising the steps of:

providing a second controller operable to be connected to a source of electrical energy and said motor, said second controller being operable for substantially continuously varying the speed of said motor between a minimum speed and a maximum speed independently of said first controller, said second controller including a first temperature sensor operable to sense the temperature of air in said conduit of said heating and cooling system, a second temperature sensor operable to sense a reference temperature of air in said space or returning from said space and circuit means operably connected to said temperature sensors for effecting a change in speed of said motor in response to a differential temperature sensed by said temperature sensors, respectively;

operably connecting said second controller to said source of electric energy and said motor; and

causing said second controller to substantially continuously change the speed of said motor between a minimum speed and a substantially maximum speed independently of said first controller and based on the differential temperature of air flowing through said heating and cooling system sensed by said temperature sensors, respectively.

2. The method set forth in claim 1 including the step of:

providing said second controller with a triac operably connected to said motor and interposed in an electrical circuit for energizing said motor, a triac firing circuit operably connected to said triac, a cross-over detector circuit, and a phase timer circuit operably connected to said triac firing circuit.

3. The method set forth in claim 1 including the step of:

causing said second controller to substantially continuously reduce the speed of said motor to a predetermined minimum speed in response to a temperature sensed by at least one of said temperature sensors so as to minimize loss of energy from said heating and cooling system and to minimize temperature stratification of air in said space.

4. The method set forth in claim 3 including the step of:

causing said second controller to effect one of shut-off of said motor at a predetermined minimum speed regardless of a temperature sensed by said temperature sensors and continued operation of said motor at said minimum speed, respectively.

5. The method set forth in claim 1 including the step of:

causing said second controller to substantially continuously vary the effective voltage imposed on said motor to vary the speed of said motor.

6. The method set forth in claim 5 including the step of:

providing said motor as at least one of a permanent split capacitor motor and a shaded pole motor.

7. The method set forth in claim 1 including the step of:

providing said second controller with a motor minimum speed clamp circuit operable to prevent operation of said motor in response to a predetermined differential temperature between a temperature sensed in said conduit and a temperature sensed at a reference point.