Furnace ignition system with draft control and loss-of-draft protection
US4239477A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 13, 1978 |
| Grant date | Dec 16, 1980 |
| Priority date | — |
| Expiry date | Nov 13, 1998 |
Classification
- Technology area (CPC F)Mechanical Engineering; Lighting; Heating
- CPC primaryF23N2235/04
- WIPO fieldThermal processes and apparatus
- WIPO sectorMechanical engineering
Abstract
A furnace ignition and draft control system includes a damper plate movable under control between a closed and an open position. When a call for heat signal is generated, a holding relay is actuated to energize a damper motor to open the damper provided the damper plate was closed when the signal was generated, otherwise the system will not operate. After the damper is run to the full open position and this is proved, a fuel control circuit is actuated to supply fuel to the furnace, and a trial-for-draft period is initiated. A draft controller energizes the damper motor to open the damper if draft is less than a first predetermined value and to close the damper if draft is greater than a second predetermined value. The predetermined draft values define a desired draft range in which the damper is not operated. If a draft greater than the second value is sensed within the trial period, the draft controller partially closes the damper to control the draft value within the desired draft range, otherwise the system locks out at the end of the trial period. If draft is lost at any time, the controller moves the damper to the open position and a loss-of-draft safety timing period commenc…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.