Fluid heating control system
US6246831A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 16, 1999 |
| Grant date | Jun 12, 2001 |
| Priority date | — |
| Expiry date | Jun 16, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05B2203/021
- WIPO fieldThermal processes and apparatus
- WIPO sectorMechanical engineering
Abstract
An improved system, method and apparatus for control of an instantaneous flow-through fluid heater system is disclosed. The control incorporates a logic control method providing modulation of power in small steps to a plurality of heating elements retaining responsiveness to closed-loop control needs without inducing light flicker. Further, the life of the coils of heating circuit electromechanical relays are extended by energizing the coils with a pulse-width-modulated drive decreasing in duty cycle and thus the latent coil heat when an increase in mains voltage is sensed. The life of the contacts of same relays are extended by inhibiting heating element triac drive immediately upon sensing loss of relay coil power, such as by an over temperature limit switch opening, thus ensuring that relay contacts open with zero heating element current. In addition to the software "watchdog timer" internal to the microcontroller, a redundant fail-safe circuit external to the microcontroller prevents a program lockup condition from leaving any heating element triac or relay drive in an energized state. A combination of control hardware and program provide self-diagnostic detection of an inopera…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.