Burner Flashback Detection and System Shutdown Apparatus

Abstract

A fuel-fired water heater is provided with a premixing type main burner and an associated pilot burner for igniting it. A specially designed protective system is operative to detect a flame flashback burning condition in the main burner and responsively shut down the water heater. In one embodiment thereof, the protective system uses main burner body heat to melt a portion of a fuel supply line connected to the pilot burner during a flame flashback condition in the main burner. Such melting responsively causes an associated fuel supply valve to close and terminate water heater operation. In a second protective system embodiment a normally closed pressure switch is opened, thereby shutting down the water heater, when the switch detects a pressure indicative of a flame flashback condition in the main burner.

1 . Fuel-fired heating apparatus comprising:
 a fuel burner operative to create a flame; and   a protective system operative to detect a pressure indicative of a flame flashback condition in said fuel burner and responsively shut down operation thereof.   
   
   
       2 . The fuel-fired heating apparatus of  claim 1  wherein:
 said fuel-fired heating apparatus is a water heater.   
   
   
       3 . The fuel-fired heating apparatus of  claim 2  wherein:
 said water heater is a gas-fired water heater.   
   
   
       4 . The fuel-fired heating apparatus of  claim 1  wherein:
 said fuel burner is a fuel/air premixing type fuel burner.   
   
   
       5 . The fuel-fired heating apparatus of  claim 1  wherein:
 said fuel burner is a main fuel burner,   said fuel-fired heating apparatus further comprises a pilot fuel burner operative to generate a pilot flame, and a normally closed fuel supply valve operatively coupled to said main fuel burner and said pilot fuel burner, and   said protective system comprises a millivolt electrical circuit having connected in series therein a thermoelectric device positioned to be impinged by said pilot flame, and a normally closed pressure switch with a pressure inlet operative to receive said pressure indicative of a flame flashback condition in said main fuel burner.   
   
   
       6 . The fuel-fired heating apparatus of  claim 1  wherein:
 said fuel burner has a hollow body portion, and said protective system is operative to detect said pressure within said hollow body portion of said fuel burner.   
   
   
       7 . The fuel-fired heating apparatus of  claim 1  wherein:
 said fuel burner is a fuel/air premixing type fuel burner having a body structure including a main body portion, a premix plenum portion, and a mixer tube interconnecting said main body portion and said premix plenum portion.   
   
   
       8 . The fuel-fired heating apparatus of  claim 7  wherein:
 said protective system is operative to detect said pressure within said main body portion.   
   
   
       9 . The fuel-fired heating apparatus of  claim 7  wherein:
 said protective system is operative to detect said pressure within said premix plenum portion.   
   
   
       10 . The fuel-fired heating apparatus of  claim 7  wherein:
 said protective system is operative to detect said pressure within said mixer tube.   
   
   
       11 . The fuel-fired heating apparatus of  claim 1  wherein:
 said fuel-fired heating apparatus further comprises a combustion chamber in which said fuel burner is disposed, and   said protective system is operative to detect said pressure within said combustion chamber externally of said fuel burner.   
   
   
       12 . The fuel-fired heating apparatus of  claim 1  wherein:
 said fuel-fired heating apparatus further comprises a combustion chamber in which said fuel burner is disposed, and a flue communicating with and extending away from said combustion chamber, and   said protective system is operative to detect said pressure within said flue.   
   
   
       13 . A fuel-fired water heater comprising:
 a tank adapted to hold a quantity of water to be heated;   a combustion chamber underlying said tank;   a flue communicating with said combustion chamber and extending upwardly therefrom through said tank;   a fuel burner disposed in said combustion chamber and having a body;   a normally closed fuel supply valve operatively connected to said fuel burner; and   a protective system operative to sense a pressure indicative of a flame flashback condition in said fuel burner and responsively terminate operation of said fuel-fired water heater, said protective system including:
 a thermoelectrically powered millivolt electrical circuit operatively coupled to said normally closed fuel supply valve, and 
 a normally closed pressure switch connected in said millivolt electrical circuit and having a pressure sensing line connected thereto and operative to receive said pressure. 
   
   
   
       14 . The fuel-fired water heater of  claim 13  wherein:
 said fuel burner is a fuel/air premixing type fuel burner, and   said body includes a main body portion, a premix plenum portion, and a mixer tube interconnecting said main body portion and said premix plenum portion.   
   
   
       15 . The fuel-fired water heater of  claim 14  wherein:
 said pressure sensing line is operatively communicated with the interior of said main body portion.   
   
   
       16 . The fuel-fired water heater of  claim 14  wherein:
 said pressure sensing line is operatively communicated with the interior of said premix plenum portion.   
   
   
       17 . The fuel-fired water heater of  claim 14  wherein:
 said pressure sensing line is operatively communicated with the interior of said mixer tube.   
   
   
       18 . The fuel-fired water heater of  claim 13  wherein:
 said pressure sensing line is operatively communicated with the interior of said combustion chamber externally of said fuel burner.   
   
   
       19 . The fuel-fired water heater of  claim 13  wherein:
 said pressure sensing line is operatively communicated with the interior of said flue.