Vehicle heaters and controls therefor
A heater for a liquid has a combustion chamber, a jacket for the liquid extending about the combustion chamber and a burner head assembly connected to the combustion chamber. The burner head assembly includes a housing having a burner mounted thereon and a hollow interior. A control module and a fan are mounted in the hollow interior, the fan being connected to an electric motor. A compressor and a fuel pump are mounted on the housing and are operatively connected to the electric motor. The control module may include controls for exercising components of the heater prior to combustion, thereby verifying operation of these components. Preferably there is a speed control for the motor, such as a closed loop speed control which regulates motor speed and accordingly output of the heater. Preferably there is a backup system using a lookup table in the event that the closed loop speed control fails. Also preferably there is provision for monitoring flame sensor functionality by providing an indicator light which mirrors operation of the flame sensor. The heater may have a selective soft start for the coolant pump which operates only when required so as to reduce unnecessary chatter on the motor relay. A system is also provided for distinguishing true overcurrent faults from overcurrents arising from voltage changes during starting of the vehicle engine. Reignition algorithms are provided to restart the burner in the event of flame sputters caused, for example, by fuel bubbles, but shut off the heater in the event that the fuel is truly cut off.
1. A method for determining whether a fault as opposed sputtering has occurred in a liquid fuel burner, the method comprising the steps of:
(a) monitoring for the presence of a flame;
(b) registering a flame-on event if a flame is present or registering a flame-off event if no flame is present; and
(c) indicating that a fault has occurred when a plurality of flame-off events is registered before a plurality of flame-on events is registered and there is no flame present more than forty percent of the time in a 25 second period.
2. A heater for a liquid, the heater comprising:
a liquid fuel combustion chamber;
a jacket for the liquid extending about the combustion chamber;
a burner head assembly connected to the combustion chamber, the burner head assembly including a burner having a burner nozzle with an ignitor;
a compressor and a fuel pump for supplying liquid fuel to the burner nozzle;
a fan for providing air to the combustion chamber;
an electric motor operatively connected to the fan and the compressor;
a flame sensor for sensing the presence or absence of a flame in the combustion chamber; and
a control module for determining whether a fault as opposed to sputtering has occurred, the control module periodically checking the flame sensor to determine whether or not a flame is present after the heater is started, a first memory of the control module registering a flame-on event if a flame is present, a second memory of the control module registering a flame-off event if no flame is present, the control module actuating the ignitor if no flame is present, and the control module indicating that a fault has occurred when a plurality of flame-off events is registered before a plurality of flame-on events is registered and there is no flame present more than forty percent of the time in a 25 second period.
3. The heater as claimed in claim 2 , wherein the sensor senses for a flame cyclically, a new cycle beginning when the plurality of flame-on events is registered before the plurality of flame-off events is registered.
4. The heater as claimed in claim 3 , wherein the flame sensor senses for the presence of a flame once per second.