US 5,020,988 AGranted

Intermittent pilot type burner control with a single control relay

AssigneeHoneywell Inc.

InventorScott M. Peterson

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Abstract

A burner control system for an intermittent pilot burner system uses a single pole double throw relay to control first and second electromagnetic valves respectively supplying fuel for both burners and for the main burner only. The normally open contact pair supplies the current for the first and the normally closed contact pair supplies the current for the second valve. By selecting the valve supplying fuel for both burners to be of the type which has an appreciably higher pull-in current than drop-out current, and by shunting the relay's normally open contacts with a properly selected resistor, only a single relay is necessary. This resistor is selected to supply current sufficient to hold the valve open (current greater than the drop-out value) after the valve has received pull-in current through the closing of these normally open contacts, but insufficient to open the valve. Use of a single relay reduces cost, size, and power, and increases safety of the control system.

Claims4

Dependent claims

In a burner control system for use in a system of the type having a pilot burner with an intermittent flame, a main burner, a first electrically controlled valve having first and second control terminals for controlling flow of fuel for the pilot and main burner, and a second electrically controlled valve having first and second control terminals, said second valve in series fuel flow connection with and downstream of the first valve for controlling flow of main burner fuel only, improved valve control apparatus wherein the first valve is one of the type having a pull-in current appreciably greater than the valve's drop-out current, comprising

a) a single pole double throw relay having a normally open contact pair controlling electrical power to the first valve and a normally closed contact pair controlling power to the second valve;
and
b) a resistor shunting the relay's normally open contact pair, said resistor of value allowing current flow to the first valve greater than the drop-out current for the first valve and less than the pull-in current for the first valve, when the normally open contact pair is open.

Dependencies are inferred from the claim text.