Control system for monitoring and adjusting combustion performance in a cordwood-fired heating appliance

Abstract

A system including temperature measuring devices, a controller, and an actuator, maintains a desired gas temperature range in the secondary combustor by proportionally making adjustments to the primary air orifice or other primary air valve of a cordwood burning appliance. Heat output of the appliance is directly related to the temperature of the gases in the secondary combustor, and sufficient engagement of the second combustor during off-gassing of volatiles from the wood will control emissions from the appliance. The operator can select a desired room temperature via the thermostat and the controller will use different secondary gas temperature target ranges in order to meet the desired room temperature as commanded by the thermostat throughout the burn event. The controller also controls the start-up phase of combustion and charcoal phase of combustion.

Description

DESCRIPTION[0001]This application claims priority of Provisional Application Ser. No. 61 / 851,343, filed Mar. 7, 2013, entitled “Control System for Monitoring and Adjusting Combustion Performance in a Cord Wood Fired Residential Heating Appliance”, the entire disclosure of which is incorporated herein by this reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to control systems designed to operate on wood stoves, furnaces, fire places, and / or other types of appliances that are designed to burn solid fuel, preferably wood, and that are equipped with secondary combustion systems, frequently called “secondary combustors”. Certain embodiments are for residential wood-burning appliances. Certain embodiments are designed to optimize burn characteristics to reduce emissions, maximize efficiency, and make operation simple for the operator.[0004]2. Discussion of Related Art[0005]Cordwood burning appliances must contend with a huge amount of...

AI Technical Summary

Benefits of technology

The present invention is about a control system for solid fuel appliances, like wood stoves, that reduces emissions and maximizes efficiency. The system measures the temperature of the secondary combustion system and controls the amount of air to maintain the desired temperature during combustion. This results in low emissions, increased efficiency, and a simple operation for the operator. The system also has automatic preset targets for secondary combustion gas temperature based on the desired room temperature, which users cannot change. The controller algorithm selects between different preset targets based on whether or not the thermostat is calling for heat. The lower preset target results in a longer burn-time and reduces emissions, but may not always be suitable for all users. Overall, the invention provides a simple and effective solution for reducing emissions and improving the performance of solid fuel appliances.

Problems solved by technology

However, this “standard” does not reflect real world conditions, and likely never will, as the number of permutations needed to understand the field emissions profile, based on the aforementioned contributing factors, are far too many.

There is increasing pressure from air regulatory authorities to clean up air sheds, but, given that laboratory testing and realized field emissions do not and will likely never correlate, the only tool regulators currently have is to lower the passing threshold for new appliances coming to market.

Therefore, success in obtaining a low emissions profile during operation of a wood burning appliance can be difficult for operators.

For example, if the air control for the appliance is closed off prematurely in order to provide a low heat output and prolong the length of the burn, then excessive emissions and low efficiency are often the result.

Therefore, the multiple goals, of trying to heat a room comfortably during use of the room, burning wood cleanly, extending length of a burn, and / or use less wood, are entirely at the discretion of the operator and are seldom all achievable by conventional, manual equipment and methods.

None of the aforementioned systems directly measure the temperature of the gases within the secondary combustion system.

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