Fuel Oil News

Fuel Oil News March 2016

The home heating oil industry has a long and proud history, and Fuel Oil News has been there supporting it since 1935. It is an industry that has faced many challenges during that time. In its 77th year, Fuel Oil News is doing more than just holding

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44 MARCH 2016 | FUEL OIL NEWS | www.fueloilnews.com BY GEORGE LANTHIER HVAC/ HYDRONICS T his article has been printed a few times and its always been a very popular piece and answers some questions that con- stantly come up when doing combustion testing on oil, gas and LP. This material was originally published in The Councilor of the Better Home Heat Council of Massachusetts in 1979 and then in Fueloil & Oil Heat, September 1991. It was again published as excerpts in the text, 'COMBUSTION & Oil Burning Equipment' in 1995—2000 and 'Advanced Residential Oilburners', 2001— 2016 and this information never seems to go out of date. Although originally written for oilburners much of the equipment covered can also be used to test gas-fired equipment. The ability to diagnose and repair oil or gas burners seems sometimes out of our control. Regrettably, as these problems have increased, we have not used all of the tools available to us. It is almost impossible today to properly service "state of the art" burn- ers by the 'let's eyeball it' method. Annoying and costly repeat calls have increased while no one seems to know why. Or do we? Some companies seem to have fewer problems than others do. Why? We hope to answer some of these questions here or at least get you to look over how and why you do it 'your way.' Since almost the beginning of the service industry we have had testing equipment available to us to analyze burner performance. In the 70s and 80s, the combustion test kit was used primarily to test "steady-state efficiency" and lost most of its credibility as a true service tool. It is as essential as our flashlight for good burner service. Since many of us may not have used the kit as often as we should, we will concentrate on reviewing the basics of instru- ment use and instrument quality. Although many, including myself, love their electronic analyzers it is always these kits we fall back on when "good goes bad." The purpose of this document is, therefore, to eliminate as many discrepancies as possible, which come about due to improper care and maintenance of the instruments used in the field. Many technicians still do not understand the importance and meaning of steady-state test conditions. For their benefit, we will re-define the term and discuss the proper use and checkout procedures for these tools. STEADY-STATE A condition that exists when the burner has fired long enough to have reached unchanging temperatures. Steady-state is most easily confirmed by the temperature of the flue gas. Steady-state conditions have been reached when there has been no change in temperature for two minutes. PREPARING THE UNIT FOR TESTING It is advised that two holes be made in the stack to speed up testing which is especially important with today's smaller units, Figure 1. Location of these holes is very important. They should be at least one flue pipe diameter from the draft regulator, dimension A and they should also both be located one to two smoke pipe diameters from the breech, dimension B, excluding all elbows, but always between the breech and draft regulator or where the test is recommended to be done by the appliance manufacturer. By inserting the stack thermometer in one hole, steady state conditions will be proved as soon as possible and leave the other hole for other tests. Another test hole must be located preferably within 12 inches over the fire or in the door closest to fire. INSTRUMENTS Before performing any tests, the instruments must be checked to insure good test readings: Checking the dry-type draft gauge —check to be sure that the gauge o p e r a t e s s m o o t h l y , F i g u r e 2 . B y twirling the hose end or by inhaling across tube, a negative pressure should register and then the instrument should return to zero. If it does not return to zero after a couple of samples, the instru- ment is most likely defective. The Care and Use of Combustion Test Equipment Checking the dry-type draft gauge —check to be sure that the gauge F i g u r e 2 . B y twirling the hose end or by inhaling across tube, a negative pressure should register and then the instrument Figure 1 Figure 2

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