In classes during last year’s training season, we were surprised to learn that many smaller companies have gone back to the use of the standard combustion test kit or ‘wet-kit’, Figure 1. Reasons given were the initial cost and maintenance of electronic analyzers and the simplicity of the wet-kit components.
We updated the material in this article to reflect current industry conditions and the fact that these kits were discontinued by MSA/Bacharach in March of 2023. However, a quick search of eBay and other resale sites found dozens of used kits and components for sale. Repair parts were also available as we’ll note at the end of the article.
We’ll go through the article as I originally wrote back in 1979 as a Technical Bulletin for members of the Massachusetts Better Home Heat Council during the ‘Retrofit Program’ and then at the end we’ll review the suggestions for replacements for discontinued components. I’m not recommending going back to these kits, just offering my help to those who have or never stopped. It’s also my opinion that any testing of combustion is better than no testing at all and that’s the truth, a fact!
This material was originally published in 1979, as previously noted, and again in Fueloil & Oil Heat, September 1991 and also published as excerpts in our texts, ‘COMBUSTION & Oil Burning Equipment’ in 1995 and ‘Advanced Residential Oilburners in 2007 and several times here in Fuel Oil News.
The ability for some to diagnose and repair oilburners seems sometimes out of 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’ burners by the ‘let’s eyeball it’ method. Also, due to the use of heavier concentrations of biofuels the ability to use the cad-cell and primary control is also going away due to the darker characteristics of bio-based flames.
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.
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 about 1911 the oilburner service industry has had testing equipment available to us to analyze burner performance. The smoke tester was introduced in 1948.
In the 1970’s and 1980’s 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 others or abandoned it for electronic types, we will concentrate on reviewing the basics of instrument use and instrument quality.
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 servicemen 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 more efficient units. Location of these holes is very important. It was previously recommended that they should both be located one to two smoke pipe diameters from the breech, excluding all elbows, but always between the breech and draft regulator. Today, most OEMs recommend at the breech.
By inserting the stack thermometer, Figure 2, 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 for overfire draft readings, Figure 3.
Instruments
Before performing any tests, the instruments must be checked to ensure good test readings:
Check the dry-type draft gauge, Figure 4, check to be sure the gauge operates smoothly.
By exhaling slightly into the instrument, a positive pressure should register and then the instrument should return to zero. By twirling 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 instrument is most likely defective.
Checking the wet-type draft gauge, Figure 5, check to be sure that gauge is level and zeroed.
Check out the same as the dry-type gauge. However, if this instrument does not return to zero after a couple of samples, thoroughly clean the instrument and recharge with clean gauge oil.
It has also been found that when draft gauges respond slowly or are sluggish, the following components should be checked:
• leads and probes may be plugged or leaking.
• pointer may be touching scale.
• shut-off rings on wet-type are leaking air.
Checking the smoke tester, Figure 6, insert clean test paper into instrument.
Block off end of sampling tube. Pull plunger handle about 1 inch and release. Handle should return to about the original position. If no resistance is met or if instrument does not return to original position, the instrument should be checked for leakage. An atmospheric test should be made of the instrument.
If, after ten full strokes, a smoke reading is observed which can be measured on the chart, another test with a clean test paper should be performed.
If after this, the instrument still measures smoke, the instrument should be disassembled and cleaned. Be sure to lubricate the plunger-type cylinder with the proper material after servicing.
NOTE: White petroleum jelly, aka Vaseline® is acceptable.
Checking the CO2 analyzer, Figure 7, testing of this instrument should be done after about 200 samples have been taken, following long storage periods, or after coming from extreme temperatures, such as hot or cold service vans.
If the CO2, scale is down, two or three drops of water or fresh fluid added to the instrument should bring up the scale fluid to the zero point. If water has been added more than a few times, a test should be performed to establish fluid strength. If the fluid, potassium hydroxide, has gone bad it should be replaced, Figure 8.
There are two ways to obtain CO2 to establish fluid strength and only one way to confirm this strength:
After taking a sample in the usual way, which requires 18 full depressions of the aspirator bulb, the instrument is inverted twice, and the test result is recorded. Then the instrument is inverted or tipped twice more. If the CO2, percent reading rises more than 1/2%, the fluid is becoming weak and should be replaced. In my opinion the instrument should be refurbished with new seals and fluid at least every three years, Figure 9.
NOTE: For a more accurate reading make 18 full depressions of the bulb and one more but don’t allow the bulb to recompress while you remove the hose from the instrument.
The second method is as follows and is called the exhaled breath test. This should only be done when no equipment sample is available. Disconnect tubing so that connector and short piece of hose, less check valve, can be attached to instrument. Take deep breath, hold for 3 or 4 seconds, depress inlet valve and exhale into instrument. Release inlet plunger at same time while exhaling. Perform double inversion test as in example #l.
Do not perform two tests on exhaled breath for establishing CO2 content. It is an increase in percent CO2, on the one-and-the-same sample which indicates weak fluid.
The sampling hose and pump should also be checked.
The filter yarn, Figure 9, in the sampling hose should be replaced whenever noticeable discoloration takes place. This will also provide easier pump operation.
The entire hose assembly, Figure 10, should be checked periodically.
The easiest way is as follows: With finger placed over inlet side or filter side, depress pump. Pump should remain depressed until vacuum is released. With finger over outlet or instrument side, apply moderate pressure to the bulb. If it cannot be depressed, the bulb and hose are all right.
For greatest accuracy when using CO2 indicators, allow them to reach room temperature. If they are cold, experience has shown that readings will be slightly high. Also, when servicing C02 indicators be cautious with the red absorbent solution. It is potassium hydroxide, which is a poison and acidic and can cause severe burns. Always avoid contact with skin, eyes and clothing.
Checking the stack thermometer: The thermometer should be checked for obvious damage and/or a bent stem. If the instrument appears in good condition, the following tests can be performed to check accuracy:
Boiling water test; insert thermometer in boiling water. If instrument reads 210-215°F, instrument is okay.
Thermotest; check thermometer against a thermocouple or good mercury thermometer.
Another good test is comparing temperature in a warm air furnace plenum against either of these two instruments.
If, when using a Bacharach thermometer, it is found that the instrument has wandered, it can be recalibrated by securing the hex-shaped nut on the back of the Tempoint® and by rotating the black dial to correspond to the correct temperature setting.
When using any of these instruments, care should be taken to handle them properly. Analyzers should be vented of all samples and be in an upright position when stored. Also, instruments should be at room temperature when in use. Under adverse conditions, disregard first CO2 test as a warm-up/cool-down procedure.
Proper use especially hinges on the proper insertion depth of sampling tubes.
The tubes should end at roughly the center of the pipe to trap the hottest and most highly concentrated flue gas samples. The thermometer’s bimetal is at the end of the probe and in the case of electronic instruments, the thermocouple is also at the end of the sending tube. One manufacturer’s use of spring clips is especially conducive to obtaining the desired insertion depth, Figure 11 (Dwyer #A357).
When using most thermometers, most of the units found in the manufacturer’s kits have stem lengths of 5 inches. This allows for accurate temperature readings for up to and including a 10-inch diameter fluepipe. When taking temperature readings on a larger pipe, a longer stem on the instrument is preferred. Bacharach makes a thermometer with an 11-inch stem, and this longer stem will properly accommodate up to a 22-inch fluepipe.
Temperature of flue gas has always been, and still is, one of the single most important tests we perform on heating plants. From knowing that a 1% CO2 change will affect temperature 25°F, we can make burner adjustments with accurate thermometers very easily. So, it is very important that we use and maintain the equipment to the best of our ability.
Finally, in this discussion about the basic use of instruments, the calculators or slide rule charts and tables should be touched upon. Some tables are temperature compensated at 50°F, but others require the subtraction of ambient temperature, i.e. the average temperature of the basement or boiler room. Subtraction of 100°F should only be used when measured ambient temperature is 80°F or better. If your test is questioned, it is probably better in these days of consumer awareness and energy auditing to be lower than higher.
A good way to confirm basement temperature is to simply carry one in your kit a regular wall thermometer or a pocket thermometer will do.
Okay, that’s the meat and potatoes of this subject now let’s look at the changes you’ll probably have to make.
The Bacharach Tempoint, Figure 2, is just a regular thermometer measuring 200-1000°F. You can replace it with any thermometer that has an equal or greater range for a lot less money, Figure 12.
The Bacharach MZF, Figure 4, has been discontinued. There are so many options available today, from electronic manometers to all kinds of wet and dry instruments, but in my opinion the Dwyer Magnehelic, Figure 13, is the best way to go. My first one lasted me 53 years, can’t beat that and for under $200.00.
The Dwyer wet-type shown in Figure 5 is still available and for under $60.00. Only disadvantage to this is the gauge oil and if you forget to close the valves it can make a mess, believe me on this I’ve done it.
The Bacharach smoke tester, Figure 6, is still around because if you test with an electronic analyzer, you still need one. But, before you replace it shop around, there’s lots of replacements and some are a lot less money, Figure 14.
Well, that’s it and again I am not recommending going back to these kits, just offering my help to those who do and also giving some other options to all those who test. Keep in mind the single most important selling point of electronic analyzers is the speed that they can deliver the numbers, but the wet-kit is just as accurate. If you do use an electronic analyzer, Figure 15, you still need a draft gauge and a smoke tester, so there ya go, options.
See ya! lFON
George Lanthier is the owner of Firedragon Academy (www.FiredragonEnt.com), a 35-year-old Massachusetts Certified School teaching gas, oil and other heating subjects. The Academy has its training facility in Webster, Massachusetts. Lanthier is the author of more than 60 books and manuals on HVAC subjects, published by Firedragon. Lanthier is a CETP, ESCO, NATE, NORA, PMAA and PMEF Proctor and has been a Massachusetts Certified Instructor since 1975.