Combustion Testing

Just like computers, the price of electronic combustion test instruments that previously cost thousands of dollars are now available almost for the price of the wet contact kits. The benefits from the investment in electronic instruments can easily justify the investment.

All heating systems are designed and engineered to operate with very specific ranges of:

	Combustion Air
	Make Up Air
	Carbon Monoxide (Carbon Monoxide air free)
	Stack Temperature
	Draft Pressure
	Smoke (fuel oil)
	Fuel Pressure
	External Static Duct Pressure (forced air)
	Temperature Rise across the heat exchanger (air flow)
	Possibly Oxides of Nitrogen and Sulfur Oxides

All heating systems are also "Listed and approved for particular applications" but certainly not tested under the wide variety of possible installations. Obviously, it would be impossible for manufactures to test their appliances under every conceivable set of circumstances.

So... who is responsible for testing each and every installation to verify safe, reliable and efficient operation? As ex-HVAC technicians we feel it is our responsibility as professionals in the industry to test every single piece of equipment during installation and service.

Combustion testing is the only way to know for sure that the system is installed properly and functioning as it was designed, engineered and approved.

Why Test?

Safety--- Obviously, we need to be concerned about the safe operation of the unit with regards to the customer.

"Is it safe for me to be working here?"

Equally as important is the safety of the technician on the job. Certainly most HVAC techs have been in an environment contaminated with carbon monoxide (not to mention all the other 'bionasties' we end up working around). It is important to be aware of the dangers and to understand how a particular manufacturer's CO analyzer calibrates when turned on in ambient air contaminated with CO. Some instruments calibrate to zero irregardless of existing ambient CO levels, some to the actual levels and some allow the user to choose. READ THE OPERATORS MANUAL!!! Refer to the FAQ section for more information on 'manual' vs 'automatic' calibration during the instrument warm up period.

Also keep in mind that carbon monoxide testing with electronic instruments is almost certainly less expensive than the tube type testers. Each tube is a couple of bucks which adds up quickly. They have a shelf life and are limited in the ability to measure in flue gas samples. Electronic analyzers are now available in the $400 range which will measure both ambient and flue gas samples. Properly maintained the sensor will last 4 - 5 years providing more economical and accurate CO testing.

Reliable Operation --- When the flue gases are tested, and test results are within the manufacture's specifications (O₂, CO₂, CO, etc), it verifies the equipment is operating as it was designed and engineered. This will help to reduce call backs and more precisely diagnose intermittent/nuisance burner problems.

Maximize Equipment Useful Service Life --- Likewise, properly set up will help ensure the unit fulfills it's expected service life.

Fume Complaints --- When a customer reports they smell fumes or perhaps even have a CO Detector alarming, you need to have the instrumentation to identify whether CO is also present in the ambient air. Of course, CO is odorless but sometimes may be present when other products of poor combustion are in the air.

Mechanical Defects --- Have you seen this one? "Always give 100% at work: 20% on Monday; 30% on Tuesday; 35% on Wednesday; 10% on Thursday and 5% on Friday." We're joking here, but, even if the manufacturer assembles the unit properly, it then gets loaded into a truck, bounces down the road (and maybe down the basement steps) before it gets installed and set up.

When the fan assist, forced air furnaces first came out, my company had about 1/4 of our brand new installs putting off over 2,000 ppm's of co in the flue gases. Eventually, we figured out that the screws holding the brackets from the gas manifold in place were stripped out which caused the orifices to point uphill. This misalignment caused the CO production.

Adequate Combustion Air --- As we all are aware, this is becoming more and more of an issue. As homes, public facilities and commercial structures become tighter, combustion air requirements are a serious a concern. Should opening a basement or mechanical room door/window to the outside result in changes in combustion/ draft readings? Of course not. While code requirements must be met, having a continuous, digital readout combustion analyzer helps the technician to verify sufficient combustion air intake under actual operating conditions and diagnose the problem.

Sufficient Make Up Air --- Additionally, make up air for exhaust systems, clothes dryers, etc can have serious impact on how the combustion equipment operates. Remember, a building operates as a system and the operation of the structure or changes (remodeling, additions, etc.) can and will impact safe, reliable and efficient heating equipment operation. Having a continuous, digital readout combustion analyzer allows the technician to determine, for example, if the operation of an clothed dryer or other exhaust effects any combustion appliances.

Verify Proper Air Flow --- Bacharach's electronic test instruments that measure draft, can also be used to calculate air flow and test external static pressure and pressure drop across a coil or filter. As heat pumps and air conditioning systems are designed to be more efficient, proper distribution becomes more critical The manufacturer's specifications have to be closely followed.

Cracked Heat Exchangers --- There are a bunch of field tests for cracked heat exchangers we've tried over the years, most of which assume the flue gases are going to leak out of a crack. This may be the case when the unit first fires up, but when the blower comes on, it is more likely that distribution air will be blown into the heat exchanger. The danger of a crack is typically not that flue gases will leak through a crack, its that if sufficient distribution air is blown in, the vent system will not exhaust the larger, cooler volume of flue gases which will then spill out the draft hood or barometric control. Watching the readout on an analyzer when the blower comes on (and a crack is present) may result in the oxygen or carbon monoxide readings changing. This provide more information as to just how dangerous a crack is.

You can shut off the disconnect, but what is the homeowner going to do just as soon as you leave? Particularly if it's cold. Showing that same customer a 'several thousand part per million carbon monoxide reading' when the blower comes on, for example, documents that it is truly dangerous to continue operation of the appliance and that it needs to be replaced immediately. Our experience is that these electronic instruments certainly help make a sale and increase the likelihood of a long term customer.

Proper Venting --- Simply put, a power burner can't push any more air in than is exhausted up the stack in the form of flue gases. Nor can an atmospheric unit (or fan assist, 80% furnace/boiler) pull in more combustion air than is drawn up the chimney as flue gases. A draft test simply measures the pressure in the vent. Combustion testing verifies that sufficient combustion air is being drawn in as designed and at a sufficient rate to allow for the introduction of additional combustion air.

Smooth Light Off --- Long before you have what we jokingly refer to as an 'audible ignition', a rough light off will produce very high levels of CO. While a 'bump' of CO will typically occur on ignition, anything more than 400 ppm's is indicative of a rough light off.

Smooth Shut Down --- Particularly important with fuel oil burners or modulating commercial burners, again more that 400 ppm's of CO on shut down is a sign that the burner is not shutting down properly.

Acceptable Emissions --- The AGA and other sanctioning bodies allow up to 400 ppm's air free carbon monoxide production. Air free CO is based on a mathematical calculation which subtracts excess air from the flue gas sample. To find out more about CO air free, refer to the Carbon Monoxide Zone in the Training Room. Commercial units may also be required to meet NOx and or SO2 emissions requirements as well.

Proper linkage adjustment and travel --- Using a continuous readout analyzer on a commercial unit will accurately track light off, ramp to high fire, high fire operation, ramp back to low fire and shut down.

Burner Alignment --- Stable, high CO readings throughout the cycle of burner operation may be indicative of a burner alignment or flame impingement problem.

Preventive Maintenance --- Developing a history on how a burner lights off, runs and shuts down will allow you to anticipate future performance. A change in the peak CO reading on light off, for example, will alert you that a component may be beginning to fail - long before it actually becomes a no heat call.

Light Off

Run Cycle

Shut Down

Documentation --- Most modern combustion analyzers have printing capabilities providing you with hard copy documentation that when you left the job site, the burner was operating safely and efficiently.

Verifying Fuel Input --- As previously mentioned, all burners are designed and engineered to operate with specific ranges of excess combustion air. For example, gas fired, atmospheric heating systems are generally designed to burn all but 7% to 9% of the 20.9% oxygen in the combustion air supply. If the draft reading is acceptable, it may suggest that the burner is under fired (if over 9%) or over fired (if under 7%). To review a 'generic' list of acceptable oxygen or carbon dioxide readings refer to the Combustion Zone in the Training Room or preferably check with the manufacturer for their specifications.

Reputation --- As you are aware, this is a very competitive business. Properly used, this equipment will help maintain your existing customer base and generate additional sales. As Mark Twain said "Bad news makes it half way around the world before good news gets it's boots on". Satisfied customers pass the word around.

	Sales Obviously, your 'first impression' means a lot when dealing with a potential customer. You walked in with a test instrument which first off is 'digital' (which impresses just about everybody!), and left the customer with a 'computerized' print out with your business card and/or along with your company sticker on the unit. That alone will make the sale in many cases. It demonstrates to the customer that you have the ability to insure safe, reliable and efficient heating system operation. It also provides the homeowner some valuable information with regards to the most cost effective furnace replacement, for example. In other cases, combustion tests may identify the reason replacement is being considered in the first place and help troubleshoot and properly service the system or verify that replacement is indeed necessary. Testing generates more work necessary to insure safe, efficient and reliable operation. Test results shown to the customer help explain the situation and document that the additional expense was a necessary and worthwhile investment.
	Save Energy and $$$$$ --- Constantly rising fuel and installation/repair costs only increase the value of combustion testing to both you and your customer. When combustion reading are within the manufacturers' specifications, it assures two things. First, that the unit is safely and efficiently burning the fuel. Large commercial operations, in particular, can substantially reduce fuel costs. Second, the system is indeed operating as it was designed, engineered, manufactured, listed and approved. This insures reliable operation and a full useful service life for the equipment.
	Increase Profits --- If you have service contracts, proper testing and evaluation of the test results will increase the likelihood of you winning the 'bet' that the unit is going to run trouble free through the season. There are also those occasional 'call backs' which, again, possibly could have been eliminated as a result of testing. You will find more work on each job. For example: while servicing the furnace (or AC system), it doesn't take but a few minutes to combustion test the hot water tank, oven or other appliance. Many electronic combustion test instruments also measure pressure and temperature. In addition to draft and stack temperature, these features allow you to check and document: heat rise, static duct pressure, building pressures and gas pressure. These are only a few examples of the potential applications.
	Keep Fuel Oil and Gas Heat Competitive --- Burner and boiler/furnace design changes have resulted in higher efficiencies but require much more attention to burner set up and operation. Those who test with the old 'shaker bottles' which measured carbon dioxide to evaluate the combustion process need to consider upgrading . That instrument first came out in 1932 and is actually now in the Smithsonian Institute - it was the first industrial use of plastics. While that type instrument is every bit as accurate as the electronic instruments, it only provides a 'snap shot' or glimpse of the flame conditions, for a few seconds, during the entire burner cycle. Continuous readout, electronic analyzers are more like a 'video' and help the tech precisely evaluate exactly what is happening during burner light off, run and shut down. Insuring proper operation throughout the entire burner cycle will help result in a satisfied customers and fewer nuisance call backs and 'soot sucking' days for the tech's.

If you're not testing, you're guessing!!

If you are interested in finding out more, go to the Training Room.

Enter the Training Room