Combustion Diagnostics Made Easier

Combustion Diagnostics Made Easier

Combustion analyzer used in a boiler application.–Photo courtesy TSI

Combustion analyzer: one tool, many functions. –Photo courtesy TSI


Contractors who have incorporated combustion diagnostics into their service offerings are aware of the degree to which technology has improved their ability to uncover mechanical deficiencies in fuel burning appliances.

A short list of the tools needed to uncover potential safety, mechanical, and efficiency problems includes:

  • Personal safety protector meter
  • Carbon monoxide exposure meter
  • Venting verifying meter: CO & O2
  • Combustion air certifying meter
  • Firing rate figuring meter
  • Pilot sizing and positioning checking meter
  • Spark, hot surface, or electrode positioning checking meter
  • Burner orifice opening meter
  • Burner alignment assessment meter
  • Manifold alignment measuring meter.

Fortunately, all of the above metering devices — and many more — can be found in one tool: a quality combustion analyzer. Combustion analyzers measure oxygen, carbon monoxide, and flue temperature. However, if you read the operation manual of most equipment, the O2, CO and flue temperature ranges are not given, merely a recommended gas pressure or nozzle size.

To make use of the tools above requires diagnostic sheets and procedures that help address these issues. Table 1 shows a sample diagnostic sheet for a conventional atmospheric furnace with a drafthood.

The diagnostic sheet gives the operating parameters at which this equipment should operate, and then plots them on a graph, which can isolate the problem to the actual cause.

In most cases, it's just as important to eliminate what is not causing the problem in order to pinpoint what needs to be done.

Once again, diagnosing each situation properly can provide a considerable increase in income and profit, reduce call-backs and result in increased customer satisfaction.

It takes a lot less time to diagnose a problem than it does to guess at it.

Once you have discovered any of the problems listed above, another assortment of tools is required to repair, and verify that the repairs you have made are performing properly.

System repair / verification tools include:

  • Fan/forced combustion air setting meter
  • Barometric venting setting meter
  • Plastic vent pipe restrictor sizing meter
  • Plastic vent pipe resizing meter
  • Pilot repositioning & resizing meter
  • Ignitor/hot surface/electrode repositioning meter
  • Burner repositioning meter
  • Manifold repositioning meter
  • Oil nozzle selecting meter.

Once again, all of these tools — and more—are contained in a single, quality combustion analyzer.

After making a correct diagnosis repairs will of course require additional materials, and some additional mechanical issues may need to be addressed, to provide more safety, efficiency, comfort, and reduced wear and tear on equipment.

Additional materials needed to complete certain repairs include:

  • Combustion air register
  • Fan/force combustion air system
  • Barometric flue dampers
  • Spill switches
  • Post-purge circuits
  • Plenum air reset controls
  • Duct modifications
  • Star kaps — flue termination
  • Make-up air systems
  • Purification system
  • Clearwave scale removal system
  • Low-level CO monitor.

These components and controls represent additional income and profit on every installation and service call. Every one of these products provides a substantial benefits to the customer, and will save them money, and, in some cases, save lives.

Qualified, competent, and credible contractors will reap the financial benefits of the true performance testing and diagnostics that a quality combustion analyzer delivers.

Jim Davis is a senior instructor at the National Comfort Institute (Sheffield Lake, OH) specializing in carbon monoxide and combustion. He can be reached at 800/633-7058, or through the NCI website, www.national comfortinstitute.com.

Vince DiFilippo is president of DiFilippo's Service Heating & Air Conditioning, Paoli, PA. He can be reached by phone: 610/240-4788.

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