Other Recommendations

For safety reasons, the CO reading is the most important in your final adjustments. To determine the Btu output of furnaces and hot water boilers, temperature, or Delta T (∆T), is a main measurement that determines the amount of Btus delivered.

∆T or air/water temperature in and air/water temperature out are used in the formula for output. ∆T is different depending on equipment efficiency. This applies to gas and oil equipment.

The following are the standard Btu calculation formulas for furnaces, packaged units, duct furnaces, etc., and boilers:

  • CFM X ∆T X 1.08 equals Btus = Output
  • GPM X ∆T X 500 equals Btus = Output.

When dealing with residential and commercial steam boilers, these formulas can’t be used. Also, when dealing
with large commercial or industrial equipment, mostly boilers, ∆T is too difficult to measure or compute.

Again, these protocols arose from decades of testing and measuring HVAC systems. But what about newer equipment that doesn’t have such a long history? Or equipment that is not typical HVAC equipment?

Non-Traditional Equipment: What Changes?

Do the combustion process or heat characteristics change because the equipment is different? By keeping O₂ as low as possible and CO below 100 ppm, you are maximizing equipment performance.

In one case, when the customer was firing pottery kilns, CO levels were well beyond the range of normal CO testers. These kilns create CO levels in the five-digit range, which helps the artists colorize their pottery. Some kilns are small and are fired indoors. Kilns are not our field of experience, but given the harm CO can cause, this would be a good opportunity to sell a low-level CO Monitor.

When it comes to equipment like Mod-Con boilers (modulating condensing boilers that operate with up to a 98% thermal efficiency rating) and tankless water heaters, their normal combustion ranges are necessary to determine their performance.

Unfortunately, not enough field data has been collected so far to have a set of fixed protocols. However, you can make some assumptions based on how similar equipment operates. You can still make some field adjustments when possible. Even with no set protocols, you can find defects in equipment that couldn’t be discovered any other way.

The Mod-Cons tested to date have had O₂ readings as low as 3% and as high as 10% in high-fire situations. Even on modulating equipment, the NCI protocols apply only to high-fire. Knowing the O₂ ranges of other equipment should tell us we want the lowest possible O₂ reading. You can only achieve this 0₂ level by adjusting the gas pressure.

The CO reading shows how far CO can go below 100 ppm, or, in some cases, slightly higher and stable. The flue temperature is also very important.

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