Heating contractor brought to inspection

Be glad to explain it to you seeing as you don’t know.

To test for cracks using a combustion analyzer, simply watch the O2/CO2 readings and the CO reading when the blower comes on - usually several minutes after the burner(s) ignite.

Typically, the O2/CO2 or CO readings will stabilize within 30 to 60 seconds after ignition. If a crack is present, when the blower energizes, air (at 20.9% O2) may be blown through the crack in sufficient quantities to raise the O2 (or decrease the CO2) reading on the combustion analyzer.

Aren’t you glad you asked?

Thank you everyone for your comments. The home owner and buyer reached a deal on a new furnace. The old furnace was inspected after it was removed and the cracks were very small and mostly rust. They were discovered by using a camera inside the furnace. Direct Energy was the first inspector. By the way I had it wrong about the owners bringing the heating contractor, it was actually the inspector who brought him along after the buyers indicated they were concerned over the age of the furnace which was about 28 years.

Good call.! It’s nice to see an inspector who knows their limitations and fulfills their clients expectations!

Unlike some who use combustion analyzers to guess at cracks, VISUAL is the only way to go. As with any test device, the results must be verified before reporting the defect. Cameras and fiber optic bore scopes allow you to see the crack. Still however, these devices only see about 45% of the exchanger from the interior. If the equipment is dismantled, you can get at about 95% without removing the cells.

Did a condo inspection with attached garage last week. Found 2 PPM CO in the furnace room. Reset the meter to 0 and activated the furnace. Meter stayed at 0 PPM. Activated the Water heater while the furnace was running and checked for back drafting of the Water Heater vent. Again reading stayed at 0 PPM. So what to report.
The condo was vacant. Where was the CO coming from?
Possible sources;

  1. The attached garage.
  2. The neighbour’s attached garage.
    Reported that CMHC accepts 2 PPM as normal, Info that came with my meter says 9 PPM is acceptable and Local gas supplier says 35 PPM is acceptable and has testified to that in court.
    As far as I’m concerned anything above 0 PPM is too high and always remove vehicle from garage as soon as you start it and close the door when the vehicle is outside.

Did you calibrate the CO meter with “zero” gas or at least in an outdoor area away from traffic to establish a zero point?

2 PPM is very small but without knowing the true zero point of your instrument it may be meaningless.

Thanks Marcel.

Hey David in answer to your question about Combustion Analyzer here is the info you didn’t seem to know about.

To test for cracks using a combustion analyzer, simply watch the O2/CO2 readings and the CO reading when the blower comes on - usually several minutes after the burner(s) ignite.

Typically, the O2/CO2 or CO readings will stabilize within 30 to 60 seconds after ignition. If a crack is present, when the blower energizes, air (at 20.9% O2) may be blown through the crack in sufficient quantities to raise the O2 (or decrease the CO2) reading on the combustion analyzer.