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Is small spike in CO when furnace turns on OK, or needing repair or replacement?

Is small spike in CO when furnace turns on OK, or needing repair or replacement?

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  #1  
Old 02-18-15, 10:27 AM
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Is small spike in CO when furnace turns on OK, or needing repair or replacement?

My city requires a furnace inspection before selling a home. Went with the least expensive ($50) inspection I could find, figuring it would be a rubber-stamped approval with us never having problems or CO alarms. (Perhaps a mistake to go cheap...) I have another furnace tech (a reputable and more expensive company) coming out to inspect, but it's going to be a few days. (Everyone is saying they're booked with people without heat.)

With the top door off, his detector found 73ppm when the furnace FIRST turned on at the FRONT of the burners. Over the next 10 seconds or so it dropped to 16ppm, and he stopped taking readings.

He found no CO in the plenum, even when the furnace was first turning on.

He's recommending that I replace the furnace for $1,400, and didn't pass it for inspection.

He also said he thinks the heat exchanger has a crack in it. He took it out and examined it, not being able to find any, but still saying there must be one causing a problem. (I see a lot of people saying this is a common scam. But the CO ppm is what I'm most concerned about.)


Is it normal for combustion to not be complete when turning on for the first few seconds? Is this a problem? Does the furnace need to be replaced? Am I being scammed?


I realize you can't say for sure, and it's really the second opinion I need. Just looking for whatever guidance you can give. Supposed to close in a few days, and trying to figure out likelihood of having to find a way to pay for a new furnace.
 
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  #2  
Old 02-18-15, 10:33 AM
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If he did not find a hole in the exchanger then the unit is fine.
 
  #3  
Old 02-18-15, 11:00 AM
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A little spillage when a furnace first starts up is normal, but the 73 is a bit higher than I would expect, but it only indicates the need for a tune-up. To be clear, I'm far from a HVAC pro, but as an energy auditor we measure CO in the furnace area and we do it under worst case conditions, which wasn't established for yours.

As Airman said, if he didn't find a hole, what was his reasoning?

Going for a second opinion with a better company was the correct move and be sure to let us know.
And welcome to the forum.

Bud
 
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Old 02-18-15, 11:11 AM
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A lot depends upon the type of furnace. If there is an exhaust blower, I wouldn't expect any CO. On the other hand, if the furnace is natural draft, it is quite normal to have some CO spillage until the exhaust warms & draft is established. By "front" of the burners, do you mean near where the gas goes in? Also, if he removed the panel over the burners, he disrupted the intended air flow pattern.
 
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Old 02-18-15, 03:00 PM
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How about having a smoke test done to determine the condition of the heat exchanger?
Just a thought.
Geo
 
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Old 02-18-15, 07:11 PM
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Geo, are you talking about a smoke bomb test? Unless the defect is pretty large, I don't think you'd be able to see the smoke.
 
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Old 02-19-15, 07:28 PM
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Thanks guys.

Yeah, by "front" of the burners, I meant with the top panel off, like an inch closer to you than the flame was. So, almost right at the point of combustion. He was saying all the CO should be sucked out the back and nothing should be there... Even though no CO was outside the unit itself or in the rest of the house.

Complete BS it looks like. And, it is a natural draft, and he was testing it at first startup.

Had one of the largest heating companies come in, and said the measurement for the city is in whatever the output vent is called, which came up as absolute zero for CO level. The guy spent a really long time examining the heat exchanger for cracks or any signs of issues, even taking the back off so he could get a great look at it, and concluded the first guy was trying to sell another furnace.
 
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Old 02-20-15, 02:25 AM
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Glad it came out good as it should have the first time. The first guy needs some negative feedback somewhere.

Bud
 
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Old 02-20-15, 06:33 AM
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Phil, It sounds like you, like many people, encountered a saleman in technician's clothing. This is something which happens way too often & really hurts the reputation of true technicians. Please let me apologize on behalf of all the good & honest techs out there.
 
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Old 02-20-15, 01:57 PM
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Bud9051 - Oh, there very well may be some negative feedback for him. My only worry is he could go to the city and make a stink that he failed it, and someone else passed it. If it was a legitimate fail, I wouldn't dare shop around hoping to get someone else to pass it. But, I'm torn between demanding my money back from him and this worry.

Grandy - Thanks, I appreciate that. That really sucked thinking we might have to find a way to pay for a new furnace as we were leaving...

I never did mention in this thread that a few hours after he left, and a few hours after I started this post, we realized the furnace wasn't working anymore. The electric igniter glowed really bright, but no flame started. I knew it must be something simple, but the external (to the furnace) gas valve was on, and I didn't see any disconnected wires inside. The bigger company I had come out was out within a few hours, and found a small inside toggle switch we hadn't noticed was even in there, and it was set to off. Not sure if the first guy didn't know what he was doing and made a mistake, or if he disabled it on purpose to try to get a sale. Not sure if anyone would fall for a furnace "failing" after a routine visit, and buying a new one from the guy who just happened to be there...

In the end, I think he was effectively performing a combustion analysis, and pointing to that at the point of combustion, there wasn't 100% efficiency, as I think there never would be.
 
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Old 02-20-15, 02:14 PM
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Just FYI: When combustion efficiency is being measured, those measurements are made in the exhaust.
 
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