Ran a call the other day identical to this thread. Odor was strong with CO levels around 15ppm. Heat exchanger was ok and draft motor rotating the right way. No economizer package to allow extra infiltration. Long story short gas valve inlet 7.9 outlet 6.0. Natural gas. Replace valve all good. The previous response to my question sunk in much more after this call

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Your welcome. I hope you find it useful. That app prevented me from being 2 hours away with the wrong parts.

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So, your inducer was spinning backwards?

 

Me too! I was thinking about that myself!

 

Glad you found and resolved the issue. I still want to know how the CO levels rose in the building

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Package units are not perfectly sealed, if theres a 10000 PPM cloud of CO surrounding the unit, some of its going to get sucked in through the seams, such as the filter door.

 

That was the problem!!! The inducer draft motor was wired wrong. I had the brown where the purple should be! Changed these two wires and it fixed it!

 

I would go back over that HX install again with a fine tooth comb.

I know the burners have a particular way they lay on each other that might be another thing to check, along with alignment in the opening.

Gravity might have already sent it too you, but I'll email you a pdf of how they go together.

 

thank you for your info. I will do some more research. I will tell you this, if I stick my fluke CO monitor at the flue exhaust it will peg out at a thousand ppm. It will burn your eyes.

 

you always have good info.

thanks

 

If you think the CO is coming from this unit, it really needs to have a combustion analysis done, because it is producing way too much CO.


Here is an explanation by Jim Davis about how much CO the unit has to produce, to get any CO inside the structure.


A 100,000 btu furnace uses 25 cfm of air for complete combustion. Furnace blower in heating move 1300 cfm on draft induced and 1500 cfm on condensing.

If you mixed 100% of the flue gasses with 1500 cfm how much CO would you have to be making to get a reading of 10ppm?

25cfm is .016% of the mixture, therefore the furnace would have to be making over 600ppm which exceeds the 400ppm "air free" they are allowed.

The furnace would have to be red-tagged without a hole or crack.

That is dumping 100% of the flue gasses into the airstream. A crack may under certain conditions may leak say 2% of the 25 cfm or say .5 cfm. .5 cfm is .003% of 1500ppm.

So to read 10ppm of CO in the airstream, the furnace would have to be making over 3000ppm of CO.

Even without the blower running the volume of air in the plenum versus the volume of air from a leak would be still be quite diluted.


Bottom line: To get measureable CO in a space an appliance,or vehicle, has to be making seriously high levels of CO, or it has to have been made over long periods of run time.

 

how would the furnace flue gases get into the home?

you are allowed by ANSI standards to have 400ppm CO airfree or "CO(0)" in the exhaust. I was trained CO under 100ppm undiluted, which I've been able to achieve on every appliance.

so if your under 100ppm CO in the flue then your good. Now you need to figure out how its getting into the home.

opened windows? blower door has a gap? heat exchanger not sealed around air gaps? have car started in garage? they cleaned the electric over and didn't ventilate the home?

 

there CO was going off audibly at 125ppm and and mine would get up there around 60 and 70 then I would stop monitoring at that point. Nothing else is running to produce the gas.

 

Yes, that got burned off already.

 

so we've gone to all this about the furnace, have we tested to see if the furnace is actually producing over 100ppm CO?

Maybe he got CO from car running in the garage?

 

What about the oil burning off the outside of the HX? That's my guess anyway.

 

orifice is 38 (.101)

 

i sent you 2 pdfs. one shows the correct way to mount the burners. maybe they got flipped. the other one shows the flue baffle.

i'm thinking flame impingement of misaligned burners or gas needs to go up or down.

you said originally the nipples arent even. the slightest offset could mess everything up. i would make sure 100% the burners are lined up perfect.

also might need the flue baffle with such a small heat exchanger

 

Thank you and congrats on your up and coming. My wife and I waited until he came out. What an awesome experience to have!

 

I tried getting the size today @ Carrier so I could match it up with what was on there but the counter guy couldn't find it so I just left it alone for the time.

 

Yes sir! Well, for a clog yes, for the right size orfice-no.

 

have you checked the orifices?

 

congratulations! I have my second one on the way in May. don't know the sex yet.

 

your parts numbers are right and the ones i gave are correct.

the new heat exchanger comes with the NOx baffle. so dont worry about that.

i would try the flue baffle. ill send you a pdf

 

sorry about the slow responses, I just had my first child two weeks ago and I have been trying to spend some time with him!! It is natural gas. That is a good idea on the draft motor. I will check that!

 

i noticed that both part #'s have a 500 in it but the part #'s i have for two of the parts have 400 in them. Such as the inducer fan assembly is a 48gs400649 and the flue box collar is a 48gs400108. I do not know if this means anything?