Should I replace OLD but working furnace?


Old 06-25-19, 04:53 PM
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Exclamation Should I replace OLD but working furnace?

hi DIY community, we have a older house with a Lennox Med efficient furnace made in 1993.. (26 yrs old)
we recently had a visit from a heating and plumbing person came just to inspect the furnace.

it is working fine now and there is no gas leak. But he put a carbon monoxide monitor right beside the flame, after 10-15 minutes told me there is 7 PPM carbon monoxide right beside the flame. No carbon monoxide (0 ppm) at the air outlets. he also said the inducer motor gets noisy and operating at maximum Amperage.

He said i should replace the furnace ASAP.

Should i be replacing this this year? or wait abit like next year or so.

thank you all

Old 06-25-19, 05:04 PM
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If your that close to replacing I'd be taking the time right now when it's not needed to search out and get the best off season deal I could, you dont want it dying on you in the middle of winter!
Old 06-25-19, 06:00 PM
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While twenty-six is getting up there for a forced warm-air furnace it is entirely possible that the mere act of inserting the sampling tube for the CO detector next to the burner caused it to make the CO. The proper place to measure for CO is at the draft hood or stack outlet.

Same as with your boiler, I think this is a fast-buck operator looking for your money.

Did you call this person or did they come knocking door-to-door?
Old 06-25-19, 06:24 PM
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Post the results of the combustion test.
Old 06-26-19, 11:23 AM
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Also check the inducer motor for oil ports. It may only need a few drops of oil.
Old 06-26-19, 08:53 PM
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Its normal to have trace amount of co in the exhaust.

Its the exhaust that needs to be checked.

The heat exchanger should be inspected from the bottom - if you don't have an evap coil on top, can also cut a hole into the plenum and check from there.

High co does not necessarily mean the furnace needs to be replaced - dirty burners, gas pressure set incorrectly can do it.

You don't need to replace a furnace just because it's old - replace it if it needs an expensive repair, to save gas and or get a more appropriate size.
Old 06-29-19, 06:18 PM
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What you encountered was a salesperson acting as a service tech. Furd nailed it.
Old 06-30-19, 08:39 AM
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For what it's worth, the last time I had my 20+ year old furnace serviced, the tech measured 10 ppm CO in the stack, and 0 CO next to the furnace. He said, "All done, looks good."

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