Replace heat exchanger or buy new furnace?

gj555 · Feb 9, 2016

I have a 2004 Bryant furnace (345 MAV), so its approx 12 years old. The furnace has the secondary heat exchanger problem that was subject to the class action law suit. My HVAC technician recently tested flue gases and came up with a reading of 237 ppm of CO AF. That seems pretty bad (though my neighbour's furnace tested out at 1200 CO AF – he is replacing his furnace as I type this). My HVAC technician has given me two options.

1) Purchase a new Carrier 2 stage furnace. Manufacturer’s rebate for replacing the defective unit plus a government rebate available in my area will help with the costs a bit.

2) Replace the secondary heat exchanger under the extended warranty offered by Carrier/Bryant. My technician says the manufacturer does not cover his full fee for this job so it will still cost me around 8% to 10% of the cost of the new furnace (based on my rough calculations).

While I would prefer not to spend on a new furnace now, the furnace is coming up on 12 years old and I am concerned about the reliability of the other parts (such as the inducer motor). Technician is of course pushing the new furnace option believing that I will have other problems with my furnace that will need repair in the upcoming years. I don't know if it impacts reliability but I do keep the furnace set to circulate air even when the heat or AC is not on.

Based on the above, anyone have any thoughts on having the exchanger replaced vs buying the new furnace?

BasnettSales · Feb 9, 2016

If money is not a major factor then replace the furnace, it will be under full warranty and hopefully sized and installed properly. Unfortunately most of these surprise expenses come at the worst time and money is the driving force behind the decision. If the furnace has been maintained regularly and is in good shape then I see no reason not to just replace the heat exchanger and ride out the furnace until you can afford a new more efficient model. We never push new furnaces, just quote both options and let the homeowner know the pros and cons of each option. Its ultimately your decision and not the technicians. Just my opinion.

gj555 · Feb 9, 2016

Thanks. Affording and not wanting to spend / being frugal are two different things. I can afford it, I just don’t want to spend and am having a hard decision with this.

Any idea what the average lifespan is for a furnace like this?

BasnettSales · Feb 9, 2016

That's a loaded question, sized, installed, and commissioned properly most are good for 18-20 years or more. Oversized, slapped in, and not set up correctly, we have pulled out furnaces only a few years old. We just replaced a Trane heat exchanger that was 7 years old, furnace was a 120k 2 stage furnace, way oversized. Explained the reasons it failed but homeowner couldn't afford new correctly sized furnace, got hx under warranty and charged for replacement. Locked furnace to run only on first stage and set for proper airflow. Not the best solution, but fit the homeowners needs and we will certainly be doing more work for this customer in the future.

gj555 · Feb 9, 2016

Really appreciate your input. I live in a subdivision where builder built cookie cutter houses and furnace was installed quickly by the builder. While the furnace is sized properly, it was installed with single pipe venting only.

BasnettSales · Feb 9, 2016

The 1 pipe install isnt the worse thing in the world, if the ductwork is ok and the furnace is sized correctly, change the heat exchanger and have him run the 2nd pipe and hope for the best. That's what I would do.

vstech · Feb 9, 2016

have him evaluate the ductwork, and perform a load calculation on the house to see if it's sized correctly.

if you decide to repair, you want the repair to last as long as possible.

if you decide to replace, be SURE a load calculation is performed, and have all the ductwork inspected to be certain it meets leakage specs! leaking ductwork is a huge waste of energy!

martyinlincoln · Feb 9, 2016

I'd replace the heat exchanger.

ziggyhere · Feb 9, 2016

fully agree with vstech

Replace heat exchanger or buy new furnace?

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