Cracked heat exchanger


Heat exchanger can crack for various reasons and should be checked every time furnace is repaired or maintained.

Visually check heat exchanger for cracks

  • You will find most cracks form near the back and where the heat exchanger metal bends, Since this is where it will be weakest due manufacturer weakening the metal by bending it.
    Watch the flames as the furnace fan starts if you see the flames are blowing around or out the front of the burners then you will need to take a closer look at the heat exchanger

Water test

  • This test worked best on the old Lennox G8 and would find cracks or pinholes on the heat exchanger that sometime could not be seen.
    If there is no air conditioning then it will be easy to access above the heat exchanger through the humidifier. Once the heat exchanger cools down spray water on the heat exchanger from the top insuring full coverage and being careful of the electronics and motors. Then watch inside the burners for water to seep through, A good heat exchanger will not let moisture into burner chamber

Using carbon monoxide detector

  • Test for carbon monoxide at return air as well at supply air and compare the two readings or test at supply air with burners on then off making sure furnace is not back drafting and compare.
    If you take reading once and only at supply air you will not be 100 percent sure the problem is with the heat exchanger. You are testing the accumulation of carbon monoxide over a long period of time from other sources like the furnace or hot water tank back drafting also it could be from outside sources like a vehicles near the intake air.

Reasons for cracks

  • If the furnace does not have enough combustion air it will cause the furnace to run hotter then designed. Then with more expansion and contraction in the heat exchanger it causes cracks. The gas pressure must be set as per furnace name plate derated for location altitude if too much gas heat exchanger will run too hot.Blower speeds must be checked by comparing furnace temperature difference to name plate rating if running too hot increase fan speed and recheck temperature supply air minus return air.

.

Any crack in a heat exchanger is dangerous and the heat exchanger must be replaced when crack is found

20121216-143414.jpg

20121222-081333.jpg

20121222-081430.jpg

20121222-081501.jpg

Click here to see my Post on protecting your home “Alarm for Home”

Thank you for visiting my blog I would appreciate any feedback I can get, Please leave a comment on whether my information has helped you. I am always interested in more topic to write so feel free to leave a comment asking about anything related to HVAC-R (Heating, Ventilation, air conditioning, refrigeration).

Thanks for reading my blog

Tagged: , ,

2 thoughts on “Cracked heat exchanger

  1. […] next step after thermostat cracked heat exchanger […]

  2. child home safety checklist cdc 12/19/2013 at 6:31 pm Reply

    Excellent article! We will be linking to this great post on our site.
    Keep up the great writing.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: