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  1. #1
    Join Date
    Oct 2005
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    27
    So, what's the best way to test a Heat Exchanger? I hear you can do a combustion C02 test, fill it up with water and see if it leaks on the edges around the chamber or smoke bomb it. What's the correct way?

    Thanks...



  2. #2
    Join Date
    Apr 2004
    Location
    Bartlett, IL
    Posts
    6,619
    Simple way is by using a saltwater solution, spray it in the chamber, and take a blue flame torch to the registers and see if the flame changes colors...cheap'n'easy way but foolproof.

  3. #3
    Originally posted by 2hot2coolme
    Simple way is by using a saltwater solution, spray it in the chamber, and take a blue flame torch to the registers and see if the flame changes colors...cheap'n'easy way but foolproof.
    I am always looking to expand my knowledge on testing heat exchangers. This sounds like a good method. I would worry about doing damage to the heat exchanger though. Salt water?

  4. #4
    Join Date
    Mar 2005
    Location
    South/West of Quebec in the other part of Canada
    Posts
    2,331
    2hot2

    can you explain a bit more on this technique,do you run fan, why does flame change, what color will flame be?
    thanx

  5. #5
    Join Date
    Oct 2005
    Posts
    69
    Test methods are like opinions, everybody has their own best method. In the city where I live the gas company uses a co detector that is calibrated every 30 days. I personally use the light method even though I own a CO meter. Mine was over $400.00. In my opinion the water method even though reliable is very time consuming. Do you have that kind of time on a Job? I have seen on post where they sprayed soapy water into the heat exchanger and turned on the fan and looked for bubbles. Keep in mind once the inside fan comes on the plenum becomes positive pressure so I'm a little confused on the salt water method.If you have a definite large crack it is usually easily visible with light thru it and every other method Is open to opinion. What if you say it cracked and they call another service company and they it isn't. No homeowner likes bad news. So I'm very cautious when I condemn somthing. I was only questioned once and the customer told me that he had been told the same thing several years ago and his buddy who is more than qualified to do this kind of work told him the serviceman was just trying to sell him a furnace. And I was full of -hit. His heat exchanger was fine. I signed off on my paperwork that I got visible light thru the crack and the furnace was considered unsafe for use. He is still using it and he isn't dead yet. It's not my house, I can only advise.

  6. #6
    cobraon is offline Professional Member-BM-bad email, server rejected
    Join Date
    Jun 2005
    Location
    Victoria, Texas
    Posts
    59
    When checking a gas furnace for CO2, I usually disconnect the blower motor and then cycle the burners until the high limit trips. By doing this, I know the heat exchanger is hot and the metal has expanded, plus this verifies the high limit is working. I then reconnect the blower and cycle the furnace again. I check at the closest supply register with a Fluke 210. If I get a positive reading I then get out my trusty halide torch and salt water bottle. If the heat exchanger is cracked and the salt water mixture enters the supply airstream through the heat exchanger, the halide flame will turn orange. So far,after 25+ yrs of testing this way(halide torch/salt water), every furnace I "red tagged" and changed out, did in fact have cracks/holes upon visual inspection.

  7. #7
    Join Date
    Nov 2004
    Posts
    2,927
    Originally posted by heatmehot
    So, what's the best way to test a Heat Exchanger? I hear you can do a combustion C02 test, fill it up with water and see if it leaks on the edges around the chamber or smoke bomb it. What's the correct way?

    Thanks...
    We use canaries...but the SPCA frowns on that practice.

    With a combustion analizer you can be certain of the problem or potential problems,and what to do to fix it.

  8. #8
    Join Date
    Apr 2002
    Posts
    11,808

    Everythiing You wanted to Know About

    Checking HXs but were afraid to ask.

    Mech Acc did an excellent post on this, it is in the FYI forum, one of the best posts in there.

    http://hvac-talk.com/vbb/showthread.php?threadid=73546
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  9. #9
    Join Date
    Nov 2002
    Location
    VA
    Posts
    296

    It’s All About Conviction To Professionalism

    (Personal Opinion verses Professional Judgment) First and foremost, heat exchanger inspection is one of the most important professional duties a HVAC Technician is required to perform (my personal opinion). All furnaces fail, (typically the Heat Exchanger is the show stopper) it’s just a matter of time, that is a given. No homeowner wants to hear the bad news that is common sense. CO isn’t to be taken lightly http://www.epa.gov/iaq/pubs/coftsht.html

    Don’t rely on here-say, the furnace vendor’s documentation needs to be carefully reviewed and more importantly understood. Premature failure is often due to inappropriate installation & setup and incorrectly sized (or installed) air distribution systems. Many other misunderstood parameters not adequately addressed will doom even the most robust equipment.

    That said, I personally had the opportunity to attend a hands-on seminar given by Ellis Prach of Heat Exchanger Experts. The ACCA-National Capital Chapter in Savage, MD sponsored this event. Rather than promoting ACCA, I would personally suggest you see if Mr. Prach is scheduled to be in your area, if so please consider trying to attend.

    http://www.heatexchangerexperts.com/

    As for testing protocols, they vary greatly according to the exact type of heat exchanger (A.K.A. primary or secondary in high efficiency units). Each protocol has its place; it is your responsibility as a professional to know exactly how best to procedure under any given set of conditions.

    This subject is the source of some heated Forum debate (which is in itself good) however owing to the delicate détente issues I (personal opinion) strongly suggest you invest a healthy amount of academic research into this subject lest you become involved it the “Heat Exchanger Scam” marketing techniques which have proven, for some in our industry, an effective revenue generator, albeit grossly unethical. Enough said.

    My colleagues in other walks of life have consistently questioned me on this particular aspect of the industry, and for good cause. Please help your service area community and become highly skilled in this one facet of our very diverse industry. Residential HVAC needs knowledgeable; proficient and ethical champions, please join in and meet this challenge.

    God Bless.

  10. #10
    Join Date
    Nov 2002
    Location
    VA
    Posts
    296

    Please review Carnak's URL

    Thank you Carnak
    and Don
    and Gary Reecher

    Good Job!

  11. #11
    Join Date
    Apr 2002
    Posts
    11,808
    The credit is all due to Mech Acc aka Gary
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  12. #12
    Join Date
    Oct 2005
    Posts
    27
    Thank you all....that is a very good document. Question though....I had two seperate companies look at my furnace. One technician said my heat exchanger is leaking around the edges (water test), other technician did a combustion test and found no C02 leakage. Which test is more accurate??

    Thanks....


  13. #13
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    probably the water test is more accurate --

    combustion analyzer depends upon the calibration of the meter, its accuracy at the read value, the placement of the probe with respect to the flue gas flow, the amount of flue flow

    the training & experience of the tech --

    but, the presence of CO is the problem

    maybe your furnace design is such that slight amount of CO is drafted away --
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

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