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  1. #1


    Help me prove a point to shut up a blowhard who thinks he knows it all. He say's; Once the overheating problem has been corrected, you can substute a damaged "snap-disc," style Hi-Limit (Like Carrier and Luxaire use) w/a 3" Camstat.
    I've told him he's wrong. You should never substitute a limit. The best ammo I have to prove my point is from the
    RUUD Installation Instruction book for their Two-Stage Gas Furnaces(-)GRK SERIES: page 10:OVERTEMPERATURE SAFETY SWITCHES. Furnaces are equipped with safety switches in the control compartment to protect against overtemperature conditions caused by inadequate combustion air supply. If a switch is tripped it must be manuslly reset.
    (Sounds like they're refering to a "spill," or "rollout," switch.)
    WARNING: DO NOT JUMPER THESE DEVICES! IF ONE OF THESE SWITCHES SHOULD TRIP, A QUALIFIED INSTALLER, SERVICE AGENCY OR THE GAS SUPPLIER MUST BE CALLED TO CHECK AND/OR CORRECT FOR ADEQUATE COMBUSTION AIR SUPPLY. BLA....BLA...BLA... REPLACE THESE SWITCHES ONLY WITH THE IDENTICAL REPLACEMENT PART. That's the best I can come up with so far. I do Recall that Carrier does specifically mention not to substitute Hi-Limits. I'm looking for manufacture printed material forbiding the use of substitute parts. HELP!

  2. #2
    So, I guess we only need to stock one length of the Honeywell fan/limit control?

    Limits are specifically mounted in a particular location. Altering there location voids the UL listing of the unit in question. Therefore, all limits and other controls should only be replaced with an approved replacement.

    Have him ask his liability insurance agent which he'd perfer him to do...the right way, or just 'get-R-done'?

  3. #3
    Sometimes it is hard to find good documentation for common sense procedures.
    I personally beleive that a manufacturer has paid for many engineering hours to find out the exact location and type of sensor to use in order to meet the UL and the performance level of the furnace.And I doubt that they will ever recommend a field replacement that they have not spent those hours of research on to replace the one they use.

  4. #4


    Whoo hoo! Carrier's Applied Heating GTH1 Gas Furnaces:
    Slide 30 page 10 "The Temperature Limit,"..."Do not change the setting or alter the switch in any way. Only direct replacements should be used if replacement becomes necessary."

    Thank's guys..... I appriciate your input

  5. #5

    Wink Here's More!

    Carrier Module GTH page 5 "....CAUTION: Be sure to use an identical part for replacement."

  6. #6
    Just to clearify, you are talking about a regular snap disc and not the insertion type that is common to Goodman & Amana...right?

  7. #7
    Join Date
    Nov 2001
    A roll out safty is alittle different then a main isert limit.

    If a roll out trips It needs to be checked for a blocked flue or craked ht exgr. If all checks out, reset and observe.

    If the main trips, check for plugged filters.
    Faulty blower or other reasons, if all checks out.

    I won't by-pass a safty, But a mian limit can get weak, due to H/O'er lack of maintenace.
    I'll put in another limit, even if it's not the exact temp.
    But only for the time it takes to get the right one in stock, and only if their are kids in the house.

    They still have heat, and still have a safty.

    I would never put a snap disc inplace of a insert.
    That is a complete misunderstanding of what the designed saftys job is.

    Not all inserts will achieve the same results, so why would someone expect a snap disc to perform as an insert.

    if thats what you mean he tried to do,
    If you try to fail, and succeed.
    Which have you done ?

  8. #8
    The question is whether you can replace a snap disc with a CamStat. (that's what the OP asked)

    But, the OP doesn't specify whether the snap disc was an insertion type.

  9. #9
    Join Date
    Mar 2002
    Concord, CA
    Originally posted by jultzya
    Altering there location voids the UL listing of the unit in question. Therefore, all limits and other controls should only be replaced with an approved replacement.
    It's an interesting dilemma. I'm told by some very smart people that replacing a faulty part with anything other than the original voids the UL and AGA certs. If that's true then all of those universal parts (ignition modules, motors, etc.) we use are, from a legal standpoint, as potentially problematic as switching from a snap disc to Camstat.

  10. #10
    Join Date
    Aug 2004
    North Richland Hills, Texas
    Once you as a technician touch it, you may as well remove the UL and AGA stuff from it anyway, its your baby.
    The last person that touched it has all the liability...
    If more government is the answer, then it's a really stupid question.

  11. #11
    Join Date
    Nov 2004
    Naples, Fla.
    Irasable - as a former factory rep & dealing w/ the legal dept far too much, I can asure you - any mfg will bail on you for ANY alteration to thier OEM design.

    This is where lawyers make all thier money w/ depositions finding experts to leave you swinging in the breeze.

    Sooner or later some semblance of common sense does kick in. If you have acted with due care to ensure the part you substituted is in all fuctional terms equal to the OEM, you're in pretty good shape - but relocating & redesigning (especally safety controls) will leave you on your own. In Fl. a certified lic. permits you build, design, service, install HVAC - in that scope, your insurance will be there.

    However, Mark is correct - the last guy on the job is holding the bag -- thus Always DOCUMENT that all safety controls are working. If any failure exist - shut it down / this is a zero tolerance issue.

  12. #12
    Join Date
    Aug 2002
    Avon Lake, Ohio
    Just for the record AGA doesn't certify anything anymore and UL only certifies components on gas equipment as a rule unless it is dual fuel, oil etc.
    Many times my students have found that the limits on a particlular appliance were assembled in an obvious wrong location because they are not assembled by engineers. So would it be wrong to put them in a proper location? No limit should ever be by-passed and in fact in most applications additional limits need to be added. The skills and expertise of technicians in the field has to exceed many times over the equipment designers skills because equipment is never designed for any specific installation or the majority of environmental conditions it will be exposed to. As long as any replacement part serves the same purpose as the part it is replacing it really doesn't matter what you use. I have seen fan & limit configurations and locations be changed in the field for 34 years. Those without the confidence, skills or intelligence to do this are not truly qualified to be doing this work in the first place.
    captain CO

  13. #13
    Join Date
    Sep 2001
    East Stroudsburg, PA
    People die and property gets damaged because of the partial literacy, arrogance and lack of reading comprehension of "technicians" like your Ralph Kramden-lookalike buddy.

    Send him here, we'll try and straighten him out.

    The worst, most scariest thing I've ever heard was "We've ALWAYS done it that way!"

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