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Flame Safeguard Signals

RayWohlfarthRayWohlfarth Member Posts: 807
Greetings from my bunker in Pittsburgh
I am working on my new book for commercial steam systems and looking to put a section together for typical flame signals. Enclosed please find what I have so far. If you have any suggestions, please let me know.
Ray Wohlfarth
Boiler Lessons
Click here to take Ray's class.
Click here to buy Ray's books.


  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,058
    My only comment is that the manufactures minimum flame signals (in my opinion) are not to be trusted. Any time i had problems and my signal was on the low side (but above the mfg minimum) I would work to try and increase the signal and that was the fix. In addition a signal on the low side may work better if it is steady than a higher signal that is erratic. Sometimes the meter can't react fast enough to show the true signal if the signal is erratic

    You have to take everything a mfg tells you with a grain of salt in my opinion
  • retiredguyretiredguy Member Posts: 221
    Let me know when your new book is available for purchase. Having worked for a company in Pittsburgh for 35 years owned by William Tauskey Sr. and later William Tauskey Jr. I saw a lot of the very old and the very new up until the year 2007 when I retired. I saw a lot of weird situations and re-engineered equipment. I once had a situation with an auburn burner controlled by a M-H R478A and a flame rod. The pilot would light as would the main flame and as was the case with most "flame rods" the flame signal was erratic and would switch between positive and negative. No one in my book of contacts could tell me what the problem was except for the old Honeywell guys that moved to a controls company, located in the South Hills. I was so glad that I had access to those old M-H guys.
  • RayWohlfarthRayWohlfarth Member Posts: 807
    Thanks @slamdunk I appreciate that.
    @EBEBRATT-Ed I agree with you on that. I was thinking I could use it to let the service tech at least know what scale to use and get the tech close. One of my rules I follow is, The manufacturer has never heard of your problem; its a lie.
    @retiredguy wow small world Hoping retirement is treating you well. I will let you know when the book is published and the people you spoke about were awesome and a wealth of information.
    Ray Wohlfarth
    Boiler Lessons
    Click here to take Ray's class.
    Click here to buy Ray's books.
  • ratioratio Member Posts: 2,447

    …No one in my book of contacts could tell me what the problem was except for the old Honeywell guys that moved to a controls company, located in the South Hills. I was so glad that I had access to those old M-H guys.

    So, what was it? I'm always eager to hear about solutions to obscure or uncommon problems.
  • retiredguyretiredguy Member Posts: 221
    edited June 25
    @ratio, the answer to my question on the flame signal reversing and the control accepting it was that "if the control allowed a signal that it was not engineered to accept, the control could not be trusted to safely shut the burner down and to replace the control". By the way, this happened when I was at a seminar that Honeywell was holding and I was ejected from a class because I ARGUED with the teacher since I would not accept his lame and wrong explanation/answer. The Honeywell guy explained that to the teacher and I was allowed back into his class.
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,058
    If I am not mistaken flame rods were considered the safest flame detector but as far as I am concerned THEY SUCK.

    I spent hours cleaning flame rods, running a separate ground wire etc.

    They were always erratic and changed many systems over to UV
  • JUGHNEJUGHNE Member Posts: 6,924
    Just to add some meager experiences with a power burner:
    Adams Speed Flame on small Kewanee HW boiler, firing at 327,000 input. HW 4795 burner control.
    It had almost weekly lock out on pilot failure since new install over 25 years ago. All employees knew how to reset the control.

    Numerous cleanings and adjustments got it down to maybe 2-3 week lock outs. This is a small school about 1 block from my house and I can see the flue pipe from my house and know if it is firing. I visit the building a lot anyway.

    Finally, after staring at the gas train I realize that the pilot supply to it's regulator was connected downstream after the main 1 1/4" regulator. Dope slap myself...duh.
    Pilot gas would almost drop out when main valve snapped open.

    The dead man who installed and connected this as such was a pretty experienced person who was self taught...I never thought to question his piping.

    That improved things a lot.
    Then realized that I had been raising the pilot pressure too much trying to correct the first problem and lifting the pilot flame off of it's burner so when main burner fired it would jump away from the flame rod.

    There have been very few lockouts since.

    Then during a fall start up the HW 4795 would call for main burner before pilot burner without proof of a flame.
    I had learned for start up to have the MMGV off and observe the sequence of operation, this was a definitely good time to do this. Often someone will just turn on a switch and walk away.

    Time for a new HW 7800 series.
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,058
    edited June 27

    a common issue even when the pilot supply is taken off the street side of the main burner regulator is suspected pilot flame dropping when the main valve opens. It happens so fast you need 6 pair of eyes to watch the manometer, flame signal, listen for the pilot valve and main valve and watch the combustion chamber at the same time :):) fun

    I can't prove this but my theory is if the pilot branch is not oversized for 6" to a foot when it comes off the main the main gas rushing through the tee when the main valve opens creates a venturi effect and pulls the pilot pressure down.

    Most regulators will lock up or close if the outlet pressure setting on the reg is above the inlet pressure. Screwing the reg down to get more gas like many do creates more problems and locks up reg.

    At least thats my theory
  • retiredguyretiredguy Member Posts: 221
    edited June 27
    According to the engineers at Honeywell the best flame signal, for a flame rod system, was attained when the flame enveloped the rod and the grounding area at a ratio of 1 part rod to 8 parts grounding surface, The flame signal will waver up and down since most pilot flames are not perfectly stable due to air flow and changing gas pressures. As it was explained to me, the flame rod works by applying an AC voltage to the rod and the electricity will pass from the rod to the grounding surface producing half wave DC rectification. The resulting short circuit or amperage to ground could be read on a micro amp meter. A 2 micro amps signal (UA) was supposed to be the lowest allowable flame signal while about 6 UA was supposed to be the high limit. Most times I was happy if I could achieve a signal of 2 UA .

    At that previously mentioned Honeywell school that I attended, the classes were entertained by the one of the old Honeywell engineers that retired and were hired by that south hills Pittsburgh dealership (there were 4 of them) showed the classes how many of the "ultra safe" flame control systems could, under the right conditions, be fooled or tricked into accepting a dangerous no flame condition and allowing the main gas valves to open. He was one of the engineers that designed those controls.

    I too changed many of the flame rod systems to UV for better burner lighting and performance. The one big problem was that many of the UV systems would prove that the pilot was lit when it wasn't because the UV detector would respond to the spark of the ignition transformer. You always had to make sure that the ignition spark was off before opening the main gas valves.
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,058

    I agree with most of what you posted except for one thing. Yes UV can pick up a spark as a false signal but I have seen many burners lock out due to the "early spark termination terminal".

    Getting a pilot to stay on reliably on a power burner with early spark termination is a challenge.

    Some burners (Power Flame C burners for instance) the ignition spark is inside the pilot burner housing and there is no way the it can be viewed with the scanner pipe which is external to the pilot housing

  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,058
    Siemens LFL they say 70 microamps minimum signal is usually 100 microamps or more.

    In my experience if you didn't get 115ua or more you are in lockout territory.

    Then they have no jack or access point to test the flame signal. You have to remove the control from the sub base, disconnect the flame detector wiring and wire your meter in series with the flame detector, reinstall the control and do your testing PITA

  • ratioratio Member Posts: 2,447
    I think I would leave one of these permanently installed if it were that difficult.

    I like using it in any case, lets me remove my meter without interrupting the flame sense; & adds a layer of safety between the line voltage sense signal & my µammeter.

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