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Maximum length of 1/4" AL pilot light tubing??

JUGHNEJUGHNE Posts: 5,778Member
I relocated the tap for the gas line for a pilot burner on a power burner. It is only about 30" longer but it seems the pressure drop is too much??
This has been a nuisance lockout on pilot failure for years. Finally watching the start up the FS dropped the pilot valve out when the main valve opened, I thought I caught the reason, I assumed due to gas pressure drop.
The pilot tap was after the MV seemed like a simple head slap...duh. The very simple gas train showed the pilot connected ahead of the MV reg. This is one of those things that has been there +20 years. Again assuming that it was correct because that is the way it was
installed years ago.
Thinking I had the sure remedy I lengthen the tubing to a tap right on the gas supply ahead of that reg. Now seldom lights. Situation worse. There might be 6-7' of tubing from main line to pilot reg which is right as the sol valve for the burner.
Have I exceeded the limitations of 1/4"


  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,914Member
    I don't know of any maximum length from the "book".

    Don't know why but I suspect this is a Power Flame??
    The pilot is supposed to be tapped from the street side of the main regulator. Make sure you have the right pilot regulator. You could always get rid of the 1/4" tubing for 1/2" od
    Pilot gas pressure on those are usually in the 1 1/2"-4" range between the pilot solenoid and the pilot.
    I have used a single pole ignition transformer with an 8,500 volt output and removed the factory 6000 volt one.

    Check your control voltage everything is rated 120 volt. If your 120 is low the flame signal and the spark from the transformer will be low.

    If it is a PF burner they are some times have problems with too much gas on the pilot.....won't light if too rich. Make sure pilot burner and all air holes are clean.

    If it's a burner like a PF where as the main valve opens the air damper is also begins to open but main gas has not reached the burner head yet the increased air can blow the pilot crazy.

    Those problems are tough to find. You need meters, manometers all hooked up and 6 sets of eyes and ears to diagnose because trial for main flame is short

    Been there
  • JUGHNEJUGHNE Posts: 5,778Member
    Thanks Ed,

    This is an Adams Speedflame power burner.
    Forced air draft is constant with the blower on.
    I will try lowering the pilot gas and see if that makes a difference.
    The pilot reg is set pretty high now, and being connected to the main line might be the issue.
    Ran out of time today, maybe tomorrow.
  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,914Member
    Just a thought. I know with some (maybe all) gas regulators that if you have the regulator set (output pressure) higher than inlet pressure the regulator will lock up and not feed. This is possible if you have low gas pressure
  • JUGHNEJUGHNE Posts: 5,778Member
    I need to add a tap after pilot reg to check that pressure.
    Need some fittings to set this up.
  • JUGHNEJUGHNE Posts: 5,778Member
    The pilot reg was set very high. Today after dropping that pressure had better results with lighting. I assume gas pressure blowing past the spark.
    Will add pressure tap between pilot reg and pilot solenoid valve later this week.
    Just installed a HW RM7895A to replace questionable RM78595, (the main burner relay was trying to pull in sometimes without pilot flame).
    Got the Keyboard display module also, easier way to monitor flame signal while less meter to connect.

    Distributor says they bring the display module out for boiler start ups and it usually gets purchased on the spot, I see why.
  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,914Member
    Display modules aren't cheap that's for sure. I carry one in my truck. We have a few jobs with them installed but most do not. Usually just use it to read the flame signal although you can do that with a meter as well. I think they store the last 5 lockouts although I never took the time to figure out all the other features
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