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  1. #1
    Join Date
    Oct 2012
    Posts
    11

    Confused ENG AIR DJ-100 wont light pilot real STUMPER !!!

    Hi all, Here's a good stumper for you.....I have a client who has many Eng air DJ-100's on the his roof, unit was working fine until the burner motor seized (common problem with these turn down burners) Pick-up a new motor, wheel and magnet from Eng Air, replace everything keeping combustion air damper in same position with no problems. Go and start the unit, burner wont fire up because the pilot wont light....Good pilot pressure, good spark, pilot air tube clean. Put a new pilot assembly in same thing.....The only way I can get this to light up is to close the combustion air damper almost closed. This unit was working fine and had a perfect combustion analysis taken 30 days ago until the burner motor died 2 days ago, the new motor, wheel and magnet is the exact same from Eng Air. The unit goes through pre-purge no problem, magnetic sensor works fine to sense "light off speed" of combustion air motor...once down to "light off speed" pilot valve opens....good spark but fails to light. I have worked on these units for almost 10 years but this has me STUMPED.. Anyone ??? Thanks

  2. #2
    Join Date
    Sep 2004
    Location
    Kansas City, Kansas, United States
    Posts
    13,833
    The PILOT itself is not lighting?

  3. #3
    Join Date
    Oct 2012
    Posts
    11
    yes, the pilot will not light. The only way I can get the pilot to light is to almost close the air damper fully. Then the pilot will light and the unit will go to main burner no problem.

  4. #4
    Join Date
    Oct 2005
    Posts
    123
    What is your combustion readings with the air damper in that position....Is it within Eng. Air's specs?

  5. #5
    Join Date
    May 2004
    Location
    Salt Lake City/Tooele
    Posts
    2,504
    Does this unit just have the basic combustion air, or does it utilize any of the G or X Trac controllers. I would assume that your getting too much air from the combustion motor and it is blowing the pilot gas being released off of and away from the spark electrode. Need to get in and double check that your combustion air % is correct, once operating check your flue outlet pressure, and get your CO and O2 readings and start making the necessary tweeks to the system and possibly gas pressure.
    I work on plenty of these too, but not one comes from the factory exactly the same. So hard to say which gas valve set-up (modulating) you have, dampers (angle or flat), type of ignition controller, etc...but I am probably preaching to the choir, my friend.

  6. #6
    Join Date
    Oct 2012
    Posts
    11
    Quote Originally Posted by jsin View Post
    What is your combustion readings with the air damper in that position....Is it within Eng. Air's specs?
    no, it's less than 1% O2 when it should be between 3.5-4.5%.

  7. #7
    Join Date
    Oct 2012
    Posts
    11
    Quote Originally Posted by slctech View Post
    Does this unit just have the basic combustion air, or does it utilize any of the G or X Trac controllers. I would assume that your getting too much air from the combustion motor and it is blowing the pilot gas being released off of and away from the spark electrode. Need to get in and double check that your combustion air % is correct, once operating check your flue outlet pressure, and get your CO and O2 readings and start making the necessary tweeks to the system and possibly gas pressure.
    I work on plenty of these too, but not one comes from the factory exactly the same. So hard to say which gas valve set-up (modulating) you have, dampers (angle or flat), type of ignition controller, etc...but I am probably preaching to the choir, my friend.
    Honeywell ignition module S8610
    Maxitrol modulating main valve ( blue valve with dc voltage control) operating at 3.5" when on high fire
    24v Pilot valve operating at 3.5" when open.
    combustion air motor is controled by the DJM 2.3 board which ramps the motor speeds up and down according to demand.

    I do agee with you that the pilot is being blown out or there is to much air to establish pilot. I have to close the air damper almost fully to get the unit to fire up, when on high fire the O2 is less than 1% which is far too low. Once running if I adjust to the min of 3.2-3.5% O2 and restart the machine it will not establish pilot. A few thing that dont make any sense.....

    1) Combustion analisys was done less than 30 days ago and all was near perfect....the air damper was set roughly is the same position as all the other machines on the roof.
    2) Machine was working with no issues until the combustion air motor failed. (all replacement parts are Eng Air OEM), not my first time replacing these motors....done probably 10-15 without issues.

  8. #8
    Join Date
    May 2004
    Location
    Salt Lake City/Tooele
    Posts
    2,504
    Wonder if the DMJ board is not operating properly, I know the light off speed is factory set, but this may be the issue. Have you tried Taking a DMJ off of another operating unit and try it on this unit?
    Another thing I was thinking of is that the burner may not be centered properly and setting too ow in the chamber causing excess air over the top. Make sure the burner is centered.
    This is a public document...sure you have it, but here is the link. If all else fails after checking all they have here, I would be contacting a factory tech and pick their brain.
    http://www.engineeredair.com/manuals/Manual1.pdf

  9. #9
    Join Date
    Oct 2012
    Posts
    11
    Quote Originally Posted by slctech View Post
    Wonder if the DMJ board is not operating properly, I know the light off speed is factory set, but this may be the issue. Have you tried Taking a DMJ off of another operating unit and try it on this unit?
    Another thing I was thinking of is that the burner may not be centered properly and setting too ow in the chamber causing excess air over the top. Make sure the burner is centered.
    This is a public document...sure you have it, but here is the link. If all else fails after checking all they have here, I would be contacting a factory tech and pick their brain.
    http://www.engineeredair.com/manuals/Manual1.pdf
    Thanks for the input, I am bringing one of my of my tech's down with me tomorrow for a 2nd pair of eyes...I have been a service tech for 25 years and every so often there is a machine that throw's you for a loop....I am hoping to solve this mystery tomorrow, will let you know. Thanks

  10. #10
    Join Date
    Oct 2012
    Posts
    11
    FIXED UP AND RUNNING...........We went back today with one of my guys and went over every inch of the burner, settings, pressures, etc......Called Eng Air and discused the situation at great lenght over multiple calls and they agreed that everything appears to be right but found it "very strange" why the pilot wont light. After multiple call back and forth Eng air decided that they are going to have to come and take a look....Just as I am packing up (not very happy as this is a prime client) I get a call again from Eng Air telling me to slighly offset the burner motor blower wheel 1/16-1/8" to the air inlet side of the housing and BOOOYAAA she fires right up runs like a charm with the air dampers in there original set-up. Take a ***** guess what the issue was......

  11. #11
    Join Date
    Sep 2012
    Location
    Central Florida
    Posts
    885
    Quote Originally Posted by b5srt View Post
    FIXED UP AND RUNNING...........We went back today with one of my guys and went over every inch of the burner, settings, pressures, etc......Called Eng Air and discused the situation at great lenght over multiple calls and they agreed that everything appears to be right but found it "very strange" why the pilot wont light. After multiple call back and forth Eng air decided that they are going to have to come and take a look....Just as I am packing up (not very happy as this is a prime client) I get a call again from Eng Air telling me to slighly offset the burner motor blower wheel 1/16-1/8" to the air inlet side of the housing and BOOOYAAA she fires right up runs like a charm with the air dampers in there original set-up. Take a ***** guess what the issue was......
    Wild shot in the dark, based on having looked at that manual that was linked earlier in the thread, speed sensor was not correctly sensing speed thus was spinning to fast??

  12. #12
    Join Date
    Oct 2012
    Posts
    11

    Cool

    Nope..

  13. #13
    Join Date
    Oct 2012
    Posts
    11
    Quote Originally Posted by Elfshadow View Post
    Wild shot in the dark, based on having looked at that manual that was linked earlier in the thread, speed sensor was not correctly sensing speed thus was spinning to fast??
    Nope.... will let a few more chime in

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