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  1. #1
    Join Date
    Feb 2008
    Posts
    23

    Confused York RTU ignition problem

    I got a call today for a youk unit m#: D4CG036N09225 not heating. Went up to the unit and found that it was not sparking. Had 24v to ignition controller, combustion fan running, all limits/rollouts switches closed. When the relay in the ignition control clicked, you could hear barley hear the spark. Tried to clean up the burner, sanded the pilot tube near the sparker and tried to light it again, no luck. I figured that the ignition controller was bad and not providing the spark necessary to light the pilot. Picked up a new ignition control, spark igniter, and flame sensor and installed them. The unit fired up and ran for a few minutes then shut off the burner, combustion fan still running. Main fan running and roll out switch still closed. Tried to fire it again and got the same weak spark that i seemed to be getting before. Had to leave the site because the business was closing and need to return tomorrow. I'm thinking it could be a grounding issue, but i did clean the grounding terminals on the gas valve. I did swap the placement of the sparker and flame rod, and the spark seemed to be good, perhaps it it a spacing issue with the new sparker? Has anyone had this problem before on an older your unit?

  2. #2
    Join Date
    Apr 2004
    Location
    Maryland
    Posts
    522
    I had this same problem checked grounding new control/ignitor flame sensor everything. Try jumping out the rollout switch. In my case it had a slight resistance through the rollout switch and I assume a voltage drop to the igntion control. The ro switch attaches directly to the ignition control on the ro terminal correct?

  3. #3
    Join Date
    Dec 2006
    Location
    philadelphia pa
    Posts
    171
    I think M-Tech has your answer, the roll-out switch, jump it out and see what happens. Your flame rod has to the furthest from your pilot supply, put the flame sensor and the ignitor back the way you found them! Is the carry-over tube blocked? do you smell gas out of the combustion fan outlet when it's sparking?

  4. #4
    Join Date
    Feb 2008
    Posts
    23
    I'm headed over there shortly, i'll let you guys know what i find. I could smell gas and i did replace the flame sensor and sparker to their proper locations, i'll keep my fingers crossed for the roll out.

  5. #5
    Join Date
    Feb 2008
    Posts
    23
    Jumping out the roll out switch worked! Got a new switch and put it in, unit is running normally again, thanks for the help!

  6. #6

    Problem Continues

    Have same problem, but ignition control ok, ro switch ok. When heat called for by Tstat combustion blower truns on, igniton and burner fire, runs about 5 minutes, burner shuts down. Combustion blower still running. If I reset, cycle repeats and I can keep doing this. What else can I look at? Thanks

  7. #7
    Join Date
    Sep 2006
    Location
    Ohio
    Posts
    494
    Quote Originally Posted by blackrh View Post
    Have same problem, but ignition control ok, ro switch ok. When heat called for by Tstat combustion blower truns on, igniton and burner fire, runs about 5 minutes, burner shuts down. Combustion blower still running. If I reset, cycle repeats and I can keep doing this. What else can I look at? Thanks
    Check the hi-limit.

  8. #8

    Hi Temp

    Will check this but if it is going out on Hi Temp would I be able to restart instantly after reset. I would think the Hi Temp would not have time to cool down.

  9. #9
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    19,319
    Check airflow. Good belt, properly tensioned, clean filters, clean coil.

    Hi limit is probably doing what it is supposed to do.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







  10. #10
    Join Date
    Mar 2007
    Location
    Toronto
    Posts
    30

    My 2 cents...

    Verify your primary voltage and the transformer secondary voltage.

    Ensure that the transformer is grounded and fused.

    Check your transformer wiring (if it’s a multi tap transformer).

    Most unit come prewired for 220/240 volts ac. If your building is 208 volt and your transformer is wired for 240 volts, you will have a reduced secondary voltage.

    This will cause your unit to operate intermittenantly. Somewhere around 18 to 19 volts ac, you ignition control can lock out on anything.

    Based on what you found, place your meter across the complete safety circuit. If you drop more than 1 volt ac, across the safety switches , find the defective switch.

    Place your meter across the transformer secondary winding, no load.
    Press min max on your meter.
    Jump R W
    What is the min voltage recorded
    Less than 20 volts ac – check your transformer and change if required.

    Good luck…

  11. #11
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    19,319
    Quote Originally Posted by steveholt View Post
    Verify your primary voltage and the transformer secondary voltage.

    Ensure that the transformer is grounded and fused.

    Check your transformer wiring (if it’s a multi tap transformer).

    Most unit come prewired for 220/240 volts ac. If your building is 208 volt and your transformer is wired for 240 volts, you will have a reduced secondary voltage.

    This will cause your unit to operate intermittenantly. Somewhere around 18 to 19 volts ac, you ignition control can lock out on anything.

    Based on what you found, place your meter across the complete safety circuit. If you drop more than 1 volt ac, across the safety switches , find the defective switch.

    Place your meter across the transformer secondary winding, no load.
    Press min max on your meter.
    Jump R W
    What is the min voltage recorded
    Less than 20 volts ac – check your transformer and change if required.

    Good luck…
    That's very thorough. You got your thinking tewk on.

    However, this is not a new unit, and it is a very fair assumption that it was working previously. So, that is going to take a miswired transformer out of the mix, eh?
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







  12. #12
    Did not check hi-limit. Made another final check on rollout switch and decided to check metal shelf on the companion unit and it is running cool. The one I am working on is running hot so found that the rollout switch is indeed tripping due to the heat build up. Now it looks like I will have to see if there is any blockage in combustion chamber, cracks, what ever. The vent motor seems to be running at speed. The pilot flame seems ok and no rollout from burners.

  13. #13
    Join Date
    Apr 2007
    Location
    Ontario Canada
    Posts
    171

    Problem repeats every 5 minutes...

    Check that the fan is running, the filters are clean, the return air is returning and the supply air is going out.
    Really sounds like a high limit problem due to lack of air flow.

    D.

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