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Crown steam gas boiler taking a long time to fire burners

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eliasjj12
eliasjj12 Posts: 21
in Gas Heating

I have a steam boiler that is taking a long time for the burners to fire up. It is an intermittent ignition system. my boiler sparks for a bit sometimes taking a long time, then lights the pilot. Then the pilot stays on for about a minute to a minute 30 seconds before the burners completely fire. The burner flame starts off weak, then gradually gets to full strength. What could be the issue causing this? I cleaned the pilot assembly and vacuumed all the burners. I also put a multimeter on the MV/PV & MV that 24 V was being fed to the valve. I believe the gas valve or pilot assembly may be defective, but I would like your guys opinion on what you think the problem is.

Comments

  • 109A_5
    109A_5 Posts: 4,531

    I would think as soon as (within a few seconds) of 24 VAC being applied to the MV & MV/PV gas valve terminals the burner should have a normal flame.

    I would be inclined to verify the gas pressure on the inlet and outlet of the gas valve as the system's ignition module goes through its sequence process. Low gas pressure or sluggish valve operation may be obvious.

    image.png

    I suppose since the Ignition module has timing circuits that could have issues. But that does not explain the " The burner flame starts off weak "

    image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • HVACNUT
    HVACNUT Posts: 7,699

    Check the flame sensor.

  • tcassano87
    tcassano87 Posts: 153

    could be as simple as needing to clean your spark igniter, try that first. Might need a manometer to checking incoming and outgoing gas pressure

  • Steamhead
    Steamhead Posts: 18,924

    Also need to determine if the gas valve is a slow- or step-opening type. @eliasjj12 , can you tell us the model number of the valve?

    Co-Founder, All Steamed Up, Inc.

    Semi-retired

    Baltimore, MD, USA

  • EdTheHeaterMan
    EdTheHeaterMan Posts: 12,759

    I would like to know what control system is on your Crown boiler. That company has been selling boilers, burners, radiators, and controls for home heating since 1949.

    The control that comes to mind as most likely to operate that way is the White-Rodgers 36C84/36E86 series combination gas valve with a mercury flame sensor. That control system takes some time to sense that the pilot is established, so the spark may continue until the mercury in the flame sensor expands enough to operate the control, energize the main valve, and shut off the pilot ignitor.

    Once the main valve is powered, if the valve is designed as a slow-opening valve, that could explain the operation that @eliasjj12 is describing.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • eliasjj12
    eliasjj12 Posts: 21

    hello thank you everyone for your suggestions. I do not know how to reply to each response individually so I’ll do it all here. I know from the other boilers with the exact same ignition system, after the pilot is litt the burners fire to regular rate right after. Mine is taking around 1 minute or longer. It begins with a weak fire rate, then gradually fire to normal fire rate. I did not check the gas pressure on the valve, as it was set upon its installation. I will have to buy a manometer to check it.

    IMG_7224.png IMG_7222.png

    I know I have adequate gas pressure coming from the street because the water heater right next to the boiler is working just fine with its burner. And I’m not sure if it’s the pressure because like I said after about a minute or two the boiler fires normally at full fire rate. The ignition panel is a UTEC model. I confirmed that there is 24V being sent to the gas valve on the MV/PV & MV terminals after the pilot fires up. I am also hearing both clicks from the PV & MV in the gas valve. As for cleaning the flame sensor, I did lightly brush it, and the entire pilot assembly and cleaned it. When did that yesterday the pilot began lightly almost instantly, as before it was taking a long time. I’m not home so I can’t get the exact model of valve, but I will attach pictures of the spark pad and gas valve.

  • eliasjj12
    eliasjj12 Posts: 21

    If it is designed to open slowly then that would explain exactly what I am seeing!, but I am not sure

  • Steamhead
    Steamhead Posts: 18,924

    The model number on that valve should be on a sticker on the other side. I'd bet it's a VR8204H or VR8304H.

    Co-Founder, All Steamed Up, Inc.

    Semi-retired

    Baltimore, MD, USA

    eliasjj12
  • eliasjj12
    eliasjj12 Posts: 21

    I can’t get to the sticker now but I will double check later. Thank you !

  • 109A_5
    109A_5 Posts: 4,531

    So you really don't know if this is a recent change of behavior for this boiler ? Or just normal operation for it.

    You would need to compare the part numbers of the ignition module and gas valves of the other boilers. And look up the gas valve in question.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • EdTheHeaterMan
    EdTheHeaterMan Posts: 12,759

    Those pictures show that it is not the White-Rodgers mercury flame sensor design I talked about in my previous post. However, there are still slow-opening Honeywell gas valves. I’m not sure that you have one of those.

    I installed that type of boiler, and I don’t remember that boiler using a slow-opening valve.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • 109A_5
    109A_5 Posts: 4,531

    Was the gas valve in question ever changed ?

    Are the other boilers the same Make and Model ?

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System

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