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    Weil-McLain gas boiler short cycling, weak flame signal and lockouts (3 Posts)

  • nbgr21401 nbgr21401 @ 11:03 AM
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    Weil-McLain gas boiler short cycling, weak flame signal and lockouts

    The boiler is a 1991 Weil-McLain  HE-3, induced draft gas hot water boiler for
    single zone baseboard hot water heat.  It
    uses a White-Rogers 50E47-842 HSI Control. Igniter and Flame Sensor are
    replaced every heating season. Gas valve and control board were new 1 year ago,
    as were several other parts. New gas line from street, and meter, installed 4
    years ago, with line gas pressure delivered to boiler satisfactorily resolved to
    5" - 5.5 WC, verified by gas company tech, HVAC tech and myself.It is installed in the dug-out portion of the house crawlspace.
    The dug-out portion has concrete block retaining walls, full concrete floor, and
    has been fully encapsulated. Ventilation is sufficient, and RH is 30 - 50% from
    fall to spring.

     House is a rental unit located 30 miles away from our
    residence, making accurate reporting and observation of problem occurrence, and
    servicing challenging.

     During recent years (past 5) there have been consistent problems
    with the "locking out", and shutting down. Many parts replacements
    have occurred, including igniters and flame sensors, gas valve, transformers
    and HSI control boards. Replacing parts usually results in a temporary fix, but
    the lockout problems recur at some (variable) time later. There does not seem
    to be any correlation between air temperature or conditions (rain / snow /
    clear) and boiler performance.   

     Just experienced another lockout (flashing red light on the
    HSI control), which somehow seems to have resolved itself for the moment, but I
    am on my annual quest for a working boiler, and am turning here for assistance.

     Documentation is: Day 1: 0800

    Tenant texts to advise of no heat that morning. He said that
    heat had been fine previously. Stated that he had turned heat down the night
    before, and when he turned it back up in the morning, it did not come one. Travelled
    to site, reset the system by turning power off / on. Unit immediately fired up,
    and completed ignition sequence. Observed rapid-flashing green light (weak flame)
    for about 30 seconds, then solid green, indicating satisfactory flame. Cycling
    time is about 3-4 minutes, raising water temperature from to 160 degrees (per
    temp / pressure gauge). Drop to 140 degrees starts cycle again. Cycling, hot
    water generation and heating continued for 2 hours of observation. Cycling was
    always in 3-4 minute range. Weak flame signal appeared on each cycling. There
    were two (2) failed 1st ignition attempts at 79 minutes and 98 minutes, but
    both recovered on second attempt. Duration of weak flame signal increased to
    about 50 seconds starting with first ignition failure, and continued for rest
    of observation, 122 minutes. Observation and presence ended, since boiler was
    firing and house heating.

    2000 hours:  Tenant
    returned home from work, reported house was cold, no heat and all pipes were
    cold. Asked him to go to boiler, and observe and report while resetting. Walked
    him through the process, advising what to do / look for. Boiler fired
    immediately on reset, and he reported that HSI control idiot light was
    immediately SOLID green (no flashing). Asked him to stay for several cycles,
    and cycling was just as short as earlier; consistent immediate solid green light
    at ignition for each of four (4) observed cycles.

     Day 2: 1300 hours. Checked residence: Toasty warm at 70
    degrees; all pipes hot. Checked boiler: output pipe so hot you could not touch
    (must have just finished cycle). Waited 45 minutes, but no further cycling
    (tight little house!).

     To start, I need to resolve the short cycling, weak flame
    signal and lockouts.

     I have some thoughts, but would appreciate questions, comments
    and recommendations to start the discussion.   
  • Empire Empire @ 4:25 AM
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    "Lock Out"?

    First off the line pressure @ 5.0/5.5"w.c. is at the low end for the house.  When other equipment is in use this number can go lower.  There is no reason the line pressure after the meter be such a lo reading.  12.0"wc....Demand the pressure be set there.  The parts that are replaced is kind of excessive, don't ya think?  What is the manifold gas pressure?  The boiler MUST be grounded Mechanical and earth ground.  If not, this will give a weak signal.  What is the ua. on the flame sensor? 
         Your 20 *f "delta T" on the supply/return is OK.  The differential is generally set at 20*f, but not always.  You can get this short cycling on a cold start.
  • unclejohn unclejohn @ 10:27 PM
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    Flame sensor

    Like he said a good ground is very important. Also clean the sensor and the burner where the sensor is, the flame must touch both burner and sensor. Is the flame lifting off the burner because of improper air adjustment? Losen and retighten all ground connections.
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