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Intermittent Explosion When WM Gas Boiler Ignites

DGB
DGB Member Posts: 11
This is probably a serious situation requiring more attention than it is getting. A couple of times a day when my home boiler ignites it will "explode/flash". I've been in the basement and witnessed the event. Flames will shoot out of the bottom of the boiler. The boiler is a Weill McClain VHE5 installed in '87. About 7-10 years ago it was modified from electronic to hot surface ignition. Is this issue likely with the HSI module or the Control Module?

Comments

  • DGB
    DGB Member Posts: 11
    Re: Boiler Ignition explosions

    Thanks, in advance for your help. Doug
  • icesailor
    icesailor Member Posts: 7,265
    WM Ignitors:

    It could be the HSI ignitor is cracked and not heating up like it should. Usually, when they are cracked, they won't light off and lock out. If they are cracked and are cracked, they will usually lock out because the resistance that the ignitor "sees' from the flame won't be correct. Not common at all but nothing is common.

    Change the ignitor and see what happens. They are cheap and a good place to start.
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    Because of the design

    of the Weil-McLain VHE and its flue passages with its built in reclaimer the flap on the connector may be staying closed and causing this. I would get a professional to come and take a look at it. If the cover to the reclaimer is removed make sure it is resealed with RTV high temperature sealant.



    The other possibility is that the bracket provided for the change over from the White Rodgers Cycle Pilot system to a hot surface adaptation may be out of position causing what we call a delayed or audible ignition.
  • DanCanDo
    DanCanDo Member Posts: 15
    My thoughts...

    It concerns me that ignition was changed from "Direct" to Hot Surface.  Hot surface takes some time to heat up to gas ignition temperature.  Timing needs to be dead on, pilot (if present) needs to be clean.  Curious if a turndown test was performed.  Finally, could possibly have a bypassing gas valve, filling the combustion area with excess, unburned fuel.
    DanCanDo
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    edited January 2011
    The change over from

    a mercury pilot system called "Cycle Pilot" was an authorized retrofit from Weil-McLain. Thousands have been done with no problem with ignition.



    It was not changed from Direct Spark Ignition but used a Mercury Sensor to sense the flame in order to open the gas valve. The pilot was ignited by a 5059 Relight Control from White Rodgers. All the VHE and HE boilers from Weil McLain used these systems. They had there problems which is why Weil McLain went to the Hot Surface Igniter retrofit.



    Any retrofit from a manufacturer must go through a complete test by them before it can be authorized including a burner safety turn-down test.



    The retrofit by the way includes an igniter, mounting bracket, module with a 34 second igniter warm up time, a gas valve and associated wiring and a sticker to place on the boiler. By the way a mercury pilot system takes30 to 40 seconds before the mercury boils and causes a SPDT switch attached to the White Rodgers gas valve to switch over and allow safe ignition. The HSI has the same warm up time!
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    Boiling mercury...

    One wonders why they took that device off the market...



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • DanCanDo
    DanCanDo Member Posts: 15
    Tim,

    I wasn't aware that they WM had a retrofit.  Obviously they know to what to do, I just see way too many field changeovers and they wonder why the heater goes BOOM when it comes on...good stuff, thanks.
    DanCanDo
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    Yes mercury boils at about

    400 degrees. The mercury was secure inside a very small capillary which was attached to a bellows type wafer that actuated a SPDT switch for pilot safety. The Cycle Pilot parts are still available today. The amount of mercury contained in that sensor is well below what is called the 8 hour time weighted average for exposure to mercury. The pilot adjustment on these was to insure that the mercury bulb tip glowed "Cherry" red as compared to a thermocouple which should glow "dull red".
  • CWMANN
    CWMANN Member Posts: 1
    Re: Boiler Ignition explosions

    Thanks for the suggestions. I will replace the igniter as soon as I can get my hands on one. I've come up with a WM p/n and a reference to a Norton 201. Is there a difference? The one that is on now came from WM as part of the conversion kit. I'm a little leary of universal replacements due to lack of experience.



    Another issue or clue to as what the problem may be: tonight the boiler has been off for a few hours despite all three zones calling for heat Boiler temp gauge read 60F. However, as soon as the shower was run and the domestic HW storage tank called for heat, the furnace fired up and began to circulate heated water to all destinations.



    The storage tank stat was set to the highest setting, thus the need to run hot water. If it is set lower, the problem is more frequent but then manually raising the stat will cause the boiler to fire while it has essentially ignored the zone stats that are calling for heat.



    Is there a relationship between these issues.



    One more piece of information: the B&G NRF33 circulator was replaced in Dec. '09 after only two years of service. Fortunately it had a 3 yr. warranty so there was no charge for the replacement. I've been a little suspicious of the new pump as the house still doesn't heat as rapidly as it once did. Don't seem to notice the "smell" of heat coming off a hot baseboard.



    I know I've thrown a lot out, but I'm trying to present as much information as I can recall. I'm really beginning to regret not taking advantage o the tax credit incentivesto replace this thing and start over........



    Once again, thanks all for you help.



    Doug
  • World Plumber
    World Plumber Member Posts: 389
    ignitor

    Did someone change the ignitor after the retrofit? I have see late ignition with some of the multifits. The gas doesn't cross them in a manor to get good ignition. Saw it on a couple of hot air furnaces. Once I got the right ignitors they quieted right down.
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    edited January 2011
    CW

    CWMANN January 9, 2011 @ 9:17 PM

    Contact this user Re: Boiler Ignition explosionsThanks for the suggestions. I will replace the igniter as soon as I can get my hands on one. I've come up with a WM p/n and a reference to a Norton 201. Is there a difference? The one that is on now came from WM as part of the conversion kit. I'm a little leary of universal replacements due to lack of experience.





    Norton makes most of the igniters the 201 is a 34 second warm up time igniter. The 34 second igniters are not available from most supply houses. They all sell the Norton 271 which is 17 second igniter. You want to be sure and replace with the same igniter as was put in at the time of the retrofit. A Weil McLain dealer like FW Webb may be able to help you.



     If the igniter is glowing and in the right position then I would not replace it.Now let us slow down your original problem was a boiler ignition explosion.



     Now you have no heat is that correct? Next question do you have zone valves or circulators?



    What is the number of the integrated boiler control? Is it a United Technology 1012-200?



    Do you have an indirect for domestic hot water? If so does it have its own circulator? Or is it connected with a zone valve?
  • Dennis Foley
    Dennis Foley Member Posts: 21
    Chekc the inside of the boiler and the chimney

    Any time I've seen flame coming out of the front of a boiler it's been related to incomplete combustion. The flue passages in the boiler may be clogged.
  • DGB
    DGB Member Posts: 11
    Re: WM Intermittent explosion

    Tim,



    The intermittent explosion issue is one of seemingly many? this boiler is having of late.



    To answer the questions per your last post: the indirect water heater has its own circulator, an NRF-22. The boiler has a single circulator pump B&G NRF-33 and three honeywell zone valves - one per floor ( basement, 1st, 2nd). Would a zone valve malfunction prevent hot water from circulating through a particular loop? How does one test a zone valve? All of the bleeders were purged in the heatless zone - no air anywhere. The other two zones are getting heat.



    The programmable thermostat in the heatless zone was replaced a few weeks ago. Wiring was checked today to be certain nothing had come loose.



    Hope this information gives a clearer picture of the layout.



    Thanks, again.



    Doug
  • DGB
    DGB Member Posts: 11
    Re: Boiler Ignition explosions

    Tim,



    By integrated boiler control, are you referring to the control module? If so. it 's a White-Rogers F50E47-170.



    Doug
  • DGB
    DGB Member Posts: 11
    Re: WM Intermittent explosion

    Tim, et.al.

    Update: I was awoken at 5AM this morning by one of the more forceful explosions/flashback that has occurred this week and arose to a very comfortable second floor ambient temp. First floor still cold. Decided to dissect the zone valve to see what I could see. Results: 24 v going into the valve, but no voltage at the thermostat. Checked wires for continuity -good. Moved the lever for manual override all the way to the right (which I don't think I reached previously) and the motor brought the lever back to the left. Repeated this process a second time. Voila! Zone now getting heat - can actually smell it again.



    So the question is, is the issue electronic as in a faulty micro switch or mechanical in that the valve was stuck?



    On to the explosion issue.........



    Thanks, again.

    Doug
  • DGB
    DGB Member Posts: 11
    Re: WM Intermittent explosion

    Tim, et.al.

    Update: I was awoken at 5AM this morning by one of the more forceful explosions/flashback that has occurred this week and arose to a very comfortable second floor ambient temp. First floor still cold. Decided to dissect the zone valve to see what I could see. Results: 24 v going into the valve, but no voltage at the thermostat. Checked wires for continuity -good. Moved the lever for manual override all the way to the right (which I don't think I reached previously) and the motor brought the lever back to the left. Repeated this process a second time. Voila! Zone now getting heat - can actually smell it again.



    So the question is, is the issue electronic as in a faulty micro switch or mechanical in that the valve was stuck?



    On to the explosion issue.........



    Thanks, again.

    Doug
  • DGB
    DGB Member Posts: 11
    Re: WM Intermittent explosion

    Tim, et.al.

    Update: I was awoken at 5AM this morning by one of the more forceful explosions/flashback that has occurred this week and arose to a very comfortable second floor ambient temp. First floor still cold. Decided to dissect the zone valve to see what I could see. Results: 24 v going into the valve, but no voltage at the thermostat. Checked wires for continuity -good. Moved the lever for manual override all the way to the right (which I don't think I reached previously) and the motor brought the lever back to the left. Repeated this process a second time. Voila! Zone now getting heat - can actually smell it again.



    So the question is, is the issue electronic as in a faulty micro switch or mechanical in that the valve was stuck?



    On to the explosion issue.........



    Thanks, again.

    Doug
  • Gordan
    Gordan Member Posts: 891
    Apparently the explosion shook you up pretty good...

    Your hands must be shaking since you posted three times. ;-)
  • DGB
    DGB Member Posts: 11
    Re:

    Sorry for the replication......didn't get a confirmation the first two times the submit button was hit.
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    It sounds

    like you have a problem with the Honeywell ZV's they may not be opening fully and that will cause the end switch to not make hence no heat, Then they may gradually make fully and slowly causing a delayed ignition.



    I want to look up the F50E47-170 Integrated White Rodgers control. I will get back to you.
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    That Integrated control

    has a 45 second igniter warm up period. Then a 7 second TFI (Trail for Ignition). It has a 4 seconds ignition activation period. If it does not light on the first try it will ties 2 more times.



    More to follow, what you want to do is see if your system is operating according to the perimeters set down by the manufacturer for the F50E47-170.
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    Dug out all my notes on the

    50E47-170 after reading this does your system operate as outlined here?



    In a typical system, a call for heat is initiated by closing the thermostat contacts. This will energize the 50E47 control. If the system is equipped with prepurge, the prepurge fan or interfacing relay is also energized through the thermo­stat contacts. In the prepurge mode, the 50E47 control will delay 30 seconds before applying power to the 767 A silicon carbide ignitor. If prepurge is not an option, the ignitor is powered within one second.



     

    The ignitor is then allowed to warm up for 17 or 45 seconds depending on the 50E47 control dash number being used (see Timing Specifications table). Various ignitors on the market must use the 45-second option to allow them to fully attain ignition temperatures at low voltage condi­tions. The W-R 15-second ignitor is especially designed to heat up quickly at a low voltage condition without overheating at a high voltage condition. Thus, the W-R 15­second ignitor may also be used with a 45-second warm­up time without detrimental effects.



     

    At the end of the ignitor warm-up time, both valves in the 36E manifold gas valve are opened. The ignitor will remain on for an additional one second (ignition activation period). A four-second ignition activation period is also available. Flame must be detected within four seconds (a seven-second trial for ignition period is available as a separate type). If flame is not detected, both valves are de-energized, the ignitor is turned off, and the 50E47 control goes into lockout.



     

    If the control is locked out, it may be reset by momentary power interruption of 120 second or longer. Either the 24 volt thermostat or line voltage may be interrupted.





     

    The 50E47 control may also be equipped with a retry option, depending on the dash number (see Timing Specifications table). This provides a 50-second wait following an unsuccessful ignition attempt (flame not detected). If the prepurge option is used, the waiting time becomes 90 seconds (3D-second prepurge plus 50-sec­ond wait).





    After this wait, the ignition sequence is restarted. An additional 10 seconds is added to the ignitor warm-up time, so a module with a 17-second warm-up time will have 27 seconds of ignitor warm-up or a module with a 45-second warm-up time will have 55 seconds of ignitor warm-up. If this ignition attempt is unsuccessful, one more retry will be made before lockout.





    All 50E47 controls will repeat the ignition sequence for a total of five recycles if flame is lost within the first 10 seconds of establishment.





    If flame is established for more than 10 seconds after ignition, the 50E47 controller will clear the ignition attempt (retry) counter. If flame is lost after 10 seconds, it will restart the ignition sequence. This can occur a maximum of five times.





    During burner operation, a momentary loss of power of 50 milliseconds or longer will de-energize the main gas valve. When power is restored, the gas valve will remain de-energized and a restart of the ignition sequence will begin immediately.





    A momentary loss of gas supply, flame blowout, or a shorted or open condition in the flame probe circuit will be sensed within 0.8 seconds. The gas valve will de-ener­gize and the control will restart the ignition sequence after waiting 50 seconds. Recycles will begin and the burner will operate normally if the gas supply returns, or the fault condition is corrected, before the last ignition attempt. Otherwise, the control will go into system lockout.

     

     
  • DGB
    DGB Member Posts: 11
    RE:

    Tim,

    Over the last couple of days I've had the following observations/experiences:

    1. Heat is fully functional in the morning, i.e. the first demand cycle of the day for all 3 zones.

    2. Problem seems to occur fon the second demand cycle after set-back. When I come in in the evening, temp in problematic zone is still at the set-back temp of 60 despite have been set to rise to 65 90 minutes earlier.

    3. Boiler appears to be in lock-out mode. If it is de-energised for several minutes it will fire. last night this had to repeated twice before the blower initated, but once it fired we had heat all night.

    4. Wednesday evening I noted the timing of the different sequences. It takes from 0-8 secs for the blower to initiate after energizing circiut. Approximately 26 secs after that the ignitor began to glow. After another 28 secs the gas valve opened and burners fired up. Unit did not run very long, maybe several minutes, before shutting down. When it was restarted  it took 11 secs after energizing for the blower to come on, 24 secs tfor ignitor to glow and another 24 secs for the gas valve to open at which time it shut down completely and woud not restart for about an hour. 

    5. When the line voltage circuit is de-energized, the motor on problematic zone rotates the valve. Is the spring causing this?

    6. At least one time there was no voltage at the thermostat for the problematic zone. What is the function of the microswitch on the valve? Could this be sticking?

    Can you explain ot me the relationship of the zone vavle to the overall operation of the system. I was under the impression that the system would function irrespective of the valve staus and that all it did was shunt water to the zone when the stat calls for it to open. Your last post implies otherwise unless I have misunderstood. Are zone valves repairable?

    Do any of the symptoms point in a particular direction? Control module? Zone Valve? Other?

    Thanks again for your tremendous help.

    Best,

    Doug



          
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    What make are the

    zone valves? Most zone valves work as follows:



    Thermostat calls - completes a 24 volt circuit to the zone valve which causes the valve to open. Once the valve is fully open an internal end switch is closed in the zone valve head. This in turn is attached to a relay or control which typically will power up the gas valve and bring on the circulator.



    When the thermostat is satisfied the zone valve is deenergized and closes causing the end switch in the zone valve head to open shutting off the gas and circulator until the next call for heat.
  • DGB
    DGB Member Posts: 11
    Re: WM Intermittent explosion

    The zone valves are Honeywell V8043F 1036. I see they can be rebuilt without cracking the system.
  • DGB
    DGB Member Posts: 11
    Re: WM Intermittent explosion

    The zone valves are Honeywell V8043F 1036. I see they can be rebuilt without cracking the system.
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    You can purchase

    just the heads, a lot of supply houses will not carry the motors or end switches, they will only have the heads.



    A way to test each head is one at a time initiate a call for heat and see if the boiler and circulator come on if not take a jumper and go to the head of that ZV and jump out the "end switch" terminals if both burner and circulator come on then that valve head is bad.



    Do that independently for each zone.
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