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Got a Munchkin headache SE

R. Swatton
R. Swatton Member Posts: 86
Try replacing the harnes with the flame rectifier cable attached.
Wiring Harness 9 pin 120volt

7250p-390


Sometimes the connection to the control board fails. This can happen when exhaust gases come back through the air intake pipe

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Comments

  • S Ebels
    S Ebels Member Posts: 2,322
    Burner lockout

    Been messing with this thing since 10 this AM. Original complaint was F-10, flame failure, intermittently. About every 3rd or 4th cycle it would fail to light after the three trials for ignition. Figured it should be no big deal, probably just needs a good scrub. Wrong. We set up the burner when installed 2 years ago and the inside of the boiler was very clean yet but I scrubbed it anyway. Checked gas pressure in and out and they are both OK.

    What's happening is that the burner will light and generate a flame signal from .7-1.1 micro amps. Green light is on but it won't hold. Flame signal has to be upwards of 1.4 to keep the gas valve open.

    When I richen up the mix to the point where CO2 is crowding 11% and CO is downright ugly, the burner will stay lit. Set to the correct parameters, 8.5-9.5 CO2, 0-20PPM CO on low and <135PPM on high, the boiler will not stay lit.

    I don't know if I have an electrical problem that's flipping out the flame sensor (new BTW) or a combustion problem that's making the flam signal go bonkers. All I know is that after staring at the thing for 4 hours, I'm not any further than when I started.

    What IS the required flame signal? I can't seem to locate that info in my manuals.

    Checked so far:

    Gas pressure OK

    Intake and exhaust Clean and unrestricted

    Combustion test Can be dialed in to spec but won't run that way.

    Flame sensor New

    Condensate trap clean enough to drink out of.


    Any thoughts while I go to the shop to get a new board? What am I missing?


    EDIT: What is the electrode to burner dimension supposed to be ?
  • John Starcher_4
    John Starcher_4 Member Posts: 794
    Have you verified.....

    ...your ground connection is ok?

    I recently had a problem with a Trinity that wouldn't stay lit. I finally undid the wirenut with the ground connection, and re-nutted it. Problem went away.

    Starch
  • Constantin
    Constantin Member Posts: 3,796
    How about a UPS...

    ... a good unit might eliminate the possibility of interference via the electrical grid. It's probably not it, but something worth checking since you've eliminated all other avenues. They haven't had any electrical work done there lately, have they?

    It certainly sounds like an issue in the flame rectification circuit... when the flame is running one way, it gets enough current, but when the thing runs well, it does not. I would take a look at the flame sensor rod and make sure it's clean.

    Furthermore, I would take a look around the boiler and see if a laundry is nearby. Given that the HTP case may not seal 100%, it might be a good idea to install the foam tape the HTP rep. suggested in another thread to ensure that the Munchkin case is sealed 100% and does not ingest silicones in vapor form from cleaning fluids, washing powders, etc. (which allegedly is the top cause for flame rods to go bad in the first place).

    I would follow the flow of electricity to and from the flame sensor, I think that is where you will find the failure, if it's not the board or the power supply to it. A UPS simply limits one of the variables and I hope the homeowners appreciate your passion in tracking this issue down.
  • S Ebels
    S Ebels Member Posts: 2,322
    No

    We wired it all new when installed. Assuming that all wiring is OK but I'll check as there has been some remodeling done in the house since then. You never know.

    I'm just puzzled as to why it'll run when I make the combustion numbers crappy and it won't when dialed in to spec.
  • S Ebels
    S Ebels Member Posts: 2,322
    Headed back

    Can't leave 'em with no heat. I like what R. Kalia said in another post. Something about your heating system not being like an I-Pod which is of little consequence if it fails.

    More news at 11 :)
  • John Starcher_4
    John Starcher_4 Member Posts: 794
    Steve,

    in my situation, the wirenut in question was in the boiler's power inlet junction box. When I took it apart, there was a small piece of broken wire in the end of the nut. I restripped the ground wires and re-nutted them. This was an install I did two years ago! It's just worth a try to eliminate a variable.

    I'm puzzled about your "crappy combustion" scenario as well. Let us know what you find....

    Starch
  • Al Corelli
    Al Corelli Member Posts: 454
    Try cleaning

    Try cleaning the flame sensor ( I know, its new) with a CLEAN, NEW scuffy pad (or whatever you clean copper with).

    All manner of flotsam and jetsam can foul the sensor, even new ones.

    Worked for me. Many times.
  • hr
    hr Member Posts: 6,106
    Sounds loke a flame rectification issue

    I had a Knight do the same thing recently. I'd suggest a flame rod cleaning or replacement. Check or replace the wire to the flame rod, often it is the wire to probe connector. And check all the connections involved with the flame rod.

    In the end it was a connector issue on the Knight.


    It sure can be a teeth gritting experience when dealing with intermitent ghosts like that. Stick with it.

    hot rod
    hot rod

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  • S Ebels
    S Ebels Member Posts: 2,322
    Still no worky

    Returned with new board and flame sensor in hand, installed them, flipped it on and watched the same thing happen.

    The boiler will light and generate between .9 and 1.2 Micro amps, seems steady until it ramps down to operating level. At about 2,300-2,400rpm the flame signal drops to .5-.6 and then the burner fails. If I place the unit in service mode and manually set it to 2,600-3,000 rpm, it will run beautifully until the cows come home. Flame signal is steady at 1.4-1.8, not great but enough to keep it going.

    The flame looks really good, two tone blue with a flicker of orange here and there. As before though, when I dial the gas adjustment back to where it should be, it won't make any more than .2-.5 MA. All 110V wiring is good, checked the ground and nuetral all the way back to the panel and even checked the service ground for stray voltage outside. Tried replacing the spade connector on the flame sensor and checked the connection on the terminal strip to no avail.

    I left them with a temporary heat source but no way to take a hot shower. Have to call Chuck Monday on this one.
  • Terry Larsell
    Terry Larsell Member Posts: 54


    I have a fussy Munchkin that I inherited from an out of town installer. It goes f10 and the homeowner pushes the reset to get 1hr to 1 week of run time. I cleaned, checked gas pressure and did all you described. Lots of head scratching. I changed the burner gasket at the local reps suggestion. It ran perfect all last winter till now. They called recently and it was doing it again. Went through the same steps and at the last resort I put in a new burner gasket (took a week to get it) I put it in on Tuesday and I haven’t heard back so it must be working. I think maybe the gasket gets damaged when the condensate plugs up and it causes the flame to burn irregular in the flame sensor area.


    I come from a building background and have really gotten the wet head bug, that is except for the no heat calls. I get thet funny feeling when the weather gets cold, like I used to get when I was into roofing and the first big rains would come. You just hope it all works like you planned it. People get real antsy when the heat doesn’t work and they look to you to fix it now. I’m learning as fast as I can but it seems like it will be in my next lifetime before I can call myself an expert troubleshooter.
  • Wayco Wayne_2
    Wayco Wayne_2 Member Posts: 2,479
    My first thought

    > I have a fussy Munchkin that I inherited from an

    > out of town installer. It goes f10 and the

    > homeowner pushes the reset to get 1hr to 1 week

    > of run time. I cleaned, checked gas pressure and

    > did all you described. Lots of head scratching. I

    > changed the burner gasket at the local reps

    > suggestion. It ran perfect all last winter till

    > now. They called recently and it was doing it

    > again. Went through the same steps and at the

    > last resort I put in a new burner gasket (took a

    > week to get it) I put it in on Tuesday and I

    > haven’t heard back so it must be working. I think

    > maybe the gasket gets damaged when the condensate

    > plugs up and it causes the flame to burn

    > irregular in the flame sensor area.

    >

    > I come

    > from a building background and have really gotten

    > the wet head bug, that is except for the no heat

    > calls. I get thet funny feeling when the weather

    > gets cold, like I used to get when I was into

    > roofing and the first big rains would come. You

    > just hope it all works like you planned it.

    > People get real antsy when the heat doesn’t work

    > and they look to you to fix it now. I’m learning

    > as fast as I can but it seems like it will be in

    > my next lifetime before I can call myself an

    > expert troubleshooter.



    was the flame sensor too, but obviously it's more than that. I remember talking to mark Hunt at Wetstock in Baltimore and him talking of problems they had concrning the ground being proper. A trick I learned along the way was to drive a 4 foot piece of metal into the ground and run a wrie into the boiler. Check for the any voltage difference on the millivolts scale. There should be none. If there is any you got a grounding issue. Short story. Had a job go South on me years back. A Polaris water heater. Right after I installed it the local water company changed the incoming water lines to plastic. The old house had been elec service had been grounded to the water lines with a clamp. When they switched the incoming water line to plastic the ground went away. Took a while to find. Had the Homeowner Drive a 7 ft. stake for a proper ground and the problem went away. Whew! Good luck and let us know what you find. WW

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  • GW
    GW Member Posts: 4,676
    simple trick

    and maybe we all do it, but when checking micro amps, continuity, and whatever ghost you're looking for...if you have a spare hand jigle the wiring in question and see if the numbers bounce.

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  • GW
    GW Member Posts: 4,676
    all glued?

    we had a ghost that resulted in my plumber (great guy, sometimes not the most detailed) not glueing the concentric outside.

    Sound like you have a different animal though. Well, not unless the unglued flue gas bypass is messing with your combustion numbers!

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  • tim smith
    tim smith Member Posts: 2,738
    F 10 lockouts

    > Returned with new board and flame sensor in hand,

    > installed them, flipped it on and watched the

    > same thing happen.

    >

    > The boiler will light and

    > generate between .9 and 1.2 Micro amps, seems

    > steady until it ramps down to operating level. At

    > about 2,300-2,400rpm the flame signal drops to

    > .5-.6 and then the burner fails. If I place the

    > unit in service mode and manually set it to

    > 2,600-3,000 rpm, it will run beautifully until

    > the cows come home. Flame signal is steady at

    > 1.4-1.8, not great but enough to keep it

    > going.

    >

    > The flame looks really good, two tone

    > blue with a flicker of orange here and there. As

    > before though, when I dial the gas adjustment

    > back to where it should be, it won't make any

    > more than .2-.5 MA. All 110V wiring is good,

    > checked the ground and nuetral all the way back

    > to the panel and even checked the service ground

    > for stray voltage outside. Tried replacing the

    > spade connector on the flame sensor and checked

    > the connection on the terminal strip to no

    > avail.

    >

    > I left them with a temporary heat

    > source but no way to take a hot shower. Have to

    > call Chuck Monday on this one.



    > Returned with new board and flame sensor in hand,

    > installed them, flipped it on and watched the

    > same thing happen.

    >

    > The boiler will light and

    > generate between .9 and 1.2 Micro amps, seems

    > steady until it ramps down to operating level. At

    > about 2,300-2,400rpm the flame signal drops to

    > .5-.6 and then the burner fails. If I place the

    > unit in service mode and manually set it to

    > 2,600-3,000 rpm, it will run beautifully until

    > the cows come home. Flame signal is steady at

    > 1.4-1.8, not great but enough to keep it

    > going.

    >

    > The flame looks really good, two tone

    > blue with a flicker of orange here and there. As

    > before though, when I dial the gas adjustment

    > back to where it should be, it won't make any

    > more than .2-.5 MA. All 110V wiring is good,

    > checked the ground and nuetral all the way back

    > to the panel and even checked the service ground

    > for stray voltage outside. Tried replacing the

    > spade connector on the flame sensor and checked

    > the connection on the terminal strip to no

    > avail.

    >

    > I left them with a temporary heat

    > source but no way to take a hot shower. Have to

    > call Chuck Monday on this one.



    Just went through the same scenario Steve, talked to Munchkin support and they came up w/ an interesting item to check. Pull the bolts that hold the Burner head to the combustion chamber mounting plate, clean surfaces where bolts touch burner flange plate and chamber mounting plate and bolts and nuts with emery etc. Make sure when putting back together that gasket seal is good. This took care of the low flame signal that plagued us that day. Combustion was good also. The only way flame signal can go to ground is through the burner flange, into bolts and out to combustion cover plate so it makes sense. Good luck, Tim
  • S Ebels
    S Ebels Member Posts: 2,322
    Another thing to check

    Chuck e-mailed that to me this AM along with switching the flame sense and electrode wires around allowing the sensor to spark to the burner and the spark electrodes to act as the flame sensor. The last suggestion only works on the 50's and 80's and is NOT a permanent solution, only to test.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,307


    Steve,

    You probably already checked but could low line voltage be a problem?? Low line voltage will cause a low flame signal.

    I'm not familier with munchkins but it sounds like a ground issue. Is there a way to run a seperate ground wire back to the control????


    ED
  • Guy_6
    Guy_6 Member Posts: 450
    Hmmm

    This is a perplexing one. I would begin by DISCONNECTING the green ground wire from the boiler and try it. The flame rectification system looks to that ground as a known ZERO, then bases the rectification off of that. If there is some stray juice running through the ground, the system only sees the delta, which when dealing in micro amps, isn't much. The burner gasket is the only other scenario that I can see. Was there ever any condensate backup in this unit? That will deteriorate the gasket, if serious enough.
  • S Ebels
    S Ebels Member Posts: 2,322
    I thank you all

    You've given me lot's of ammunition to go back to the job with tomorrow morning. The folks were kind enough to let me come back Monday as I have a TON of stuff going on today. The wife and I are "managing", if that's possible, 45 kids in our church's Sunday school program, practice after church this AM, dress rehersal for the Christmas choir this afternoon and we sing it tonight. I'm the director so I kinda' have to be there. Drew went to pick up a couple extra spares from the supply house this AM. Sadly, they didn't have a burner gasket in stock.
  • Ragu_5
    Ragu_5 Member Posts: 315
    Steve...

    I mean this for real: maybe, stay away from the cheap stuff in the future? It ALWAYS gets me in trouble. Jack


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  • GW
    GW Member Posts: 4,676
    notes

    I've written all these nice responces in my treo's notes. What a bunch of smart people here!

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    Northampton, MA
    [email protected]
  • S Ebels
    S Ebels Member Posts: 2,322
    Clean as a whistle inside

    No indication of condensate backup at all Guy. I'm seeing a common thread to all the replies and private e-mails I'm getting regarding rectification current path. Seems like there are more than a few scenarios which can interrupt or redirect the flame current. Every piece of equipment has its own quirks and I'm sure we'll learn more as all this new condensing equipment begins to age.

  • Terry H
    Terry H Member Posts: 8


    Did you mention wether this is natural or lp gas?

    T
  • Rich daplumber
    Rich daplumber Member Posts: 14
    here we go again

    I am a Munchkin heat tech, I have gone out on at least 500 calls in about 2 years.
    At least 98% of all the problems I have encountered were instalation errors.

    No primary secondary.
    Condensate back up.
    Re circ of exhaust coming back into the cabinet.
    Wrong size gas piping .


    I have a Munchkin installed in my house for over 5 years.
    I tune it up every 2 years. Same control board, blower, gas valve.



    So don't blame the product all the time.
  • S Ebels
    S Ebels Member Posts: 2,322
    PROBLEM SOLVED

    It was, most definitely, absolutely, positively............. (drum roll here)

    The burner screws.

    Details at 11
  • Mark Hunt
    Mark Hunt Member Posts: 4,909
    Tim


    Just wondering how long this situation has been known to HTP?

    First time I have ever heard of the "fix".

    Mark H

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  • Wayco Wayne_2
    Wayco Wayne_2 Member Posts: 2,479
    Damn!

    The burner screws?????? I'm riveted for the answer to this one. (no pun intended.) Let us have it please. WW

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  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928


    Is there any reasonable way to attach a spade connector to the burner unit and run a ground wire? If so, wouldn't that prevent the problem at its source?
  • brucewo1b
    brucewo1b Member Posts: 638
    I.ll wager

    that the screws are the ground path back to the control to prove flame and when they get cruded up you loose good signal. have that a lot on different burners, just depends on what ground path the burner is using for proving flame.
  • brucewo1b
    brucewo1b Member Posts: 638
    Mike T

    I do that a lot on Burnhams but its just a matter of time before the same thing happens on the ground strap too.
  • Leo G_99
    Leo G_99 Member Posts: 223
    Mark,

    I was told about this about 8 months ago.

    Leo G
  • Leo G_99
    Leo G_99 Member Posts: 223
    Mike

    funny thing is, the last rectification probe I changed, had a spade fitting for the ground. Almost thought about cutting into the ground on the spark, but figured that it may be hooked up in a different area. Just cleaned the bolts, and she was off and heating once again!

    Leo G
  • S Ebels
    S Ebels Member Posts: 2,322
    OK.......so it's not 11:00

    I was so happy to get this thing figured out that I took the wife out Christmas shopping. If you knew how much I "enjoyed" shopping, you'd have a better sense of my elation.

    Here's what I did. I replaced the new flame rod with another new one just to be sure. No change. I removed the molex connector with the flame sense wire in it and sprayed the male and female ends with contact cleaner. Tried it again. No change. I traced the ground allll the way back to the breaker box, for the third time. All was good. I installed a new control board. Still no change. So after re-installing the original board, I removed the burner assembly again, took out each of the four burner screws one at a time, buffed the screw and the surface it mated to with a stainless steel brush and replaced them before removing another. This was to avoid disturbing the burner gasket. After all 4 were polished and buffed to a semi gloss finish, I re-assembled and test fired with the Simpson hooked in series with the flame rod. PRESTO!!!! Instant 4+ Microamps!! Solid as a rock. High fire, low fire and every size fire inbetween. Dialed combustion back into spec and the flame current remained just a strong as you please. Combustion specs were 16PPM CO and 9.1% CO2 on Low, 65PPM CO with 9% CO2 on high.

    The fact of the matter is that the burner screws were the problem the whole time. They are the only thing that electrically "bonds" the burner itself to the boiler casing. Being that they live in a very intense heat/cool environment, they are bound to loosen up or become corroded with time. Too much expansion contraction going on, especially when you consider that the screws are stainless steel and the material they thread into is aluminum alloy of some type. Loss or degradation of continuity has to be almost certain to occur at some point.

    Chuck called to see how I was doing and I related this briefly to him. He told me that he was going to include this scenario and the repair of it in his seminars and training from now on. I suggested that a service bulletin might be advantageous also but I don't know if they could effectively get this info out to all the people that install Munchkins. However HTP handles it, at least they know the cause, effect and the cure.

    Chalk this one up to some help from HTP and the wisdom of the Wall.


    BTW Swampy Mike......There is no way to bond the burner to the housing with a wire. The buner tube is of course inside the combustion chamber and a wire would have to be run from it to the outside of the burner casing. Won't work.
  • S Ebels
    S Ebels Member Posts: 2,322
    Correct my good man

    See my 11:00 post below.
  • Weezbo
    Weezbo Member Posts: 6,232
    it is great you managed to finger that out...

    next time you are having problems with a control...i have heard a copper crush star washer is a good thing....

    with lots of plastic,shorter and smaller screws,it is becomming a mystery only the overly experienced can think through.. it would be funny if it wasnt so real...
  • Weezbo
    Weezbo Member Posts: 6,232
    today ,i had an interesting experience..buh thats another story

    :)
  • Wayco Wayne_2
    Wayco Wayne_2 Member Posts: 2,479
    Thanks for sharing

    > :)



    this with us. As many Munchkins as there are out there, you know it will happen again, and now we are forewarned and thusly ready to look smarter than we really are. :) WW

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  • Al Corelli
    Al Corelli Member Posts: 454
    Persistence

    Thank you for sticking with this issue and sharing your data with us.

    It is appreciated.
  • Brian_18
    Brian_18 Member Posts: 94
    I've printed this Thread

    I've printed this entire thread, and put it into the document jacket hanging next to my boiler. Thanks for allowing us DIY H.O.'s to lurk and gather this valuable info. Brian
  • Plumdog_2
    Plumdog_2 Member Posts: 873
    Check the analyser

    I had a scenario like that and it turned out the CO analyser had a sensor going south on a northbound donkey.
This discussion has been closed.