Munchkin backfiring problem

JBurke

I installed a Munchkin 140M about 4 years ago.  Since then we have had nothing but problems.



Now it backfires and I'm afraid of a gas explosion.



1. The unit was not installed high enough for the condensate to drain properly by gravity.  Solution: We installed a stand alone pump and have replaced it at least once.  Condensate back-up was causing an F09 error.  The pump seems to have resolved that problem- condensate line is clear and drains.



2.  We continue to get F09 errors and an occasional F11 error.  I have replaced the "sparkplug" twice, most recently last week.  I checked and cleaned the heat sensor probe.  The blower came on after a reset, lit and worked for about a day.  I saw the spark and flame through the viewing window.  The fan comes on a few seconds before the spark.  ? Purging gas build-up?



3.  The circuit board was replaced a year ago.



4.  There had been a whiff of gas on one occasion just after I replaced the ignighter.  The gas company checked all the lines and tell me everything is fine- no leak.  I think I sniffed some residual gas from the chamber while the ignighter was out.



THE MUNCHKIN BACKFIRES!  It seems to ignite properly, burn and provide hot water for a few hours, then BOOM! there is a very loud backfire.  I suspect this occurs when it has been off for a while and tries to turn back on.  On two occasions I looked and it appeared to be working after the backfire- the controller indicated hot water and no red lights or error. After the last backfire I got an F09 error and I shut everything down.



HELP!  The original installer no longer services them and referred me to a new company who will be here next week.

tim smith

Re: Munchkin backfire

Find another company who can get there sooner as long as they have a decent amount of experience with servicing them. The boiler needs cleaning, thorough cleaning. May need new target wall. After all cleaned up, they must use combustion analyzer to set burner combustion up properly. Good luck, Tim

blade10

misfiring

the most common problem with munchkins is improper installation (as u have stated) and most importantly VERY thorough maintanence EVERY year! In my companies experience with the htp munchkin the biggest problems we have had is with the Target walls and burner gaskets. what can happen is the gas to oxygen mixture becomes too great and will not ignite properly causing an excessive amount of gas to build up thus leading to your "explosion' noise. The ignitions will become periodic and eventually sieze altogether. Have a qualified company come out and replace both and then make sure they have a combustion analyzer with them cause without one u will be wasting ur time and money!

JBurke

Thank you

Thank you for the insight.  I'll make sure they have an analyzer and learn how to do yearly cleaning.