Results 1 to 8 of 8
  1. #1

    Confused keeprite has short prepurge

    I was having small explosions taking place in the chamber, after professional inspection of the furnace ,it was determined the heat exchanger was bad,broken eylets. the exchanger was replaced. However right after the replacement ,after a few heat calls the explosions started again intermittently. After cleaning of the burners and pilot assembly, it happened again intermittently.
    I now believe the problem is the prepurge cycle is to short,upon a call for heat the vent motor starts up and within 3 to 5 seconds the pilot lights. Is this too short of a prepurge. how long should it be. Is the circuit board what gives the delay for the prepurge prior to ignition trail or is the diaphram in the pressure switch weak.
    I noticed a diode on the board (R1),is broken ,could this be the problem in the prepurge being so short.
    your help is much appreciated

  2. #2
    Join Date
    May 2006
    Location
    east central indiana
    Posts
    1,117

    prepurge

    I dunno about all that. There used to be furnaces that were designed with no prepurge at all. There was one called Quattro that lit the pilot before the inducer even started, it would light & prove the pilot, then start the inducer.

    R1 sounds more like a resistor than a diode, it could actually be a jumper that was cut intentionally.

    JMO.
    This space for rent.

  3. #3
    Join Date
    Mar 2007
    Location
    Madison, Wisconsin
    Posts
    2,260
    not enough info. We need Model and Serial if possible. Who replaced the HX and why did they not take care of this problem?
    I r the king of the world!...or at least I get to stand on the roof and look down on the rest of yall

  4. #4
    FURNACE IS A KEEPRITE DC90 HIGH EFFECIENCY, MODEL NUGMO75,SERIAL NUMBER L9636-44470.THE CONTRACTOR TOLD ME THE HEAT EXCHANGER WAS FAULTY THUS CAUSING THE PROBLEM, AFTER HE WAS DONE HE FIRED THE FURNACE A FEW TIMES AND ALL FIRED PROPERLY, AFTER HE LEFT IT FIRED ONE OR TWO MORE TIMES,THEN IT HAPPENED AGAIN,IT HAPPENS ONCE EVERY 6 TO 7 STARTUPS.
    tHE INLET PRESSURE WAS 7 WC AND OUTLET WAS 3.5 WC.
    AND R1 IS A RESISTOR,AND THERE LOOKS LIKE THERE WAS SOME RUST ON IT WHICH CORRODED ONE SIDE OF WIRE THAT WAS SOLDERED TO THE BOARD.
    ALL THE THREADS THAT TELL YOU WHAT MAY BE THE PROBLEM WHEN YOU HAVE THESE SO CALLED EXPLOSIONS HAVE ALREADY BEEN ADDRESSED.
    I NEED SOMETHING NEW TO GO WITH

  5. #5
    Join Date
    Jul 2002
    Location
    Slacking off right now
    Posts
    7,546
    Hey Numb Nuts - the all cap post is hard to read And I won't bother - plus it means you are shouting

    I recomend you adjust yer attitude
    www.vetopropac.com - The best tool bags on the market - The offical tool bag of choice by techs everywhere

    Arguing with some people is like wrestling a pig - eventually you realise the pig actually enjoys it

    Gonads serve a useful purpose but are no substitute for brains

  6. #6
    Join Date
    Dec 2004
    Location
    newton,mass.
    Posts
    6,109
    Quote Originally Posted by The Penguin View Post
    Hey Numb Nuts

    How did you know his nuts were numb...


    .
    "Nothing else can poison our culture, corrupt our society or ruin the character of our people like unearned money or unearned opportunity." -- James R. Cook

    "Fooling around with alternating current is just a waste of time. Nobody will use it, ever." Thomas Edison, 1889.

  7. #7
    Join Date
    Jul 2002
    Location
    Slacking off right now
    Posts
    7,546
    Quote Originally Posted by vmc1161 View Post
    How did you know his nuts were numb...


    .
    He typed in all caps
    www.vetopropac.com - The best tool bags on the market - The offical tool bag of choice by techs everywhere

    Arguing with some people is like wrestling a pig - eventually you realise the pig actually enjoys it

    Gonads serve a useful purpose but are no substitute for brains

  8. #8
    Join Date
    Jun 2004
    Location
    Howell, Michigan
    Posts
    16,176
    Call a contractor back to repair the problem. This is not a DIY forum. Delayed ignition is dangerous, shut it off until it's repaired.


    *********************THREAD CLOSED***********************

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event