Results 1 to 11 of 11
  1. #1
    Join Date
    Feb 2005
    Location
    Kentucky
    Posts
    57
    HAS ANY BODY RUN INTO ANY PROBLEMS WITH A HIGH LIMIT TRIPPING ON A CAMBRIDGE AIR MAKEUP MOD#C1900. AFTER HIGH LIMIT TRIPS YOU CAN CHECK TEMPERATURE ON DIGITAL CONTROL IN CONTROL PANEL AND EVERY THING SEEMS OK AT 120 DEGREES. IT WILL RUN FINE WHEN YOU CYCLE IT ON AND OFF. BUT IN A WEEK OR SO IT WILL TRIP OUT AGAIN. HIGH LIMITS ARE PRESET AT 180 DEGREES. BELTS AND AIRFLOW IS FINE, I HAVE SEEN THIS ON MORE THAN ONE UNIT BUT DID NOT HAPPEN AS MUCH.

  2. #2
    Join Date
    Jan 2005
    Location
    Area 51
    Posts
    984
    Does the burner have a modulating gas valve on it with a high and low fire gas pressure limit setting and does the burner reset the discharge temperature off of outside air. or heated space temperature. The company I work for had one that would trip the limit and the high fire limit in the Maxitrol valve was never set and when the space got cold enough the burner would over fire.
    "Paddle faster, I hear banjo music"

  3. #3
    Join Date
    Feb 2005
    Location
    Kentucky
    Posts
    57
    IT DOES HAVE A MODULATING VALVE THAT IS CONTROLLED BY A MAXITROL CONTROL. AS FAR AS HIGH AND LOW GAS PRESSURE SWITCHES, IT DOES NOT HAVE THEM. IT HAS A SPACE TEMP SENSOR AND DISCHARGE AIR SENSOR THAT CONTROLS HIGH AND LOW FIRE. I HAVE TRIED TO TURN DOWN MAX SETTING ON THE ACTUAL MAXITROL AND THAT DID NOT HELP.

  4. #4
    Join Date
    Mar 2003
    Location
    Cincinnati
    Posts
    7,977
    Please push this button

    It hurts to read with all caps.

    [Edited by mattm on 03-10-2005 at 08:47 PM]

  5. #5
    Join Date
    Apr 2003
    Location
    the Great Pacific Northwest
    Posts
    607
    are my ears bleeding?

  6. #6
    Join Date
    Mar 2005
    Posts
    56

    try disconnecting a wire

    on the space sensor- should make the maxitrol go to full fire- confirm it is by dc volt reading at valve (5v?)- then check manifold pressure under this condition with a manometer & compare to hi-fire pressure spec.

  7. #7
    how much outside air are u pulling in and is it mixed.
    If amplifier is proven good then i would check discharge air sensor calibration.

  8. #8
    Join Date
    Nov 2004
    Location
    up in the hizzy
    Posts
    1,376
    Have you checked the filters and the outside air intake? and if the filters are good there is a temp. set point built into the maxitrol make sure that its not set over 140 F ,Also meke sure that the discharge temp sensor is clean.
    If my memory does not fail me I' believe that if you pull wire #8 out the maxitol the unit will run in high fire and you should be getting 10 to 15 volts at the valve. than by pulling wire #3 the unit will go on low fire and you should be getting 0 to 5 volts.
    if everything checks out fine. I' would change both the discharge sensor and the limit.

  9. #9
    Join Date
    Jan 2005
    Location
    Area 51
    Posts
    984
    Disconnecting wires 2 and 4 from the amplifier will cause the valve to go to high fire on a series 44 amplifier.Disconnecting wire 8 will cause it to go to low fire. On a M411,511 or 611 valve the low fire is adjusted on the side of thee valve and the high fire is set at the pressure regulator to the burner. On a MR212 valve both high and low are adjusted seperatly on the top of the valve.
    "Paddle faster, I hear banjo music"

  10. #10
    Join Date
    Feb 2005
    Location
    Kentucky
    Posts
    57
    I checked it out again on a mild day and found it overfiring. It had a ts144 dicharge sensor that was reading 36,000 ohms, anything over 6,000 ohms should be replaced. I installed new sensor and everything came back in line. Thanks for the help.

  11. #11
    Join Date
    Dec 2004
    Location
    toledo, ohio
    Posts
    179
    close to the box that holds the high limit at the temp sensor, there are 2 screw heads with nuts holding locking them. these bolts are connected to 2 cup like things. they basicly divert the heat from the limit and sensors. some times these go out of adjustment.

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