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F13 error on Munchkin T50

I have a T50 HTP Munchkin which was installed by a reputable and skilled contractor (thank you, Palmer Heating) six or so years ago and has been serviced each year since then, including combustion gas checks.

The boiler has suffered F13 error (combustion fan speed low) lockouts four times in about the past four months. Resetting the boiler with the S4 switch on the 925 controller clears the fault and the boiler runs without problem for a month or more. I have checked the line and DC voltages at the respective Molex connectors on the blower and tested the duty cycle at power up. All were fine (120VAC, 37VDC, and ramping up to 100% quickly, respectively.)

According to the HTP diagnostic checks, this means the combustion blower needs to be replaced. I assume the fan bearings could be worn just enough that the fan speed falls far enough below specs to only trip the error sometimes, but is there anything else you would recommend checking before I spend hundreds of dollars on a new fan?

Thank you for any assistance, insight, or education you can provide.


  • venting

    Is your boiler vented out of the sidewall of the house? Are both the intake and vent pipes side by side?  Is there at least 18 inches vertical seperation between the two pipes?

    sounds to me like your boiler is sucking up it's exhaust gasses. this causes corosion on the electrical connections and electronics parts inside the blower ans the 925 controller.

    Replace the blower and rework the vent pipe ( raise the vent pipe 18 inches ) so that it looks like a periscope.
  • JamieJamie Posts: 103
    I believe the venting is OK.

    Thank you for the suggestion.

    The boiler is vented vertically through a chimney which is used as a chase for the exhaust, while the remaining space surrounding the exhaust pipe acts as the combustion air duct. The exhaust pipe discharges vertically after passing through a vent cap (like the one pictured at the start of the ModCon Icing on Chimney thread), while the intake air is pulled horizontally through the grates on the vent cap. So there is about a foot of vertical separation between the intake and exhaust.

    I don't suspect any mixing of gasses. The ducting installation conforms in essential respects to the installation manual guidelines, the interior of the boiler cabinet does not show any signs of corrosion, and when I pulled the Molex connectors to make sure the wiring connections were tight, I did not see corrosion.

    I will look again for signs of corrosion, but are you suspicious because in your experience (1) these blower fans almost never fail unless there is exhaust gas recirculation or (2) these fans often or sometimes fail because of recirculation?
  • experiance

    As any mechanical/electrical part they can fail at any time.

    BUT - reversion can and will destroy the blower and the 925 controller.

    Is this an R1 or R2 version - or just a first generation T50?

    If it is just a T50 you could have exhaust gasses rising out of the blower after the burner and blower shut down. The R2 version runs the blower longer after burner shut down to clear the moist gasses out of the combustion chamber to stop this.

    I have vented a few high efficient boilers the same way you have. Works great.

    Under speed/over speed is one of those problems that are hard to diagnose without the computer hook up I have. You can see what the RPM is supposed to be and what it actually is.
  • JStarJStar Posts: 2,668

    The intake is the chimney?!? That's no bueno.
    - Joe Starosielec
    [email protected]
  • Jstar

    That is an approved method of venting. As long as the chimney is NOT used for anything but as a chaseway. Weil McLain even has it in their install manual.
  • JStarJStar Posts: 2,668

    To take intake air from the chimney? I believe you, but I don't like it.
    - Joe Starosielec
    [email protected]
  • Steve WhitbeckSteve Whitbeck Posts: 669
    edited January 2013


    It is open at the top to draw in outside air and sealed at the bottom arround both pipes.
  • JStarJStar Posts: 2,668

    Hope not to derail this thread.

    I don't like the idea of using a brittle beat up chimney to supply "fresh clean air" to a sensitive piece of technology. Plus, chimneys are designed to send air out of a structure. It bothers me to fight that natural movement. And it seems like it basically oversizes your intake pipe size. All of those factors make me uneasy. But, you said you've done it with great success. Can't argue that.
    - Joe Starosielec
    [email protected]
  • JamieJamie Posts: 103

    It is the Revision 1 (R1) version. It has a 925 controller and was manufactured in August 2004, IIRC.

    The 925 controller displays fan speed. When I just checked it, it was at 1250 RPM and the boiler was at fairly low fire. But I can't tell if the boiler is at its lowest or second lowest modulation rate and I don't know what the fan speed is supposed to be at each modulation rate. If you can help me with either of those pieces, I would appreciate it. (I would infer that if the fan is running somewhat below expected/specified speed at all times, that would further support the conclusion that the fan assembly should be replaced.)

    Thank you for your responses/input.
  • JamieJamie Posts: 103
    edited January 2013
    fan speed

    Looking again, the fan is now at 1700 RPM. The boiler is on a higher fire than it was when the fan speed was 1250, but I do not know which step in the modulation sequence it is at.

    And later still, it is at 1370 RPM.

    At post-firing purge, it was 2990--3000 RPM.
  • Steve WhitbeckSteve Whitbeck Posts: 669
    edited January 2013

    Jamie - This is VERY important -  You need to get someone over there with a carbon monoxide detector ( combustion analyzer ) Get them to test for CO leakage at the back of the heat exchange. The 2004 T50 and T80 had a problem with exhaust leakage at the back of the heat exchanger. This leakage is what is taking out the blower. HTP will replace this defective boiler. IF it has leakage. don't replace the blower until it is tested. And don't let the testing company tell you different. If they show leakage contact the HTP distributor for your area. If they won't help you get back to me and I will see what I can do.


    Sorry - I should have caught this earlier.
  • JamieJamie Posts: 103
    CO leakage

    Thank you very much for this information. I will call the original contractors, who have been very good, in the morning and ask them to send someone with a combustion analyzer.

    I feel safe continuing to run the boiler because, in addition to the regular UL smoke/CO detectors, I have low-level CO detectors (COExperts) on the first floor and in my bedroom and I replaced them less than a year ago.
  • T50

    I have replaced a few of these defective boilers. You will have to pay for labor. If there aren't any more T50 available pay for the upgrade to the EliteFT.

    The FT is a much better boiler and is new tech.
  • JamieJamie Posts: 103
    edited February 2013
    The results

    The technician inspected the boiler, disassembled the blower assembly, and blew a ton of sawdust out of it. (This is presumably the result of having woodworking tools in the same basement as the boiler. I will try to seal the boiler cabinet somewhat and---to some extent---wall off the room in which the boiler lives. [It can only be to some extent because the clothes dryer is in the same room and it draws combustion and make-up air from the surrounding space.]) He found no leakage at the heat exchanger, performed an annual cleaning and combustion check, and restored the boiler to operation.

    He also left me a new combustion fan in a sealed box. If there are no further fan speed failure codes, I will simply ship back the unopened container. If the sawdust has too severely compromised the original blower and it continues to exhibit the same symptoms, I will replace it.

    Many thanks to those who made suggestions and thanks to Palmer Heating for the skilled service.
  • JamieJamie Posts: 103
    The Outcome

    Bump the edited post.
  • TimTim Posts: 5
    Update ??

    Jamie, how did that last service call go? Did it solve your problem?
  • JamieJamie Posts: 103
    Last service call

    As described above, the technician cleaned the blower assembly. I've sealed up the boiler cabinet and the chimney clean-out. No problems since then.
This discussion has been closed.


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