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Munchkin T80 E14 followed by F14 fan speed error codes

Hi: Munchkin boiler T80, standard control board (no Vision - in this system I'm the outdoor reset controller) installed 15 yrs ago, working flawlessly without the need to replace any parts. Hydronic system consisting of combination of cast iron radiators (original house) and in-floor/underfloor radiant heating (addition) using injector pumps and a few wax actuators. Yes, there is a strainer in the water recirc loop, right before the main circulator inlet.

I did a search and found a previous discussion about fan speed helpful, but am still stumped.

Just recently- of course during a recent spate of unusually cold weather- the unit has started to throw first an E14, then an F14 code (high air blower speed) when the thermostat calls for heat after our night-time setback. The unit cycles, lights and runs normally after pressing the RESET button to clear the fault code.

When the thermostat calls for heat, the unit does what I presume is its pre-purge by running the blower at high speed. It does not run the blower for 30 much less 60 seconds before fan speed drops and the E14 code comes up on the display. After a number of seconds, the code changes from E14 to F14 and the unit just sits there. If you wait for several minutes and then press the reset, the unit fires up normally and will run, modulating properly, all day long.

There is no sign of condensation corrosion (from exhaust re-breathing, apparently a common problem) on top of the blower motor, but I have not pulled the blower yet to inspect its internals- waiting for warmer weather.

Comments

  • HomerJSmith
    HomerJSmith Member Posts: 1,562
    edited February 2021
    A type E fault is a warning before a hard F fault occurs. An F14 is as you said, the fan running too fast, but not a deteriorating fan or exhaust gas recirculation problem.

    Check both plugs to the blower and check the plugs for the blower at the control board.
    Unplug and re-plug them.

    Check the negative pressure switch and tubing to the blower if you have one.

    You can check the rpm of the blower in the service programing.
  • Does the circuit board have a red transformer or a black one. If it's red, you may need to upgrade to a 926 control board. When the older 925 boards get old, they start throwing out erroneous codes.

    At 15 years old, you may want to consider getting a new boiler. Has it been serviced regularly? If the coffee grounds build up in the heat exchanger, they will eat right through the stainless steel and start leaking.
    Often wrong, never in doubt.
    kcopp
  • latemnetlom
    latemnetlom Member Posts: 1
    Thank you both so much for your replies!

    It's a T80M. Definitely the 925 controller with the red transformer. Next time it's off, I'll unplug and replug the connectors- the connector in the display unit I already had to reseat once so I guess they can be flaky after a while.

    It has a blocked vent pressure switch but I"m not getting a blocked vent (FLU) error code (and the vent definitely isn't blocked).

    I won't be opening it up until warmer weather unless it totally conks out- happy to keep pushing the reset button once a day until spring. Flame stability has been excellent and there have been no problems with the condensate drainage at all so far. It's been a remarkably reliable unit actually.

    If I were looking at a replacement- I don't know how long these units should be expected to last- what would you recommend? Preferably something which will NOT require me to re-run the vent line at 3"...I have a Navien tankless that we use for domestic hot water (there was a government deal here which basically paid me to install it to replace the previous tank HWH) and it has the 3" CPVC vent. Fitting a larger vent in the furnace room would require major work in a tight space. The way it is, both the vent and air intake lines are nice short, simple runs, but at 2"...
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 3,243
    edited February 2021
    I like the IBC SL series https://www.ibcboiler.com/consumer/products/sl-series/

    We installed one a few months ago to replace a Munchkin. The side tappings are great in tight spaces.
    Often wrong, never in doubt.
    kcopp
  • latemnetlom
    latemnetlom Member Posts: 1
    A week later and I have a new Navien NHB-55 installed and heating the house. The Munchkin's problem revealed itself to be a leak in the heat exchanger presumably into the combustion chamber. I started losing pressure in the system and had to top up (manually). By the time I had the Navien and the fittings necessary to do the installation, the Munchkin was depressurizing in a matter of a few hours. I'll do a post mortem on the thing once I get around to it and report back. Looks like I have a working control board, Dungs valve and blower available if anyone needs one...
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 3,243
    edited February 2021
    The usual symptom of a leaking HX is a "Pr0" error code, the sound of water running and an active condensate drain. Interesting that yours was a blower code.

    I've never paid much attention to Navien boilers, but their HX looks just like an on-demand water heater, at least on the NHB series.
    Often wrong, never in doubt.
    kcopp